Meat, fish and fat intake in relation to subsite‐specific risk of colorectal cancer: The Fukuoka Colorectal Cancer Study

Colorectal cancer is one of the most common cancers in the world, accounting for nearly 10% of all incident cases.⁽¹⁾ In Japan, mortality from and incidence of colorectal cancer, especially of colon cancer, have increased markedly over the last decades,⁽²⁾ and it has been argued that the increase is primarily due to Westernization of the Japanese diet.⁽³⁾ Of the dietary factors possibly linked with colorectal cancer, fat intake has long been a matter of interest. Substantial data from animal and metabolic studies support a role for dietary fat in colorectal carcinogenesis, with high intake of saturated fat and n‐6 polyunsaturated fatty acids (PUFA) documented to increase the incidence of chemically induced colon cancer in animal models.^(4,5) However, results from case‐control and cohort studies have consistently suggested a null association between total fat intake and colon or colorectal cancer, as reviewed elsewhere extensively.^(6,7) It remains uncertain whether saturated or animal fat is related to increased risk of colorectal cancer.^(6,7) However, high intake of red meat has been implicated as being associated with an increased risk of colon or colorectal cancer.^(8,9)

There has been much interest recently in the role of n‐3 PUFA and fish oil in colorectal cancer prevention. Studies in experimental animals have suggested that n‐3 PUFA may be protective in colorectal carcinogenesis,⁽¹⁰⁾ but epidemiological findings are limited and inconsistent. A protective association between fish consumption and colorectal cancer was observed in a cohort study of women in New York,⁽¹¹⁾ and a large cohort study in Europe,⁽¹²⁾ but not in other cohort studies in Western countries as noted in a recent review.⁽¹³⁾ A case‐control study of French Canadians showed a clear protective association between dietary intake of n‐3 PUFA and colorectal cancer,⁽¹⁴⁾ whereas other case‐control studies have generally failed to find a protective association with fish or n‐3 PUFA intake in different countries.^(15–17) In Japan, fish consumption was unrelated to colorectal cancer in two cohort studies,^(18,19) but one of these found a decreased risk of colorectal cancer in individuals, especially in men,...