Protein, Fat and Crohn's Disease

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Protein, Fat and Crohn's Disease

Reference: Shoda R, Matsueda, K, Yamota S, Umeda N. Epidemiologic analysis of Crohn's disease in Japan: increased dietary intake of n-6 polyunsaturated fatty acids and animal protein relates to the increased incidence of Crohn's disease in Japan. Am J Clin Nutr 1996;63:741-745.

Summary: In this 19-year epidemiologic analysis, Crohn's disease was strongly correlated with increased dietary total fat, animal fat, polyunsaturated fats, animal protein, milk protein and the ratio of n-6 to n-3 fatty acid intake. It was less correlated with intake of total protein, was not correlated with intake of fish protein, and was inversely correlated with intake of vegetable protein. The strongest independent risk factor in the diet was an increased intake of animal protein.

Comments/Opinions: This study was meticulous in its execution. Crohn's disease was specifically defined through a barium study and/or a colonoscopic examination with histopathologic study of the biopsied specimens. The chronologic change in intake of dietary elements was taken from yearly interviews assessing precise dietary intake over a five day period. Although this study was undertaken in Japan, it appears the results can be cautiously generalized to the U.S. population. The incidence of Crohn's disease in Japan (and the U.S.) has been steadily increasing in recent decades. Because the genetic background of the Japanese people is relatively homogeneous and has changed only slightly, the increased incidence of Crohn's disease there may be due to environmental changes such as alterations in eating habits. As Crohn's disease has a much higher incidence in Western industrial nations than in Japan, a fruitful area to explore is therefore the relationship of the disease to the increased prevalence of the "Westernized" diet in Japan.

A number of studies have shown that total parenteral nutrition or total enteral feeding with an elemental diet are effective in active Crohn's disease, as well as effective in maintaining remission. It would appear that the reason for the effectiveness of this therapy is the role dietary fat and/or antigenic dietary protein has in the etiology and pathogenesis of this disease. Recently, administration of an n-3 fatty acid, EPA, has been shown to mediate ulcerative colitis, which has some similarities to Crohn's disease. It therefore makes intuitive sense that there would be a dietary connection. This study seems to support the conclusion that n-3 fatty acids may be beneficial. It has been reported that milk proteins aggravate Crohn's disease and that there is a good correlation between disease activity and antibody titers against some milk proteins in Crohn's disease patients. This is also in line with the results here.

Although several epidemiologic studies have shown Crohn's disease is clearly linked with certain geographic features, its exact etiology is still somewhat of a mystery. Genetic factors no doubt play a role. Studies assessing intestinal permeability have shown a relationship between increased permeability and disease activity and relapse. It has also been shown that first degree relatives of Crohn's patients have a statistically significant increase in permeability as compared to controls. However, the increased incidence of this disease in the genetically homogeneous population of Japan suggests environmental factors play a strong role, and this has been born out in U.S studies as well. Although there are always some limitations to an epidemiologic study of this type, nonetheless this report can be added to the growing body of literature that implicates specific dietary factors in the etiology of this chronic inflammatory disorder.

Natural Product Research Consultants, Inc.

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By D. Lukaczer

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