A large review of studies has found no solid evidence that vitamin and mineral supplements have any effect in preventing cognitive decline or dementia.
The meta-analysis, published in the Cochrane Database of Systematic Reviews, included 28 trials with more than 83,000 cognitively healthy people 40 and older.
The reports covered a wide range of vitamins and minerals, alone and in combination, in various dosages, with follow-ups as long as 18 years. Eight studies looked at the antioxidants beta carotene, vitamin C and vitamin E. One compared vitamin D and calcium to placebos. A trial of zinc and copper supplementation included more than a thousand participants, and one on selenium had more than 3,700. There were 17 trials of B vitamins or combinations of them with antioxidants and minerals.
The scientists were unable to find any good evidence that vitamin or mineral supplementation had a meaningful effect. There was some suggestion of a benefit in long-term supplementation with antioxidants, but even there the evidence was weak.
“We’re a little disappointed,” said Dr. Naji Tabet, a researcher in psychiatry at Brighton and Sussex Medical School in England and one of the study’s authors. “We expected to find some evidence of a noticeable impact. But based on this study — the largest of its kind, I believe — there is no effective vitamin or mineral supplement that a clinician can feel comfortable in recommending to prevent cognitive decline.”