Adding low-sodium soy sauce or tofu to the fish will enhance the benefits, said the researchers.
The study’s lead researcher, Lixin Meng, Ph.D candidate at 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 vs. fried fish, but one can tell from the (risk) ratios, boiled or baked fish is in the protective direction but not fried fish."
The results suggest that the cardioprotective benefits vary by gender and ethnicity, possibly depending on preparation methods, genetic susceptibility or hormonal factors.
The study examined the source, type, amount and frequency of dietary omega-3 intakes among groups of different gender and ethnicity. The researchers focused on 82,243 men and 103,884 women of African-American, Caucasian, Japanese, Native Hawaiian and Latino descent. The group’s age ranged from 45 to 75 years and none had a history of heart disease. Researchers studied the intake of canned tuna, other canned fish, fish excluding shell fish, or soy products that contain plant omega-3s (soy, tofu and shoyu) and preparation methods: Raw, baked, boiled; fried; salted or dried. Grilled fish was not included in the study.
The group with highest consumption of omega-3 fatty acids consumed a median 3.3 grams of omega-3 fatty acids a day compared with a median of 0.8 grams a day by the lowest consumption group.
Omega-3 intake was inversely associated with overall risk of death due to heart disease in men — a trend mainly observed in Caucasians, Japanese Americans and Latinos. But few blacks or Hawaiians were included in the study, so the results should be interpreted cautiously, said Meng.
Men who ate about 3.3 grams per day of omega-3 fatty acids had a 23 per cent lower risk of cardiac death compared with those who ate 0.8 grams daily.
For women, the omega-3 effect was cardioprotective at each level of consumption but not consistently significant, she added. Salted and dried fish was a risk factor in women, according to the study.
Meanwhile, consuming less than 1.1 gram/day shoyu and teriyaki sauce was protective for men but not for greater than 1.1 gram/day. For women, shoyu use showed a clear inverse relationship to death from heart disease, said Meng.
Eating tofu also had a cardioprotective effect in all ethnic groups.
"Our findings can help educate people on how much fish to eat and how to cook it to prevent heart disease," said Meng. "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 personalized to ethnic groups, and future study could identify susceptibility at the genetic level."
Source: The American Heart Association.
Published: News release from the American Heart Association.
Title: An American Heart Association Pacific Mountain Pre-doctoral Fellowship grant funded the study.
Authors: Lixin Meng, Lynne Wilkens, Dr. P.H., and Laurence Kolonel, M.D., Ph.D.