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Fish Consumption Advice for Alaskans

Fish and fish oils are known to have a favorable effect on a variety of factors that are known or suspected of reducing cardiovascular disease risk.128-130 Dietary intake of omega-3 polyunsaturated fatty acids shifts the eicosanoid balance from proaggregatory and vasoconstrictory to antiaggregatory and vasodilatory. 128,131

While all of the mechanisms by which omega-3 polyunsaturated fatty acids work to improve cardiovascular f u n c t i o n i n g r e m a i n t o b e d e t e r m i n e d , o n e i m p o r t a n t m e a s u r e i s t h e d e c r e a s e d r i s k o f s u d d e n d e a t h (i.e., myocardial infarction) among men without evidence of prior cardiovascular disease.132 The potential

decrease in cardiovascular mortality from increased omega-3 polyunsaturated fatty acid consumption is quite large. In one review of the evidence from three large clinical trials, the authors suggest that omega-3 polyunsaturated fatty acids may be as important as statins for the prevention of death in post-myocardial infarction patients.133 Another recent review concluded that modest fish consumption (1–2 servings per week), especially fatty fish rich in omega-3 polyunsaturated fatty acids, reduces the risk of coronary death by 36%, and total mortality by 17%. 134

Cancer Cancer incidence rates among Alaska Native people have increased by nearly 50% during the last 30 years.138 While the causes for this increase are likely complex, concern among Alaska Natives exists that exposure to contaminants in traditional foods contributes to the problem:

“People on the island are very concerned about the animals we eat now. They think there might be something wrong because they are getting very skinny. A couple of years ago there was a lot of dead birds all over the beach. I wonder why this is happening. The elders said that there never used to be cancer but now they are getting cancer. They think it might be from the Northeast Cape site.”

Herman Toolie, Savoonga (quoted in 139)

Recent ecologic studies involving cross-national comparisons have documented an inverse relationship between per capita fish consumption and the incidence of breast and prostate cancer, and a temporal association exists between decreased fish consumption over time and increased incidence of these cancers (reviewed in 140). These temporal trends are also seen in Alaska where data from 1984–1998 indicate that the greatest increases in cancer incidence among Alaska Native people are for lung, breast, and prostate cancers.138 During the first five years of the Alaska Native Cancer Registry (1969–1974), Alaska Native women developed breast cancer half as often as white women in the United States; however, this has changed to the extent that the incidence rates in both groups were nearly equal during the years 1984–1998, primarily due to an increase in incidence among Alaska Native women. 138

In recent years, many studies have worked to evaluate the relationship between fish consumption and cancer. Unfortunately, many of these studies have evaluated total fish consumption, and have not given consideration to intake of omega-3 fatty acids, which are more plentiful in fatty fish compared with lean fish. Studies indicate that the omega-6 to omega-3 ratio is more important than total fish consumption to the risk of developing cancer. A recent review of the literature on associations between polyunsaturated fatty acids and breast and colorectal cancer identified the omega-6:omega-3 ratio as “crucial,”141 as omega-3 fatty acids act through competitive inhibition. Thus, the inhibitory effects of omega-3 polyunsaturated fatty acids on the enzyme systems involved in cancer development and progression appear to depend on the relative levels of omega-6 polyunsaturated fatty acids. In addition, a diet high in omega-6 polyunsaturated fatty acids leads to oxidative DNA damage, and increases the risk for breast and colon cancer, and for metastatic cancers. Thus, the mixed results from epidemiologic studies may result from incomplete consideration of the fatty acid ratio.142 Another complicating factor is that food frequency questionnaires might not be sensitive enough to accurately estimate fish and omega-3 polyunsaturated fatty acid consumption. 141 143

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