Diet And Cancer
Before closing the discussion of nutritional pathology, it is worthwhile to sum up the relationship of constituents of the diet with carcinogenesis discussed in the previous chapter and the role of some foods in cancer prevention.
Table of Contents
Read And Learn More: General Pathology Notes
Diet And Carcinogenesis
The following mechanisms build up the relationship of diet with the pathogenesis of cancer:
- Dietary Content of Exogenous Carcinogens:
- The most important example in this mechanism comes from the naturally-occurring carcinogen aflatoxin which is strongly associated with a high incidence of hepatocellular carcinoma in those consuming grain contaminated with mold, Aspergillus flavus.
- Artificial sweeteners (e.g. saccharine cyclamates), food additives, and pesticide contamination of food are implicated as carcinogens derived from the diet.
- Endogenous Synthesis of Carcinogens or Promoters:
- In the context of the etiology of gastric carcinoma, nitrites, nitrates, and amines from the digested food are transformed in the body to carcinogens—nitrosamines and nitrosamides.
- In the etiology of colon cancer, low fibre intake, and high animal-derived fats are implicated. High-fat diet results in rise in the level of bile acids and their intermediate metabolites produced by intestinal bacteria which act as carcinogens.
- The low-fiber diet, on the other hand, does not provide adequate protection to the mucosa and reduces the stool bulk and thus increases the time the stools remain in the colon.
- In the etiology of breast cancer, epidemiologic studies have implicated the role of animal proteins, fats, and obesity but the evidence is yet unsubstantiated.
- Inadequate Protective Factors: Some constituents of diet (vitamin C, folate, selenium, beta carotene) in normal amounts in the body act as antioxidants and protect the cells against free radical injury.
Cancer Preventing Foods
Apparently, there are some foods that help in prevention and reduce the risk of certain cancers.
- Plant-based Foods: These are fruits and vegetables which contain naturally-occurring phytochemicals that lower cancer risk.
- The examples are:
- Carotinoids present in red, orange, yellow, and dark green vegetables. Lycopene is a carotenoid present in tomatoes, grapes, watermelons, apricots.
- Polyphenols found in certain herbs, spices, vegetables green tea, and apples.
- Allium compounds are found in garlic and onions.
- The examples are:
- Dietary fiber: Fibre in the diet helps in adding bulk to the stool and thus food moves down through the digestive tract, and lowers risk of some cancers, particularly colorectal cancer.
- Foods containing dietary fibre are:
- Whole grains and seeds and their products.
- Pulses and legumes.
- Vegetables and fruits.
- Antioxidants: These include a few vitamins (C, E, folate), minerals (selenium) and beta-carotene.
- Vitamins: Vitamin C lowers the risk of stomach cancer. But vitamin E does not have any protective role; instead its excess increases risk of prostate cancer. Low folate level has a higher risk of some cancers for example Breast, Colon, and Prostate; Thus supplementation of folate reduces cancer
risk. - Minerals: Selenium lowers the risk of cancer of the prostate, lung, and colon.
- Beta carotene: Contrary to past reports, there is no added advantage of high dose of beta carotene in preventing cancer. However, the role of many other constituents of diet remains unproven yet as regards their high-risk association or role in lowering cancer risk.
Diet and Cancer:
Diet plays an important role in health and disease.
- Mechanisms of dietary components acting in carcinogenesis are due to certain exogenous carcinogenic agents in diet, endogenous synthesis of carcinogens or their promoters, and dietary content poor in protective factors against cancer, mainly antioxidants.
- Some constituents of diet lower cancer risk. These are: dietary phytochemicals, fibre, and antioxidants (vitamin C, folate, selenium, beta-carotene etc)
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