The bodily benefits of vegetarianism have long been known. Less meat typically means less saturated fat and more antioxidants, which leads to improved heart health. But the impact of vegetarianism on mental functioning is less clear. Nutritionist Bonnie Beezhold at Arizona State University surmised that vegetarians have impaired mood, since most consume no fish and have extremely low levels of DHA and EPA, omega-3 fatty acids critical to brain cell function. But she found quite the opposite. Vegetarians who had low levels of omega-3s were happy campers, reporting fewer negative mood states than omnivores. The meager EPA and DHA furnished by their vegetarian diets is adequate as long as they consume significant amounts of ALA, or alpha-linolenic acid, found in many plant oils. Under the right conditions, the body can convert some of it into EPA. Vegetarians can load up on ALA by eating flaxseeds, pumpkin seeds, and walnuts.
Because of their role in maintaining brain cell membranes, consumption of long-chain omega-3 fats from fish, it was thought, might prevent cognitive decline and stave off dementia. But a report in the American Journal of Clinical Nutrition finds that moderate intake of omega-3s does not lower dementia risk over the long haul. Those with a regular fish intake developed dementia at the same rate as those who ate no fish during the 10-year study.
The ALA naturally found in many plant oils is not merely a substitute for the omega-3 fats found in fish. It has cardiac virtues all its own, according to a report in the journal Circulation. It has direct antiarrhythmic properties. As a result, it prevents sudden cardiac death. The effect is above and beyond whatever protection fish-based omega-3s provide.
ALA may be a particular boon to stroke patients. An animal study shows that it not only reduces brain damage, it actively promotes neuronal plasticity, stimulating the growth of new nerve cells and enhancing nerve-growth factors like BDNF that protect against depression. Researchers report in Neuropsychopharmacology that injection of ALA into animal brains results in increased survival rates .
Women seem to have an edge over men in converting ALA into omega-3 fatty acids, particularly DHA. Researchers believe nature may have conferred the advantage to ensure sufficient DHA for meeting the demands of the fetus and neonate during pregnancy and lactation, when DHA is scooped up for the developing nervous system. It's not yet clear whether estrogen abets ALA conversion.
Growing up is hard to do. For brains, the process involves migration of neurons that will carry out important functions throughout life. Especially during pregnancy, a maternal diet rich in ALA and DHA is essential for neuronal migration in the fetal hippocampus and cortex. Fetal and infant brains deprived of ALA and DHA fail to organize properly or to make a full array of neuronal connections, resulting in permanent deficits.