An estimated one-third of American adults and one-fourth of children and adolescents take multivitamins, with combined US sales of $8 billion in 2020, according to the National Institutes of Health’s Office of Dietary Supplements.
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Some experts believe that a nutritious, balanced diet should be enough for many people. “I’m a big believer in whole foods,” says Donald D. Hensrud, associate professor of nutrition and preventive medicine at the Mayo Clinic College of Medicine. “I’m focused on helping my patients eat healthily.”
But other experts say it’s more complicated because people often need more vitamins at certain stages of life or have health conditions that make it difficult to get vitamins from food. Some also need nutritional supplements in addition to multivitamins.
“Some nutrients, like vitamin D, are very difficult to get from food because very few are found naturally in food,” says Bonnie Liebman, director of nutrition at the Center for Science in the Public Interest (CSPI). “Many older people do not produce enough stomach acid to extract natural vitamin B-12 from milk, meat or eggs. Vitamin B-12 deficiency can cause irreversible nerve damage and mimic dementia—something you want to avoid.”
The facts about multivitamins
Scientists who study multivitamins say there is mounting evidence that multivitamins may also provide additional health benefits, including delaying cognitive decline in older people. For example, a recent three-year study funded by the National Institute on Aging of more than 2,200 participants ages 65 and older found that those who took a daily multivitamin showed significant cognitive improvement in skills that tend to decline with normal aging, including short-term memory and such Executive functions such as decision-making compared to those receiving a placebo.
The unpublished results, presented at a fall scientific meeting, showed that multivitamin users experienced only 1.2 years of mental decline instead of three years. Put another way, they retained their mental acuity for 1.8 years — nearly 60 percent. The research was part of a larger study looking at the effects of multivitamins on cancer. The cognition results are expected to be published shortly.
The larger study, known as the COcoa Supplement and Multivitamin Outcomes Study, or COSMOS, began in 2014 in an attempt to replicate the findings of an earlier study, the Physicians’ Health Study II, which ran from 1997 to 2011. PHS II saw an 8 percent reduction in overall cancer incidence among those over 50 who took daily multivitamins, but – unlike COSMOS – showed no cognitive benefits. The COSMOS study, on the other hand, which only ran for 3½ years, found no decline in cancer incidence.
About half of parents give their children a dietary supplement
But the researchers – who are the same in both studies – emphasize that differences in the design and length of the two studies are responsible for the seemingly contradictory results.
“COSMOS just wasn’t long enough to map out the effects of cancer,” says Howard Sesso, associate professor of medicine at Harvard Medical School and one of the researchers. “With cancer, you really need more time to see the effects of dietary interventions. We continue to follow participants and send out surveys to find out if they are still taking multivitamins and if they have cancer.”
There were also significant differences between the two studies in how they measured cognition. For example, the first baseline cognitive assessment in PHS II occurred one to two years after starting the pills, meaning the researchers would have missed any cognitive improvements that occurred in those first two years, Sesso says.
“COSMOS had a better study design,” he says. “The first baseline cognition assessment took place before they started taking the multivitamin or placebo. The potential benefits were identified at one, two and three year follow-up visits.”
Regardless, experts say multivitamins are important for those suffering from impaired absorption, the result of medication, gastric bypass surgery, or such digestive disorders as Crohn’s disease, ulcerative colitis, inflammatory bowel disease, and celiac disease.
Multivitamins can also provide the necessary nutrients at certain life stages. Anyone considering pregnancy should take multivitamins before and during pregnancy to ensure they are getting enough folic acid, which helps prevent fetal neural tube defects such as spina bifida. On the other hand, postmenopausal women should avoid iron-containing multivitamins because they no longer lose iron through menstruation.
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Some people also need additional supplements, such as B-12 and vitamin D. The latter, necessary for bone health, is often insufficient in those who avoid sun exposure — a smart practice to prevent skin cancer — and in those who spend time indoors stop, e.g. B. in nursing home residents.
Manson has conducted several studies on vitamin D supplements that suggest taking supplemental vitamin D may reduce the risk of developing autoimmune diseases and reduce, but not prevent, deaths from cancer. “Vitamin D can change the biology of tumors, making them less likely to metastasize,” she says.
She’s also studying vitamin D’s effect on coronavirus symptoms – specifically whether it can reduce upper respiratory tract infections – but there are no results yet. Still, she thinks it’s a good idea to take some more of it. (The recommended daily allowance or RDA is 600 international units or IU or 15 micrograms, but the amount will vary by multivitamin.)
“During the pandemic, I recommend 1,000 to 2,000 IU, although the jury is still out on the benefits during Covid,” she says. “It’s very safe. For bone health and other chronic diseases, 600 to 800 is sufficient.”
Experts say it’s also wise to take vitamin B-12 supplements later in life. Most multivitamins contain 2.4 micrograms, the RDA for adults, but some people may need more, experts say.
“About 15 percent of people over the age of 65 have an early vitamin B12 deficiency,” says Hensrud. He suggests his patients in this age group take 500 to 1,000 micrograms daily. “Vitamin B-12 isn’t well absorbed and has a large safety margin,” meaning high doses won’t hurt, he says. “It’s probably the safest vitamin there is.”
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CSPI cautions consumers against relying on multivitamins for adequate calcium and potassium. “You’re better off getting enough potassium by filling half your plate with fruits and vegetables than looking for a supplement,” says Liebman. “Whether you need calcium supplementation depends on how much you get from food.”
Premenopausal women and men up to the age of 70 need 1,000 milligrams of calcium daily, she says. “You can’t count on a multi getting it because it wouldn’t fit in a single pill and you might get enough of the food.”
Women need 2,600 milligrams of potassium daily, while men need 3,400 milligrams, she says. “Potassium may help lower blood pressure or keep it from rising with age,” says Liebman. In addition to fruits and vegetables, other sources of potassium include dairy products, beans, and seafood.
Most experts agree that taking a multivitamin can’t hurt and probably could help, and people don’t have to spend a lot of money to do it.
“I think a standard multivitamin and mineral supplement is adequate for a lot of people,” says Liebman. “You don’t need the Cadillac of multivitamins. A Chevy is fine. Many private labels are usually perfectly adequate.”
What Vitamins Should Be in Your Multivitamin?
Vitamin A 700-1,050 mcg (2,300-3,500 IU)
Vitamin D 20-25 mcg (800-1,000 IU)
vitamin E 13-35 mg (20-80 IU)
Thiamine (B-1) 1.1 mg or more
Riboflavin (B-2) 1.1 mg or more
folate Premenopausal women 660–680 mcg DFE (dietary folic acid equivalent) (400 mcg folic acid); all others 400-680 mcg DFE (235-400 mcg folic acid)
Vitamin B12 2.4 µg or more
calcium Don’t rely on a multivitamin
iron Premenopausal women 18 mg; all others (no more than 8 mg)
potassium Don’t rely on a multivitamin
(Note: “Or more” does not mean that a nutrient is safe at every dose, but that levels in multivitamins are unlikely to be high enough to cause harm. This list does not apply to prenatal multivitamins for pregnant women. Consult your doctor on .)
Source: Center for Science in the Public Interest