Scan the vitamin aisle in your local supermarket and you'll find plenty of products promising to improve brain function. With names like "Memory Complex," "Neuro Optimizer," "Brain Elevate," and "Sharp Thought," they tout the remarkable powers of compounds from phospholipids and omega-3 fatty acids to acetyl-L-carnitine, citicoline, and Gingko biloba.
Manufacturers claim these supplements will enhance cognition, improve memory, and delay age-related decline. But they also include an important caveat on their packaging: "These statements have not been evaluated by the Food and Drug Administration." Supplement production and marketing are largely unregulated, so there's no way to tell at a glance whether a product really has the power to strengthen your mental faculties. It turns out most of these nutrients are still being studied to determine if and how they affect the adult brain.
There is ample evidence to indicate a link between prenatal brain development and sufficient maternal intake of both folic acid and the omega-3 fatty acid DHA, but research on adults is less conclusive. Recent studies Reviews published in 2000 and 2003 looking at a number of supplements promoted as brain enhancers concluded that for most compounds, evidence of improved mental performance was only mildly suggestive at best.
Because little is known about the potential toxicity of high doses of these compounds, researcher John Fernstrom at the University of Pittsburg School of Medicine has cautioned against pharmacological use of these supplements until their benefits and risks are better understood.
More recently, however, a handful of studies have indicated that certain dietary deficiencies may negatively affect brain function, and that supplements could be used to correct these deficiencies. Iron deficiency, for example, has been associated with poor mental performance. A study published last year in the American Journal of Clinical Nutrition found that women of reproductive age (18 - 35 years) who had low levels of iron in their blood performed more poorly on tests of attention, memory, and learning that those who had sufficient levels of iron.
When the iron-deficient women were treated with iron supplementation, their scores improved. Although the biological mechanism for this improvement is unclear, one possible explanation is that low levels of iron can negatively interfere with neurotransmission. Similarly, low levels of the omega-3 fatty acid DHA, found in fish oil, may contribute to Alzheimer's disease.
Researchers at the University of California at Los Angeles recently investigated the effect of DHA on the production of the protein LR11, which is lower in people with Alzheimer's disease than in the general population. By administering fish oil to rodents that had been genetically altered to develop Alzheimer's, the researchers found that LR11 levels increased with treatment.
Cultures of human neuronal cells also responded to DHA treatment by increasing production of LR11. Because LR11 inhibits the growth of plaques formed by the protein beta amyloid, which is believed to be toxic to the brain and has been associated with Alzheimer's, the researchers concluded that DHA may help prevent the disease. Dietary folic acid may also play a role in Alzheimer's disease and other forms of dementia.
A study published last year in the Archives of Neurology found that higher folic acid intake was related to lower risk of developing Alzheimer's, while, conversely, a separate study published this year in the British Medical Journal found that low levels of folate in the blood corresponded to a tripled risk of dementia. Low levels of folate are associated with higher blood levels of the chemical homocysteine, which, because it can degrade the arteries, is a risk factor for stroke and may also play a role in Alzheimer's.
These studies indicate that dietary supplements containing iron, DHA, or folic acid may have some potential to promote brain health. It's important to note, however, that the studies focused on correcting deficiencies in order to restore normal brain function and protect against disease.
They do not provide any evidence that intake of these nutrients beyond dietary requirements will result in improved mental performance, or that in the absence of mental impairment they would contribute to any positive change. Eat right and take your vitamins But if you're looking for something to give you an extra mental edge, there may still be hope.
A long-term study of the effects of beta carotene, published last year in the Archives of Internal Medicine, found that men who took the supplement for an average of 18 years demonstrated higher verbal memory scores than those who took a placebo. Gingko biloba may also have protective effects against aging: A study published this year in the journal Neurology found that participants taking the extract showed a lower rate of dementia and reduced decline in memory over the course of three and a half years.
Both beta carotene and Gingko are thought to counter oxidative damage, and Gingko may have the potential to improve blood flow. It seems clear that adequate nutrition is a vital aspect of mental performance, but that those who choose to take allegedly brain-boosting supplements should do so with a grain of salt.
By and large, there is little evidence that mega-doses of any particular nutrient will result in extraordinary brain power, and the risks of such intake are still unknown. The soundest strategy for shoring up your synapses appears to be a rich and varied diet accompanied (with your doctor's approval) by a comprehensive multivitamin and, perhaps, a cup of Gingko tea.
-- By Elisabeth Andrews
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References: Dodge, H.H., Zitzelberger, T., Oken, B.S., Howieson, D., & Kaye, J. A randomized placebo-controlled trial of Gingko biloba for the prevention of cognitive decline. Neurology, 2008, 70: 1809-1817.
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