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CL Answers (83)

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Recalls & Warnings (39)

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Clinical Updates (52)

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Up To a Point, Alzheimer's Risk Falls with Vitamin D

A new study shows that, up to a point, the risks of developing Alzheimer's disease and other forms of dementia fall with higher blood levels of vitamin D. However, the research also clarifies that exceeding a certain blood level of vitamin D provides no further benefit. In fact, additional research suggests that too much vitamin D can have negative effects. The message: Make sure you have a sufficient, but not excessive level of vitamin D. For details about these levels, as well as results of our tests of vitamin D supplements, see the updated Vitamin D Supplements Review >> 

Optimum Level of Vitamin D

New research shows that blood levels which are too low or too high for vitamin D are associated with increased risk of heart attack and earlier death. Find the "sweet spot" for vitamin D levels as well as test results for 55 vitamin D supplements in the updated Vitamin D Supplements Review >>

Type 2 Diabetes and Vitamin D

Maintaining an adequate level of vitamin D is associated with a lower risk of type 2 diabetes. But does giving vitamin D to people with existing type 2 diabetes help them with glucose control? Find out what research is showing in the What It Does section of the Vitamin D Supplements Review. (Also see our Top Picks among vitamin D supplements.)

Vitamin D Supplements: Same Dose, Different Results?

Taking the same dose of vitamin D may lead to greater increases in vitamin D status in some people than in others, according to recent research. Find out why in the How Much Do You Need section of our Vitamin D Supplements Review. Also see our Top Picks among vitamin D supplements.

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.

Vitamin D & Diabetes

Vitamin D supplementation can improve insulin sensitivity in some people at risk for type 2 diabetes according to a recent clinical study. For details about this, as well as related research, see the Diabetes, insulin resistance and glucose control section of the Vitamin D Supplements Review. Also see our Top Picks for vitamin D.

Football & Vitamin D

The outcome of today's Super Bowl 50 may be influenced by players' levels of vitamin D. Several studies show that having the right amount of vitamin D in the body reduces the risk of falls in the elderly, but research also shows benefits for younger adults — including fewer injuries among NFL football players. Get the details in the Vitamin D Supplements Review and enjoy the game!

Vitamin D for Autism

A recent study among young children with autism found that high-dose vitamin D reduced autism symptoms from moderate to mild. This is a preliminary study and more research is required. For details about this study and other uses of vitamin D, as well as our tests and comparisons of products, see the "What It Does" section Vitamin D Supplements Review »

How Vitamin B6 May Backfire

Supplementing with high-dose vitamin B6 can sometimes cause the same nerve toxicity associated with deficiency of B6. New research explains why this may happen and suggests how to avoid it. For details, see the "Vitamin B6" section of the B Vitamin Supplements Review >>

Too much vitamin D may increase the risk of dying

A recent study of nearly a quarter million people found those with vitamin D levels above that considered sufficient, but not much higher, had the lowest risk of dying over the study period. People with high levels of vitamin D were more likely to have died. Some earlier research suggests the same. What does this mean for you? See our update to the Vitamin D Supplements Review for more information. More >>

Can Vitamin E and/or Selenium Help Prevent Cataracts?

A study in older men in the U.S. found that taking large daily doses of vitamin E and/or selenium did not significantly reduce the risk of developing cataracts. But could the dose have been too high to be helpful? Other research has shown that "less is more" when it comes to antioxidant supplementation for cataracts. For more information, see the updates to the Vitamin E Supplements Review and the Selenium Supplements Review >> 

How To Get Vitamin K From Food

Many of the benefits of vitamin K - such as proper blood clotting and calcium utilization for bone and heart health - are associated with getting adequate vitamin K from foods. The good news? Brand new research has found much higher amounts of vitamin K2 (the form associated with cardiovascular benefits) in dairy foods than previously known. However, the amounts vary tremendously depending on whether these foods are full-fat, or reduced-fat or fat-free. Get the details in the "Vitamin K from food" section of the Vitamin K Supplements Review. If you're interested in a vitamin K supplement, see our Top Picks among brands.

Surprising Role of Potassium in COVID-19

New research out of China suggests that many patients hospitalized with COVID-19 are low in potassium. For details see the information about Potassium in our answer to the question: What are natural remedies for coronavirus (COVID-19)? Do supplements like zinc, vitamin C, or herbals work?

Does Taking Vitamin D Reduce the Risk of Heart Disease?

Earlier research has suggested an association between higher vitamin D levels in the blood and reduced risk of heart attack. But blood levels are affected by both sun exposure as well as intake of vitamin D. A new study shows that men with higher vitamin D intakes from foods and supplements have a 14% reduction in their risk of cardiovascular disease and stroke. However, the study found no reduction among women. The amount of vitamin D intake shown to be beneficial and possible reasons why a benefit was not found in women are provided in the updated "What It Does" section of our Product Review of Vitamin D SupplementsMore >>

Concern Over Carnitine Causing Cardiovascular Disease

Intake of L-carnitine from supplements (and from red meat) may foster atherosclerosis (hardening of the arteries), according to new research. Once ingested, L-carnitine is converted in some people to a compound which reduces the normal clearing of cholesterol from arteries.

For more details, see the updated reviews of B Vitamin Supplements & Energy Drinks and Protein Powders, as some of these products contain L-carnitine. The Acetyl-L-Carnitine Supplements review has also been updated because acetyl-L-carnitine is chemically similar to L-carnitine, suggesting a potential concern.


Find out why ivermectin is generally not recommended for COVID-19 outside of clinical trials, despite some research suggesting a benefit.

Feeling fatigued? Iron may help

It's well known that fatigue can result from iron-deficiency anemia, but new research shows that some women who are not anemic can also benefit from iron. Women ages 18 to 53 with unexplained fatigue given iron experienced a nearly 50% reduction in fatigue in a recently published study. Get details about the treatment (including the dosage, duration, and type of iron supplement used) in the update to the Iron Supplements Review, which includes our tests of iron supplements similar to that used in this study. More >>

Glucosamine May Increase Eye Pressure

New research suggests that people with glaucoma or intraocular hypertension could have worsening eye pressure if they take a glucosamine supplement. Get the details (along with our tests of glucosamine and other joint health supplements) in the updated Glucosamine/Joint Health Supplements Review >>

What You Need to Know About Fish Oil

Most fish oil in supplements is not natural, but is a semi-synthetic form. This affects how much you absorb and new research is revealing other differences. Time to throw out what you take, or switch brands? Probably not, but if you use fish oil, it's worth knowing about these differences. Get the details in the update to the Fish Oil and Omega-3 Fatty Acid Supplements Review (Including Krill, Algae, and Calamari Oil) >>

Magnesium and Bone Health

New research shows why getting adequate magnesium is important for bones -- but this doesn't mean that you must take a magnesium-containing supplement. Get more information in our updated Magnesium and Calcium-Magnesium Supplements Review >>

Selenium and Prostate Cancer

A new study suggests that men who have prostate cancer should not take supplements providing high-dose selenium. Earlier research has similarly advised against high-dose selenium for people with already adequate selenium intake. For details and more about selenium, see the Selenium Supplements Review >> 

Melatonin Increases Bone Density

Research has begun to suggest that melatonin may have a positive effect on the skeleton. The latest study shows that giving post-menopausal women with bone loss daily melatonin causes small, but significant improvements in bone density. Details, including dosage, as well as our tests of melatonin supplements, are found in the Melatonin Supplements Review >>

Probiotics May Not Work As Thought

Research continues to reveal promising uses for probiotics, but it's also showing that probiotics don't necessarily work by changing the types of organisms in our gut. A new study with Culturelle sheds light on this. Details, along with information about what probiotics can and cannot do and our tests of 43 probiotic supplements, are found in the Probiotic Supplements Review >>

Resveratrol for Alzheimer's Disease?

High doses of a synthetic resveratrol stabilized a marker of disease progression in people with mild to moderate Alzheimer's, a recent study reports. However, more research is required to determine if resveratrol is effective for Alzheimer's. Get the details about this and other studies with resveratrol, and our tests and comparisons of products, in the Resveratrol Supplements Review >>

Curcumin May Help Prevent Diabetes

Past research has suggested a potential role for curcumin (from turmeric) in blood sugar control. A recently published placebo-controlled study of curcumin given daily to people with prediabetes (those with blood sugar levels somewhat higher than normal) produced dramatic results in reducing the percentage of such individuals progressing to diabetes. Get the details in the latest update to's Turmeric and Curcumin Supplements Review -- which includes quality ratings of products and other potential uses of curcumin. More >>

Insulin Sensitivity and Magnesium

A recent study found that magnesium supplementation improved fasting glucose levels in insulin insensitive, obese people. While a similar effect has been seen in magnesium deficient people, the new study found benefit in people who had normal magnesium levels. The research suggests that magnesium may help prevent the onset of type 2 diabetes in some people. See the Magnesium Supplements Review for the type and dose of magnesium used and more >>

Omega-3s Drop in Farmed Salmon

Farmed salmon has historically provided more omega-3 fatty acids (EPA and DHA) than wild salmon. But new research shows this is changing, as discussed in the "Farmed vs. Wild Salmon" section of the Fish Oil Review >>

Prebiotics for Appetite Control?

A study suggests that a prebiotic supplement may be helpful for appetite control — although more research is needed. Prebiotics fuel the growth of beneficial bacteria in the gut. For more information about the study and prebiotics (including how to get prebiotics from foods), see the "Prebiotics" section of the Probiotics Supplements Review (which includes our tests of products) >>

Acetyl-L-carnitine + Alpha-Lipoic Acid for Lowering Blood Pressure?

We were recently asked if taking a combination of acetyl-L-carnitine and alpha-lipoic acid can help lower blood pressure. Find out what research shows in the What It Does section of the Acetyl-L-Carnitine Supplements Review. Also see our answer to the question: Which supplements can help to lower blood pressure?

Caution With Melatonin & Diabetes

Research is raising concern regarding the use of melatonin by people with diabetes. For more details – as well as other concerns with melatonin – see the Concerns and Cautions section of the Melatonin Supplements Review. Also see our Top Picks for Melatonin.

Curcumin for Blood Sugar Control?

Preliminary research suggests that curcumin (from turmeric) taken with meals can reduce the increases in blood sugar and insulin levels that occur after eating. But does curcumin help people with pre-existing type 2 diabetes? See what a recent study found in the What It Does section of the Turmeric and Curcumin Supplements & Spices Review. Also see our Top Picks among turmeric and curcumin products.

CoQ10 for Migraine

CoQ10 and its active form, ubiquinol, have been studied in several clinical trials to treat migraine headache. Find out what the research is showing in the Migraine section of the CoQ10 and Ubiquinol Supplements Review. (Also see our Top Picks among CoQ10 and ubiquinol supplements.)

Probiotics a Waste of Money?

Some headlines this week suggested that probiotics are not worthwhile. The stories cited a new research study which found that probiotics do not cause a lasting effect on the gut. The headlines are misleading, as we explain in the "What It Does" section in our Probiotic Supplements Review >>

Caveat With Prescription Fish Oil Study

Some of the cardiovascular benefit reported for a prescription fish oil may have actually been due to a problem with the placebo to which it was compared, according to new research. Get the details in the Prescription Fish Oil vs Supplements section of our Fish Oil Supplements Review. Also see our Top Picks among fish oil supplements.

NAC and Lung Cancer

Was there a study that showed that animals given NAC developed lung cancer? Find out what research in animals suggested in the Concerns and Cautions section of our NAC supplements Review.

Can Collagen Lower Blood Sugar?

Can taking collagen supplements lower blood sugar levels? Find out what research suggests in the What It Does section of our Collagen Supplements Review. Also see our Top Picks among collagen supplements.

Human Milk Oligosaccharides (HMOs) for IBS?

Are symptoms of IBS improved with use of human milk oligosaccharides (HMOs)? Find out what research suggests in our answer to the question: Do any supplements help for irritable bowel syndrome (IBS)?

Copper and Alzheimer's Disease

Can excess copper from the diet or supplements increase the risk of Alzheimer’s disease? Find out what research suggests in the Copper section of our Multivitamin and Multimineral Supplements Review.

Mushrooms and Blood Sugar

Find out if supplementing with reishi or oyster mushrooms helps with blood sugar control. See what the latest research showed in our Reishi Mushroom Supplements Review.

Coffee and Arterial Stiffness

Does drinking coffee increase arterial stiffness, a predictor of heart disease? Find out what research shows in our updated answer about Coffee and Heart Health.

Herbal Treatment

Are traditional Chinese medicines, such as astragalus, helpful in treating or preventing COVID-19? Find out what reviews of the research have concluded in our article about Supplements and COVID-19.

COVID Infectiousness

Be aware that even without symptoms, people with COVID-19 can emit high amounts of virus as aerosols, according to recent research. Get the details and find out what researchers recommend to help protect yourself when indoors.

Coffee And Fatty Liver Disease?

Can drinking coffee help prevent fatty liver disease and liver fibrosis (scarring)? Find out what research suggests in our CL Answer about supplements and diets for fatty liver disease.

Bergamot for lowering cholesterol?

Can supplementing with citrus bergamot reduce high cholesterol levels? Find out what the research is showing in our updated answer to the question: Which supplements can help lower cholesterol and keep my heart healthy? Are there any to avoid?

Mixing Boosters for J&J Recipients?

Find out why some experts support mixing boosters for J&J vaccine recipients. Also see new research indicating that an mRNA vaccine may be the best booster for those already given a J&J-type vaccine.

A Sunscreen Combination to Avoid

Combining certain ingredients in sunscreen may inadvertently reduce sunscreen protection and generate toxic compounds, according to new research. Find out which ingredient combinations to avoid in our answer to the question: Which compounds in sunscreen should I be concerned about?

Magnesium for Parkinson's Disease?

Can taking magnesium help treat Parkinson’s disease? Find out what research shows in the What It Does section of our Magnesium Supplements Review. Also, be aware that Parkinson's medication can affect absorption of magnesium and vice versa.

Fish Oil Interaction With Medication

High-dose fish oil can significantly increase blood levels of certain immunosuppressants, according to new research. Get the details in the Concerns and Cautions section of our Fish Oil Supplements Review, which includes information about other drug interactions with fish oil.

Coffee and Heart Disease

Research published this week suggests a link between a moderate coffee consumption and reduced risk of cardiovascular disease and death. Get the details in our article about Coffee and Heart Health.

Saw Palmetto May Not Work

It's used by many men hoping to reduce urinary symptoms caused by benign growth of the prostate, or BPH, but a new, well-designed study suggests that it doesn't work. Some other recent research suggest the same. Even when doubling and tripling the standard dose, the high-quality saw palmetto extract used in the new study failed to provide benefit.

What should you do? You may want to consider a different supplement -- beta-sitosterol, a phytosterol. The evidence remains fairly good for beta-sitosterol. To find out more about saw palmetto, beta-sitosterol, and the supplements we have tested, see the Prostate Supplements ReviewMore >>

News Releases (55)

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