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Question: I would like to know about different sources of vitamin K2. I have been told it is from natto or fermented soy and from a flower called geraniol. Can you tell me the difference? Is one source better than another?
Two forms of vitamin K2 are typically found in supplements: MK-4 (synthetic) and MK-7 (natural, from natto). There are significant differences between them: in paticular, MK-7 has a longer half-life, so a smaller dose can be used. Two newer forms of MK-7 are available that are synthetic. Get the details in the Review of Vitamin K Supplements, which includes our tests and comparisons of products containing both forms of K2 as well as vitamin K1.
Question: Is it better to get vitamins from foods or supplements, and are natural vitamins better than synthetic vitamins?
Answer: It is generally best to get your vitamins (as well as minerals) naturally from foods or, in the case of vitamin D, controlled sun exposure. For example, recent research on the mineral calcium suggests that it is safest to get your calcium from foods that are naturally rich in calcium than from supplements. Older women who get high amounts of calcium from supplements seem to have a higher risk of kidney stones, strokes, and even a greater risk of dying over periods of time. A small increased risk of death has also been seen in studies of people taking supplements containing vitamin A and beta-carotene compared to those who did not.
Exceptions to the "foods are better" rule are two B vitamins. Ten to thirty percent of older people don't properly digest and absorb natural vitamin B-12 from foods, so it is recommended to get B-12 from a supplement if you are over age 50. Folic acid (vitamin B-9) from supplements and fortified foods is absorbed twice as well as from regular food. Consequently, pregnant woman are advised to get folic acid from a supplement (or fortified food) as well as regular foods. Also keep in mind that if you get your iron from plant foods, it is absorbed only half as well as iron from meat -- although eating your spinach (or iron supplement) with a source of vitamin C will boost the absorption of its iron.
Using supplements made from whole foods won't necessarily give you more vitamins (in fact, they typically contain more modest amounts of vitamins than other dietary supplements), but you will get other plant compounds which could be of potential benefit (as well as some grams of fiber if you are consuming, for example, spoonfuls of a whole food powder as opposed to a pill). Paying a premium price for this, however, may not be worthwhile and ConsumerLab.com has found lead contamination in some whole food and "greens" products.
Regarding natural vs. synthetic forms of vitamins in dietary supplements, sometimes natural is better, sometimes synthetic is better, and sometimes it doesn't matter. Keep in mind that all can help prevent or treat deficiencies and other conditions, and nearly all are known to be harmful at too high a dose.
Natural may be better in the case of vitamin E. At low doses, either natural (d-alpha-tocopherol) or synthetic (dl-alpha-tocopherol) can be fine, although you need more IUs of synthetic (1.6 IU) to get the same amount of active vitamin E as from 1 IU of natural vitamin E. There is also a greater risk of bleeding problems with synthetic vitamin E at high doses, so that the upper limit for vitamin E for adults is 1,100 IU of synthetic vitamin E, but 1,500 IU of natural vitamin E. Naturally, vitamin E also contains other tocopherols and tocotrienols, which may have benefit. However, ConsumerLab.com tests show that not all "natural" vitamin E products contain these additional natural compounds.
Natural may also be better with vitamin K. A form of vitamin K-2, known as MK-7, naturally derived from fermented soy beans and used in supplements is better at raising vitamin K levels than supplements with synthetic K-1 or synthetic K-2, known as MK-4.
Natural or synthetic sources are both fine for getting vitamin C. Rose hips or acerola or synthetically produced vitamin C all provide the same compound -- ascorbic acid. The inclusion of citrus bioflavonoids (naturally present or added) may improve absorption.
Sometimes synthetic forms of vitamins offer advantages over natural forms. A synthetic form of niacin (vitamin B-3) called inositol hexanicotinate, for example, causes less flushing of the skin than niacin.
Use the links above to get more information about each vitamin or mineral, including ConsumerLab.com's tests and reviews of supplements containing those nutrients. For recommended daily intakes of these and other vitamins and minerals also see the Recommended Daily Intake tables, which includes upper intake limits.
Question: I've been buying nutritional supplements in powder form, as I find them cheaper than tablets and capsules. I am concerned about the effect of air when I open the bottles daily because sometimes my powdered supplements get clumpy. Should I be concerned?
Question: Are supplements which claim increased absorption or improved bioavailability telling the truth? Is it worth paying more for these? Are there concerns?
It is true that some supplements contain special ingredients, or enhancers, which can improve the absorption or bioavailability (amount of ingredient circulating in your blood) of certain supplements, such as CoQ10, curcumin, milk thistle, green tea, grape seed, ginkgo, and resveratrol. Enhancers typically act in the gut to either improve solubility or reduce the amount of enzymatic breakdown which occurs there. By allowing you to absorb more active ingredient, the supplement may be more potent, meaning that a smaller dose may be used. At the same time, enhancers may increase the absorption or otherwise interact with other supplements or drugs which you take, so it is important to use caution.
The four main types of enhancers currently found in supplements are emulsifying agents, like lecithin; self-emulsifying systems, which involve an oil; phytosomes made from phosphatidylcholine; and enzyme inhibitors, like black pepper extract. Liposomes and nanoparticles have also shown promise for improving absorption. Pros and cons of these enhancers, and the types of ingredients with which they may be useful, are discussed below (and in many of ConsumerLab.com's Product Reviews). See the full answer >> >>
Question: Which supplements are important after bariatric surgery (i.e., weight loss or stomach-reducing surgery)? Are there any I should avoid?
Answer: Weight loss surgeries such as gastric bypass, gastric sleeve, and gastric band procedures, reduce the amount of food and liquid a person comfortably digest in one sitting, leading to smaller meals and potentially, inadequate nutrient intake. Gastric bypass (re-routing around the stomach) and gastric sleeve surgery (removing a portion of the stomach) also reduce stomach acid and normal digestive action, leading to reduced absorption of various vitamins and minerals. The use of supplemental vitamins and minerals is recommended for gastric bypass and gastric sleeve patients, and sometimes for gastric band patients. However, for bypass and sleeve patients, the changes in digestion and nutrient absorption also mean that some supplements may not be tolerated or absorbed as well as others. For details about supplements to take or avoid, see the full answer >>
Question: Are enterically coated supplements better than non-enterically coated ones?
Answer: Enteric coatings help protect supplement ingredients from being released in the stomach and keep them away from stomach acid and enzymes. This allows the supplement to stay intact until it reaches the less acidic small intestine (where most nutrient absorption takes place). An enteric coating may also be desirable for ingredients which, for some people, otherwise cause an unpleasant aftertaste. Consequently, with ingredients that need protection it is sometimes worthwhile to purchase an enterically coated supplement. However, enteric coatings are not always necessary or beneficial, and, in some case, may just be an expensive gimmick. There are also some concerns about enteric coatings of which you should be aware. See the full answer (with information about enteric coatings for fish oil, marine oils, probiotics, garlic, and SAMe)>>
Question: Which supplements can help keep my heart healthy? Are there any to avoid?
Answer: Heart disease remains the leading cause of death for both women and men in the U.S. Some supplements may help keep your heart healthy, but others may potentially contribute to heart disease.
Garlic has been shown to reduce total cholesterol and triglycerides, and may slow the development of atherosclerosis. One brand of garlic in particular has been shown to lower triglycerides more than others. You can get more information about these, including our tests and reviews of products in the Garlic Supplements Review >>
Soy protein, in adequate dosage, has been shown to modestly lower total cholesterol and improve LDL/HDL ratio. Preliminary research suggests lunasin, a specific protein peptide isolated from soy, may play a major role in soy’s effects. Our Review of Cholesterol-Lowering Supplements includes information about these and other supplements for reducing cholesterol – also see the Soy article.
CoQ10 has been shown to significantly reduce the risk of adverse cardiovascular events by 50% in people with moderate to severe heart failure, and may be helpful in reducing some of the side-effects of cholesterol-lowering statin drugs. You can get more information about CoQ10 (and ubiquinol, a related compound), including our tests and reviews of products, in the CoQ10 and Ubiquinol Supplements Review >>
Vitamin D may lower the risk of cardiovascular disease in those with low blood levels of vitamin D but not be of benefit for people who do not have a vitamin D deficiency. You can get more information about vitamin D, including our tests and reviews of products in the Vitamin D Supplements Review >>
Certain probiotics may modestly lower systolic and diastolic blood pressure, and "bad" LDL cholesterol — although they do not appear to increase "good" HDL cholesterol. There is mixed evidence as to whether probiotics reduce triglyceride levels. More information, plus our tests of popular products, is found in the Probiotic Supplements and Kefirs Review >>
Supplements That May Be Harmful: Vitamin E supplements, once touted for heart health, have not been found to provide a benefit for people with cardiovascular disease, and could actually be harmful for some heart disease patients, since they could reduce the effectiveness of cholesterol-lowering agents.
There is reason to believe that L-carnitine and lecithin could actually contribute to atherosclerosis in certain people, and it may be wise to avoid long-term supplementation with either one.
Supplements That May Not Help: Calcium -- Although getting sufficient calcium may decrease your risk of dying from cardiovascular disease, too much may be harmful. A study found that calcium (800 mg) given once daily to post-menopausal women with high cholesterol caused a significant increase in serum cholesterol (up by about 50 mg/dL) and an increase in the thickness of lining of the carotid artery - changes associated with heart disease. Only if you don’t get enough calcium should you consider a supplement, and it generally recommended that calcium supplementation not exceed 500 mg per dose, or more than 900 mg per day. You can get more information about these supplements, including our tests and reviews of products, in the Calcium Supplements Review >>
Fish Oil -- Despite the fact that omega-3 fatty acids that have been linked to some heart healthy effects, it seems that the benefits come from consumption of fish, and not supplements. Only if you don’t eat fish might fish oil supplements provide some heart benefit. Also, because fish oil supplements can have a blood-thinning effect, they should be used with caution in people taking other blood-thinning supplements or medications.You can get more information about these supplements, including our tests and reviews of products, in the Fish/Marine Oil Supplements Review >>
Policosanol -- Although there is some evidence from several studies from Cuba suggesting a cholesterol-lowering effect, other studies have failed to find this effect, as noted in our Cholesterol-Lowering Supplements Review>>
Question: I take levothyroxine (Synthroid), a thyroid hormone to treat hypothyroidism. Are there supplements I should avoid, or be taking, due to this drug?
Although often promoted for thyroid health, iodine supplements will not help your thyroid work better, and may even cause problems, unless you have an iodine deficiency.
Also, be aware that some thyroid-boosting supplements, including herbal supplements, have been found to contain thyroid hormones at significant levels, which are not listed and may be due to drug spiking. See the details in our Warnings section.
Cruciferous vegetables such as broccoli, brussel sprouts and cabbage contain compounds that can interfere with thyroid function. However, these compounds appear to be deactivated in vegetables that are cooked (McMillan, Hum Toxicol 1986).
Question: How much calcium from supplements is too much?
Answer: Maintaining adequate calcium intake is important for bone and cardiovascular health. However, getting too much calcium, particularly from supplements, can be harmful, and has been associated with an increased risk of prostate cancer, kidney stones, and heart attack, especially in post-menopausal women. Use of calcium supplements has also been associated with an increased risk of dementia in elderly women who have evidence of cerebrovascular disease or who have a history of stroke.
For adults over age 50, 1,200 mg is the recommended daily intake of calcium from food and supplements combined. If you can get it all from food, great. If you can get most of it from food, then limit your calcium supplement to just the amount you need. It is generally felt that calcium supplementation should not exceed 500 mg per dose and no more than 900 mg per day.
More information about calcium, including amounts of calcium in foods and our tests of calcium supplements, is found in the Calcium Supplements Review >>
Question: I was surprised when my doctor told me to stop taking supplements because my kidney function was low. But after stopping the supplements, my kidney function returned to normal. Can taking a lot of supplements really damage the kidneys?
Answer: The effect of supplements on kidney health depends, in part, on an individual's underlying health issues, and which supplements are taken. However, there are reports of certain supplements causing kidney problems. A 2012 review of supplement-induced kidney dysfunction lists 15 herbs and supplements reported to have caused kidney problems, including chromium, creatine, licorice, willow bark, vitamin C and yohimbe (Gabardi, Clin J Am Soc Nephrol 2012).
Taking high doses of vitamin C (1 gram or more daily), for example, has been associated with an increased risk of kidney stones, especially in people with a history of kidney stones (see the Cautions section of the Vitamin C Review for more information). Supplementation with cranberry tablets may pose a similar risk in people with a history of kidney stones (Terris, Urology 2001).
In diabetes patients with advanced kidney disease, high daily doses of B vitamins (folate, B6 and B12) were found in one study to worsen kidney function and double the risk of heart attack stroke and death (see the Cautions section of the B Vitamins Review for more information).
The National Kidney Foundation advises people with kidney disease, people who are on dialysis, and people who have received a kidney transplant to avoid all herbal supplements, and provides a list of supplements that may be the most harmful. The foundation also warns that some minerals, like potassium, may be present in supplements in which you may not expect them, like turmeric rhizome, evening primrose, noni and garlic leaf can all contain potassium.
Heavy metal contamination from supplements is another potential cause of kidney problems (Gabardi, Clin J Am Soc Nephrol 2012). Long-term exposure to excessive cadmium (which accumulates in kidneys), for example, can cause irreversible kidney damage and may also weaken bones. ConsumerLab.com has reported surprisingly high concentrations of cadmium in some popular cocoa powders. To avoid unnecessary exposure, it's best to use supplements that have been tested by an independent testing organization, like ConsumerLab.com, to be sure that a supplement does not exceed heavy metal limits.
Question: I have low blood pressure. Are there any supplements I should avoid?
Answer: Certain supplements can cause decreases in blood pressure and should be used with caution if you already have low blood pressure. These are melatonin, arginine and large doses of magnesium. Calcium may also cause a very small decrease in blood pressure. Preliminary studies have found black cohosh may lower blood pressure in animals, but it is unclear whether it has this effect in people.
There are also a number of supplements that have been shown to lower blood pressure in people with hypertension (high blood pressure). These include CoQ10, fish oil and omega-3 fatty acids, garlic, potassium, flaxseed, certain strains of probiotics, and green coffee bean extract. While much of the evidence for these is focused on people with high blood pressure, they could potentially lower blood pressure in others. So, if you take one of these supplements and find your low blood pressure becomes even lower, try eliminating the supplement and see if your blood pressure improves.
For more about using these supplements, including the evidence, potential side effects, and our tests of products, use on the links above.
Question: Is there cause for concern with "gummy vitamins?" There are many different gummies out there. Are some better than others?
Answer: When gummies first became popular, ConsumerLab.com found that some did not contain their listed amounts of vitamins or minerals, or contained impurities. We have seen improvements in quality over time, but continue to find more problems with candy-like vitamins than with traditional forms, such as tablets and caplets. Manufacturing challenges associated with candy-like products likely explain the higher incidence of problems.
A benefit of gummies is that they may be more palatable than a pill. Also, being chewable, there is not the risk that the product won’t properly break apart, as there is with a tablet.
A risk with any candy-like supplement, particularly with children, is that too many will be consumed, potentially resulting in toxicity. It’s therefore best to give young children vitamins as needed and not leave them out. Also, keep in mind that not all vitamins and other ingredients are easily incorporated into gummies, so, if you are interested in a gummy supplement, check that it lists the ingredients you want.
Question: Does Prevagen really improve memory?
Answer: According to the company’s website, people who use people Prevagen (Quincy Bioscience) can “experience improved memory, a sharper mind, and clearer thinking. Unfortunately, no peer-reviewed studies have been published to back up these claims. In addition, the FDA has warned Quincy Bioscience in the past against claiming Prevagen could treat conditions such as head injuries and Alzheimer's disease and for failing to report adverse reactions. The FDA has also claimed that the key ingredient, apoaequorin, a synthetic protein, is not an acceptable ingredient in a dietary supplement.
Question: Can taking fish oil or calcium supplements increase my risk of prostate cancer? My doctor recommended that I stop taking them since I have an enlarged prostate.
Answer: The evidence regarding fish oil and prostate cancer is mixed: some observational studies have found an increased risk among men with high blood levels of omega-3 fatty acids DHA and EPA, but fish oil supplementation has not been found to increase the risk of prostate cancer. There are studies currently underway that are investigating this issue.
Similarly, the research on calcium supplementation and prostate cancer is far from conclusive. However, the evidence suggests that most men over the age of 50 can probably get all the calcium they need from foods, and should limit their total intake from foods and supplements.
Question: Which supplements help reduce the risk of colorectal cancer?
Answer: There is good evidence that getting adequate folate and fiber from foods and supplements can reduce the risk of developing colorectal cancer. (Listen to ConsumerLab.com's Fiber Supplements Webinar for more on fiber and colon health).
In people with low blood levels of selenium, selenium supplements have been found to reduce the risk of colon cancer, and in people who smoke, taking curcumin can reduce early changes in the colon that can lead to cancer.
Maintaining higher levels of vitamin D in the body -- which can be achieved through exposure to sunlight or obtained from foods and supplements -- is associated with a reduced risk of developing colorectal cancer.
Calcium supplements may possibly reduce the risk of colon polyps or colon cancer.
Although a high dietary intake of CLA (conjugated linoleic acid) from high-fat dairy foods has been associated with a reduction of colorectal cancer by up to 39% in women, it is not known if taking CLA supplements has this potential benefit.
For more information about each of these supplements, use the links above. Also see the Cancer Prevention article in our Natural Products Encyclopedia.
Question: Is calcium hydroxyapatite really better than other forms of calcium?
Answer: Calcium hydroxyapatite is a form of calcium derived from cow bone and typically includes an array of other minerals as well as bone proteins. However, it is not necessarily a safer form of calcium, as explained in the Calcium Supplements Review >>
Question: Is there a danger of getting too much calcium from Tums? I take them frequently for heartburn.
Answer: Taking Tums can significantly contribute to your daily calcium intake, and it can be easy to exceed the recommended daily intake for calcium if you take several tablets per day. Since getting more than 1,000 mg of calcium daily from sources other than food is associated with certain risks, it's important to consider how many tablets you are taking and what strength they are (i.e. regular, extra strength, "ultra," etc.). More information about this is found in the Calcium Supplements Review.
Calcium can also interfere with the absorption of certain medications and other minerals. See the Cautions section of the Calcium Review and the Encyclopedia article about Antacids for more about this.
Question: Is it important to take calcium and magnesium together?
Answer: No, it is not necessary to take calcium and magnesium together. In fact, if you need to take large amounts (250 mg or more) of either of these, you may be better off taking them at separate times, as they can compete with each other for absorption.
Question: Is it safer to get calcium from foods than from supplements? How about from calcium-fortified orange juice and non-dairy milks?
Answer: In general, it appears to be preferable to get most of your calcium from foods which contain it naturally, and to restrict the amount you get from supplements (including calcium-fortified drinks and foods — which are like taking a supplement with food). For example, getting too much calcium from supplements has been associated with an increased risk of kidney stones, heart attack and death in women, and an increase in the risk of heart attack in men. Taking calcium supplements has also been associated with an increased risk of dementia in elderly women who have evidence of cerebrovascular disease or who have a history of stroke. Nevertheless, calcium from all sources counts toward the upper tolerable intake level (UL) above which the risk adverse effects increase — although it is rare to exceed this limit from food alone.
Question: Are plant-based calcium supplements, like AlgaeCal, better than regular calcium supplements?
Answer: AlgaeCal (Basic) contains calcium, magnesium and trace minerals derived from algae with added vitamin D. AlgaeCal Plus also includes added vitamins C and K, boron, and additional magnesium. Testing by ConsumerLab.com in 2011 found AlgaeCal Plus to also contain a higher amount of lead (a toxic heavy metal) than many other calcium-containing supplements. Studies sponsored by the makers of AlgaeCal found that it increased bone mineral density in healthy men and women, although there were weaknesses to the study design. There do not appear to be any studies comparing the effects of AlgaeCal to other forms of calcium, such as calcium carbonate or calcium citrate in people nor to other calcium + vitamin D supplements. For more about this, plus evidence for other forms of calcium, see the Calcium Supplements Review >>
Update (11/17/15): We were recently informed by a CL member that AlgaeCal provided the following information in response to the member's inquiry about lead in AlgaeCal Plus. In the response, AlgaeCal appears to acknowledge the amount of lead found by ConsumerLab.com in 2011, but provides information which we consider misleading regarding how that amount of lead compares to what is found in the U.S. diet:
"There are 5.2 mcg of lead in a daily dosage of 4 capsules of AlgaeCal Plus. It is just like taking a daily serving of other typical plant foods according to the FDA's publication, Total Diet Study Statistics on Elements Results (December 11, 2007): Food Amount of Lead in a 4 Ounce Serving Mixed nuts, roasted 10.2 mcg Brussels sprouts, fresh, boiled 7.9 mcg Sweet potato, fresh, baked 7.2 mcg Spinach, boiled 7.0 mcg Avocado, raw 4.5 mcg. Furthermore, the US Government's Centers For Disease Control publication 'Inorganic Lead Exposure, Metabolism and Intoxication' states that 'typical intakes of lead from food, beverages and inhaled air are in the order of 300 to 500 mcg per day.' "
The most recent Total Diet Study (FDA 2014) shows much lower amounts of lead in foods than AlgaeCal states above. The FDA found no detectable lead in peanuts or Brussels sprouts and, based 3 oz servings, only, 1.1 mcg in sweet potatoes (0.013 mcg/gram or mg/kg), 0.3 mcg in spinach (0.004 mcg/g) and 0.085 mcg in avocado (0.001 mcg/g). We could not find the CDC publication referenced by AlgaeCal, but found another CDC publication (ATSDR Public Health Statement for Lead 2007) which states that, based on recent studies, "the average dietary intake of lead was about 1 microgram (a microgram is a millionth of a gram) per kilogram of body weight per day." For an adult weighing 70 kg (154 lbs), this would be 70 mcg -- nowhere near the 300 to 500 mcg stated above. In short, the amount of lead in AlgaeCal Plus is higher than in most foods and calcium supplements and adds significantly to one's intake of lead, although it would not be likely, in itself, to cause toxicity in an adult.
Question: Are there negative interactions between the following supplements I take twice each day, as well as 60 mg of beta-sitosterol with dinner: Vitamin C (500 mg), CoQ10 (100 mg), grape seed extract (100 mg), fish oil (500 mg), vitamin D3/calcium/magnesium/zinc (200 IU/333 mg/113 mg/5mg)?
Answer: You may want to cut back on the vitamin C. The required daily intake is not even 100 mg and if you already get that, taking another 500 mg or 1,000 mg may actually reverse vitamin C's ability to reduce the risk of cataracts, as noted in the Vitamin C Supplements Review.
The amounts of the other supplements you take are generally safe and are at doses which may be helpful -- depending on your health conditions. It is also good that you have broken up your intake of calcium over the day, since you can't absorb more than 500 mg at a time, as discussed in the Calcium Supplement Review.
If you have high blood pressure, be aware that one study found the combination of vitamin C and OPCs (the active component of grape seed extract) to increase blood pressure (as noted in the Safety Issues section of the article on OPCs).
The beta-sitosterol which you take is at a dose which may help with symptoms of an enlarged prostate. Be aware that beta-sitosterol is also used at a much higher dose for lowering cholesterol (by competing with cholesterol for absorption in the gut) and, at this higher dose, you would not want to take it at the same time you take the fat-soluble supplements -- vitamin D and CoQ10, both of which are best taken with a meal containing some fat.
If you take also take prescription medications, be sure to look up the supplements with which they may interact using our Drug Interactions information.
Note: ConsumerLab.com staff is not able to regularly respond to requests from members to evaluate their supplement regimens. However, it tries to do so from time-to-time and often responds to questions of more general interest, such as those below.
Question: After developing kidney stones, I was told to avoid tea -- but recently I've heard that green tea might actually be helpful for kidney stones. Is that true?
Answer: As discussed in the Green Tea Review, both black and green tea contain oxalate, high levels of which can contribute to the development of kidney stones in some people. However, for a number of reasons, this is not much of a concern with green tea (which may even help), and there are even ways to minimize the kidney-stone risk when drinking black tea. Get the details in the "Concerns and Cautions" section of the Green Tea Review >>
Be aware that too much calcium or vitamin C from supplements may increase the risk of kidney stones.
For information about other supplements that may be helpful or harmful regarding kidney stones, see the Encyclopedia article about Kidney Stones.
Question: What is Prelief? Does it really help for heartburn and/or bladder pain from acidic foods?
Answer: Prelief (from AkPharma Inc.) is promoted as a "food de-acidfier" to reduce the acidity of foods which can trigger "painful bladder, frequent urination, indigestion, and occasional heartburn." While lowering the acidity of certain foods can potentially reduce the risk of heartburn, ConsumerLab.com found that the evidence for Prelief and its main ingredient, calcium glycerophosphate, in reducing heartburn and bladder pain is extremely limited. See the full answer >>
Question: I read an article stating that some of the ingredients in Centrum multivitamins may be dangerous or toxic. Is that true?
Answer: The safety of certain ingredients in some Centrum multivitamins - especially binders, fillers and coloring agents - has been questioned on various websites. These ingredients are not unique to Centrum vitamins but are found in many brands of multivitamins and other supplements and include polyethylene glycol, polyvinyl alcohol, BHT, modified corn starch, and coloring agents such as Yellow 6 Lake and titanium dioxide.
ConsumerLab.com has reviewed the evidence regarding the safety of these ingredients (which are listed as "Other ingredients" on supplements and as "Inactive ingredients" on medicines to distinguish them from "Active" ingredients). It is true that in amounts higher than that used in Centrum supplements, some of these ingredients can have dangerous or toxic effects. More information about these ingredients is found in our review article about Inactive Ingredients. Note that some ingredients, such as certain coloring agents, may cause allergic reactions in sensitive individuals.
In the amounts in which they occur in Centrum multivitamins, they are safe. By law, any inactive ingredient added to a supplement must be an FDA-approved food additive or generally recognized as safe (GRAS).
Centrum multivitamins also contain calcium in the form of calcium carbonate and this, too, has been mentioned as a concern on some websites. However, calcium carbonate (the form found in oyster shells and most commonly used in supplements and antacids), is not inherently unsafe. While there are some differences to consider when choosing which form of calcium to take, the potential for issues such as increased risk of heart attack with large servings of calcium and interactions with medications and other minerals is not limited to calcium carbonate, but includes any supplemental calcium.
You can check the full list of ingredients for each product tested in ConsumerLab.com's Review of Multivitamin and Multimineral Supplements (and in any of our many other Product Reviews) by clicking on "Ingredients" underneath the product name in the first column of the results table. In the results table, itself, we also point out if a product is free of artificial colors, flavors, and/or preservatives, or has other special features, such as being gluten-free.
Question: Are the "% DV" numbers on vitamin supplement labels really based on what I need?
Answer: Unfortunately, the % DV (percent of Daily Value) numbers are not nearly as useful as they could be. One reason is that they are woefully out of date. The DVs are based on calculations done in 1968 (with some additions in 1989) and do not reflect the latest intake recommendations from the Institute of Medicine which show that some DVs are too high and others are too low. In addition, the DVs do not distinguish nutritional needs by age and gender since the DVs are intended to cover healthy adults and children over 4 years of age (except pregnant and lactating women), while the needs of people vary significantly within this expansive group — even between men and women of the same age.
In some situations, the DVs actually exceed the upper tolerable intake levels for adults and/or children. In these cases, when you get 100% or more of the DV from a supplement, you are actually putting yourself at risk of toxicity.
In other situations, 100% of the DV or more is simply much higher than the current recommendations. What appears be 100% of the DV could actually be as much as 1,000% of what you need.
For several popular vitamins and minerals, if you get 100% of the DV, you are actually getting much less than the current recommendations.
The DVs do not include the special needs of women or are pregnant or lactating, whose needs are often much greater than 100% of the DV.
The nutrients for which the DVs can be particularly misleading are vitamin A, vitamin B12, vitamin C, vitamin D, vitamin K, biotin, calcium, chromium, copper, folate, iron, iodine, magnesium, molybdenum, niacin, pantothenic acid, potassium, and zinc.
Question: Which supplements can help treat constipation?
Answer: A number of supplements may be helpful in treating or preventing constipation. Fiber supplements, such as psyllium and glucomannan (a water-soluble fiber) may help to relieve constipation (Note: there is a safety concernwhen using glucomannan). Ground flaxseed, another source of fiber, may also be helpful. (See ConsumerLab.com's Fiber Supplements Webinar for more information about these supplements for constipation as well as for other uses.)
A specific probiotic product was found to significantly increase the number of bowel movements per week in people with chronic constipation. (Other strains have been found to be helpful for constipation associated with IBS).
Magnesium and aloe vera juice (with latex) can help to relieve constipation due to their laxative effects (Note: There are safety concerns with aloe latex -- see the "Concerns and Cautions" section of the Aloe Vera Review before using).
See the Encyclopedia article about Constipation for information about other proposed treatments.
Be aware that constipation may be a side-effect of certain supplements, especially iron, and to a lesser degree, calcium (see the "ConsumerTips" sections of the respective ConsumerLab.com Reviews for more about forms of these minerals which may be less likely to have this effect). Other supplements reported to cause constipation, although less frequently, include nattokinase, chlorella, NAC (N-acetyl cysteine) and beta-sitosterol.
Excessive intake of vitamin D as a supplement can cause hypercalcemia (too much calcium in the blood) with symptoms including constipation.
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Product Review:Calcium Supplements (Including Vitamin D, Vitamin K, and Magnesium)
Intial Posting: 4/4/15 Last Update: 10/13/16
Caution with Calcium Supplements Containing Added Bone Health Ingredients!
Be Sure You Are Taking a Quality Product. Find Out Now If Yours Passed!
Alphabetical list of calcium supplements reviewed and rated in report
Bayer Citracal Slow Release 1200
Douglas Laboratories Calcium Citrate
Rainbow Light Food Based Calcium
Andorra Life Collagen Calcium
Finest Nutrition (Walgreens) Calcium
Bayer Citracal Petites
GNC Calcium Plus 1000 with Magnesium & D3
Solgar Calcium Citrate with Vitamin D3
Bayer Flintstones Healthy Bone Support Calcium & Vitamin D3
Jarrow Formulas Bone-Up
Spring Valley [Walmart] Calcium plus Vitamin D3
Caltrate 600+D Plus Minerals
Kirkland Signature [Costco] Calcium Citrate Magnesium And Zinc
Standard Process Calsol
ChildLife Liquid Calcium With Magnesium
Nature Made Calcium Magnesium Zinc
Trader Joe's Calcium Citrate with Vitamin D
Country Life Bone Solid
Nature's Way Alive Calcium Bone Formula
USANA Active Calcium
Nature's Way Alive Calcium Gummies
Viactiv Calcium Plus D - Milk Chocolate
DG Health [Dollar General] Calcium
Nutrilite Cal Mag D Advanced
Yummi Bears Vegetarian Sour Calcium + Vitamin D3
Make sure the calcium supplement you take passed our review and is right for you!
Isn't your health worth it?
Calcium is critical for building and maintaining strong bones and preventing osteoporosis. Calcium is also needed for the proper functioning of nerves, muscles, glands, and the cardiovascular system.
Some people don't get enough calcium and can benefit from calcium supplements. But you need to be careful! If you take too much calcium from supplements, you may be increasing your risk of heart attack and kidney stones.
You also need to be concerned about the quality of calcium supplements. Out of 15 calcium supplements recently purchased by ConsumerLab.com, 3 failed quality testing because they contained incorrect amounts of other key ingredients -- one contained 183% of its listed amount of vitamin D, another contained 89% of its listed vitamin D, while a third contained none of its listed vitamin K2.
You must become a ConsumerLab.com member to get the test results and quality ratings for the calcium supplements we tested, including combination products with vitamin D, vitamin K, and magnesium. You will get results for 27 calcium supplements: 15 selected for testing by ConsumerLab.com and 12 others that passed the same tests through CL's voluntary Quality Certification Program. In this comprehensive report, you'll discover:
Which calcium supplements failed our quality ratings and which passed -- including combinations with vitamin D, vitamin K, and magnesium
Cost comparisons to help you choose a calcium supplement offering the best value based on amounts of elemental calcium
The pros and cons of different forms of calcium such as carbonate, citrate, oyster shell, and coral calcium and which may be best for you
Recommendations on calcium dosage by age and gender and for specific uses, as well as how much calcium may be too much and how best to take calcium supplements
Potential drug interactions and side effects of calcium supplements
ConsumerLab.com Answers -- for Calcium Supplements (Including Vitamin D, Vitamin K, and Magnesium)
Question: I would like to know about different sources of vitamin K2. I have been told it is from natto or fermented soy and from a flower called geraniol. Can you tell me the difference? Is one source better than another? Get the answer >>
Question: Is it better to get vitamins from foods or supplements, and are natural vitamins better than synthetic vitamins? Get the answer >>
Question: I've been buying nutritional supplements in powder form, as I find them cheaper than tablets and capsules. I am concerned about the effect of air when I open the bottles daily because sometimes my powdered supplements get clumpy. Should I be concerned? Get the answer >>
Question: Are supplements which claim increased absorption or improved bioavailability telling the truth? Is it worth paying more for these? Are there concerns? Get the answer >>
Question: Which supplements are important after bariatric surgery (i.e., weight loss or stomach-reducing surgery)? Are there any I should avoid? Get the answer >>
Question: Are enterically coated supplements better than non-enterically coated ones? Get the answer >>
Question: Which supplements can help keep my heart healthy? Are there any to avoid? Get the answer >>
Question: I take levothyroxine (Synthroid), a thyroid hormone to treat hypothyroidism. Are there supplements I should avoid, or be taking, due to this drug? Get the answer >>
Question: I was surprised when my doctor told me to stop taking supplements because my kidney function was low. But after stopping the supplements, my kidney function returned to normal. Can taking a lot of supplements really damage the kidneys? Get the answer >>
Question: I have low blood pressure. Are there any supplements I should avoid? Get the answer >>
Question: Is there cause for concern with "gummy vitamins?" There are many different gummies out there. Are some better than others? Get the answer >>
Question: Is it safer to get calcium from foods than from supplements? How about from calcium-fortified orange juice and non-dairy milks? Get the answer >>
Question: Are plant-based calcium supplements, like AlgaeCal, better than regular calcium supplements? Get the answer >>
Question: Are there negative interactions between the following supplements I take twice each day, as well as 60 mg of beta-sitosterol with dinner: Vitamin C (500 mg), CoQ10 (100 mg), grape seed extract (100 mg), fish oil (500 mg), vitamin D3/calcium/magnesium/zinc (200 IU/333 mg/113 mg/5mg)? Get the answer >>
Question: Which supplements can help with indigestion and/or heartburn? Get the answer >>
Question: After developing kidney stones, I was told to avoid tea -- but recently I've heard that green tea might actually be helpful for kidney stones. Is that true? Get the answer >>
Question: What is Prelief? Does it really help for heartburn and/or bladder pain from acidic foods? Get the answer >>
Question: I read an article stating that some of the ingredients in Centrum multivitamins may be dangerous or toxic. Is that true? Get the answer >>
Question: Are the "% DV" numbers on vitamin supplement labels really based on what I need? Get the answer >>
Question: Are there any supplements I should avoid when taking an antibiotic? Are there any that may be helpful? Get the answer >>