Thursday, November 26, 2009

Method of Fish Preparation Affects Cardiac Benefits

The cardioprotective effects of omega-3 fatty acids from fish consumption vary by ethnicity and method of preparation, a new study suggests. This is likely because of the types of fish consumed and the preparation methods used by different cultures, say the researchers.

Although the amount of fish consumed was key--along with whether it was high in omega-3 fatty acids, as is wild salmon and tuna--the results also indicate an important role for the method of cooking.

Those consuming adequate amounts of baked or boiled fish had lower rates of coronary heart disease (CHD) mortality during follow-up than those eating little fish. But those eating deep fried fish every day actually had higher mortality, as did those consuming salted or dried fish, she noted. The only method of frying fish that seemed protective was stir-frying, used primarily by the Japanese.

"Our findings suggest the method of preparation of fish may modify the protective effect of omega-3 fatty acids. The results can help educate people on how much fish to eat and how to cook it to prevent heart disease," Meng said. "If you want to eat fried fish, do it occasionally, but try to avoid it. Or eat it the Japanese way and stir fry it."

23% Reduction in Heart Disease Among Men Who Ate the Most Fish

Meng said that CHD mortality is known to differ by ethnicity in Hawaii, and that the disparities are not fully accounted for by known risk factors. She and her colleagues examined the source, type, amount, and frequency of dietary omega-3 consumption among participants in the Multiethnic Cohort (MEC) Study living in Los Angeles, CA and Hawaii. The cohort consisted of more than 80 000 men and 100 000 women of African American, Caucasian, Japanese, Native Hawaiian, and Latino descent, aged 45-75 years at recruitment, which occurred from 1993 to 1996; those with a history of myocardial infarction or angina were excluded. Food frequency questionnaires were used to examine fish consumption and omega-3 intake from other sources, such as plant materials like soy sauce.

The fact that the different ethnic groups in the MEC study have different sources of omega-3 provides a unique opportunity to look at this issue, and also to examine ethnic-specific data on methods of fish preparation, she said.

During an average of almost 12 years of follow-up, there were 2604 male and 1912 female deaths due to CHD.

Among men, those in the highest quintile (consuming a median of 3.3 g of dietary omega-3 fatty acids per day) had a 23% lower CHD mortality than those in the lowest quintile (median, 0.8 g per day), Meng said.

The benefits of omega-3 were more apparent in white, Japanese, and Latino men than in African Americans and native Hawaiians, she noted.

12%-15% Increase in CHD Death With Deep Fried, Salted, and Dried Fish

But these benefits were confined to raw fish or fish prepared by boiling or baking, she noted. Among both men and women, consumption of more than 6.2 g of deep fried fish per day (excluding stir-fried fish) led to a 12% increase in CHD mortality, Meng stressed, and even smaller amounts of salted or dried fish daily upped mortality by 15%. This latter effect could be due to the amount of sodium found in fish prepared in this way, she said.

Among men, Japanese ate the most fried fish, but they tended to prepare it by stir-frying, which does not seem to have the same risk as deep frying, Meng said. Second in consumption of fried fish were native Hawaiians, who also ate the most salted and dried fish, followed by African Americans.

Among women in general, the relation between fish consumption and mortality was "all in a protective direction," Meng said, but there was not as strong a dose-response as for men. Plant sources of omega-3, such as soy sauce and tofu, were particularly protective for women, she said, stressing that low-sodium products are best.

Source: http://www.medscape.com/viewarticle/713037

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