According to a recent study, studied on African tribe, most of the things being equal including one's genes eating a diet rich in fish appears to be healthier for the heart than eating a vegetarian diet. The findings suggest a diet high in fish helps the body control blood levels of leptin, a substance secreted by fat tissue. High leptin levels have been associated with increased risk for heart attack and stroke.
Lead author of the study, Dr. Virend K. Somers in Rochester, said the results are particularly significant because the people studied have the same genetic makeup but simply eat different diets. Somers observed that leptin levels usually increase as people gain weight but in the new study people who ate fish continued to have low leptin levels even as they gained weight.
Heart researchers have been interested in leptin for several years because leptin in animals controls eating by sending a message to the brain when sufficient food is consumed. This "satiety" aspect of leptin also works in normal weight humans, but as people gain weight the leptin message is muted, Somers felt that in obese people there are higher leptin levels because more leptin is needed to send the message when a person is 'full'.
The new findings indicate fish somehow "changes the relationship between leptin and body fat and helps the body be more sensitive to the leptin message," Somers said. Not only did leptin levels not increase as weight increased among those eating the fish diets, but the fish had an even more marked effect on women, who normally have higher leptin levels than men. In this study "women's leptin levels were half that of men on the vegetarian diet," said Somers.
The average leptin level for men on the fish diet was 1.5 nanograms per milliliter. For women the average was 4.0 ng/mL. Men on the vegetarian diet registered an average leptin of 11.2 ng/mL and for women it was 11.8. Somers and colleagues studied 300 people who ate diets rich in fish and 200 who ate vegetarian diets.
Somers agreed that the populations in his study are not typical of Americans. The subjects studied were members of a tribe living in Tanzania. Some of the tribe members live in a village close to a lake, while others live inland. The lake-dwelling tribe members eat a diet that includes 300 to 600 grams of fish a day and accounts for about a fourth of their total daily calories. The inland-dwelling tribe members eat a vegetarian diet. Both groups consume about 2100 calories a day.