Product Reviews and Information for Hepatitis (A, B, C)

10/10/2014

Caution with St. John's Wort

St. John's wort is known to interact with a large number of prescription drugs. That number grew larger recently when the FDA approved two new drugs to cure hepatitis C infection. Taking these drugs while using St. John's wort may lead to reduced therapeutic effect and is not recommended. More information about this and other drug interactions with St. John's wort is found in the "Concerns and Cautions" section of the St. John's Wort Supplements Review >>

9/02/2015

CLA Linked to Acute Hepatitis

CLA supplements are popular for slimming, but a recent report of acute hepatitis (liver inflammation) associated with use of CLA is concerning. Get the details, plus more about evidence, safety, and our tests of popular products in the CLA Supplements Review >>

1/08/2012

Additional Nutrients For the Brain

An new study found that various nutrients and fats in the blood correlate with better brain functioning and brain volume in the elderly (mean age of 87). Higher levels of B vitamins and vitamins C, D, and E, as well as marine omega-3 fatty acids (EPA and DHA) appeared helpful. On the other hand, higher levels of trans-fats (from hydrogenated oils) had a negative impact. You can learn more about each of these nutrients in our various reports. An abstract of the study is online.

3/26/2019

Red Yeast Rice & Liver Injury

Hepatitis was recently reported in a woman in the U.S. who was taking a red yeast rice supplement. Other cases have been reported. For details, see the Concerns and Cautions section of the Red Yeast Rice Supplements Review. Also see our Top Pick among products.

3/25/2020

Another Case of Liver Injury With Turmeric

Although believed to be rare, we’ve been reporting a steady stream of cases of liver injury (hepatitis) with turmeric supplements. Learn the symptoms and read the latest in the Concerns and Cautions section of the Turmeric and Curcumin Supplements Review.

6/10/2017

Hip Fracture Risk With Too Much B-6

A new study found that older men and women who took a high daily dose of vitamin B-6 had a 42% increased risk of hip fracture. Get the details in the "Vitamin B-6" section of the B Vitamin Supplements Review. Also, be aware that many supplements on the market contain the amount of B-6 used in this study, or more, in a daily serving! For help choosing a B-Complex or B-6 supplement that suits your needs without providing too much B-6, see our Top Picks among B vitamin supplements.

3/19/2025

Bad B-12 Supplements Sold on Amazon

Eleven out of 23 vitamin B-12 supplements sold on Amazon and tested by a competing brand contained less B-12 than listed on labels, including two with no detectable B-12. Get the details in our B Vitamin Supplements Review, which includes our Top Picks for B-12, B-complexes, and other B vitamin supplements.

9/29/2025

Is Vitamin B-12 Better from Yeast?

Some supplements claim to contain the "methylcobalamin" form of vitamin B-12 from yeast. Is this better than other forms of vitamin B-12? Find out in the Forms of B-12 section of our B Vitamin Supplements Review, which includes our Top Picks for B-12 and other B vitamins.

12/09/2024

B-12 Plus Intrinsic Factor?

Do vitamin B-12 supplements with “intrinsic factor” boost blood levels of B-12 better than B-12 alone? Find out what research suggests in the B-12 section of our B Vitamin Supplements Review, which includes our Top Picks for B-12.

11/21/2024

Laughing Gas & B-12

Although rare, be aware that use of nitrous oxide (i.e. laughing gas), such as during a medical procedure, can inactivate vitamin B-12 in the body. Let medical professionals know if you are B-12 deficient. Get the details in the B-12 section of our B Vitamin Supplements Review. Also see our Top Picks for vitamin B-12 and other B vitamin supplements.

8/25/2023

B-12 for Ringing Ears?

Low levels of B-12 have been linked with tinnitus (ringing in the ears) and other issues, but does taking B-12 reduce tinnitus? Find out in the B-12 section of our B Vitamin Supplements Review, which includes our Top Picks for B-12 and other B vitamins.

Also see our article about supplements that may improve or worsen tinnitus.

2/22/2023

Symptoms of Too Much B-6

High doses of vitamin B-6 from supplements may cause adverse effects, even when doses do not exceed the established tolerable limit for B-6, as highlighted by a recently reported case. Learn about getting too much or too little vitamin B-6 in our B Vitamins Supplements Review, which includes our Top Picks among B-6 and other B vitamin supplements.

2/15/2022

B-12 Deficiency and GI Symptoms

Severe vitamin B-12 deficiency can cause a range of gastrointestinal symptoms, as highlighted in a recent case. Learn about these and other symptoms of B-12 deficiency in the B-12 section of our B Vitamin Supplements Review. Also see our Top Picks for vitamin B-12 and other B vitamin supplements.

7/13/2021

Hidden Forms of B-12 Deficiency

Vitamin B-12 deficiency can occur even in people with "normal" blood levels of B-12, as was most recently reported in a 30-year-old man. Learn more, including the wide range of symptoms of B-12 deficiency and information about testing for B-12 deficiency in our B Vitamin Supplements Review. Also see our Top Picks for B-12.

8/10/2021

Best Form of B-12 for Vegans?

What form of vitamin B-12 appeared best at raising B-12 levels among people on plant-based diets in a new study, and how did this compare to getting B-12 from plant-based foods? Find out in the B-12 section of our B Vitamin Supplements Review. Also see our Top Picks for vitamin B-12.

12/24/2021

Oral Symptoms of B-12 Deficiency

Vitamin B-12 deficiency can cause a range of symptoms in the mouth, as described in a recent report. Learn about oral and other symptoms of B-12 deficiency in the B-12 section of our B Vitamin Supplements Review. Also, see our Top Picks for B-12 and other B vitamins.

8/25/2020

B-12 Supplements vs. Injections

Can taking a B-12 supplement work as well as an injection to correct vitamin B-12 deficiency? See what a new study found in the B-12 section of the B Vitamin Supplements Review. Also see our Top Picks for vitamin B-12 and other B vitamin supplements.

6/27/2015

How Vitamin B-12 Causes Acne

Vitamin B-12 is a critical nutrient and many people, particularly those over 50, should supplement with B-12 to avoid deficiency. However, at doses higher than those used to prevent deficiency, B-12 may occasionally trigger acne. A new study appears to explain the B-12/acne connection. For details, see the "Cobalamin (B-12)" section of the B Vitamin Supplements Review >>

11/29/2019

B Vitamins for Cognition

Increasing vitamin B-12 intake by those deficient in B-12 can help slow age-related declines in memory and cognition, but the dose needs to be sufficient, as suggested by a recent study. For details see the Memory, Cognition, and Alzheimer's Disease section of the B Vitamin Supplements Review. Also see our Top Picks for B-12 and other B Vitamins.

11/18/2020

B-12 for Singers

It is commonly believed that a shot of vitamin B-12 improves the performance of professional singers. A placebo-controlled study put this belief to the test. Get the results in the B-12 (cobalamin) section of our B Vitamin Supplements Review. Also see our Top Picks for B-12 and other B vitamins & complexes.

4/05/2022

B-12 Deficiency Can Cause Reversible Cognitive Decline

Treating B-12 deficiency improved rapid cognitive decline and stopped hallucinations in an older man, according to a recent report. Get the details in the B-12 section of our B Vitamin Supplements Review. Also see our Top Picks for B-12 and other B vitamins.

2/04/2022

Risk of Too Much B-12

It’s easy to get way more vitamin B-12 than one needs from supplements. Unfortunately, high blood levels of B-12 are being linked to higher risks of death and disease, as shown in a recent U.S. study. Get the details in the Upper Limit for B-12 section of our B Vitamin Supplements Review. Also, see our Top Pick among B-12 supplements.

7/15/2022

B Vitamins for Parkinson's?

People with Parkinson's disease tend to have lower levels of vitamin B-6 and B-12. Find out if supplementing with B-6 or B-12 is beneficial and whether B-6 can interfere with drugs for Parkinson's.

11/11/2022

Nutritional Yeast for B Vitamins?

Is nutritional yeast a good source of B-12 and other B vitamins? That depends on whether or not it is fortified. Get the details in the Getting B-12 from food section of our B Vitamin Supplements Review, which includes a list of foods containing B vitamins.

6/13/2023

Vitamin B-12 Allergy

Rarely, vitamin B-12 supplementation can cause an allergic reaction, as highlighted by a recent case. Be aware of the risks of B-12 as explained in our B Vitamin Supplements Review, which includes our Top Picks for vitamin B-12 and other B vitamins.

8/29/2023

Symptoms of B-12 Deficiency

Be aware that vitamin B-12 deficiency can cause a range of side effects. Among these are low blood cell counts, as described in a recent case report. Get the details in the Symptoms of B-12 deficiency section of our B Vitamin Supplements Review.

Also see our Top Picks for B-12 and other B vitamins.

10/31/2023

Can B-12 cause allergic reactions?

Although rare, vitamin B-12 can cause allergic reactions, but so can “inactive” ingredients in B-12 and other supplements. For details see the Risks of B-12 section of our Vitamin B-12 Review, which includes our Top Picks for B-12.

2/06/2025

Why High-Dose B-12?

A CL member asked why so many B-12 supplements contain very high doses of B-12, such as 1,000 mcg or more. Find out when this is, and isn't, appropriate in our article about B-12. Also see our B Vitamin Supplements Review for our Top Picks for vitamin B-12.

6/07/2024

Oral B-12 for Deficiency?

Can taking vitamin B-12 by mouth treat B-12 deficiency, or are injections necessary? Find out what a recent study showed in the Oral B-12 vs Injection section of our B Vitamin Supplements Review, which includes our Top Pick for high-dose B-12.

12/19/2023

Caution With High-Dose B Vitamins

Vitamin B-6: Regularly taking a higher than required dose of vitamin B-6 may cause nerve damage, as was recently reported. Get the details in the B-6 section of our B Vitamin Supplements Review.

Niacin: A large increase in niacin dosage may cause fainting, as was recently reported. Get the details in the Niacin section of our B-Vitamin Supplements Review.

5/20/2025

B-12 Deficiency

There are many possible causes of B-12 deficiency and a wide range of symptoms. A recent highlights the diverse symptoms in a man who underwent stomach surgery. Learn more in the B-12 section of our B Vitamin Supplements Review, which includes our Top Picks for vitamin B-12 and other B vitamin supplements.

6/05/2025

Too Much B-6 from Nuts

Getting too little vitamin-B-6 can cause serious problems, but getting too much vitamin B-6 can as well -- including from foods such as nuts -- as recently reported in two case reports. Get the details in our B Vitamin Supplements Review, which includes our Top Picks for vitamin B-6 and other B vitamins.

11/04/2017

B Vitamins for Memory

Many studies suggest that adequate intake of B vitamins slows age-related declines in memory and cognition. This was recently shown again in a study in England. Find out which B vitamins help, and how much you need, in the "What It Does" section of the B Vitamin Supplements Review >> [Also see our Top Picks for B vitamin supplements in the Review.]

1/10/2017

Potential Risk with High B-12

Among people who are malnourished, those with elevated vitamin B-12 levels in their blood were twice as likely to die when hospitalized as those with lower B-12 levels, according to a new study. The study authors suggest caution with inappropriate supplementation. For more details about the study, and vitamin B-12, see the B Vitamin Supplements Review >>

10/30/2011

B Vitamins May Help Memory

A recently published study of individuals aged 70 years or more with mild cognitive impairment found that a daily dose of three B vitamins (folic acid, vitamin B-12, and vitamin B-6) over 2 years appeared to slow cognitive and clinical decline, particularly in those who started with elevated levels of plasma homocysteine. See the B Vitamin Product Review for details including the dosage used.  More >>

9/21/2013

B Vitamin Supplements for Stroke?

A review of 14 clinical studies suggests that B vitamins may help prevent stroke. However, a deep reading of the report shows the benefit to be slight, at best.  For details about the study, other uses of B vitamins (including B6, B-12, folic acid, niacin and complexes), and tests of these supplements, see the B Vitamin Supplements Review>>  

12/23/2020

B-12 for Eczema?

Can vitamin B-12 deficiency worsen eczema and can supplementing with B12 help? Find out what happened in a recent case in the vitamin B-12 section of section of our B Vitamin Supplements Review. Also, see our Top Picks for vitamin B-12.

1/18/2022

B-12 Vitamin Deficiency and Darkening of the Skin

Low levels of vitamin B-12 can cause darkening of the skin, as evidenced in a recent case. Get the details and learn about other symptoms of B-12 deficiency in our B Vitamin Supplements Review. Also, see our Top Picks among B-12 supplements.

11/27/2024

B-12 Deficiency & GI Symptoms

Vitamin B-12 deficiency can cause many symptoms, including chronic diarrhea, as described in a recent report. Learn about symptoms of B-12 deficiency in our B Vitamin Supplements Review, which includes our Top Picks for B-12.

12/05/2024

Difficulty Walking and B-12 Deficiency

Be aware that vitamin B-12 deficiency may present with a variety of neurologic symptoms, including difficulty walking due to spinal cord degeneration, as described in a recent report. Get the details in the B-12 section of our B Vitamin Supplements Review, which includes our Top Picks for vitamin B-12.

6/14/2024

B-12 for Vegans

What happens when a vegan stops supplementing with B-12? Find out in the Vegan section of our B Vitamin Supplements Review. Also see our Top Picks for B-12 and other B vitamin supplements.

8/15/2024

Best Way to Take B-12?

What’s the best way to take vitamin B-12? Find out more in our article about vitamin B-12. Also see our Top Picks for vitamin B-12 in our B Vitamin Supplements Review.

9/06/2024

Side Effect of High-Dose B-12

Although there is no established upper limit on intake of vitamin B-12, too much can cause a side effect noted in several case reports. Get the details in the Vitamin B-12 section of our B Vitamin Supplements Review, which includes our Top Picks among B vitamins.

10/24/2024

B Vitamin Confusion

Be aware that a B complex supplement Approved by us in 2022 has a similar name to a product NOT Approved in our most recent tests. The two products are different, as explained in the What CL Found section of our B Vitamin Supplements Review, which includes our current Top Picks for B vitamin complexes and single B vitamins.

9/19/2023

Does B-6 Reduce Antibiotic Side Effects?

Did supplementation with vitamin B-6 reduce antibiotic-related side effects in people treated for H. pylori infection (a common cause of peptic ulcers)? Find out in our B Vitamin Supplements Review, which includes our Top Picks for vitamin B-6 and other B vitamins.

Also see: 8 Supplements That May Help Treat Peptic Ulcers – And Some to Avoid

10/04/2022

Nerve Pain & Vitamin B-6

Vitamin B-6 deficiency can cause nerve pain and weakness, even resulting in inability to walk, as shown in a recent case. However, getting too much B-6 from supplements can also cause these symptoms. Find out how much B6 you should be getting in the Vitamin B-6 section of our B Vitamins Supplements Review.

For information about supplements that may help with other forms of nerve pain, see our answer to the question: Do any supplements, like Nervive, help with nerve pain, like sciatica or diabetic neuropathy?

6/28/2022

B-12 Deficiency & Stomach Surgery

Many people who have had bariatric (stomach-reducing) surgery need to supplement with B-12 and other B vitamins. Find out what happened to such a person who discontinued supplementation in the Vitamin B-12 section of our B Vitamin Supplements Review.

7/26/2022

B-6 or B-12 for Anxiety?

Can taking high-dose vitamin B-6 or B-12 improve self-reported anxiety? Find out what a recent study showed in the Anxiety section of our B Vitamin Supplements Review.

Also see our answer to the question: What are the best supplements for depression and anxiety?

5/03/2022

Severe B-12 Deficiency Can Be Missed

B-12 deficiency can cause severe symptoms, even when B-12 levels in the blood are not low, as shown in a recent case. Find out why, and which tests can help, in the B-12 section of our B Vitamin Supplements Review.

3/25/2022

B-12 Deficiency in Infants

Although not common, B-12 deficiency can occur in infants. A recent study showed common symptoms and risk factors. Learn about B-12 deficiency in infants as well as in men and women in the B-12 section of our B Vitamin Supplements Review.

4/07/2025

Caution With Vitamin B-6

Taking more than the recommended daily allowance of vitamin B-6 may cause nerve damage, according to recent case reports. Get the Details in the B-6 section of our B Vitamin Supplements Review, which includes our Top Pick for B-6 (that should only be used if you’re deficient).

1/27/2026

High-Dose B-12 for Nerve Pain?

Did a very high dose of vitamin B-12 reduce nerve pain more than a lower dose in people with type 2 diabetes? Find out what a recent study showed in our B Vitamin Supplements Review, which includes our Top Picks for B-12 and other B vitamins.

11/10/2025

Can B-12 Slow Cognitive Decline?

Higher B-12 levels were associated with slower memory loss in older men and women. Learn more in our B Vitamin Supplements Review, which includes our Top Picks for B-12 and other B vitamins.

12/14/2013

B-12 Deficiency and Acid Inhibitors

A large, new study found the risk of vitamin B-12 deficiency to be significantly higher among people taking proton pump inhibitors (e.g., Prevacid, Prilosec) or H2-blockers (e.g., Pepcid, Zantac) than among those not taking these medications. The drugs reduce acid production in the stomach, but acid is needed to release B-12 from foods, so deficiency can occur. B-12 supplements can help because acid is not needed for their absorption. For details -- and our reviews of supplements with vitamin B-12 -- see the updated B Vitamin Supplements Review,   

For more information, see ConsumerLab's answer to the question, I take omeprazole (Prilosec), a proton pump inhibitor, to reduce stomach acid. Are there supplements I should avoid, or be taking, due to this drug?.

8/14/2021

Danger With Too Much B-6

A CL member recently told us about a friend who developed progressively worsening neuropathy (nerve damage) after taking very high dose vitamin B-6. It's important to be aware of the upper daily limit for vitamin B-6 and that taking too much can cause nerve damage, as well as skin lesions and other adverse effects, as discussed in detail in our B Vitamin Supplements Review.

1/08/2012

B-12 and Folic Acid for Memory

Small but significant improvements in short and long-term memory were found to occur in older people (aged 60 to 74) given modest daily amounts of vitamin B-12 and folic acid. But don't expect immediate results. Improvements were seen only after 2 years of supplementation. See the update in the B Vitamins Review for the dosage used, as well as our ratings of supplements with vitamin B-12 and folic acid.

5/27/2013

Alzheimer's Changes Slowed with B Vitamins

A combination of B vitamins was found to slow brain loss in areas of the brain associated with Alzheimer's disease. This same combination of vitamins has also been shown to slow cognitive decline. Get the details on who may (or may not) benefit, dosage, plus test results for over 35 B vitamin supplements in the updated B Vitamin Supplements Product Review >>

12/16/2012

Higher Vitamin Level May Slow Cognitive Decline

An 8-year study of people in their 70's found that cognitive functioning (memory and other mental skills) declined faster among those with lower blood levels of vitamin B-12 compared to those with higher levels. Particularly surprising was that 40% of the people in the study fell into the lower B-12 group, many of whom had levels which would not normally define them as deficient in B-12. This and other recent studies suggest a role for vitamin B-12 in minimizing cognitive decline in older people. For details, see the updated B Vitamin Supplements Review. More >>

11/16/2014

Do B Vitamins Boost Memory?

This week, a study was reported in the media suggesting that taking vitamin B-12 and folic acid does not help with memory. But a closer look at this and related studies shows a benefit for some people. Get the details, plus our tests and comparisons of B-vitamin supplements, in the B Vitamin Supplements Review >> 

8/06/2014

When Vitamin C May Curb a Cold

A recent small study among men with low to adequate levels of vitamin C showed that supplementing with vitamin C reduced the incidence of colds compared to placebo. The men taking vitamin C also reported having more energy -- although this finding was not statistically significant. Learn more about what vitamin C can and cannot do, the dose used in this study, and results of our tests of vitamin C supplements, in the update to the Vitamin C Supplements Review >>

6/12/2016

B Vitamins & Autism Risk

Excessive blood levels of B-12 and/or folate in pregnant women were found to be associated with an increased risk of autism in their children, according to a new study. While these vitamins are critical, too much may be problematic. Get the details in the B-12 and Folate sections of the B Vitamin Supplements Review >>

8/26/2017

High-Dose B Vitamins & Cataract Risk

Taking high doses of B vitamins, including B vitamin complexes, folic acid and B6, was associated with a higher risk of age-related cataracts among middle-aged men and women, according to a new study. For details, see the "ConsumerTips" section of the B Vitamin Supplements Review >>

10/09/2018

Can a B Vitamin Lower High Blood Pressure?

A common mutation of the MTHFR gene is associated with an increased risk of hypertension. A recent study tested whether supplementing with a specific B vitamin could reduce blood pressure in affected individuals. Get the results in the MTHFR section of the B Vitamin Supplements Review. (Also see our Top Picks among B vitamins.)

8/06/2020

B Vitamins and Fracture Risk

High homocysteine levels have been linked with increased fracture risk in older people. Taking B vitamins can lower homocysteine levels, but does it lower fracture risk? Find out what a recent study using folic acid and B12 showed in the What It Does section of the B Vitamin Supplements Review. Also see our Top Picks for B vitamins.

8/02/2022

Increasing Folate from Beans & Peas

Beans and peas are great dietary sources of folate (vitamin B-9), but the right preparation can more than double their folate levels, according to a recent study. Find out how in the Folate section of our B Vitamin Supplements Review.

Also see our table of Foods Containing B Vitamins to find out other foods that are good sources of folate and other B vitamins.

8/02/2022

Metformin and B-12 Deficiency

If you take metformin for diabetes, be aware that you are at risk for vitamin B-12 deficiency. See the latest guidelines to monitor for this in the B-12 section of our B Vitamin Supplements Review.

7/08/2022

B-5 for Arthritis?

Can vitamin B-5 supplementation improve symptoms of rheumatoid arthritis or osteoarthritis? Find out what research suggests in the B-5 (Pantothenic Acid) section of our B Vitamins Supplements Review.

4/29/2022

MTHFR Mutations and B Vitamin Deficiencies

People with a certain MTHFR gene mutation (C677T) may be more likely to develop B vitamin deficiencies. But what about those with a less common MTHFR mutation – A1298C? Find out what research suggests in the MTHFR gene mutation and B vitamin metabolism section of our B Vitamin Supplements Review.

8/09/2022

B-12 and Insomnia?

A CL Member had trouble sleeping when taking high dose B-12 to correct a deficiency and asked us if this is common. Find out in the B-12 section of our B Vitamin Supplements Review.

Also see: Supplements That May Help or Worsen Insomnia.

4/26/2022

B-12 for Nighttime Leg Cramps

Raising lower blood levels of vitamin B-12 may help with nighttime leg cramps according to some reports. Get the details in the B-12 section of our B Vitamin Supplements Review.

For information about other supplements that may help, see our answer to the question: Do any supplements, foods, or oils help reduce muscle pain, muscle cramps, or nighttime leg cramps?

6/19/2025

Liposomal Vitamin C?

Some vitamin C supplements, including one from Life Extension, use a liposomal "hydrogel" to sustain higher vitamin C levels. Is this better than regular or other liposomal versions? Learn more in the Forms of Vitamin C section of our Vitamin C Supplements Review, which includes our Top Picks for vitamin C.

8/03/2016

Is Ester-C Better?

One of the forms of vitamin C in supplements is Ester-C. In addition to being non-acidic, a recent study suggests another possible benefit over regular vitamin C (ascorbic acid). Get more information about this and other forms of vitamin C in the "ConsumerTips" section of the Vitamin C Supplements Review >>

12/21/2021

Vitamin C for Mood?

Can vitamin C from the diet or supplements help boost mood, including symptoms of depression? Find out what current evidence suggests in the Vitality and Mood section of our Vitamin C Supplements Review, which includes a list of foods high in vitamin C and our Top Picks for vitamin C.

10/16/2020

Vitamin C for Vitality?

Can taking a vitamin C supplement or eating a vitamin C-rich food improve mood, energy, or overall well-being? Find out what a recent study showed in the What It Does section of the Vitamin C Supplements Review. Also see our Top Picks for vitamin C.

9/22/2018

Vitamin C and Prostate Cancer

Does taking vitamin C reduce the chance of developing prostate cancer? Find out what studies are showing, including one reported this month, in the What It Does section of the Vitamin C Supplements Review. (Also learn about vitamin C and cataracts and see our Top Picks for vitamin C.)

1/31/2020

Not Enough Vitamin C

Vitamin C deficiency is known to cause scurvy, characterized by bleeding gums and other connective tissue problems. But vitamin C deficiency was recently reported to cause a very different array of symptoms in several people. Learn more in the What It Does section of the Vitamin C Supplements Review. Also see our Top Picks for vitamin C.

9/13/2024

Liposomal Vitamin C?

Is it worth spending more for the liposomal form of vitamin C? Find out what a recent study showed in our Forms of vitamin C section of our Vitamin C Supplements Review, which includes our Top Picks for vitamin C.

7/11/2025

Liposomal Vitamin C

We recently wrote about a liposomal "hydrogel" vitamin C product from Life Extension purported to have improved bioavailability, but we could not locate a supporting published study. Life Extension recently directed us to the study, now discussed in the Forms of Vitamin C section of our Vitamin C Supplements Review, which includes our Top Picks for vitamin C.

9/19/2024

Niacin-Induced Liver Failure

Be aware of the risk of liver injury from use of very high dose niacin, as recently reported in an otherwise healthy, young woman who was taking niacin to manage anxiety and depression. Get the details in the Niacin (Nicotinic Acid) (B-3) section of our B Vitamin Supplements Review, which includes our Top Picks for B vitamins.

Also see: Is there a risk of liver toxicity with certain supplements?

3/15/2024

Carcinogen in Folic Acid

Several folic acid supplements were recently recalled in Canada due to a carcinogenic impurity that can occur with folic acid (vitamin B-9). For details, see the Quality Concerns section of our B Vitamins Review, which includes our Top Picks for folic acid and B complexes.

10/02/2024

Benfotiamine & Alzheimer’s

Can taking benfotiamine (a derivative of vitamin B-1) slow cognitive decline in people with mild cognitive impairment or Alzheimer’s disease? See what research suggests in our B Vitamins Supplements Review, which includes our Top Picks among B vitamins.

Also see: Do any supplements, foods or lifestyle modifications help with brain function, like memory and cognition?

7/25/2023

Best Way to Take B Vitamins?

We’ve added information about the best way to take vitamins B-6, B-12, and folate to our article about the best way to take vitamins and minerals.

12/08/2023

Dementia & Folic Acid

Taking folic acid without getting enough B-12 has been linked to increased risk of Alzheimer’s disease and dementia. Learn more in the Folate section of our B-Vitamin Supplements Review, which includes our Top Picks among B-Complexes.

Also see: Do any supplements, foods or lifestyle modifications help with brain function, like memory and cognition?

4/08/2022

Vitamin B-12 Deficiency and Dementia

Correcting B-12 deficiency may improve cognition in people with dementia, according to a recent study and case reports. Get the details in the Memory, Cognition, and Alzheimer’s Disease section of our B Vitamin Supplements Review.

10/25/2022

Symptoms of B-12 Deficiency

Vitamin B-12 deficiency can cause a wide range of adverse effects affecting the nervous system, cognition, blood and blood pressure, and more. Learn about the symptoms and recent cases, and find out who is most likely to be deficient in our B Vitamin Supplements Review.

Also see our article: Top 8 Supplements for Vegetarians and Vegans.

5/24/2017

POTS and Thiamin

A small study among people who suffer from POTS (postural tachycardia syndrome) suggested that supplementing with thiamin (vitamin B-1) may help some. For details, see the Thiamin (B-1) section of the B Vitamin Supplements Review >>

1/20/2017

Side-Effect With B-12

Certain formulations of vitamin B-12 contain additional ingredients that can cause diarrhea and bloating in some people — particularly if taking more than one pill. An apparent case of this was reported to us this week. To help you avoid this, read the details in the "What CL Found" section of the B Vitamin Supplements Review (which includes our tests of products) >>

5/20/2012

B Vitamin May Lower Blood Pressure

According to a new study, approximately 10% of the population is genetically prone to high blood pressure which may respond dramatically to a low dose of riboflavin (vitamin B-2). Read the update to the B Vitamin Supplements Review for details, including the dose used and amount of blood pressure reduction achieved. More >>

9/01/2020

Folate & Memory

Older people with high blood levels of folate are more likely to perform worse on tests of memory and cognition unless they have sufficient levels of another B vitamin, according to a recent study. Get the details in the What It Does section of our B Vitamin Supplements Review. Also see our Top Picks among B vitamin supplements.

10/24/2018

B Vitamin Cancer Risk?

Giving high-dose vitamin B12 along with a modest amount of folic acid to older people was found to significantly increase the risk of colorectal cancer. See the B12 section of the B Vitamins Review for details. (Also see our Top Picks for B12 and other B vitamins.)

5/18/2019

Hip Fracture Risk with B6

Another study has shown a significantly increased risk of hip fracture with high intakes of vitamin B6 from supplements. For details, see the B-6 section of the B Vitamins Review. Also see how much B6 is in popular B vitamin supplements and our Top Picks.

5/28/2019

Vitamin B12 & Depression

Deficiencies in B vitamins, such as B12, can cause depression. A recent study suggests that, in pregnant women, even low-normal B12 levels are associated with a much higher risk of depression. For details, see the Depression section of the B Vitamin Supplements Review. Also see our Top Picks for B vitamins.

11/28/2017

Growing Concern with Biotin Causing False Lab Results

Biotin (a B vitamin found in B-complex and hair and nail supplements) can interfere with laboratory results resulting in the missed diagnosis or misdiagnosis of cardiovascular and hormonal conditions, such as Graves' disease (a form of hyperthyroidism). Physicians and lab personnel may be unaware of this interference. For details, see the "Biotin" section of the B Vitamins Review >>

12/14/2017

Danger from Too Much Vitamin B6

A women who was consuming large amounts of an energy drink as well as a B-vitamin complex developed symptoms of vitamin B6 (pyridoxine) toxicity (which may not be reversible), according to a recent report. Get the details in the "B6" section of B Vitamin Supplements Review >>

CL has long warned that energy drinks and shots often contain large amounts of B6 and other B vitamins.

11/04/2020

Muscle Cramps from Lack of Vitamin

Painful muscle cramps in an older person resolved after correcting a deficiency in one of the B vitamins, according to a new report. Get the details, and learn which conditions and medications increase the risk of this deficiency, in the B Vitamin Supplements Review. Also see our Top Picks for B vitamin supplements.

4/30/2012

Vitamin C and Blood Pressure

Vitamin C supplements may modestly reduce blood pressure, particularly among people with elevated blood pressure, according to a review of the latest clinical studies. Get the details, as well as our tests of vitamin C supplements, in the updated Vitamin C Supplements Review. More >>

7/23/2016

Vitamin C and Breast Cancer

Higher intakes of vitamin C from foods are linked to lower risk of postmenopausal breast cancer in women, but getting vitamin C from supplements on top of that may increase the risk, says a new study. Get the details in the Vitamin C Supplements Review >>

8/03/2018

Vitamin C for Colds?

Taking vitamin C may modestly help with colds, according to a new study -- but there's a catch. Find out in the What It Does section of the Vitamin C Supplements Review. (Also see our Top Picks for vitamin C supplements.)

9/09/2015

Vitamin C: The Exercise Replacement?

A small clinical study recently found that taking vitamin C had a positive effect on blood vessels similar to a daily walk. The study focused on overweight and obese individuals, in whom blood vessel tone is compromised. Long-term effects were not studied. Get details about the study (including dose) and other pros and cons of vitamin C in the Vitamin C Supplements Review >>

2/12/2019

Vitamin C for Blood Sugar Control

High-dose vitamin C was found to help control blood sugar levels in people with type 2 diabetes in a recent study. For details, see the What It Does section of the Vitamin C Supplements Review. Also see our latest Top Picks for vitamin C.

2/11/2020

Vitamin C & Lungs

Supplementing with vitamin C to correct deficiency can reverse a form of lung disease, as exemplified in a recent report. For details, see the What It Does section of the Vitamin C Supplements Review. Also see our Top Picks for vitamin C.

12/03/2019

Vitamin C and Kidney Damage

High doses of vitamin C have been reported to cause a form of kidney damage, although this is more common in people with certain pre-existing medical conditions. For details, see the Concerns and Cautions section of the Vitamin C Supplements Review. Also see our Top Picks for vitamin C supplements.

10/31/2020

Vitamin C for COVID-19?

Does high-dose vitamin C help people critically ill with COVID-19? Find out what a new report showed in the COVID-19 section of our Vitamin C Supplement Review. Also see our Top Picks for vitamin C.

10/03/2020

Vitamin C for Foot Ulcers?

Can taking vitamin C help heal foot ulcers in people with diabetes or vascular disease? Find out what a new study showed in the What It Does section of our Vitamin C Supplements Review. Also see our Top Picks for vitamin C.

2/03/2021

Vitamin C for Bleeding Gums?

Does vitamin C supplementation reduce the tendency for gums to bleed? Find out what research shows in the What It Does section of our Vitamin C Supplements Review. Also see our Top Picks for vitamin C.

9/17/2021

Vitamin C For Fatty Liver?

Can taking high-dose vitamin C improve liver function or insulin resistance in people with NAFLD (non-alcoholic fatty liver disease)? Find out what a recent study showed in the What It Does section of our Vitamin C Supplements Review. Also see our Top Picks among vitamin C supplements.

11/23/2021

Vitamin C Serums for Wrinkles?

Can applying vitamin C to the skin reduce wrinkles or help prevent sun damage? Find out in the Skin Health section of our Vitamin C supplements review.

Also learn what features you should look for if selecting a vitamin C serum.

4/26/2022

Vitamin C & Mortality

Higher blood levels of vitamin C were associated with increased risk of death over a 10-year period in a recent study. Get the details in the Concerns and Cautions section of our Vitamin C Supplements Review. Also see adequate intake amounts for vitamin C.

10/27/2023

Vitamin C & COVID

Did large, frequent doses of vitamin C help people hospitalized with COVID? Find out in the COVID-19 section of our Vitamin C Review. Also see our Top Picks for vitamin C.

4/25/2023

Vitamin C for Colds?

Does vitamin C shorten the duration of colds? Get the details, and learn about one study that was recently retracted. See the Colds and immune system health section of our Vitamin C Supplements Review.

Also see our Top Picks among vitamin C supplements.

11/25/2024

Vitamin C & Urine Tests

Taking vitamin C may interfere with certain urine tests, including those for glucose and bilirubin. See the details in the Concerns and Cautions section of our Vitamin C Supplements Review, which includes our Top Picks for vitamin C.

Also see: Which vitamins and supplements should be stopped before getting blood work, laboratory tests, or medical imaging?

10/18/2024

Vitamin C & Kidney Injury

Be aware that high-dose vitamin C can contribute to kidney stones in some people and even cause kidney injury as highlighted in our Vitamin C Supplements Review, which includes our Top Picks for vitamin C.

Also see: Which supplements and foods reduce or increase the risk of kidney stones?

10/31/2024

Scurvy After Stomach Surgery

A man developed scurvy (due to vitamin C deficiency) years after undergoing gastric sleeve surgery. Be aware of this and other risk factors for vitamin C deficiency, in the Deficiency section of our Vitamin C Supplements Review, which includes our Top Picks for vitamin C.

Also see: Which supplements are important after bariatric surgery?

3/02/2026

Vitamin C for Gout?

Does vitamin C reduce uric acid levels or the risk of gout? Find out in our Vitamin C Review, which includes our Top Picks for vitamin C.

Also see our article about supplements and gout.

12/09/2018

Vitamin C and Kidney Damage

High doses of vitamin C can cause kidney stones and damage kidneys. People with certain diets or medical conditions may be more prone to these problems. Get the details, including those of a recent case, in the Concerns and Cautions section of the Vitamin C Supplements Review.

3/26/2019

Vitamin C Blunts Exercise Benefits

If you are trying to build muscle with resistance exercise, go easy on vitamins C and E, according to a recent study. Get the details in the Concerns and Cautions section of the Vitamin C Supplements Review.

2/07/2014

Vitamins C & E Blunt Exercise Effect

A recent study found that giving high-dose vitamin C or vitamin E to people involved in intensive exercise training blunted cellular changes thought to be important for improving muscular endurance. These and similar results recently reported with resveratrol raise concerns about high-dose antioxidant supplementation during exercise training. For details, see the updates to the "Concerns and Cautions" sections of the Vitamin C Supplements Review >>  and the Vitamin E Supplements Review >> 

9/05/2021

Vitamin C & Statins

Does taking vitamin C reduce the cholesterol-lowering effects of statins? Find out in the What to Consider When Using section of our Vitamin C Supplements Review.

1/13/2021

High-Dose Vitamin C for COVID-19?

Does high-dose vitamin C help in people with severe COVID-19? See what a new study showed in the COVID-19 section of our Vitamin C Supplements Review.

5/03/2022

Vitamin C & Blood Thinners

Is it safe to take vitamin C if you take anticoagulants like warfarin? See the answer in the Concerns and Cautions section of our Vitamin C Supplements Review.

9/16/2022

Caution with Vitamin C for COVID

Taking very high-dose vitamin C doesn’t seem to provide protection against COVID-19 and it may increase the rate of kidney stones, according to recent data. Get the details in the Vitamin C section of our CL Answer about Supplements and COVID-19.

4/11/2023

Do Antioxidants Reduce Exercise Gains?

Does supplementing with high doses of vitamin C and/or vitamin E hinder beneficial changes that occur during high-intensity interval training? Find out what a recent study showed in the Concerns and Cautions section of our Vitamin C Supplements Review.

Also see our Top Picks for vitamin C.

6/05/2025

Probiotic for C. difficile Infection?

Did taking a probiotic along with antibiotics help treat C. difficile infection? Find out what a recent study showed in our Probiotic Supplements Review. Also see our Top Pick probiotic for preventing C. difficile infection.

5/09/2011

Does folic acid affect the risk of colon cancer?

Supplementation with higher amounts of folic acid (vitamin B-9) has been shown to increase the risk of prostate cancer, but its effect on the risk of colon cancer has been unclear. A new study found no increase in colon cancer due to folic acid supplementation. But if you supplement with folic acid, be careful. See the B Vitamin Supplements Review for more >>

3/15/2015

Folic Acid Reduces Risk of Stroke

A large study in people taking blood pressure-lowering medication found that the addition of a daily folic acid (vitamin B-9 or folate) supplement significantly reduced the chance of having a stroke. This benefit is most likely to occur among people whose blood levels of folate are low. More details, including dosage and ConsumerLab.com's test-based quality ratings of folic acid supplements, are found in the B Vitamin Supplements Review >>

5/16/2015

Niacin Reduces Skin Cancer

A recent study suggests that high-dose niacin (vitamin B-3) may reduce the risk of developing certain types of skin cancer. A closer look at the study, however, raises questions about its relevance to people in North America. Get the details, as well as more information about niacin and our product test results & comparisons, in the B Vitamin Supplements Review >> 

1/20/2016

Omega-3's May Be Important in Preventing Cognitive Decline

We have reported in the past that a certain combination of B vitamins slowed cognitive decline as well as brain shrinkage in older people. Now, further analyses finds that these benefits only occurred in people having certain blood levels of omega-3 fatty acids (as found in fish oil). Get the details in the B Vitamins Supplements Review >>

7/05/2016

Folic Acid Supplementation Mitigates Alzheimer's

A recent study in people with Alzheimer's disease found that folic acid supplementation decreased inflammation and slightly improved mental functioning. However, participants began the study unusually low in folic acid relative to normal U.S. levels. For more details see the B Vitamin Supplements Review >> Also see results of a folate/B-12 study which showed reduced brain shrinkage in Alzheimer's patients.

10/22/2016

Too Much Folate & Nerve Damage

One quarter of American men and women have a gene variation which puts them at higher risk of nerve damage if consuming too much of folate (vitamin B-9) daily, according to a new study. Considering that most older Americans consume more than this amount (largely due to excessive supplement use) this should be a warning to many. For more details, see the "Folate" section of the B Vitamins Review >>

1/13/2018

B12 for Cognition

Numerous studies show that getting adequate intake of B vitamins, such as B12, and, perhaps, omega-3 fatty acids from fish, may slow age-related declines in memory and cognition. But not everyone should expect a benefit, as shown in a recent study. For details, see the Memory, Cognition, and Alzheimer's Disease section of the B Vitamin Supplements Review. (Also see our Top Picks among products.)

8/20/2016

Biotin Caution

Very high-doses of biotin (vitamin B-7) can cause misleading laboratory results and lead to unnecessary antithyroid treatment, according to a new report. For details, see the Biotin section of the B Vitamins Supplements Review >>

7/19/2014

High-Dose Niacin with Statins Not Worth It

Further evidence was published this week showing that the addition of high-dose niacin (vitamin B-3) to cholesterol-lowering treatment with statin drugs provides no worthwhile benefit and appears to increase the risk of adverse side events. For details, see the Review of B Vitamin Supplements and Energy Drinks >> 

7/20/2019

Is Niagen Safe?

Niagen (nicotinamide riboside) was recently studied for its safety and ability to raise NAD+ in the body. See the results and learn more about this form of niacin (which is also in the product Basis) in the Niacin section of the B Vitamin Supplements Review. Also see our Top Picks for niacin and other B vitamin supplements.

8/29/2017

High-Dose B Vitamins & Lung Cancer Risk

A recent study found that taking high doses of vitamins B6 and B12 was associated with an increased risk of lung cancer among men, particulary among those who smoke. For details, see the "ConsumerTips" section of the B Vitamin Supplements Review >>

11/20/2018

Liver Toxicity With Niacin

The death of a woman from acute liver failure highlights the risk of a particular formulation of high-dose niacin. For details, see the Niacin section of the B Vitamin Supplements Review. (Also see our Top Picks for niacin and other B vitamins.)

12/23/2017

Folic Acid for Cognition

Giving folic acid to older people with relatively low levels of blood folate resulted in improved cognitive performance, according to a recent study. For details, see the "Memory, Cognition, and Alzheimer's Disease" section in the B Vitamin Supplements Review >> (Also see our Top Picks for folate and other B vitamin supplements.)

1/08/2019

B Vitamins & Breast Cancer

A reduced risk of breast cancer was associated with supplementing with certain amounts of folic acid and vitamin B12 for women predisposed to breast cancer in a new study. See the details in the "Breast cancer" section of the B Vitamin Supplements Review.

12/05/2017

Biotin Interference With Vitamin D Test

Last week we reported that high doses of biotin (found in B complexes and hair and nail supplements) can interfere with certain blood tests. A study recently showed that biotin can also artificially inflate a test for vitamin D. Get the details in the "Biotin" section of the B Vitamin Supplements Review >>

3/07/2018

B12 Dosage

A study compared the effects of a high weekly dose of vitamin B12 versus a much lower dose given daily. Both worked equally well. Find out why and get more details about B12 dosing in the B-12 section of B Vitamin Supplements Review.

4/28/2020

Early Sign of Thiamin Deficiency

Thiamin (vitamin B1) deficiency can cause lasting neurologic damage and affect heart function. It can occur with poor nutrition and as a result of taking certain diuretics. A recent case highlighted an early sign of thiamin deficiency that involves the eyes. We've added this information to the Thiamin section of the B Vitamin Supplements Review. Also see our Top Pick for thiamin and B complexes that contain thiamin. You can also get thiamin from a good multivitamin.

2/25/2020

Cognitive Impairment From B12 Deficiency

Vitamin B12 deficiency can cause a wide range of symptoms. This includes cognitive impairment, as shown in a recent case. For details about the symptoms of B12 deficiency see the B12 section of the B Vitamin Supplements Review. Also see our Top Picks for B12 and other B vitamin supplements.

11/26/2017

Signs of B12 Deficiency

B12 deficiency is not uncommon, most often affecting older people. Symptoms include anemia, fatigue, tingling in the arms and legs and loss of balance -- but a recent case report highlights a lesser-known sign of B12 deficiency. Find out more, plus how much B12 you should get in the "B12" section of the B Vitamins Review >> (Also see our Top Picks for vitamin B12 and other B vitamins.)

2/11/2020

Vitamin B12 and Risk of Death

A study found higher blood levels of vitamin B12 to be associated with an increased risk of death -- suggesting caution when supplementing. For details, see the B-12 section of the B Vitamin Supplements Review. If you do need to supplement with B12, see our Top Pick among products.

8/13/2019

Folic Acid and Colon Cancer

Several studies have evaluated whether folate from food and/or folic acid from supplements affect cancer risk. Find out what a recent report suggests about long-term, high-dose folic acid supplementation in the Folate section of the B Vitamin Supplements Review. Also see our Top Picks for folic acid and other B vitamin supplements.

7/16/2019

Is Methylfolate the Best Form of Folate?

Methylfolate has been promoted as a better form of folate (vitamin B9), particularly for people with certain common genetic variations. A clinical study recently put methylfolate to the test against folic acid and folinic acid. The results were surprising. Get the details in the Folate section of the B Vitamin Supplements Review. Also see our Top Picks among folate and other B vitamin supplements.

2/03/2021

Thiamin Deficiency from Bowel Disease

People with inflammatory bowel disease (such as Crohn’s or colitis) can develop thiamin (vitamin B-1) deficiency, which can lead to life-threatening brain injury, as noted in a recent review of 31 cases. Learn more about this and other causes of thiamin deficiency in the Thiamin section of our B Vitamin Supplements Review.

3/23/2021

Folic Acid and Colorectal Cancer

Do higher intakes of folic acid and other sources of folate increase or decrease the risk of colorectal cancer? It may depend on time, according to a new study discussed in the Folate section of our B Vitamin Supplements Review. Also see our Top Picks among B vitamin supplements.

11/11/2020

Biotin for MS?

High-dose biotin was tried in people with multiple sclerosis (MS) to see if would reverse MS-related disability. Find out if it helped the Biotin section of the B Vitamin Supplements Review. Also, learn about concerns with high-dose biotin and see our Top Picks for biotin and other B vitamin supplements.

6/17/2022

Vitamin C & Kidney Stones

High intake of vitamin C has been linked with an increased risk of kidney stones, but is the risk similar among men vs women?

7/22/2022

B-6 or Zinc for Pyrrole Disorder?

Can supplementing with vitamin B-6 or zinc improve psychiatric conditions associated with pyrrole disorder? Find out by using the links.

12/09/2022

Thiamin Alternative?

Is thiamin tetrahydrofurfuryl disulfide (TTFD), a derivative of thiamin, absorbed and used by the body better than thiamin itself? Find out, and learn about possible health effects, in the Thiamin (B-1) section of our B Vitamin Supplements Review.

8/19/2022

B-6 Depleted by Parkinson’s Drug?

Can vitamin B-6 levels in the body be depleted by carbidopa, a drug taken in combination with levodopa for Parkinson's disease? Find out what evidence suggests in our updated CL Answer about supplements for Parkinson's disease.

10/07/2022

Biotin for Skin Health?

Biotin has been promoted for reducing wrinkles, but does clinical research support this? Find out in the Biotin (B-7) section of our B Vitamin Supplements Review, which also discusses the evidence for biotin for treating brittle nails and hair loss.

Also, see our CL Answer about supplements for reducing wrinkles and tightening the skin.

9/30/2022

Folic Acid & Risk of Self-Harm

Can taking folic acid (vitamin B-9) reduce the risk of self-harm and suicide? Find out what a recent study found in the Depression section of our B Vitamin Supplements Review.

6/01/2022

Too Much B-6 After Stomach Surgery?

People who have had gastric bypass, gastric sleeve, or gastric band surgery may be supplementing with too much B-6 after surgery, according to a recent study. Get the details in our updated article about the Best Vitamins to Take After Bariatric Surgery.

1/28/2022

B-12 From Chlorella and Spirulina?

A reader asked if chlorella and spirulina are good sources of B-12. The answer is both "yes" and "no," as explained in our Greens and Whole Foods Powders and Pills Review, which includes our recent tests result and Top Picks for chlorella and spirulina supplements.

1/20/2025

Nicotinamide for Glaucoma?

Some preliminary research suggests nicotinamide (a form of niacin) may help with glaucoma, but is this recommended? Find out in our B Vitamins Supplements Review, which includes our Top Picks among B vitamin supplements.

2/18/2025

PFAS in Oral-B?

Does Oral-B Glide Advanced Bacteria Defense Floss contain PFAS (“forever chemicals”)? Find out in our article about PFAS, which includes our Top Picks among flosses, dental picks, and dental tapes, and information for more than 85 different products.

2/02/2024

Thiamin for Fibromyalgia?

Can taking thiamin reduce symptoms of fibromyalgia? Find out in the Thiamin section of our B Vitamin Supplements Review. Also see our Top Picks among B vitamins.

Also see: Can any supplements improve or worsen symptoms of fibromyalgia?

3/24/2023

Plant-based Sources of B-12?

Find out if there are good plant sources of B-12, if certain foods can increase the availability of zinc, and if vegetarians or vegans should supplement with taurine.

1/06/2023

Best Way to Get B Vitamins?

Is it better to get B vitamins through supplements, foods, or a combination of the two? See our answer.

9/26/2023

Allergic Reaction to Folic Acid

Although rare, severe and life-threatening allergic reactions to folic acid from supplements have been reported. Get the details about this, as well as risks from too much folic acid, in the Folic Acid section of our B Vitamin Supplements Review, which includes our Top Picks for folic acid and folate, and other B vitamins.

9/29/2023

Nail Growth

Does biotin help nails to grow faster? Find out what research suggests, and also learn which topical treatment for hair growth may help nails to grow, in the Biotin section of our B Vitamin Supplements Review, which includes our Top Picks for biotin and other B vitamins.

5/22/2025

Niacin for Skin Cancer

Some research suggests that taking high-dose niacin (as nicotinamide, also called niacinamide) can reduce skin cancer risk. Learn more about this (and an observational study of its safety) in the Niacin section of our B Vitamins Review, which includes our Top Picks for niacinamide supplements and other B vitamins.

10/27/2025

Vitamin Deficiency from Fasting

Be aware that extreme fasting (water only) can cause thiamin deficiency and neurological symptoms, as was recently reported. For more details see our B Vitamin Supplements Review, which includes our Top Picks for thiamin and other B vitamins.

9/19/2025

Niacin May Reduce Skin Cancer?

Taking high-dose nicotinamide (a common form of niacin) may reduce the risk of certain types of skin cancer, according to a new study. Get the details in the Niacin section of our B Vitamin Supplements Review, which includes our Top Picks for niacin/nicotinamide and other B vitamins.

8/19/2025

Allergy to Folic Acid

Although rare, be aware that some people can be allergic to the folic acid in supplements and fortified foods. This may be more common in people allergic to certain medications that resemble folic acid. Get the details in the Folate section of our B Vitamin Supplements Review, including our Top Picks for folate and folic acid and for other B vitamins.

9/16/2025

Folic Acid for Cognition?

Did taking folic acid improve cognitive function among older people with small vessel disease? Find out what a recent study showed in the Folate section of our B Vitamin Supplements Review, which includes our Top Picks for folate and other B vitamins.

3/16/2026

GLP 1 With B-12?

A recent study raises red flags about compounded tirzepatide (the GLP-1 agonist in Zepbound and Mounjaro) mixed with vitamin B-12. Learn more in our article about supplements to take or avoid with GLP-1s and whether GLP-1s affect vitamin D levels.

3/16/2026

Biotin: A Possible Migraine Trigger?

One case report suggests high-dose biotin may worsen migraine frequency and intensity. See the details in our B Vitamins Supplements Review, which includes our Top Picks for biotin and other B vitamins.

8/05/2022

Vitamin C or Melatonin for COVID?

Find out if supplementing with vitamin C or melatonin reduced symptoms in people with mild to moderate COVID in a recent study.

8/23/2022

Can-C Eye Drops for Dry Eye?

A product called Can-C Eye Drops has been promoted for improving dry eye as well as reducing the risk of cataracts. Does the evidence support this? Find in our updated CL Answer about supplements for dry eye.

8/22/2023

Sodium Benzoate and Benzene

Vitamin C can promote the conversion of sodium benzoate, a preservative, to benzene, a toxic chemical. Should you be worried about consuming products such as lemon juice (a source of vitamin C) preserved with sodium benzoate? Find out in the Preservatives section of our article about Inactive Ingredients.

7/03/2021

Probiotics for C. difficile infection?

New guidelines recommend against probiotics for treating or preventing C. difficile infection, one cause of diarrhea in people taking antibiotics. Find out why in the What They Do section of our Probiotic Supplements Review.

11/04/2020

Vitamin C to Boost Iron?

Vitamin C is often touted to boost iron absorption. But does it really work? Find out what a recent study found in the ConsumerTips section of our Iron Supplements Review. Also, see our Top Picks for iron.

4/08/2017

Exercise Benefit Lost With High-Dose Vitamins

Older men asked to perform resistance (strength) training for 12 weeks showed less gain in bone density if they were given high daily doses of vitamins C & E than if they were given a placebo. This is not the first time that  high-dose antioxidant supplements have been shown to reduce benefits from exercise. For details, see the "Concerns and Cautions" section of the Vitamin C Supplements Review >>

6/09/2013

Vitamin C: Does It Fight Colds?

A new analysis says it can help — a little. Get the bottom line, plus test results for 27 products, in the updated Vitamin C Supplements Review >>