Its not clear how anyone actually becomes a celebrity fitness guru. There are no classes to attend or tests to pass that we can find.

So any advice you hear from a celebrity fitness guru is best kept in the same category as a National Enquirer headline: Interesting, but Dont Bet Your Life On It.

Case in point: renowned fitness and nutrition expert Harley Pasternaks advice on eating fish.

Back in August, Mr. Pasternak wrote on People.com that tuna rates sky-high in mercury. Not true. According to the FDAs own study of mercury levels found in commercial fish, canned light and white tuna contains levels that are seven to 10 times lower than the FDAs limit. And that FDA limit contains a built-in 1,000 percent safety factor. The infinitesimal amount of mercury in tuna doesnt even come close to this limit.

Yet again, Mr. Pasternak botched his advice on mercury in fish, this time on the Ricki Lake Shows Pregnant and 40 episode. He instructed breastfeeding women the very group that should be eating 8 to 12 ounces of seafood per week according to the latest USDA Dietary Guidelines for Americans to stay away from fish with mercury without offering any specifics.

Here are the essential facts: Government guidelines urge women who are pregnant, might become pregnant, or are nursing mothers to eat 12 ounces of seafood per week because of all the health benefits it provides to developing babies (better neurological and developmental outcomes). Pregnant women should only avoid four rarely consumed commercial species:shark, king mackerel, swordfish and tilefish. All of the top 10 most popular fish consumed in America including canned tuna are low mercury fish.

Instead of scaring women about seafood, Mr. Pasternak should have looked out for their babies health by encouraging them to eat the recommended amount of fish.

Celebrity fitness gurus would be well advised to put down their National Enquirers and pick up a good book on nutrition. They might learn something thats actually true.