Results from a new clinical trial published in Neurology adds to doubt that B vitamin supplements improve cognitive function in elderly people.
For decades, scientists have observed that people with high levels of homocysteine in their blood have a higher risk of cognitive decline, dementia, and other age-related health problems. Supplementation with B vitamins like B9 (folate), B12 (cobalamin), and B6 (pyridoxal phosphate) can reduce homocysteine levels , so scientists theorized that B vitamin supplementation might help prevent dementia or treat patients with dementia or cognitive impairment.
Over a decade ago, the Alzheimer's Drug Discovery Foundation co-funded a pilot clinical trial in Alzheimer's patients to test these theories. Despite some promising initial results, two recent meta-analyses of randomized trials revealed that B vitamin supplements have generally not improved cognitive function in elderly people.
Some proponents of B vitamins have argued that most trials have failed because they have rarely targeted people with high homocysteine levels. In other words, the trials tested elderly people in general rather than the people most likely to benefit from a reduction in homocysteine. The trial results reported this week, however, focused specifically on elderly people with high homocysteine levels. Nearly 3,000 elderly volunteers with high homocysteine levels were treated with either a placebo or a combination of 400 micrograms of folic acid and 500 micrograms of vitamin B12 for two years. The B vitamins did lower homocysteine levels but did not appear to have a significant effect on cognitive function.
Proponents of B vitamins also argue that the available trials have been too short to detect a benefit. A two year trial, for example, cannot easily test whether vitamins protect from dementia. Instead, most trials have looked at cognitive function in elderly people. But some five year trials have been no more likely to detect cognitive benefits from B vitamins. Observational research might give further clues about long-term use if it included information on homocysteine levels, associated risk of dementia, and whether increased B vitamin intake decrease that risk.
Dr. Penny Dacks was previously the Director of Aging and Alzheimer’s Disease Prevention at the Alzheimer's Drug Discovery Foundation. She was trained in neuroscience at the Mount Sinai School of Medicine, the University of Arizona, and Queen's University (Canada) with individual fellowships from the National Institute of Health, the Evelyn F. McKnight Brain Research Foundation, the ARCS Foundation and the Hilda and Preston Davis Foundation. She has authored over 18 peer-reviewed scientific articles and is a member of the Society for Neuroscience, the Gerontological Society of America, the Endocrine Society and the Association for Women in Science.
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