Dietary fat and cancer

The relationship between diet and cancer risk is extremely complex (7). Factors that appear to enhance carcinogenesis under one set of conditions may have no effect or even inhibit carcinogenesis under different conditions (2). The link between dietary fat and cancer is complicated by many factors, in particular total calorie intake and fatty acid composition (2). Among the fatty acids that comprise lipid, only linoleic acid is clearly linked to the enhancement of carcinogenesis in rat manunary gland (5), pancreas (4) and colon (5). 

High intake of total fat is correlated with an increased incidence of breast cancer in international comparative studies. In addition to the usual factors that confound associations between dietary fat and cancer in this type of study, countries with a high fat intake also have a lower age at menarche, later age at first birth, lower parity and higher post-menopausal body weight, which are risk factors for breast cancer (Willett, 2001b Kushi and Giovannucci, 2002). 

In response to the U.S. food labeling regulations in 1994, the FDA has proposed to define nutrient-content claims such as fat free, low fat, and reduced fat. Products labeled fat free and low fat must contain less than 0.5 g of fat per serving and less than 3 g of fat per serving, respectively. Reduced or less fat may be used on the labels of products that contain 25% less fat than regular (fuU-fat) products. Products labeled percent fat free should be based on 100 g, when product meets the definition of low fat or a 100% fat free, claim can be made when products meet the definition of fat free (contains no added fat) (12). Proposals have also been published to permit health claims for a relationship between the level of dietary fats and cardiovascular disease, as well as for a relationship between the level of dietary fats and cancer. 

Zock, P.L., Dietary fats and cancer, Curr. Opin. Lipidol, 12, 5-10,2001. 

Pariza, M.W. (1988) Dietary fat and cancer risk evidence and research needs. Annu. Rev. Nutr. 8, 167-183. 

Miwa and Yamamoto (31) described a simple and rapid method with high accuracy and reliability for the determination of C8 0-C22 6 fatty acids, which occur in esterified forms in dietary fats and oils and in living cells [the biological effects of routinely consumed fats and oils are of wide interest because of their impact on human health and nutrition (28,29), in particular, the ratio of cu-3 polyunsaturated fatty acid to w-6 polyunsaturated fatty acids (w-3/cu-6) seems to be associated with atherosclerosis and breast and colon cancers (30)]. They report improved separation of 29 saturated and mono- and polyunsaturated fatty acids (C8-C22), including cis-trans isomers and double-bond positional isomers, as hydrazides formed by direct derivatization with 2-nitrophenylhydrazine hydrochloride (2-NPH HC1) of saponified samples without extraction. The column consisted of a J sphere ODS-M 80 column (particle size 4 /xm, 250 X 4.6-mm ID), packed closely with spherical silica encapsulated to reach a carbon content of about 14% with end-capped octadecyl-bonded-spherical silica (ODS), maintained at 50°C. The solvent system was acetonitrile-water (86 14, v/v) maintained at pH 4-5 by adding 0.1 M hydrochloric acid with a flow rate of 2.0 ml/min. Separation was performed within only 22 min by a simple isocratic elution (Fig. 6). The resolution of double-bond positional isomers, such as y-linolenic ( >-6) and a-linolenic acid ( >-3) hydrazides and w-9, >-12, and >-15 eicosenoic acid hydrazides was achieved by use of this column. 

Clinton, S.K. and Visek, W.J. (1985) The Interactions of Dietary Fat and Protein on Breast Cancer. This Volume. 

A case-control study in Canada indicated an elevated risk for those with an increased intake of calories, total fat, and saturated fat (20,21). This study estimated levels of fat consumption by combining information from diet histories with information on the fat content of foods A recent case-control study in Utah Mormons indicated a positive association between dietary fat and colon cancer (10). 

The possible role of dietary fat on colon carcinogenesis has received support from studies in animal models. In several earlier studies on dietary fat and colon cancer, interpretation of results between high- and low-fat diets was complicated by the use of diets of varying caloric density and confounded by different intakes of other nutrients. However, recent studies in which the intake of all nutrients and total calories were controlled between the high-fat and low-fat groups, indicated that the amount of dietary fat is an important factor in colon carcinogenesis (27). 

Dietary Fat and Fiber and Bile Acid Excretion. In order to understand the specifics of the mechanisms whereby dietary fat influences colon cancer, the effect of type and amount of dietary fat on biliary and fecal bile acids was studied in rats (40,47,48). These... 

Over the past ten years the role of various levels and types of dietary fat and dietary antioxidants in modifying chemically induced cancer has been actively investigated in this laboratory with most of the work centering on mammary cancer. 

Epidemiological studies show that dietary fat and protein are most frequently correlated with colon cancer incidence in man (10-14). A number of studies in laboratory animals suggest that dietary fat enhances colon tumor incidence (15) although others have failed to show such enhancement (16). Summarized in this communication are animal experiments conducted by our laboratory to examine the effects of dietary protein on DMH induced carcinogenesis, mutagenesis, and toxicity. 

Nutrition and Experimental Breast Cancer The Effects of Dietary Fat and Protein... 

Singh, J., Hamid, R., and Reddy, B.S., Dietary fat and colon cancer modulation of cyclooxygenase-2 by types and amount of dietary fat during the postinitiation stage of colon carcinogenesis, Cancer Res.,... 

Erickson, K.L. 1998. Dietary fat, breast cancer, and nonspecific immunity. NutrRev 56(1) Part II S99-S104. 

Opposing effects of certain individual fatty acids could have influenced the lack of a relationship between dietary fat and fat type with the risk of breast cancer. Well-conducted animal studies suggest that linoleic acid promotes development of mammary tumors, whereas saturated, monounsatu-rated, and trans fatty acids have little or no effect. In many cases, w-3 polyunsaturated fatty acids suppress tumor development. Conjugated linoleic acid (CLA) is the most potent anti-cancer fatty acid in that amounts of 1% or less of dietary fat can substantially inhibit the development of mammary tumors (Ip, 1997). 

Basic treatment for cancer includes chemotherapy, radiations, and surgery. Strategies for prevention include modification of lifestyle factors and dietary interventions. The role of dietary fat in cancer is controversial. Many prospective studies found an increase in cancer risk (82-84), whereas others reported no association between fat intake and cancer (85-87). 

The role of dietary fat in cancer development may be a result of its influence on fecal bile acid concentrations. The release of bile acids is stimulated following ingestion of dietary fat. These acids are then converted by colonic flora to secondary bile acids, which are associated with bowel mucosal irritation and cell proliferation responses and may promote tumor growth. ... 

This chapter will provide an overview of the factors which have been studied most extensively as potential inhibitors of cancer. It will stress data in the areas where recommendations have been made to the public (1,2). We will begin with a discussion of the macro-nutrients which have received the greatest attention for their potential for modifying cancer risk, dietary fat and fiber, and the relation of these nutrients to calorie Intake. 1 will then describe data suggesting that mlcronutrlents such as vitamins A, C, and E, and the trace element selenium, may have some potential in the inhibition of cancer. Finally, I will present some recent data in support of cancer prevention by some non-nutrient components of fruits and vegetables. 

Brown, B.D. W. Thomas A. Hutchins M.C. Martini J.L. Slavin. Types of dietary fat and soy minimally affect hormones and biomarkers associated with breast cancer risk in premenopausal women. Nutr. Cancer 2002, 43, 22—30. 

Prentice, R.L. C.A. Thomson B. Caan F.A. Hubbell G.L. Anderson S.A.A. Beresford M. Pet-tinger D.S. Lane L. Lessin S. Yasmeen, et al. Low-fat dietary pattern and cancer incidence in the women s health initiative dietary modification randomized controlled trial. J. Natl Cancer Inst. 2007,99, 1534-1543. 

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