Fats and Smarts
A diet high in saturated fat not only can make you depressed and downright antisocial, it can also impair general mental performance. So will a diet high in total fat and one that is deficient in essential fatty acids (EFAs).
Once dietary fats are broken down into fatty acids, the body uses them for myriad purposes. They go into all hormones. They are critical to body metabolism. And they are also a constituent of the outer membrane of every cell in the body, including those in the brain. Of the numerous fatty acids the body uses, two are called "essential" because they cannot be manufactured in the body; they must be supplied by daily diet. These arelinoleic acid, or n-6, and linolenic acid, or n-3; both are super-unsaturated fats. (You need only about a tablespoon of EFAs daily.)
N-3 fatty acids--popularly called omega-3s--are known to be particularly crucial for proper development of the human brain, both before birth and in infancy. It is through the lipid-rich cell membrane of neurons that all nerve signals must pass. In addition, as learning and memory forge new connections between nerve cells, new membranes are formed to sheath them. All brain cell membranes continuously need to refresh themselves with a new supply of fatty acids. Preliminary research suggests that EFAs -- particularly n-3s -- are best suited for optimal brain function.
In a key animal study soon to be published, Carol E. Greenwood, Ph.D., and colleagues fed rats various amounts and types of fat for a three-month period and then measured their performance on memory tests. Fat content ranged from 40 percent of calories -- approximating that of the average American -- to 10 percent of calories. Rats fed the high-fat diet that was highest in saturated fat (from lard) performed the worst. Those on the diet lowest in saturated and total fat did the best.
The old saw about fish being brain food is true; they are rich in n-3s. Long a proponent of adding more n-3-rich fatty fish to the diet as a way to reduce the risk of heart disease, William Connor, M.D., of the Oregon Health Sciences University, contends that the special n-3s in fish oil are tailor-made for the brain. Chemically speaking, they are long-chain fatty acids, containing strings of 20 or 22 carbon atoms. One such long-chain n-3 fatty acid, docosahexaenoic acid, is identical to that found in abundance in neuron membranes.
Plants also contain n-3 fatty acids, but their n-3s are arrayed in medium-length chains. Better, Connor says, to deliver to the brain -- especially during development -- precisely the type of fatty acid it needs and readily absorbs.
Connor sees ample evidence that long-chain n-3s have a critical bearing on intellectual performance in humans. He cites a well-controlled study of premature infants fed by tube, either standard American infant formula or breast milk. The children given breast milk had significantly higher IQs, an advantage they maintained over the eight-year study. Their IQ superiority rests exclusively on docosahexaenoic acid, Connor insists. It's a known component of breast milk. While infant formulas sold in Japan and Europe contain docosahexaenoic acid, most American formulas do not.
N-3 fats may also have the ability to protect the brain from damage, or heal it once damage occurs. In Fish and Human Health (Academic Press, 1986), biochemist William E. M. Lands, Ph.D., cites a study demonstrating that fish oil reduced the degree of brain damage in cats experiencing cerebral stroke.
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