Staying svelte.
Mice on a high-fat diet bulk up (middle), but those on a high-carb diet (left) or a high-fat diet supplemented with taurine (right) don't.

Nobuyo Tsuboyama-Kasaoka

Sushi's Slimming Secret?

Sushi lovers may now have even more reason to indulge. A Japanese group has found that large supplements of taurine, an amino acid synthesized within the body and also found in seafood, can largely reverse the health hazards of a high-fat diet in mice. Observers caution that more work is needed to prove taurine's protective role and to extend the work to humans.

There is evidence that societies with fish-based diets suffer less obesity and related problems than do those that primarily eat meat. Noting that taurine is abundant in fish but not terrestrial animals and that previous animal experiments had shown increased intake of taurine reduced high blood pressure and cholesterol levels, Nobuyo Tsuboyama-Kasaoka, a nutritional biochemist at Japan's National Institute of Health and Nutrition, Tokyo, and colleagues set out to probe the relationship between taurine and obesity.

They put groups of mice on high-carbohydrate or high-fat diets. The team found that compared to mice on the high-carbohydrate diet, mice fed a high-fat diet got fat and had lower levels of taurine in the blood and reduced amounts of the enzyme that synthesizes taurine in their adipose tissue, the fat-storing connective tissue found primarily under the skin. The team noted that the decrease in the production of taurine occurred 14 days or more after the high-fat diet was started, leading them to speculate that the reduction resulted from diet-induced changes in the adipocytes. "This creates a vicious cycle promoting obesity," says Tsuboyama-Kasaoka. Her team found, however, that a daily dose of taurine--3 milligrams per gram of a mouse's weight--prevented mice on the high-fat diet from getting obese. By measuring energy expenditure, the team concluded that mice fed a high-fat diet plus taurine burned off the fat because of higher at-rest energy consumption. They reported their findings online in Endocrinology on 20 April.

"This work raises some very interesting questions," says Martha Stipanuk, a biochemist at Cornell University who studies taurine. She cautions that additional work is needed to determine whether taurine is really involved in the increased fat-burning. She also notes that a human would have to consume a whopping 150 to 250 grams of taurine daily to get a dose equivalent to what was given to the mice. Tsuboyama-Kasaoka says her group is already planning mouse and human experiments to pinpoint the role of taurine and investigate whether lower doses of supplemental taurine are effective in humans.