Multi dilemma: should you take one?
That might have come as a surprise to those who saw this headline in the Times the previous October: "Multivitamin Use Linked to Lowered Cancer Risk."
Millions of Americans take a multivitamin every day. To most people, a multi is insurance against a less-than-perfect diet.
Are they helping or hurting themselves?
"Breast health," "heart health," "immune health," says Target's Up & Up Women's Daily Multivitamin. "Energy support," "prostate health," "fights cell aging," says GNC Mega Men.
Sounds like taking a multi may lower your risk of cancer, heart disease, stroke, and more. Yet a handful of headlines have made multivitamins sound dangerous.
In fact, few studies have found that a multi can lower or raise the risk of disease. But they may be worth taking anyway.
A SHORTER LIFE?
When an Op Ed last June in The New York Times warned readers, "Don't Take Your Vitamins," it wasn't referring to multivitamins like Centrum or One A Day. Instead, Philadelphia physician Paul Offit cautioned that high doses of antioxidants like vitamin E and beta-carotene could raise the risk of cancer and heart disease.
"I think multivitamins don't hurt you," Offit told CNN, though he added that he didn't believe people needed a multi.
The Mayo Clinic had a different take. In a large study of older Midwestern women, noted Mayo's column in the Chicago Tribune in January, "taking a multivitamin appeared to increase risk of premature death."
In the Iowa Women's Health Study, those who reported taking a daily multivitamin were 6 percent more likely to die over a 19-year period than those who said that they didn't take a multi. (1)
"You want to be very careful in interpreting the results from observational studies," cautions Eric Jacobs, an epidemiologist at the American Cancer Society in Atlanta.
An observational study watches people. In the Iowa Women's Health Study, for example, researchers gave the women a questionnaire asking what they ate, how often they exercised, what supplements they took, and more. Then the researchers waited for 19 years to see which women got which diseases or died.
But an observational study can't tell whether taking a multi caused any illness or death. Those who chose to take a multivitamin may have differed in some way from those who didn't take a multi.
"Sometimes people start taking multivitamins because they feel sick or low in energy," notes Jacobs. "They may be more likely to die prematurely for reasons unrelated to their multivitamin use."
Or the opposite can happen. "Multivitamin users tend to have healthier lifestyles," says Jacobs. "So if they have a lower risk of disease, that may be the reason, not their multivitamin use."
To get at cause and effect, researchers randomly assign people to take either a multivitamin or a look alike but inactive placebo. Since all the people are drawn from the same pool, the only difference between the groups in a randomized controlled trial is that one is taking a multi and one isn't.
"Randomized controlled trials are a better way of judging the impact of taking a multivitamin," says Jacobs.
In the largest and longest randomized controlled trial of multivitamins, the Physicians' Health Study II, more than 14,000 men took either Centrum Silver (a basic multivitamin-and-mineral for people 50 and older) or a placebo every day for 11 years. (2,3)
"The risk of dying was not significantly different between men taking multivitamins versus men taking the placebo," says Harvard epidemiologist Howard Sesso, who led the study.
A LOWER RISK OF DISEASE?
Will a multivitamin cut your risk of disease? For heart disease and stroke, the answer appears to be no.
"In the Physicians' Health Study II, we found no evidence overall that taking a multi for more than a decade prevented heart attacks or strokes any more than taking a placebo," says Sesso. "But it didn't increase risk, either."
That's consistent with the results of most observational studies. In the Multiethnic Cohort Study and the Women's Health Initiative cohort, for example, people who said that they took a multivitamin were no more or less likely to suffer a heart attack or stroke than those who said that they didn't take one. (4,5) Nor did they have a lower or higher risk of cancer.
That's why the Physicians' Health Study II made big news last year.
"Men taking a multivitamin were 8 percent less likely than men taking a placebo to be diagnosed with a cancer," says Sesso.
About half of the cancers diagnosed during the 11-year study were of the prostate, almost all of them the indolent, slow-growing kind that don't necessarily need treatment (see Nutrition Action, Sept. 2013, cover story). Taking a multi had no impact on them.
And the lower risk for other kinds of cancer wasn't statistically significant for any specific cancer.
"That may have been primarily because there weren't enough cases to detect significant differences," says Sesso. (A study may not have enough power to see a statistically significant difference if only a small number of people are diagnosed with, say, bladder or colorectal cancer.)
But it's also possible that the lower risk of cancer in multi takers was due to chance.
"The fact that there wasn't a clear reduction in risk for any specific cancer raises a question about whether multivitamins had an impact at all," says the American Cancer Society's Eric Jacobs.
How might a multivitamin prevent cancer? "It may mimic the dietary patterns we try to recommend, such as an increased intake of fruits and vegetables that are rich in a variety of nutrients," says Sesso.
And that raises the question: Is it worth taking a multivitamin to make up for what we don't get from our diets?
"We know that even people who make a concerted effort to add more nutrient-dense foods to their diets still might not be meeting their nutrient requirements," says Diane McKay, an assistant professor at the Friedman School of Nutrition Science and Policy at Tufts University in Boston.
In 2000, in a study sponsored by a California supplement company, McKay and her colleagues randomly assigned 80 healthy, well-nourished adults who were living in the Boston area to take either a standard multi or a placebo for two months. (6)
"Even in these healthy people, we found a significant boost in the blood levels of certain nutrients up to levels that are associated with a lower risk of disease," says McKay.
The percentage of multi takers with suboptimal vitamin D levels, for example, dropped from 7 percent to 0 percent, and the percentage with suboptimal vitamin B-12 fell from 42 percent to 27 percent.
McKay's bottom line: "Taking a multivitamin formulated at about 100 percent of the Daily Value for vitamins and minerals can be a pretty convenient and cost-effective way of filling in the gaps that may exist between what you need and what you're actually consuming."
In 2010, the U.S. Dietary Guidelines Advisory Committee identified seven "shortfall nutrients of public health concern": vitamin B-12, vitamin D, folic acid, iron, calcium, potassium, and fiber.
Multivitamins aren't a good source of fiber, potassium, or calcium, which are too bulky to fit into a multi. But a multivitamin can provide close to--or all of--a day's worth of the other four.
* Iron. From 7 to 16 percent of women aged 12 to 49 are iron deficient. Many multis contain the Daily Value (18 milligrams), which is the recommended level for premenopausal women. Men and postmenopausal women need only about 8 to 10 mg.
* Vitamin B-12. Adults 50 years and older should get the Recommended Dietary Allowance (2.4 micrograms) mainly from fortified foods or a supplement, says the Institute of Medicine.
That's because an estimated 10 to 30 percent of older adults don't make enough stomach acid to separate the B-12 from protein in foods. You don't need stomach acid to absorb the B-12 in supplements and fortified foods because it isn't bound to protein.
Vegans (who eat no dairy, eggs, seafood, poultry, or meat) should also get B-12 from a multi or fortified food because plant foods have no B-12. A vitamin B-12 deficiency can lead to irreversible nerve damage and dementia.
* Vitamin D. "Our body's ability to convert sunlight into active vitamin D declines as we get older," notes Tufts University's McKay. And in the winter, sunlight lacks the UV rays that make vitamin D unless you live as far south as Atlanta or Los Angeles. That and the fact that few foods are rich in vitamin D means that many people have less-than-optimal blood levels.
The Institute of Medicine recommends 600 IU a day of vitamin D for adults up to age 70 and 800 IU for those over 70. Most multivitamins have at least 400 IU.
Scientists are still investigating whether vitamin D may lower the risk of cancer, heart disease, stroke, diabetes, memory loss, depression, and more.
* Folic Acid. Folate is a B vitamin that helps cells grow and divide. Folic acid is the form of folate that's added to foods and supplements. Women need the vitamin early in their pregnancy--often before they know that they're pregnant--to reduce the risk of spina bifida and other neural tube defects. (The incidence of spina bifida has dropped by 31 percent since 1998, when the Food and Drug Administration started requiring companies to add folic acid to most breads, pasta, rice, cereals, and other grains.)
But some researchers worry that too much folic acid from supplements, grains, and fortified breakfast cereals may harm people who unknowingly harbor precancerous or cancerous cells in their body.
"If you've done studies in cells and in animals, as I have, you know that consuming too much folic acid can enhance the development of cancer," says Joel Mason, director of the Vitamins and Carcinogenesis Laboratory at the Human Nutrition Research Center on Aging at Tufts University.
"If you think about the role folate plays in the cell, helping to synthesize new cells, this makes eminent sense."
But a meta-analysis published earlier this year eased some of the fear. In 13 randomized controlled trials that included 50,000 people, those who took an average of 2,000 micrograms of folic acid every day for five years had no higher risk of any kind of cancer than those who got a placebo. (7) Most multivitamins have only one-fifth that much (400 meg).
Mason is still uneasy. "It typically takes eight to 12 years for a tiny precancerous bump in your colon to fully evolve into a true cancer," he says. "So it's possible that the trials weren't long enough to see the effects of folic acid on cancer risk."
Still, "the good news is that if folic acid does increase the risk of cancer, you'd have to take a fair bit for that to happen," notes Mason. "It's probably safe to take the folic acid in a single multivitamin each day."
The Institute of Medicine says that 1.000 micrograms of folic acid a day is the highest safe level adults can consume, because more than that can cover up a vitamin B-12 deficiency.
Americans get an average of about 270 meg a day of folic acid from fortified grains (bread, pasta, rice, etc.) and breakfast cereals. But that average includes people who eat a cereal like Kellogg's Raisin Bran, which has 100 meg of folic acid (the label says "25% DV") in every cup and those who eat All-Bran, which has 400 meg ("100% DV" on the label) in every half cup.
"If you took a multivitamin in the morning, a B complex in the afternoon, and ate cereals and energy bars fortified with folic acid, you could exceed 1.000 micrograms of folic acid a day," says Mason. "That could mask a B-12 deficiency and possibly increase cancer risk."
The Best Multi List
Here's a selection of multivitamins from some major brands that meet our criteria, plus a few that just miss for reasons that don't matter (see footnotes). If yours isn't on the list, don't panic; we didn't look at every multi. You can check any label against our "What Your Multi Should Contain" list.
Men & Postmenopausal Women
Centrum Men Under 50 * (1)
Centrum Silver Adults 50+
Centrum Silver Men 50+
CVS Daily Multiple Tablets for Men
CVS Spectravite Adult 50+ Multivitamin
Equate Complete Multivitamin Adults 50+
Equate Complete Multivitamin Men's 50+
Equate Complete Multivitamin Women's 50+ *
Equate One Daily Men's Health
Nature Made Multi for Her 50+
Nature Made Multi for Him
Nature Made Multi for Him 50+
Nature's Bounty ABC Plus Senior
Nutrilite Daily Multivitamin Multimineral *
One A Day Men's 50+ Healthy Advantage (2)
One A Day Men's Health Formula
One A Day Women's 50+ Healthy Advantage (2)
Target Up & Up Adults' Multivitamins
Walgreens A thru Z Select Multivitamin
* Contains 6 or 8 mg of iron (other multis in the list have no iron).
(1) Contains 1.3 mg of riboflavin.
(2) Contains 117 meg of selenium
Centrum Adults Under 50
CVS Daily Multiple Tablets for Women
CVS Spectravite Ultra Women's Multivitamin (1)
Equate Complete Multivitamin Adults Under 50
Equate One Daily Women's Health (2)
Kirkland Signature Daily Multi
Nature Made Multi Complete
Nature's Bounty ABC Plus
Nature's Bounty Multi-Day Plus Minerals
Nature's Bounty Multi-Day Women's (2)
One A Day Women's
Sundown Advanced Formula SunVite
Sundown Naturals Complete Daily with Iron
Target Up & Up Multivitamin
Target Up & Up Women's Daily Multivitamin (2)
Walgreens One Daily for Women (2)
(1) Contains 25 meg of chromium.
(2) Contains 10 mg of niacin.
Not So Smart
If Smarty Pants gummy multivitamins are so smart, why are they called "complete" when they're missing so many nutrients? And why is the central ingredient in the Smarty Pants Weight Management gummy something that's been shown not to help people lose weight?
One day's dose of Smarty Pants Adult Complete--6 gummies, costing about $1--has two teaspoons of sugar and 50 calories but no vitamin B-2, vitamin K, selenium, chromium, iron, copper, magnesium, or calcium. And its 128 milligrams of the omega-3 fish oils DHA and EPA is what you'd get in about a tablespoon of salmon. Wow!
Smarty Pants Weight Management Complete gummies (6 a day, for about $1.50 and also less than complete) feature 6 grams of inulin, "to create a feeling of fullness, promote digestive health and regularity." Yet in two studies, people who took 12 grams of inulin every day for one to three months felt no fuller, ate no less food, and lost no more weight than similar people who took a placebo. (1,2)
Looks like Smarty Pants could use some remedial education.
(1) Br. J. Nutr. 78: 215,1997. (2) Nutrition J. 11: 44, 2012.
* It's worth taking a multivitamin if it supplies nutrients--like vitamins D and B-12--that you may not be getting enough of from your food.
* Don't count on a multi to "support" your heart, breast, immune system, skin, colon, brain, or anything else.
* You don't need to pay more than $5 a month for a high-quality multi.
HOW TO READ A MULTIVITAMIN LABEL
This made-up multivitamin label shows how much of each vitamin and mineral we need to get every day (from foods and supplements combined), according to the National Academy of Sciences' Institute of Medicine (IOM). The IOM's Recommended Dietary Allowances (RDAs) vary slightly by age and gender. In most cases, we picked the highest level for adults, excluding pregnant and breastfeeding women. Multivitamin labels list the Daily Value (DV) for each nutrient, not the RDA. Some of the DVs are outdated.
VITAMIN A. Most multivitamins contain some combination of retinol (vitamin A) and beta-carotene (which our bodies convert to retinol). The outdated DV for vitamin A--5,000 IU from retinol and beta-carotene combined--is higher than the RDAs: 3,000 IU for men and 2,310 IU for women. High doses of beta-carotene (25,000 to 50,000 IU) increase the risk of lung cancer in smokers and, possibly, former smokers. (Beta-carotene from carrots and other foods is safe.) Too much retinol from supplements (10,000 IU or more) can cause birth defects in pregnant women. Look for a multi with no more than 5,000 IU of vitamin A (any combination of retinol and beta-carotene).
VITAMIN D. It helps prevent falls in older people and helps keep bones strong. A large trial is testing whether vitamin D prevents cancer, heart disease, stroke, diabetes, memory loss, depression, and more. Our bodies make vitamin D from the sun's UV rays. A few foods (like salmon and tuna) contain D, which is added to others (like milk, breakfast cereals, and yogurt). Most multivitamins contain the outdated DV (400 IU), but the IOM recommends that adults get 600 IU a day (800 IU for those over 70). More than 4,000 IU a day may lead to dangerously high blood levels of calcium.
THIAMIN (B-1), RIBOFLAVIN (B-2), NIACIN (B-3), B-6. Don't expect them to make you energetic, but higher-than-DV levels are safe. Exceptions: taking 50 mg of niacin can cause flushing of the skin, and more than 100 mg of B-6 can cause (reversible) nerve damage and skin lesions.
VITAMIN B-12. People over 50 should get at least 2.4 micrograms a day of B-12 from supplements or fortified foods because they may not make enough stomach acid to absorb B-12 from meats, eggs, and dairy foods. Vegans (who eat no meat, dairy, or eggs) also need a supplement or fortified foods. A B-12 deficiency can cause anemia, dementia, and irreversible nerve damage. Most multivitamins contain the DV (6 meg). Doses up to 1,000 or 2,000 meg are safe.
BIOTIN, PANTOTHENIC ACID. Ignore. We get enough from our food.
IRON. Premenopausal women, who lose iron through menstruation, should get the DV (18 milligrams). High levels of iron stored in the body may increase the risk of heart disease, some cancers, and type 2 diabetes, though the evidence for all three is weak. To be safe, men and postmenopausal women should look for a multivitamin with no more than 10 mg of iron.
MAGNESIUM. About half of Americans get less magnesium than the IOM recommends. Low intakes may raise the risk of high blood pressure and diabetes. Taking more than 350 milligrams from supplements can cause diarrhea and stomach cramping. Nuts and whole grains are good sources, but you're best off loading up on leafy greens.
SELENIUM . The RDA is 55 micrograms, but Americans average twice that much from their food. I Taking a supplement with 200 meg or more may increase the risk of type 2 diabetes, so look for a multivitamin with no more than about 100 meg.
CHROMIUM. Men need 30 to 35 micrograms a day, and women need 20 to 25 meg. Taking up to the DV (120 meg) is safe, but most multivitamins have less.
IODINE, MANGANESE, MOLYBDENUM, CHLORIDE, BORON . The Centers for Disease Control and Prevention says that many women aged 20 to 39 may not get enough iodine, which the developing brain needs during pregnancy. Everyone should aim for the DV (150 micrograms). Dairy foods and seafood are good sources. We get plenty of the other minerals from our food.
NICKEL, SILICON, TIN, VANADIUM. Ignore. It's not clear that we need them.
RDA. The Recommended Dietary Allowance is the Institute of Medicine's recommendation for how much we should get every day (from food and supplements combined). The numbers shown here are for the adult group with the highest RDA, excluding pregnant and breastfeeding women. The RDAs, which don't appear on supplement (or food) labels, are more up to date than the DVs.
DV. The Daily Value for each vitamin and mineral is set by the Food and Drug Administration. Some DVs are outdated and don't reflect the latest recommendations (RDAs) from the Institute of Medicine. The DVs appear on supplement (and food) labels.
VITAMIN C. The outdated DV (60 milligrams) is lower than the RDA (90 mg a day for men and 75 mg for women). Smokers need an extra 35 mg. Most people get enough vitamin C from their diet. Taking more than 1,000 mg at one time can cause diarrhea.
VITAMIN E. Vitamin E supplements don't prevent heart attacks or strokes, and in a large trial, men who took 400 IU a day for 51/2 years had a slightly higher risk of prostate cancer. Most multivitamins contain the DV (30 IU). To play it safe, look for a multi with no more than 100 IU. Good sources include nuts, oils, whole grains, and leafy greens.
VITAMIN K. The IOM recommends 120 micrograms a day for men and 90 meg for women. Most multivitamins have less than the DV (80 meg), since vitamin K can interfere with blood-thinning drugs like warfarin (Coumadin). Look for a multi with 10 meg or more. If you're taking a blood thinner, check with your doctor before you start (or stop) taking a multivitamin with vitamin K. Leafy greens are the best source.
FOLIC ACID. Women who could become pregnant need 400 micrograms a day (the DV) to reduce the risk of birth defects like spina bifida. Too much folic acid can mask a vitamin B-12 deficiency, so look for a multivitamin with no more than 400 meg. If the serving of breakfast cereal you typically eat has 400 meg or more, consider taking your multi every other day. Nutrition Facts labels list folic acid as a percentage of the Daily Value ("%DV"), so you may have to do a little math.
CALCIUM. It helps keep bones strong and may help prevent colon cancer. Calcium is bulky, so multivitamins usually contain far less than the DV (1,000 milligrams). If you don't get enough calcium from milk, yogurt, cheese, or fortified foods, consider taking a calcium supplement. Pre-menopausal women and men up to age 70 need 1,000 mg a day (from food and supplements combined), while postmenopausal women and men over 70 need 1,200 mg. Taking a daily supplement with 1,000 mg or more of calcium may raise the risk of constipation and kidney stones.
PHOSPHORUS. A multivitamin won't have much, but most people get enough from their food. More than 4,000 milligrams of phosphorus a day can pull calcium out of bones.
ZINC, COPPER. Most multivitamins contain the DV for zinc (15 milligrams), but some have more. Too much zinc (more than 40 mg) can make it harder to absorb copper. That includes zinc from foods (like meat, poultry, seafood, dairy, and beans). In a large trial, people who took 80 mg of zinc a day for five years had a higher risk of urinary tract infections, an enlarged prostate, or (in women) stress incontinence. Look for a multi with no more than 30 mg of zinc and with 0.5 to 10 mg of copper.
POTASSIUM. Less than 2 percent of American adults get the recommended amount of potassium (4,700 milligrams a day), which can help lower blood pressure. Don't count on a multi for help. They don't contain much. And the potassium chloride in supplements won't help prevent kidney stones and bone loss like the potassium citrate in fruits and vegetables.
(1) Arch, intern. Med. 171:1625, 2011.
(2) JAMA 308:1871,2012.
(3) JAMA 308:1751, 2012.
(4) Am. J. Epidemiol. 173: 906, 2011.
(5) Arch. Intern. Med. 169: 294, 2009.
(6) J. Am. Coll. Nutr. 19: 613, 2000.
(7) Lancet 381:1029, 2013.
What Your MULTI Should Contain Vitamin A No more than 5.000 IU (including any % as beta-carotene) Vitamin C 60-1,000 mg Vitamin D 400 IU or more Vitamin E 20-100 IU Vitamin K 10 meg or more Thiamin (B-1) 1.2 mg or more Riboflavin (B-2) 1.7 mg or more Niacin (B-3) 14-35 mg Vitamin B-6 2-100 mg Folic Acid No more than 400 mcg Vitamin B-12 6 mcg or more Calcium Don't rely on a multi (1) Iron Premenopausal women 18 mg Everyone else No more than 10 mg Magnesium 50-350 mg Zinc No more than 30 mg Copper 0.5-10 mg Selenium 20-110 mcg Chromium 35 mcg or more Potassium Don't rely on a multi (1) Men: Your multi should have no more than around 250 mg of calcium. Note: "Or more" doesn't mean that a nutrient is safe at any dose, but that levels in multivitamins are unlikely to be high enough to cause harm.
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|Title Annotation:||COVER STORY|
|Author:||Schardt, David; Scarmo, Stephanie|
|Publication:||Nutrition Action Healthletter|
|Date:||Nov 1, 2013|
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