Science

Vitamin supplements may slow cognitive decline in older adults

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While some nutritional supplements are marketed for their protective properties against the effects of brain aging, research done on this subject is inconclusive. A group of American researchers set out to evaluate the real effects of these multivitamin preparations in a three-year randomized clinical trial. The results show that taking a daily multivitamin and mineral supplement can slow down cognitive aging.

Alzheimer’s disease and other forms of dementia affect more than 46 million people worldwide. To date, there is no treatment to prevent cognitive decline in asymptomatic older adults. On the other hand, some nutrients are known for their ability to preserve cognitive function. Cocoa, for example, is rich in flavanols, a subfamily of flavonoids that, when consumed regularly, can slow cognitive decline by improving cerebral vasodilation, blood flow, and new vessel formation.

Similarly, vitamins and minerals are known to affect several biological pathways that support the normal functioning of the body and brain; Thus, a deficiency in these nutrients may increase the risk of cognitive decline. Several studies have looked at the effects of certain vitamins (vitamin B9, vitamin D) and omega-3s on cognition, but the results have been inconclusive, in part due to design issues with those studies. The COSMOS-Mind project (CO-coa and Mind Multivitamin Outcome Study) is the first large-scale, long-term study investigating the effects of daily cocoa and/or vitamin and mineral supplementation.

No significant effect of cocoa on cognition

This study is actually a follow-up to another clinical trial (COSMOS), a placebo-controlled trial that is investigating the effects of daily intake of cocoa extract and multivitamin and mineral preparations on the risks of cardiovascular disease and cancer.

The COSMOS-Mind study included more than 2,200 participants, averaging 73 years old, 60% of whom were women. They were in good health (no recent stroke, cancer, or serious illness) and had not taken any nutritional supplements prior to the study. They were divided into four groups: one received daily cocoa extract and a vitamin preparation; the second group took cocoa extract and placebo; the third group took a placebo and a vitamin preparation; finally, the last group had placebo only. Self-reported adherence to treatment was comparable in all groups (most of them took more than 75% of the pills during the study).

Cocoa extract contains 500 mg of flavanols, including 80 mg of epicatechins and small amounts of theobromine (about 50 mg) and caffeine (about 15 mg), which may enhance the central and vascular effects of flavanols. The multivitamin formulation was typical of commercial products; it contained vitamins (mainly A, D, K and B9), calcium, magnesium, phosphorus, chromium, molybdenum, lutein, lycopene, etc.

Participants’ cognitive abilities were assessed by telephone interview at the beginning of the trial and then annually for three years. These interviews were designed to assess general cognitive status, episodic memory, and executive functions. Tests included short delay word list recall (10 minutes), long delay additional word list recall (40 minutes), immediate and delayed story recall, and assessment of the participant’s fluency.

The results of the study show that the scores obtained by participants who took cocoa extract (or its placebo) did not differ significantly; Thus, cocoa consumption does not appear to affect cognitive function.

Vitamins that preserve memory and executive function

On the other hand, scores obtained by participants who received vitamin-mineral supplements suggest a “significant therapeutic effect” compared to placebo, the researchers emphasize in their paper. The team also notes that this effect was most pronounced in participants with a history of cardiovascular disease.

Evolution of global cognition in participants who received cocoa extract versus those who received placebo (A) and in participants who received a multivitamin preparation versus those who received placebo (B). © L. Baker et al.

The vitamins and minerals caused a relative improvement in both memory and executive function. There was no evidence of any interaction between cocoa extract supplements and vitamin supplements for general cognition or for memory and executive function. In other words, cocoa extract did not affect the effect of vitamins on cognitive function. It remains to determine the mechanisms by which these vitamins preserve cognitive function.

“While the Alzheimer’s Association is encouraged by these findings, we are not prepared to recommend the widespread use of multivitamin supplements to reduce the risk of cognitive decline in the elderly,” said Dr. Maria C. Carrillo, the association’s chief scientist. Independent confirmatory studies in larger and more diverse populations are needed before any recommendation. If the effects are confirmed, older people will have an easy and inexpensive way to maintain their cognitive abilities.

In the meantime, the Alzheimer’s Association encourages patients to discuss the benefits and risks of all dietary supplements, including multivitamins, with their doctors and pharmacists. An excess of certain nutrients can indeed have harmful effects: overabsorption of vitamin D can, for example, lead to hypercalcemia, and high doses of vitamin C can cause gastrointestinal upset.

L. Baker et al., Alzheimer’s disease and dementia.

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