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Harvard Commentaries
Harvard Commentaries
Reviewed by the Faculty of Harvard Medical School

Minding Your Mind Minding Your Mind

Can Vitamin Supplements Protect Your Brain?

November 22, 2013

By Michael Craig Miller M.D.

Harvard Medical School

There is good evidence that regular physical activity and a Mediterranean-style diet are good for our brains.

How great it would be if you could also protect your brain by taking your vitamins everyday. The truth is that there is little proof that taking more than the recommended amount of daily vitamins gives you an added mental boost or can prevent the mental decline or dementia that comes from other causes.

But this doesn't mean that vitamins have no effect on your mental abilities. Here's what the evidence says about the most studied vitamins.

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First, Avoid Deficiencies

Your best defense may be to avoid any vitamin deficiencies. (See the chart below.) These are more common as we age.

Vitamin B12 is a good example. Older adults make less stomach acid than younger people. This interferes with the ability to get this vitamin from common foods. Age-related changes also make older adults less efficient at producing vitamin D from sun exposure.

Certain vitamin deficiencies, if they are severe enough, can impair brain function. Again vitamin B12 deficiency is the example. It can cause disorientation and confusion similar to the symptoms of Alzheimer's disease and other types of dementia. People can prevent or treat a vitamin B12 deficiency by taking supplements or eating fortified foods, which don't need stomach acid to be absorbed.

Evidence is growing that other sorts of vitamin deficiencies are also associated with mental decline or dementia. Researchers are studying whether, as in the case of a vitamin B12 deficiency, taking supplements might prevent deterioration or treat symptoms once they appear. If taking more than the daily requirement could provide added protection, so much the better.

Recommended Daily Allowance for Vitamins (Institute of Medicine, 1997)

Vitamin B6
1.7 milligrams (men)
1.5 milligrams (women)
Vitamin B12
2.4 milligrams
Folic acid
400 micrograms
Vitamin D*
600 IU (age 50-70)
800 IU (age > 70)
Vitamin E
15 milligrams (about 33 IU)
800 IU (age > 70)

*The IOM updated the RDA in November 2010.

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What's the Evidence?

Here's a quick review of other vitamins researchers are studying to help protect mental abilities as we age.

B vitamins

Three B vitamins — B6, B12 and folic acid — help break down homocysteine, an amino acid released during digestion. Studies of large groups of people have found that high levels of homocysteine are associated with heart and blood circulation diseases, as well as Alzheimer's disease.

It's not clear what underlies this link. One theory is that B vitamins affect mental function indirectly by keeping homocysteine levels in the normal range. For example, one study found that as the level of homocysteine rises, so does the risk for Alzheimer's.

But most studies have shown that vitamin B supplements do not appear to prevent mental decline, help treat dementia, or slow disease progression in patients with either dementia or mild cognitive impairment (a condition that often precedes Alzheimer's). For example, one large well-designed study found that high doses of B vitamins did not slow the mental decline of patients with mild to moderate Alzheimer's disease who took the vitamins for 18 months, even though the vitamins lowered homocysteine levels by about one-third.

Vitamin D

Vitamin D not only helps to keep bones healthy, it also helps keep blood vessels healthy. This means that brain cells get the nutrients and oxygen they need. In addition, brain cells have vitamin D receptors, suggesting that this hormone directly affects brain tissue.

While the evidence is mixed, most epidemiological studies have concluded that when people don't have enough vitamin D, they are more likely to experience a mental decline or develop dementia. But a large national survey, which involved almost 5,000 people between the ages of 60 and 90, found no association between vitamin D levels and mental performance.

No study, however, has shown that more is better. That is, taking more than the recommended amount of vitamin D does not appear to be more protective. Experts do agree on one point, however: Many older adults are deficient in this vitamin. Surveys have found that 40% to 90% of people around the world — even those living in sunny climates — have vitamin D levels that are lower than they should be.

Even if we don't know for sure if vitamin D protects mental abilities, it plays many roles in maintaining overall health. That's why experts are beginning to agree that many adults need to get more vitamin D. The easiest way to do so is to take daily supplement, which is safe and inexpensive.

Vitamin E

Vitamin E is an antioxidant. It counters the effects of free radicals — highly reactive molecules that can damage cells. Research in animals suggests that brain cell damage by free radicals may contribute not only to age-related mental decline but also to mild mental impairment or Alzheimer's. In studies of people, researchers have found an association between low levels of vitamin E and impaired mental function and Alzheimer's.

Researchers tested whether vitamin E supplements might either prevent or treat mental decline or dementia. Early studies were encouraging, but later studies did not show mental benefits from vitamin E supplements. For example, one well-designed study of more than 750 people with mild mental impairment failed to show that vitamin E supplements would slow progression to Alzheimer's. After three years, there was no significant difference between the group that received vitamin E and the group that received a placebo.

Another large study of women over 40, which evaluated vitamin E, vitamin C, beta-carotene and combinations of the three was also disappointing. None of these supplements slowed mental decline.

At this point, there is not enough evidence to recommend taking extra vitamin E to protect the brain.

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The Bottom Line

No vitamin supplement can ever replace a healthy diet, which provides vitamins, minerals, and a host of other naturally occurring nutrients necessary for your body and brain. You can take a daily multivitamin to ensure that you are getting the recommended daily amounts of all vitamins. But for now, there is not enough evidence to recommend taking extra supplements to revitalize the brain.

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Michael Craig Miller, M.D. is editor-in-chief of the Harvard Mental Health Letter and an assistant professor of psychiatry at Harvard Medical School. Dr. Miller has an active clinical practice and has been on staff at Beth Israel Deaconess Medical Center for more than 25 years.

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