Correlating Nutrition to Recent Cancer Mortality Statistics

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No doubt, all of us in cancer research were excited and pleased to see, 25 years after the signing of the National Cancer Act, a reduction in the mortality rates of several major cancers ( 1 ). As to be expected, success, in contrast to failure, has many “fathers.” Some of the credit must go to improved early detection and therapy. At the same time, we need to examine what role lifestyle changes may have played. In the long overdue reduction of lung cancer in U.S. males, reduction in cigarette smoking has obviously played a determining role. Unfortunately, however, this is not the case for U.S. women, for whom we are likely to see a continued increase, in part because women appear to be at greater risk for lung cancer for a given amount of tobacco exposure than men ( 2 ).

With respect to breast, prostate, and colon cancers, all three sites show a reduction in mortality for 1989–1994 of over 6%. Could it be that a similar change in lifestyle, such as altered dietary patterns, could have equally affected all three sites? We have considered for some time that dietary fat, particularly with respect to saturated and unsaturated fatty acids, significantly affects the promotion and progression of these cancers. The evidence for this assertion is based largely on geographic variations in the mortality from these cancers that correlate with nutritional differences, as well as on studies in laboratory animal models and mechanistic studies on the effect of the amount and type of specific fatty acids on such variables as endocrine responses, immune functions, and gene expression. Two major sources of saturated fat in our diet are beef and dairy products. During recent decades, the per capita consumption of beef and of whole milk has declined substantially ( 3 ). Moreover, several national surveys, including the U.S. Department of Agriculture (USDA) Nationwide Food Consumption Survey, the USDA Continuing Survey of Food Intakes of Individuals, and the National Health and Nutrition Examination Surveys, indicate that overall fat intake in the U.S. population has declined steadily during the past three decades from over 40% of total calories in the 1970s to approximately 36%–37% in the 1980s and to 34% in the 1990s ( 4 , 5 ). Saturated fatty acids as a percentage of total daily calories declined from 15% in the 1970s to 13% in the 1980s and to 12% in the 1990s ( 4 ). Levels of cholesterol in plasma (mean mg/dL; age adjusted for ages 20–74 years) declined from 214 in the 1970s to 213 in the 1980s and to 205 in the 1990s ( 6 ). Correlations by themselves, of course, do not mean causation, but if these correlations are consistent with ecologic, biologic, and mechanistic evidence, then we have reason to believe that decreased total fat intake may be one of the factors responsible for the decline in the mortality rates for breast, prostate, and colon cancers.