Weve all heard a lot about the heart-healthy benefits of salmon lately. Countless books by well-known doctors tell us that eating salmon two or three times a week will keep our hearts, brains and joints sound, and even erase our wrinkles and crows feet. But theres an important detail that has been overlooked. Certain kinds of salmon do not provide these health benefits. And unfortunately, the kind of salmon you are most likely to be eating is the least healthy kind of all.

You are what you eatand so are salmon.

Salmon earned its reputation as a superfood because it is naturally high in omega-3 fatty acids. These healthy fats help to reduce inflammation, keep your blood flowing easily, and prevent the build-up of artery-clogging plaques in your heart and brain.

The problem centers around the kind of fish-food that is fed to farm-raised salmon. Most of the salmon sold in the United States today is farm-raised. And as the salmon industry has boomed, farmers have begun to look for ways to cut costs. One way is to use a cheaper feed made from vegetable oils instead of more expensive fish-oil based feed. As you might expect, the quality of the food that salmon eat affects the quality of the resulting product.

Recently, some Norwegian scientists set out to measure the effects of different feeds on the nutritional composition of the fish. Not surprisingly, they found that the fish fed vegetable oils had a much less favorable fatty acid composition than the salmon that consumed only fish oils. Taking the analysis one step further, they found that heart disease patients that ate the vegetable-oil fed salmon did not show the same cardiovascular improvements as patients who ate fish-oil fed salmon. (Seierstad, European Journal of Clinical Investigation, January 2005.)

Separate analysis using the IF Rating system (a formula that calculates the inflammatory potential of foods) confirms that a serving of wild-caught salmon has an IF Rating of +518 (strongly anti-inflammatory), while the same sized serving of farm-raised salmon rates -180 (inflammatory).

What can you do to be sure that the salmon you are eating is actually good for you?

As the Norwegian scientists found, farm-raised salmon is fine--as long as it has been fed a 100% fish-oil based diet. But it is almost impossible to determine what kind of food was fed to the salmon that end up at your local fish-market. If you want the maximum anti-aging and disease prevention benefits from salmon, your best bet is to select wild-caught salmon.