ConsumerLab.com Answers
Question:
Some websites are highly critical of magnesium stearate, which is in many supplements. Is this substance toxic and should I avoid it?
Answer:
As you note, magnesium stearate is a commonly used "inactive ingredient" in dietary supplements, but some websites have cautioned that it is potentially "hazardous" and "harmful." The reasons typically given are that magnesium stearate may adversely affect the gastrointestinal tract and the immune system. At the same time, magnesium stearate is generally recognized as safe by the FDA for use in supplements. So what should you believe? ConsumerLab.com investigated the facts to help you decide whether or not you should be taking supplements containing magnesium stearate. See full answer>>
You can also get information about other inactive ingredients in supplements in our report on Inactive Ingredients in Supplements.
ConsumerLab.com Answers
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?
Answer:
ConsumerLab.com Answers
Question:
What is the benefit of magnesium orotate compared to other forms of magnesium?
Answer:
Magnesium orotate is a complex of magnesium plus orotic acid. Some people use it for its magnesium content (to prevent or treat magnesium deficiency) while others take it for its orotic acid, which is used for improving athletic performance and endurance, and for heart health.
As a magnesium supplement, it is often promoted as a better source of magnesium than other forms (e.g., magnesium oxide) due to improved absorption. Some websites claim that orotate carries magnesium across cell membranes and produces higher levels of magnesium within the cells. However, research does not show that minerals (such as magnesium or zinc) bound to orotic acid have improved absorption ( Andermann, Eur J Drug Metab Pharmacokinet 1982). In fact, magnesium orotate probably isn't the best choice as a magnesium supplement for preventing or treating magnesium deficiency because it doesn't appear to offer an advantage over others and it can cost up to 9 times more than other magnesium products. To get, for example, 200 mg of magnesium from magnesium orotate supplements you might spend 10 to 18 cents. In contrast, you can get the same amount of magnesium for as little as 2 cents, as shown in ConsumerLab.com's Magnesium Supplements Review.
Magnesium orotate might have a protective role in heart disease. A preliminary clinical study in people with heart failure found that giving 6,000 mg of magnesium orotate daily for one month, followed by 3,000 mg daily for 11 months reduced the risk of dying during the study by about 25%. It also improved heart failure symptoms in about 40% of patients (Stepura, Int J Cardiol 2009). Preliminary research in animals and humans suggests that this protective role of magnesium orotate may relate to its involvement in the synthesis of genetic material such as RNA and DNA (Rosenfeldt, Cardiovasc Drugs Ther 1998).
Although magnesium orotate is often promoted and used to improve athletic performance or endurance, there is no reliable evidence that it works for this purpose.
Some concerns about the safety of orotic acid from supplements such as magnesium orotate have been raised. Research in animals shows that doses of 100 mg/kg/day or more of orotic acid have tumor promoting effects in experimental tumors. Lower doses of 50 mg/kg/day did not have this effect (Laconi, Carcinogenesis 1993, Laconi, Carcinogenesis 1993, Laconi, Carcinogenesis 1988). Based on these data, a panel of the European Food Safety Authority (EFSA) concluded that orotic acid-containing products, such as magnesium orotate, represent a safety concern when used in amounts of 100 mg/kg or more daily (e.g., 7,000 mg for a 70 kg [154 lb] adult) (EFSA Journal 2009).
The bottom line:
Magnesium orotate is not the best choice as a magnesium supplement and despite preliminary evidence of a benefit for people with heart disease, there is also evidence suggesting a potential safety concern at around the high dosage used for that purpose. Until more is known about the potential benefits and risks, it may be best not to use magnesium orotate.
For more information, see the article about magnesium in the Encyclopedia on this website.
ConsumerLab.com Answers
Question:
Are supplements with amino acid chelated minerals better than those with other forms of minerals?
Answer:
Minerals, like magnesium and iron, are metal ions which like to attach to other compounds. The compounds to which they attach can affect how well they are absorbed and how available they are for use in the body. An amino acid chelated mineral is one in which a mineral has been chemically attached to an amino acid, and there is evidence that some, but not necessarily all, of these types of compounds may improve mineral absorption. For information about specific chelated amino acids, such as iron bis-glycine, magnesium diglycinate, zinc bis-glycinate, and selenomethionine (a chelate of selenium), see the full answer >>
You can also learn more about forms of calcium, magnesium, iron, zinc and other minerals in ConsumerLab.coms reviews of these supplements, and in the Review of Multivitamin and Multimineral Supplements.
ConsumerLab.com Answers
Question:
Are enteric coated supplements better than non-enteric 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)>>
ConsumerLab.com Answers
Question:
Do magnesium supplements, like Magtein, help memory or protect against Alzheimer's disease?
Answer:
Magnesium plays an important role in brain cell function and some preliminary research in animals has suggested it may influence cognitive functions like memory and learning. A preliminary study in people found that magnesium-L-threonate (Magtein or Clarimem) may modestly improve certain measures of cognitive function. Overall, however, there is very limited evidence that taking magnesium improves memory or learning, or prevents Alzheimer's disease, in humans. For details, see the "What It Does" section of the Magnesium Supplements Review >>
ConsumerLab.com Answers
Question:
Can taking certain forms of potassium, such as potassium citrate, reduce my chances of getting kidney stones? I've read a study that says it can, but it's unclear how much I should take.
Answer:
Yes, there is good evidence that potassium citrate can inhibit kidney stone formation in a large percentage of people with recurrent kidney stones. In addition, potassium phosphate can lower levels of excess calcium in urine and also reduce the risk of calcium kidney stones.
Interestingly, it is not potassium itself which makes these treatments work but the citrate and phosphate portions of the compounds, and there are many other potential sources of citrate, such as citrus fruits. Get more information about the evidence for these compounds in reducing kidney stones, including doses used in clinical studies and how this compares to amounts found in supplements, in the Potassium Supplements Review >>
ConsumerLab.com Answers
Question:
Do any supplements help with migraines?
Answer:
There is evidence that magnesium, CoQ10 and riboflavin (B2) may help to reduce the frequency or severity of migraine headaches. The amino acid 5-HTP may also reduce frequency, although the evidence is mixed.
Some herbal supplements, such as butterbur and feverfew may also be helpful. One preliminary study suggests ginger may help reduce the severity of migraine headaches. However, be aware that taking St. John's wort with migraine medications or the painkiller tramadol can cause adverse effects.
One clinical study found that a DAO (diamine oxidase) supplement reduced the duration of migraine attacks by 30%, but did not reduce pain or frequency.
For more information, see the article about Migraine in our Encyclopedia, and also use links above.
ConsumerLab.com Answers
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 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.
Note that sexual enhancement supplements with undeclared drugs, such as sildenafil (Viagra) or tadalafil (Cialis) may also lower blood pressure (see the list of Recalls and Warnings for supplements found to contain these drugs).
For more about using these supplements, including the evidence, potential side effects, and our tests of products, use on the links above.
ConsumerLab.com Answers
Question:
Which is the best form of magnesium to take - one that contains the most magnesium and is best absorbed?
Answer:
While different magnesium compounds vary in the amount of magnesium they contain (for example, just 16.2% of magnesium citrate is actual magnesium -- the rest is citric acid, while 14.1% of magnesium glycinate is magnesium), manufacturers are required to list the amount of actual, or "elemental" magnesium on labels so you can compare the actual amount of magnesium provided by supplements, even if they contain different forms. However, be aware that ConsumerLab.com has found some magnesium supplements in the past which were not labeled properly.
Absorption and even certain side-effects can vary by form, as can cost. You can read more about this in the "What to Consider When Buying" section of the Magnesium Supplements Review. In addition, we identify products which contain a form of magnesium with good absorption, and which specific product was the most economical way to get this type of magnesium.
ConsumerLab.com Answers
Question:
How can the Recommended Daily Allowance (RDA) for magnesium be higher than the Upper Tolerable Intake Level (UL)? That is, how can an amount which is healthful also put you at risk for harm?
Answer:
It is true that, at first glance, there seems to be a contradiction. For example, the UL for magnesium (above which the risk of adverse effects increases) is 350 mg per day for adults and children over age 8, but the RDA (the amount one needs) can be as high as 420 mg for many people within this group depending on gender and stage of life. However, the magnesium one consumes from food does not count toward the UL; only magnesium from supplements and medicine can cause adverse effects and counts toward this limit. So, as long as you're not getting more than 350 mg of magnesium per day from supplements and/or medicine and are getting some magnesium from foods (like whole grains, nuts, beans, and green leafy vegetables) you can satisfy the RDA without exceeding the UL.
For more about this, see the "What to Consider When Using" section of the Magnesium Supplements Review.
The ULs established for niacin and folate also only apply to the amounts consumed from supplements and fortified foods and not from foods naturally containing these vitamins. For vitamin E, the upper limit is higher for the natural form than the synthetic form.
For recommended daily intakes and upper limits for these and other nutrients, based on gender and stage of life, see ConsumerLab.com's Recommended Daily Intakes and Upper Limits page.
ConsumerLab.com Answers
Question:
Do any supplements help for irritable bowel syndrome (IBS)?
Answer:
Several different types of probiotics have been found to reduce symptoms of IBS, but the appropriate probiotic may depend on whether the IBS is causing predominantly diarrhea or constipation. (See the "What It Does" section of the Probiotic Supplements Review for details.)
Prebiotics have also been promoted for IBS, although the evidence is mixed.
Interestingly, several small studies suggest melatonin may improve symptoms of IBS, possibly by affecting the nervous system in the digestive track. (See the "What It Does" section of the Melatonin Review for details).
Preliminary evidence suggests psyllium, a type of fiber, may be helpful for people with IBS with constipation.
Information about other potentially helpful supplements, including peppermint oil and flaxseed, is found in the Encyclopedia article about IBS.
Be aware that a number of supplements, including fish oil, magnesium, high doses of vitamin C, berberine and turmeric/curcumin can cause diarrhea, so you may want to avoid these or reduce your dosage if you find they are exacerbating IBS symptoms. See the "Concerns and Cautions" section in each review for details.
ConsumerLab.com Answers
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.
See answers to these related questions:
Which vitamins and minerals should be taken together or separately? >>
When taking a water-soluble version of CoQ10, do I still need to take it with food? >>
Do I need to divide my daily 300 mg dose of CoQ10 into smaller doses, or can I take it all at once? >>
As vitamin D is a fat-soluble vitamin, why is it necessary to take it every day? >>
A blood test showed my vitamin D level is low. How do I know how much vitamin D to take? >>
Is it possible to take too much vitamin C? >>
Which supplements should be taken with food? >>
I read that sterol supplements to lower cholesterol like CholestOff can block the absorption of vitamins. Is that true? >>
ConsumerLab.com Answers
Question:
Help! How do I know how much magnesium I am actually getting from my supplement? The label says it contains 500 mg of magnesium "as magnesium citrate" -- but how much of that is magnesium and how much is citrate?
Answer:
This is a good question, since magnesium can make up less than half the weight of compounds which include it, such as magnesium citrate, magnesium chloride, and magnesium glycinate.
The amount of actual magnesium (sometimes listed as "elemental magnesium) you are getting from your supplement should be indicated on the label, but that's not always the case, so it's important to notice how the information is stated. For example, if your supplement label states: "Magnesium (as magnesium citrate)....500 mg" it should contain 500 mg of actual magnesium. However, if the label says "Magnesium citrate 500 mg," this means the entire compound is 500 mg — of which only a small percentage is magnesium (in fact, it's only 16.2%). Also, remember that even when a supplement appears to be properly labeled, the only way to know for sure whether it contains what it claims is if it has been tested by an independent group like ConsumerLab.com. Not all products contain what they claim.
For more about how to read magnesium supplement labels, including an example of a misleading label from a product reviewed by ConsumerLab.com, see the Magnesium Supplements Review >> (The Review includes the results of our latest product tests and information about what magnesium does, proper dosage, side effects, and how the forms of magnesium differ.)
Note that this labeling rule applies to other essential minerals, such as calcium, iron and zinc. See the "ConsumerTips" section of our Reviews of supplements made from each for more about the different forms and what to look for on labels.
ConsumerLab.com Answers
Question:
Which supplements reduce the risk of stroke? Which increase the risk of stroke?
Answer:
Certain supplements have been shown to reduce the risk of stroke, while others may increase that risk. In addition, certain nutrients from foods may reduce the risk of stroke — although the benefit does not necessarily carry over to those nutrients when obtained from supplements, as discussed below. Also be aware that some supplements may increase the risk of stroke, as noted below.
Keep in mind that there are different causes of stroke. The most common type of stroke, called ischemic stroke, occurs when blood flow to a part of the brain is blocked, either by a blood clot or plaque build-up in arteries (atherosclerosis), depriving the brain of oxygen. The second, less common, type of stroke is hemorrhagic stroke, which occurs when a blood vessel inside the brain leaks blood or ruptures, creating pressure which damages brain cells. Risk factors for stroke include high blood pressure, diabetes, high cholesterol, atherosclerosis, atrial fibrillation, heart failure, and carotid artery disease (build up of plaque in the main artery in the neck which carries blood to the brain). Lack of physical exercise and being overweight, frequent use of NSAIDS (such as ibuprofen), stress and depression also increase the risk of stroke.
Supplements that may reduce the risk of stroke: (Use the links for more details such as dose.)
Getting a certain amount of vitamin D per day from food and/or supplements may reduce the risk of ischemic and hemorrhagic stroke in men, but this benefit has not been shown in women.
Folic acid (vitamin B-9) supplementation may decrease the risk of stroke in people who have very low or deficient levels of folic acid. However, be aware that there are risks associated with getting too much folate, and current supplement labels may mislead you to consume more folate than you need or is safe for you. It's also important to note that consuming high doses of other B vitamins from supplements, such as B-6 and B-12, may increase the risk of stroke, as well as heart attack and death, in people with diabetes who also have advanced kidney disease.
Nattokinase supplements may decrease blood-clotting factors in the blood, however, there are no published clinical studies in people showing that these supplements reduce the risk of blood clots (which, as discussed above, can cause ischemic stroke).
A daily dose of NAC (N-acetyl cysteine) was found to reduce the incidence of cardiovascular events, including ischemic stroke and heart attack, by 40% compared to placebo in people with end-state renal failure.
As discussed in the Encyclopedia article about Strokes, several other supplements, such as policosanol, vinpocetine and glycine have been proposed to help reduce the risk or improve recovery from stroke, although the evidence for these is not strong.
Be aware that taking a daily multivitamin has not been found to reduce the risk of stroke.
Foods that may reduce the risk of stroke:
The following types of foods may reduce the risk of stroke — although the substances in these foods have not been shown to provide the same benefit when given as supplements.
Higher intakes of calcium from foods are associated with a reduced risk of coronary artery calcification (a form of atherosclerosis), while the use of calcium supplements is associated with an increased risk.
Higher intakes of vitamin K2 from foods are also associated with a reduced risk of coronary calcification — while this benefit has not been shown from vitamin K supplements.
Eating fish has been associated with a 6% to 12% lower risk of ischemic and hemorrhagic stroke, depending on how many servings of fish per week were consumed. However, taking fish oil supplements has not been found to have the same benefit.
Getting more magnesium from your food can help reduce the risk of stroke: One study found that people who consumed more magnesium per day than average had an 8% lower risk of strokes of any kind and a 9% lower risk of ischemic stroke. However, this does not mean that magnesium supplements necessarily have the same risk-lowering effect.
In men and women at high risk for cardiovascular disease, consuming a certain amount of extra-virgin olive oil daily, as part of a Mediterranean diet was found to reduce the risk of ischemic and hemorrhagic stroke, heart attack and death by 30%.
In observational studies, drinking several cups of green tea per day was found to reduce the risk of ischemic stroke by up to 21%.
Supplements that may increase the risk of stroke:
There is concern choline from supplements and foods can increase the risk of stroke. However, a specific form of choline may help to improve recovery from stroke.
People who have had a stroke or are at risk for a stroke, should not take Ginkgo biloba.
Be aware that a case of hemorrhagic stroke associated with the consumption of a popular energy drink has been reported.
Also, be careful if you choose to use a weight loss supplement — the FDA has issued many warnings about weight loss supplements found to contain undeclared sibutramine, a drug which can substantially increase blood pressure and pulse rate in some individuals, and may present a significant risk for people with a history of stroke (Scroll down to the "Warnings" section here for a list of some of these products).
ConsumerLab.com Answers
Question:
How do I choose the best magnesium supplement?
Answer:
Choosing a magnesium supplement can be tricky due to the many different forms (e.g., magnesium aspartate, bicarbonate, carbonate, chloride, citrate, gluconate, hydroxide, lactate, malate, orotate, oxide, taurate, threonate, and trisilicate) and suggested serving sizes ranging from less than 50 mg to over 1,000 mg. Making matters worse, we've found that you can spend less than 5 cents to nearly $2 to get the same amount of magnesium from a supplement.
ConsumerLab.com has tested and reviewed hundreds of magnesium supplements in its continually updated Magnesium Supplements Review. If you are a CL member, you can check out our latest test results and Top Picks. But here is some of the good general advice found in the Review.
First, choose a form of magnesium that matches the reason you're taking it. Some forms, such as magnesium citrate and magnesium chloride, are absorbed better than others -- and magnesium chloride is less likely to cause diarrhea and other side effects. Other forms may be best suited for use as laxatives, or for reducing the frequency and severity of migraines. Some forms, such as magnesium orotate, are much more expensive than others without added benefit. Also be aware that one popular form of magnesium has been shown, as a tablet, to absorb so much water from the air that it can ruin itself and other supplements around it. (See Choosing the right form of magnesium and Storage for details).
Secondly, it's important to choose a magnesium supplement that provides the right dose of magnesium to suit your needs and does not exceed the upper tolerable intake level for magnesium and cause adverse side effects (see Dosing and how to take).
When looking at a label be sure it lists the amount of actual magnesium (or "elemental" magnesium) per dosage unit. We've occasionally come across magnesium and other mineral supplements that are incorrectly labeled -- leading you to think you are getting more magnesium than you really are (see What to Consider When Buying for an example of such a label). Our tests have also revealed supplements that simply contain less magnesium than claimed, are contaminated with lead, or are tablets that fail to properly disintegrate -- suggesting that they may not fully deliver their ingredients.
Although magnesium is often sold in combination with calcium, it may be best to take these minerals separately when taking high doses, as they can compete for absorption.
Also, keep in mind that magnesium supplements should be used with caution by people with certain medical conditions, and that magnesium should not be taken along with certain medications (see Concerns and Cautions).
See our most current Magnesium Supplements Review, and check out our Top Picks for highest quality and value.
ConsumerLab.com Answers
Question:
Will an Epsom salt bath increase magnesium levels in my body like a supplement?
Answer:
Epsom salt (magnesium sulfate) added to a bath can raise magnesium levels in the body, according to a preliminary study. Details, including the amount of Epsom salt needed, are found in the Epsom salt section of the Magnesium Supplements Review. Also see the evidence regarding other transdermal methods of obtaining magnesium (e.g., creams, sprays and oils) and our Top Picks among magnesium supplements.
Be aware that it can be dangerous to ingest large amounts of Epsom salt. Learn more about this and other Concerns and Cautions with magnesium supplementation.
ConsumerLab.com Answers
Question:
What is Prelief? Does it really help for heartburn and/or bladder pain from acidic foods?
Answer:
Prelief (from DSE Healthcare Solutions) 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 >>
ConsumerLab.com Answers
Question:
Is there an accurate test for magnesium deficiency?
Answer:
There are a number of tests designed to measure magnesium levels, however, most (including the most common test, serum magnesium concentration, or SMC) do not provide a complete assessment of magnesium status. For this reason, doctors use a combination of testing and evaluation of symptoms to diagnose magnesium deficiency. These include the serum magnesium concentration (SMC) test, the red blood cell (RBC) test, the magnesium loading test, the 24-hour excretion test, and others. Get more details about each of these in the ConsumerTips section of the Magnesium Supplements Review >>
Also see related CL Answers:
Which is the best form of magnesium to take - one that contains the most magnesium and is best absorbed? >>
What is the benefit of magnesium orotate compared to other forms of magnesium? >>
Help! How do I know how much magnesium I am actually getting from my supplement? The label says it contains 500 mg of magnesium "as magnesium citrate" -- but how much of that is magnesium and how much is citrate? >>
Is it true that I should not keep magnesium supplements in a daily pill pack mixed with other supplements and medicines? >>
How can the Recommended Daily Allowance (RDA) for magnesium be higher than the Upper Tolerable Intake Level (UL)? That is, how can an amount which is healthful also put you at risk for harm? >>
ConsumerLab.com Answers
Question:
I've read that magnesium deficiency is rare but also that most people don't get enough magnesium. How can these both be true?
Answer:
They are both true. Surveys of the U.S. population show that most people do not get the recommended daily intake of magnesium from what they eat and drink. This is particularly true of older men and adolescent girls. However, our bodies compensate for this to prevent symptoms of overt magnesium deficiency, such as seizures and abnormal heart rhythms.
Nevertheless, increasing magnesium intake to adequate levels in the diet or with some supplementation has cardiovascular benefits, such as modestly reducing blood pressure and reducing the risk of stroke. It may also help prevent hearing loss from excessive noise, migraine headaches, and menstrual pain, and it can improve insulin sensitivity in people with type 2 diabetes. This is discussed in the Magnesium Supplements Review, which includes information about recommended intakes, dosage, and ConsumerLab's tests and comparisons of magnesium supplements.
ConsumerLab.com Answers
Question:
Do magnesium creams, sprays and oils really work?
Answer:
Topical magnesium products such as MagPro, Fibro Flex and BetterYou are often promoted as easy, effective ways to get magnesium and to reduce muscle pain and cramps, improve flexibility, and promote relaxation and sleep. However, there is little reliable clinical evidence showing these products are effective and topical magnesium products may cause skin irritation, itching and rash. This is discussed in the Magnesium Creams, Sprays and Oils section of the Magnesium Supplements Review.
Be aware that some companies claim this irritation is a sign of magnesium deficiency, but this is not scientifically supported.
If you need supplemental magnesium, see our Top Picks among the magnesium supplements that have passed our tests of quality.
ConsumerLab.com Answers
Question:
Are the "% DV" numbers on vitamin supplement labels really based on what I need?
Answer:
Yes and no. The most current DVs (Daily Values), updated by the FDA in 2016, do accurately reflect the basic daily intake requirements for vitamins and minerals. However, companies are not required to use the updated DVs on product labels until at least 2020. In the meantime, many vitamin and supplement labels will be misleading — providing "%DV" values based on terribly out-dated DVs establish in the 1960s. The new DVs include separate values for infants, very young children, and women who are pregnant and lactating.
Some important changes in 2016 to the DVs for most adults and children over age 4 include the following. (Keep in mind that your supplement label is most likely still based on old DVs):
- Vitamin D: The DV doubled, from 400 IU (10 mcg) to 800 IU (20 mcg). (Note: Many people who are not deficient in vitamin D may already be taking too much.) Labels will also have to list vitamin D in different units (mcg), but can include the familiar IU (international units) values (1 mcg = 40 IU).
- Folate: Recognizing that about 70% more folate is absorbed from supplements containing folic acid (synthetic folate) than from foods naturally containing folate, the DV (which remains at 400 mcg) is now based on "dietary folate equivalents," shown as "DFE". A supplement with 400 mcg of folic acid is to be labeled as providing 170% DV rather than 100% DV.
- Vitamin B-12: The DV decreased from 6 mcg to 2.5 mcg
- Biotin: The DV decreased from 300 mcg to 30 mcg
- Niacin: The DV decreased from 20 mg to 16 mg
- Chromium: The DV decreased from 120 mcg to 35 mcg
- Vitamin C: The DV increased from 60 mg to 90 mg.
- A DV for choline has been established the first time, at 550 mg.
For more about these changes, see "ConsumerLab.com Helps Consumers Make Sense of the FDA's Updated Daily Values (DV) for Vitamins and Minerals."
ConsumerLab.com lists the new DVs (as well as RDAs and Upper Tolerable Intake Levels (ULs)) for each vitamin and mineral at www.consumerlab.com/rdas.
You'll find further information about each nutrient within our Product Reviews, including our tests, reviews, ratings, and comparisons of products.
ConsumerLab.com Answers
Question:
Are there any supplements I should avoid when taking an antibiotic? Are there any that may be helpful?
Answer:
Antibiotics can be affected by the supplements you take, and they can affect your ability to absorb certain vitamins and minerals.
The interactions will depend on the type of antibiotic you are taking. You can search for the specific antibiotic you are taking by name in the Drug Interactions section of our ConsumerLab.com.
Some of the most common antibiotics are listed below, followed by the supplements with which they can interact. Use the links for more details:
Amoxicillin (Amoxil, Trimox, Wymox): Bromelain, vitamin K
Cephalosporins (cephalexin (Cefanex, Keflex, Keftab, Biocef), cefdinir (Omnicef), etc.): Vitamin K
Fluoroquinolones (ciprofloxacin (Cipro), levofloxacin (Levaquin)): Calcium, magnesium, iron and zinc, fennel, Dong Quai, St. John's Wort
Tetracyclines (doxycycline (Bio-Tab, Doryx, Doxy-Caps), tetracycline hydrochloride (Achromycin V, Panmycin etc.): Calcium, magnesium, iron and zinc, Dong Quai, St. John's Wort, citrate (i.e. potassium citrate)
Trimethoprim/sulfamethoxazole (Bactrim, Cotrim, Septra, Sulfatrim): Folate, PABA (para-aminobenzoic acid), potassium, white willow, St. John's wort
Interestingly, some of the supplements noted above (folate and vitamin K) may, at times, be helpful when taking certain antibiotics, as can probiotics.
ConsumerLab.com Answers
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 concern when 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.
See these related CL Answers:
What is Skinny Fiber and does it really work? I see that glucomannan is a key ingredient. What is that? >>
Can curcumin with black pepper extract cause constipation? I had this problem when taking a curcumin formula with piperine, but it resolved when I switched to a curcumin supplement without this added ingredient. >>
Do any supplements help for irritable bowel syndrome (IBS)? >>
Can psyllium help control hunger and appetite? >>
Is it possible to get too much vitamin D? >>
ConsumerLab.com Answers
Question:
Which supplements can cause diarrhea?
Answer:
There are a number of supplements which can cause diarrhea. Discussed below are some of the most common culprits. Diarrhea can also be caused by certain medications, illness and infection, and certain health conditions, such as irritable bowel syndrome (IBS) and lactose intolerance -- so be sure to consult with your physician if you experience severe or chronic diarrhea.
Supplements with a laxative effect:
Magnesium supplements can cause diarrhea and, in fact, are often taken for their laxative effect. However, if you are taking magnesium for other reasons, and want to avoid this effect, certain forms of magnesium are less likely to cause diarrhea. Taking your magnesium supplement with food can also reduce the occurrence of diarrhea.
Aloe supplements containing latex are also known for their laxative effect. If you are taking aloe for a different purpose, be sure to choose a product labeled as aloe gel or vera leaf juice which has been processed to remove the latex.
Be aware that many weight loss supplements contain herbs with laxative properties, such as cascara, frangula, rhubarb root and senna, so be sure to carefully read the label if you are taking a supplement for weight management or "cleansing", such as certain acai supplements and drinks.
Certain types of fiber can also have a laxative effect, but do not necessarily cause diarrhea — some forms of fiber, in fact, may be helpful for diarrhea associated with IBS.
Other common supplements that can cause diarrhea:
Fish oil and other supplements containing omega-3 fatty acids, or a combination of omega-3 and omega-6 fatty acids, such as flaxseed oil and borage oil, can cause diarrhea. Taking smaller doses throughout the day, rather than a single, large dose, may help reduce this effect.
Taking large doses of vitamin C can cause diarrhea. Other supplements which can cause diarrhea when taken in high doses include ashwagandha, NAC (N-acetyl-cysteine), lysine, iodine and kelp supplements which contain iodine, D-limonene, and yacon syrup.
Other supplements which can cause diarrhea include curcumin/turmeric, St. John's wort, berberine, creatine, 5-HTP, nattokinase, chlorella, modified citrus pectin (MCP), and beta-sitosterol, a common ingredient in cholesterol-lowering supplements and prostate supplements.
Unexpected sources:
An often-over-looked cause of diarrhea from supplements can be from added sugar substitutes such as sorbitol. Sorbitol can be found in protein and nutrition bars (ConsumerLab.com lists amounts of sugar alcohols (such as sorbitol and mannitol) in popular bars in its Review) and some protein powders and drinks and meal replacement and weight management meals and shakes. These chemicals can also be found in certain zinc lozenges and some B12 supplements, especially dissolvable tablets, liquids and sprays, although occasionally in regular tablets as well.
ConsumerLab.com Answers
Question:
Are there drug interactions with magnesium supplements?
Answer:
Magnesium can decrease the absorption and effectiveness of a number of medications, including several common antibiotics, certain statin drugs, and a drug prescribed for atrial fibrillation. On the other hand, one form of magnesium may increase the absorption of certain anti-diabetes drugs, potentially affecting blood sugar control. In some cases, magnesium can still be taken, but only several hours before or after taking these drugs.
Be aware that these interactions apply not only to magnesium in supplements but also in over-the-counter antacids and laxatives.
In addition, certain medications can deplete levels of magnesium in the body, or interfere with magnesium's laxative effects.
For details, see the Cautions and Concerns section of the Magnesium Supplements Review >>
ConsumerLab.com Answers
Question:
Do any supplements help for restless legs syndrome?
Answer:
Although no large studies have been conducted, smaller studies suggest a possible role of supplements in reducing the symptoms of restless legs syndrome (RLS), a condition that causes uncomfortable "creepy-crawly" sensations, agitation, and the need to move the legs when trying to fall asleep. Women are twice as likely to suffer from restless legs syndrome than men, and it occurs more often with increasing age (Wang, Sleep Med 2009).
People with deficient or low blood levels of iron are also more likely to experience RLS. As discussed in more detail in the "What It Does" section of the Iron Supplements Review, a study found that taking a combination of high-dose iron and vitamin C (which helps to increase iron absorption) can decrease symptom severity in people whose blood levels of iron are low. However, it's important to consult your physician before supplementing with iron for RLS.
As discussed in the "What It Does" section of the Magnesium Supplements Review, a preliminary study suggested that taking magnesium in the evening could be helpful for RLS; however, there have not been large, well-controlled studies investigating this treatment.
Similarly, as discussed in the "What It Does" section of the Potassium Supplements Review, one preliminary study suggested that potassium may help reduce the severity of RLS symptoms, but no well-controlled studies have been conducted to prove this.
As discussed in our Encyclopedia article about Restless Legs Syndrome, there is very preliminary evidence that folate and vitamin E might be helpful. Be aware that caffeine, alcohol, SSRI antidepressants, antihistamines, and most antipsychotic and antinausea medications can potentially increase RLS symptoms (Cotter, Ther Clin Risk Manag 2006).
Also be aware that RLS can occur as a result of kidney or liver disease. People with these conditions should consult with a healthcare professional before taking supplements (Cotter, Ther Clin Risk Manag 2006; Franco, J Clin Sleep Med 2008).
ConsumerLab.com Answers
Question:
Is it true that I should not keep magnesium supplements in a daily pill pack mixed with other supplements and medicines?
Answer:
If you are using magnesium chloride, it should be kept in a well-sealed container away from all types of other pills, as explained in the ConsumerTips section of Magnesium Supplements Review >>
ConsumerLab.com Answers
Question:
Do any supplements help for ulcerative colitis?
Answer:
Several types of supplements, when taken along with standard treatment, may help to reduce the severity of symptoms of ulcerative colitis and/or promote remission.
These include curcumin, a form of glucosamine called N-acetyl-glucosamine (NAG), Boswellia, and phosphatidylcholine. (You can use these links for more details, including dosage).
Although there is some evidence that a specific probiotic formula may be helpful, overall, there doesn't appear to be strong evidence to support the use of probiotics for ulcerative colitis.
There is some very preliminary evidence that supplementation with aloe vera gel or bromelain may be helpful.
Reducing or eliminating carrageenan (a substance used to thicken and improve the texture of certain foods and supplements ) from the diet may also helpful.
Be aware that ulcerative colitis may make some people more prone to deficiencies in minerals such as magnesium and selenium.
For information about other proposed treatments, including fish oil, evening primrose oil, andrographis and wheat grass, see the Encyclopedia article about Ulcerative Colitis.
ConsumerLab.com Answers
Question:
Does taking a laxative interfere with the absorption of vitamins or minerals?
Answer:
Some laxatives can interfere with the absorption of particular vitamins or minerals, potentially causing vitamin deficiencies or electrolyte imbalances if taken for prolonged periods of time Short-term and occasional use should not cause an issue. Get the details for specific laxatives, such as mineral oil, magnesium, psyllium, oat bran, fiber, bisocodyl, senna, lactulose, and polyethylene glycol >>
ConsumerLab.com Answers
Question:
Do any supplements help reduce the symptoms of premenstrual syndrome (PMS)?
Answer:
There is fairly good evidence that calcium supplements can significantly reduce the major symptoms of PMS, such as mood swings, pain, bloating, irritability, depression, back pain, and food cravings. There is also some evidence that magnesium, vitamin E, Gingko biloba, royal jelly, and chasteberry, may be helpful for reducing symptoms of PMS.
The evidence is mixed on whether or not other supplements which are commonly promoted for PMS, such as vitamin B6 and evening primrose oil, are helpful.
More about the evidence for these supplements, dosage, and information about other proposed treatments, is found in the Encyclopedia article about Premenstrual Syndrome.
In addition, be aware that women with a high intake of iron from certain sources have been shown to have a lower risk of suffering PMS than those with lower intakes -- while high intakes of potassium have been associated with an increased risk of PMS.
See these related CL Answers:
Will pregnenolone help slow down aging?
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Product Review: Magnesium and Calcium-Magnesium Supplements Review |
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Initial Posting: 6/3/17 Last Update: 3/20/18
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Choosing the Right Magnesium SupplementHow to Choose the Best Magnesium Supplement? ConsumerLab Reveals Its Top Picks
Tests and Reviews of 40+ Popular Supplements, Including Combinations with Calcium, Vitamin D and Vitamin K
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Magnesium supplements are available in so many different forms, dosages and ingredient combinations, how do you know which one is best for you?
To answer these questions, ConsumerLab.com staff spent several months testing of over 40 popular magnesium supplements on the market (including combination products with calcium, vitamin D or vitamin K). Our tests revealed that several contained less magnesium than claimed, took longer than normally expected to break apart in disintegration testing, were contaminated with lead, or were improperly labeled. We also found that one type of magnesium supplement rapidly absorbs so much water from the air that it damages tablets and other supplements which may be nearby.
Fortunately, we also identified many high quality magnesium supplements that contained what they claimed and passed all of CL's tests — some of which provide a good dose of magnesium for just a few cents per day.
You must become a ConsumerLab.com member to get the full test results for magnesium supplements, including quality ratings and CL's Top Picks among magnesium supplements. You will get results for 45 magnesium supplements: 27 selected for testing by ConsumerLab.com and 18 others that passed the same tests through CL's voluntary Quality Certification Program, as well as information about five supplements similar to ones that passed testing.
Although most people get enough magnesium in their diets, people with diabetes, diseases of the digestive tract, and those who use medications such as Nexium and Prilosec may be at increased risk of deficiency. Magnesium supplementation may also improve glucose status in people with pre-diabetes, and may be helpful for restless leg syndrome, migraines and menstrual pain. It is also an effective laxative and antacid. However, it's important to choose supplements carefully based on your needs, as certain forms of magnesium forms are better absorbed than others or are more likely to cause diarrhea.
In this comprehensive report, you'll discover:
- Which magnesium failed our quality ratings and which passed — including combinations with calcium, vitamin D and vitamin K
- CL's Top Picks among the best magnesium supplements
- Cost comparisons to help you choose a magnesium supplement offering the best value
- The pros and cons of different forms of magnesium, including magnesium aspartate and orotate, magnesium citrate, magnesium chloride, magnesium lactate and lactate dihydrate, magnesium oxide and magnesium-L-threonate
- How to get adequate magnesium from food
- The causes and symptoms of magnesium deficiency
- How much magnesium to take to treat or prevent magnesium deficiency and other conditions/li>
- The evidence for and against using magnesium supplements for restless leg syndrome, leg cramps, migraines and more
- Potential drug interactions and side-effects of magnesium supplements
Learn More About Magnesium SupplementsQuestion:
Some websites are highly critical of magnesium stearate, which is in many supplements. Is this substance toxic and should I avoid it? 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:
What is the benefit of magnesium orotate compared to other forms of magnesium? Get the answer >>
Question:
Are supplements with amino acid chelated minerals better than those with other forms of minerals? Get the answer >>
Question:
Are enteric coated supplements better than non-enteric coated ones? Get the answer >>
Question:
Do magnesium supplements, like Magtein, help memory or protect against Alzheimer's disease? Get the answer >>
Question:
Can taking certain forms of potassium, such as potassium citrate, reduce my chances of getting kidney stones? I've read a study that says it can, but it's unclear how much I should take. Get the answer >>
Question:
Do any supplements help with migraines? Get the answer >>
Question:
I have low blood pressure. Are there any supplements I should avoid? Get the answer >>
Question:
Which is the best form of magnesium to take - one that contains the most magnesium and is best absorbed? Get the answer >>
Question:
How can the Recommended Daily Allowance (RDA) for magnesium be higher than the Upper Tolerable Intake Level (UL)? That is, how can an amount which is healthful also put you at risk for harm? Get the answer >>
Question:
Is it important to take calcium and magnesium together? Get the answer >>
Question:
Do any supplements help for irritable bowel syndrome (IBS)? 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:
Help! How do I know how much magnesium I am actually getting from my supplement? The label says it contains 500 mg of magnesium "as magnesium citrate" -- but how much of that is magnesium and how much is citrate? Get the answer >>
Question:
Which supplements reduce the risk of stroke? Which increase the risk of stroke? Get the answer >>
Question:
Which supplements can help with indigestion and/or heartburn? Get the answer >>
Question:
How do I choose the best magnesium supplement? Get the answer >>
Question:
Will an Epsom salt bath increase magnesium levels in my body like a supplement? Get the answer >>
Question:
What is Prelief? Does it really help for heartburn and/or bladder pain from acidic foods? Get the answer >>
Question:
Is there an accurate test for magnesium deficiency? Get the answer >>
Question:
I've read that magnesium deficiency is rare but also that most people don't get enough magnesium. How can these both be true? Get the answer >>
Question:
Do magnesium creams, sprays and oils really work? 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 >>
Question:
Which supplements can help treat constipation? Get the answer >>
Question:
Which supplements can cause diarrhea? Get the answer >>
Question:
Are there drug interactions with magnesium supplements? Get the answer >>
Question:
Do any supplements help for restless legs syndrome? Get the answer >>
Question:
Is it true that I should not keep magnesium supplements in a daily pill pack mixed with other supplements and medicines? Get the answer >>
Question:
Do any supplements help for ulcerative colitis? Get the answer >>
Question:
Does taking a laxative interfere with the absorption of vitamins or minerals? Get the answer >>
Question:
Do any supplements help reduce the symptoms of premenstrual syndrome (PMS)? Get the answer >>
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Update:
(7/11/17): A company selling one of the products covered in this Review was recently sent a Warning Letter from FDA indicating that the product is being marketed online with claims regarding its ability to cure, prevent, or treat diseases, and this is not permitted for a supplement. For details, see the "Update" at the top of the full Review.
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