Older people who are deficient in vitamin B12 may run the risk of developing anaemia and cognitive impairment if they're getting too much folate. Previous studies have suggested that excess folate can mask or worsen vitamin B-12 deficiency, which is common among older people. Given that the US has been fortifying all enriched cereal-grain products with folate since 1998 in order to prevent pregnant women from having children with neural tube birth defects, it's possible that many people may be getting too much of the nutrient. To investigate the interaction between folate and vitamin B-12 in older people, researchers from the Tufts University in Boston, USA, looked at blood levels of the nutrients and risk of anaemia and cognitive impairment in nearly 1,500 people. About one-quarter of the men and women in the study had low blood levels of vitamin B-12. It was found that subjects with low serum vitamin B-12 and high serum folate were 3 times more likely to have cognitive impairment and 3 times more likely to have anaemia. However, among people with normal B-12 levels, high levels of folate were protective against cognitive impairment. It is extremely difficult for a person to know whether or not he or she has adequate levels of B-12, given that there's no real gold standard test. People must consume adequate amounts of the nutrient, which is contained in animal proteins, but a substance called intrinsic factor must be present in the stomach in order for people to absorb B-12 properly. The researchers advise seniors to look at the folate content of the enriched foods they're eating, for example breakfast cereals. If they are already getting 1200 percent of their required folate from breakfast cereal, a multivitamin is questionable. Older people should not take a supplement with folic acid unless their doctor recommends it. The only younger people who need to be concerned about getting too much folate, are vegetarians who are not taking B-12 supplements.
American Journal of Clinical Nutrition,
January 2007