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by Sonya Collins
Updated September 28, 2022
Your body uses all eight B vitamins to turn food into energy: B1 (thiamin), B2 (riboflavin) B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folate) and B12 (cobalamin). Researchers, however, have examined the roles of only a few of these in brain health — namely, B6, folate and B12. Most people get all the B vitamins they need from their diet. According to a report from AARP’s Global Council on Brain Health, the research on B vitamins doesn’t suggest that healthy people of any age will get added brain benefits from B vitamin supplements unless a health care provider has identified a deficiency.
“People who may benefit are those who have a restricted or limited diet, such as vegans or habitual avoiders of fruits and vegetables, because B vitamin deficiency or borderline deficiency can lead to cognitive impairment,” says Timothy Kwok, a member of the Global Council’s expert panel on supplements and a professor in the department of medicine and therapeutics and the School of Public Health at the Chinese University of Hong Kong. Some health conditions that interfere with the absorption of nutrients, such as Crohn’s disease or celiac, may also lead to a deficiency, as can weight-loss surgery.
That said, he adds, “If you feel better with B vitamins, there is no good reason to stop, as they are generally safe.” But Kwok cautions that before you start stocking your medicine cabinet with them, you should know that too much can have toxic effects. “Try to avoid taking B vitamins at high doses long term.” Too much may enhance existing cancers and increase risk for nerve damage, among other consequences.
You need B12 to make red blood cells (the ones that carry oxygen throughout your body), nerve cells and DNA. You get B12 from beef liver, clams, red meat, pork, fish, dairy products and foods to which it is added artificially, such as cereal.
Vitamin B12 plays a big part in brain health. People who lack it can feel depressed, confused and have memory loss. If you don’t get treatment for insufficient B12, the deficiency can lead to dementia. Most people, however, get all the B12 they need without thinking about it. A few exceptions are vegans and vegetarians, since animal-based foods are the only ones to contain the vitamin naturally, and older adults, who might not absorb B12 as well as they used to. In the United States, 4.4 percent to 15 percent are estimated to have a B12 deficiency, and close to 20 percent of those over age 60 in the United Kingdom are estimated to be deficient in B12.
Besides the cognitive effects of low B12, you may feel weak and tired and have tingling or loss of feeling in your hands and feet. If you have symptoms of B12 deficiency, talk with your doctor. If not, there’s no scientific research that suggests supplements will help preserve your memory or prevent dementia, the Global Council concluded.
Vitamin B9 (Folate)
Folate is so important that it’s added to the food supply in as many as 53 countries or more worldwide. Folate deficiency in pregnancy can cause brain and spinal cord birth defects, such as spina bifida. Supplementing the diet with the B vitamin may reduce these defects by up to 70 percent. That’s why, in 1996, the Food and Drug Administration mandated that manufacturers add folic acid (synthetic folate) to wheat flour, breads and cereals. Since then, folate deficiency has been rare in the United States.
Everybody needs folate to make DNA and for cells to divide — two of the most basic functions required to keep your body going. Like B12, folate may play a role in mental health. People who lack the nutrient may be more prone to depression and may not do as well on antidepressants. It’s possible that folic acid supplements could help people who are low in it respond better to antidepressants. It’s not clear, however, whether these supplements could improve everyone’s response to an antidepressant.
You can get folate naturally from many vegetables, in particular asparagus, brussels sprouts and dark leafy green vegetables like spinach and kale. Oranges and orange juice, as well as other fruits and fruit juices, provide folate, too. Nuts, beans and peas are also a good source of the nutrient. In addition, you can get folic acid through bread, flour, cornmeal, pasta, rice and cereal.
Folic acid supplements don’t seem to improve memory and thinking or prevent dementia or Alzheimer’s disease. Experts agree, though, that there’s a need for more research in the area. One thing they know for sure is that you can get too much folate. High doses of the stuff can speed up the progression of cancer in people who already have it.
“The upper safety limit of folate intake is 1,000 micrograms a day,” Kwok says. “One should, therefore, be cautious about folic acid supplementation over 400 micrograms daily, especially in countries where flour is fortified with folic acid.”
Vitamin B6 is a workhorse in your body’s metabolism. It’s involved in some 100 chemical reactions that take place as part of metabolism. Like folate, B6 is a part of fetal brain development.
Its role in brain function is apparent throughout life, since lack of the nutrient can cause depression and confusion. Some studies show that older adults who have higher levels of B6 in their bloodstream have better memory, but supplements don’t seem to yield that benefit. Added B6 through supplements doesn’t appear to improve cognitive function in healthy people or people who have dementia.
Most people in the United States get plenty of B6 from their diet, anyway. Fish, poultry and organ meats (such as liver) are high in the B vitamin. Potatoes and other starchy vegetables and noncitrus fruits are major sources of B6, too.
Even though B6 is abundant in a variety of foods, people with certain health conditions (those with poor kidney function, autoimmune disorders and alcohol dependence) can run low on it. If you think you’re not getting enough B6, talk with your doctor. But remember, as with other B vitamins, you can get too much of a good thing.
Too much B6, Kwok says, can damage the nerves in your arms, legs, hands and feet.
A mysterious interaction
B vitamins have an inverse relationship with an amino acid in the blood called homocysteine. You get it mostly from eating meat. High blood levels of this amino acid are linked to increased risk for stroke and cognitive decline, though researchers don’t completely understand why. But B vitamins break it down and convert it into other substances that your body can use. That’s why when you have a lot of homocysteine circulating in your blood, it could be a sign that you’re low on B vitamins.
Though B vitamins lower homocysteine, research as to whether supplements directly lower risk for dementia and stroke is mixed, the Global Council concludes.
• "The Real Deal on Brain Health Supplements: GCBH Recommendations on Vitamins, Minerals, and Other Dietary Supplements," Global Council on Brain Health, 2019. Read the full report.
• "Dietary intakes and biomarker patterns of folate, vitamin B6, and vitamin B12 can be associated with cognitive impairment by hypermethylation of redox-related genes NUDT15 and TXNRD1," Clinical Epigenetics, October 2019. In this study, 2,533 participants were followed for an average of 2.3 years; they took questionnaires about their dietary habits and underwent cognitive tests. Among the researchers' findings was an association between adequate vitamin B6 intake and better cognitive reserve. As a population study, it shows a correlation but does not prove cause and effect. Read the full study.