Adding soy sauce or tofu to a fishy meal, as Asian people often do, enhances the benefits, it is claimed.

Researchers in the U.S. studied omega-3 consumption among more than 82,000 men and almost 104,000 women from Hawaii and Los Angeles. Participants included a wide mix of people of different ages and ethnic origins.

Omega-3 intake ranged between 3.3g and 0.8g per day. In men, higher consumption levels of the essential fatty acid were associated with a reduced risk of death due to heart disease.

Men at the top end of the intake scale were 23% less likely to die from heart problems than those at the bottom.

The scientists also looked at the different ways fish was prepared. People with Japanese and Hawaiian backgrounds ate more fish than whites, blacks and Latinos and employed a range of cooking methods.

Lead researcher Lixin Meng, from the University of Hawaii at Manoa, said, "It appears that boiling or baking fish with low-sodium soy sauce (shoyu) and tofu is beneficial, while eating fried, salted or dried fish is not. In fact, these methods of preparation may contribute to your risk.

"We did not directly compare boiled or baked fish versus fried fish, but one can tell from the (risk) ratios, boiled or baked fish is in the protective direction but not fried fish."

The study, the first part of an on-going investigation, did not consider grilled fish.

The findings were presented at the American Heart Association's Scientific Sessions in Orlando, Florida.

For women, omega-3 was also found to be protective but the effect was not consistently significant. Salted and dried fish was a heart disease risk factor for women.

Adding a small amount of low-sodium soy or teriyaki sauce to fish provided an extra benefit for men, and soy was clearly protective in women. Eating tofu also helped to reduce heart disease risk in all ethnic groups.

The scientists now plan to monitor participants' dietary patterns over time and use blood samples to check their omega-3 levels.

"Our findings can help educate people on how much fish to eat and how to cook it to prevent heart disease," said Meng, a PhD candidate.

"Alternately, if it is verified that the interactions between fish consumption, risk factors and ethnicity are due to genetic susceptibility, the heart-disease prevention message can be personalised to ethnic groups, and future study could identify susceptibility at the genetic level."

From the November 23, 2009, Prepared Foods E-dition