September 1992, Volume 42, Issue 9

Editorial

DIET AND CANCER

Fatima Nizami  ( Pakistan Medical Research council, Research Centre, Jinnah Postgraduate Medical Centre, Karachi. )

The evidence, reviewed by the Committee of National Cancer Institute (NCI) Of USA, suggested that cancers of most major sites are influenced by dietary pattern and in principle should therefore be preventable. NC! also points out that different dietary components have a specific role in the incidence or prevention of cancer of specific sites1. Vitamin C reduces the cancer risk of oral and laryngeal cancers in addition to other sites2,3. The protective effect of vitamin C and beta carotene intake has also been reported in pharyngeal cancers4. Epidemiological evidence shows people with above average blood retinol levels or beta carotene intake are at low average risk of cancer5-7. Other studies have shown an association between dietary fat, especially the saturated fat and the occurrence of cancer at several sites8-10. Diet is responsible for 60% of cancers in women1. International differences in breast cancer morbidity and mortality are substantial and suggestive of the influence of environmental factors11. Although it is difficult to rule out a small contribution of genetic factors to such differences, studies of population migration12 indicate that environmental factors (diet) predominate in the incidence of breast cancer. Dietary factors such as sugar13, butter14,15, cheese, liquid milk and green vegetable intake16 and particularly total fat intake8,13-19 were also correlated with breast cancer. Graham et al20 reported cruciferous vegetables to have a protective effect (benzpyrene hydroxyl activity against cancer development) in a case control study. Studies in buffalo have proposed a biological rationale for this hypothesis21.
Following foods and nutrients are regarded as the most important factors among causes of cancer and are related to cancer in a complex manner22:


1. Grains (such as peanuts and corns) growing in the hot and humid countries are contaminated with carcinogenic mycotoxins such as aflatoxin B1 produced by aspergillus flavus.
2. Some kinds of foods additives such as AF2 and butter yellow are mutagenic and carcinogenic.
3. Some types of mutagens/carcinogens are produced by heating foods.
4. From foods or their components which are non-carcinogenic, some types of carcinogens are formed in the gastrointestinal tract. For example, nitrosamines are formed in the mouth or stomach when nitrites contained in the saliva and foods or nitrites reduced from nitrates contained in pickled vegetabies and some other foods, react with the low grade amines contained in the meat of fish.
5. High fat and low fibre diet is regarded as a high risk factor for colorectal cancer through abnormal metabolisms of bile acids.
6. High concentration of salt is regarded as a high risk factor for stomach cancer from epidemiological and experimental studies. $
7. Vitamin A (carotene) and vitamin C have inhibitory effects for carcinogenesis.
8. It is possible that poor nutritional status increases the susceptiblity to viral infection (including on­cogenic viruses) and conversely over nutrition promotes cancer growth. In addition to these factors, hardness and volume of foods, eating practices (such as chewing and regularity of meals) and the methods of preserving foods (salting, smoking, refrigeration and freezing) have been suspected to be related directly or indirectly to car­cinogenesis22. The following table23 summarizes the relationship between food/nutrients and cancers which are frequent or increasing in Japan and which have been suggested to be associated with dietary habits in the previous epidemiological studies.

REFERENCES

1. Grobstein, C Executive summaty; diet, nutrition and cancer. Committee on Diet, Nutrition and cancer. Asaembly of Life Science. Nutst Res, Council Nutrition Today, 1982, pp. 20-25.
2. Graahm, S., Mittlin, C, Msrshall,J., Priore, It, Rzeplta,T. andShedd, D. Dietaty factors in the epidemiology ofcancer of the larynx. Am.J. Epiderniol., 1981; 111:675-79.
3. Graham, S., Haughey, B., Marshall, 3., Priore, R., Byers, T., Rzepka, T., Mettlin, C and Ponies, i.E. Diet in the epidemiology of carcinoma of the prostate gland. JNcL, 1983; 70:687-92.
4. Wine, D.M., Ziegler, R.G., Pickle, LW., Gridley, G., Blot, W.J. and Hoover, R.M. Diet in the etiology oforal and phatyngeal cancer amongwomen from the Southern United States. Cancer Res., 1984;44:1216-22.
5. Bjelka, B. DietaryvitaminAand human lung cancer. Int.J. Cancer. 1975;15:561-65.
6. Wald, N., Idle, M. and Boreham, 3. Low serum-vitamin-A and subssequent risk of cancer. Preliminary results of a prospective study. Lancet, 1980;2:813-1S.
7. Willet, W.C., Polk, B.F, Underwood, B.A., Stampper, M.J., Presell, S., Rosner, B., Taylor, J.O., Schneider, K. and Hawea, C.G. Relation of serum vitamin A and E and carotenoida Co the riskof cancer. N. EngI. 3. Med., 1984;310:430-34.
8. Carrole, K.K. and Kher, lit Dietary fat in relation to tumorigenesis. Proc. Biochem. PharmaäoL, 1975;10:308-53.
9. Tinslay, L.J., Schmitz, J.A. and Pierce, D.A. Influence of dietary fatty acids on incidence of mammary tumoucs in the C3H mouae. Cancer Res., 1979;39:4430-37.
10. Abraham, S. and Hillyard, LA. Effect of dietary 18-carbon fatty acids on growth of transplantable mammary adenocarcinornas in mice. JNCI., 1983;71:601-5.
11. MacMshon, B., Cole, P. andBrown,i. Etiology of human breastcancer; a review.JNCL, 1973:50:21-24.
12. BuelI, P. Changing incidence of hreaat cancer in lapaneac- American womcn. JNCL, 1973;51:1479-83.
13. Hems, 0. Epidemiological characteristics of breast cancer in middle and late age. Br.J. Cancer, 1970;24:226-34.
14. Lea, AJ. Dietary factors associated with death rates from certain neoplasms in man. Lances, 1966;2:332-33.
15. Dratar, B.S. and Irvin, D. Environmental factors of cancer of the colon and breast Br.J.Cancer, 1973;27:167-72.
16. Ingram, D.M. Trends in diet and breast cancer mortality in England and Wales 1928-1977. Nutr. Cancer, 1981;3:75-80.
17. Carroll, K.K., Gammal, ES. and Plunkett, ER. Dietaryfatandmammarycancer. Canad. Med. Asaoc. J., 1968;98:590-94.
18. Armstrong, B.and Doll, It Environmental fsctorsandcancerincidenceand morralityin differentcountrieswithspecialreferenceto dietarypractices; Int.J. Cancer., 1975;15:617­-31.
19. Carroll, K.K. Experimental evidenceofdietaryfsctorsand hormone-dependent cancers. Cancer Res., 1975;35:3374-83.
20. Graham, S., Dayal, H. and Swanson, M. Diet in the epidemiology of cancerof the colon and rectum.JNCL, 1978;61:709-14.
21. Wattenberg. LW. and Loab, WD. Inhibition of polycyclic aromatic bydroacarbon­induced neoplasia by naturallyoccurring indoles. Cancer Res., 1978;38:1410-13.
22. Tominaga, S. Cancer and dietary habits. Data Book of Food, Nutrition and Health. Association of Nutrition Survey (ed,) Ishiyaku-Shuppan-Kabushikigaisha, 1983, pp. 135-41.
23. Tominaga, S and Kato, I. Dietand Cancer. Asian Med. J., 1987;30:268-74.

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