Can food improve brain function?

by Pascale Michelon, Ph. D
http://www.sharpbrains.com/blog/2008/09/08/can-food-improve-brain-health/

In other words, may some foods be specifically good for brain function?
For a great in-depth review of the effects of food on the brain you can check out Fernando Gomez-Pinilla’s recent article in Nature Reviews Neuroscience (reference below). Here is an overview of the state off the research.

Several components of diet seem to have a positive effect on brain function.

Omega-3 fatty acids
These acids are normal constituents of cell membranes and are essential for normal brain function. Omega-3 fatty acids can be found in fish (salmon), kiwi, and walnuts. Docosahexaenoic acid, or DHA, is the most abundant omega-3 fatty acid in cell membranes in the brain. The human body produces DHA but not enough. So we are dependent on the DHA that we get from what we eat.

A randomized double-blind controlled trial (which means seriously conducted scientific study) is currently looking at the effect of taking omega-3 fatty acids on children’s performance at school in England. Preliminary results (Portwood, 2006) suggest that the group of children who received omega-3 fatty acids showed some level of improvement in school performance compared to the group of children who received a placebo. More research is needed to confirm these results but they look promising.

Fatty acids are also regarded as a promising but untested treatment as mood stabilizer. Hibbeln (1998) showed a negative correlation between fish consumption (i.e., omega-3 fatty acid intake) and major depression in many countries including the United States, Canada, Germany and France. A negative correlation means that as consumption of omega-3 decreases, the prevalence of major depression increases. Note that a correlation does not imply causation: we cannot conclude that low omega-3 consumption causes major depression.

Folic acid (or folate)
Folate is generated by the liver, after the intestine has absorbed vitamin B. It is found in spinach, orange juice and yeast. Adequate levels of folate are essential for brain function.
Corrada and colleagues (2005) have shown that people who take more folate than others have less risks of developing Alzheimer’s disease. Note again that this is a correlation so more research is needed to determine whether folate is indeed responsible for the risk reduction.

Flavonoids
These are found in cocoa, green tea, Ginko biloba tree, citrus fruits, wine and dark chocolate. The antioxidant effects of flavonols have been shown in vitro (in the test tube) but more research is needed to establish the effects of flavonols in vivo (in a living organism). So far, Ginko biloba extracts have been shown to reduce memory impairment in mice…with mixed effects in humans, at best.

Antioxidant foods
The brain is highly susceptible to oxidative damage. This is why antioxidant food has become popular for their positive effects on brain function.
Antioxidants are found in a variety of food: Alpha lipoic is found in spinach, broccoli and potatoes; Vitamin E is found in vegetable oils, nuts, green leafy vegetables; Curcumin is found in the curry spice; Vitamin C is found in citrus fruit and several plants and vegetables. Berries are well known for their antioxidant capacity but it is not clear which of their many components has an effect on cognition.

Guts and the brain
We have seen that what we eat can affect brain function. Interestingly, it has also been shown that guts hormones themselves can directly influence brain function. Indeed, several gut hormones such as leptin (which sends signals to the brain to reduce appetite), ghrelin (which acts as an appetite stimulant) or insulin (which is secreted by the anticipation of meals and during digestion) have been found to enhance memory formation through their action on the hippocampus. As you know, the hippocampus is one of the brain structures crucial for spatial learning and memory formation. These gut hormones have an effect on the plasticity (the ability to change) of the connections between neurons in the hippocampus. For instance ghrelin promotes the formation of new synapse during learning. Insulin can enter the brain and interact directly with cells in the hippocampus.

Final note of caution
Please note that most of the studies showing positive effects of all these nutrients on the brain have been conducted in mice. A few human studies are now published but more research is clearly needed to establish and understand the effects of specific foods on brain function.