Nutrition and Cancer

INTRODUCTION

The field of investigation of the role of nutrition in the cancer process is very broad (1). It is becoming clearer as research continues that nutrition plays a major role in cancer. It has been estimated by the American Institute for Cancer Research and the World Cancer Research Fund that 30–40 percent of all cancers can be prevented by appropriate diets, physical activity, and maintenance of appropriate body weight (2). It is likely to be higher than this for some individual cancers.

A possible relation of dietary fat intake to cancer incidence has also been hypothesized because the large international variations in rates of cancers of the breast, colon, prostate, and endometrium are strongly correlated with apparent per capita consumption (3-5).  However, these associations are due to correlations with intake of animal fat, not vegetable fat (6); raising the possibility that fat per se is not the responsible factor.

Based on epidemiologic investigations and animal studies, dietary fat increasing has been hypothesized to act by excretion of bile acids, which can be converted to carcinogens or promoters (7). One of the most important messages of modern nutrition research is that a diet rich in fruits and vegetables protects against cancer. There are many mechanisms by which fruits and vegetables are protective, and an enormous body of research supports the recommendation for people to eat more fruits and vegetables (2).

The evidence that high consumption of fruits and vegetables can reduce the risk of many cancers is strong, but the constituents of these foods that are responsible for these reduced risks are less clear. These foods contain many biologically active chemicals, including recognized nutrients and many more nonnutritive constituents, which could potentially reduce cancer incidence (8). Potentially protective factors include various carotenoids, folic acid, vitamin C, flavonoids, phytoestrogens, isothiocyanates and fiber.

Fiber has been hypothesized to reduce risk of colon cancer by diluting potential carcinogens and speeding their transit through the colon, binding carcinogenic substances (9), altering the colonic flora (10-12), reducing the pH (13), or serving as the substrate for the generation of short-chain fatty acids that are the preferred substrate for colonic epithelial cells (14). Higher intake of fiber has also been hypothesized to reduce risk of breast cancer by interrupting the enterohepatic circulation of estrogens (15). However, in prospective studies, little or no relationship has been observed between fiber intake and risk of breast cancer (16-18).

Data on vitamin supplement use and cancer incidence are limited. High-dose supplements of vitamins C and E have not been associated with reductions in breast cancer incidence (16, 19). Selenium is a mineral with anti-cancer properties. Many studies in the last several years have shown that selenium is a potent protective nutrient for some forms of cancer. The Arizona Cancer Center posted a selenium fact sheet listing the major functions of selenium in the body (20).

CONCLUSION

What is the result when all of these things are put together? What if all of these factors reviewed here were taken into account and put into practice? This anticancer diet would have:

• Adequate, but not excessive calories.
• 10 or more servings of vegetables a day, including cruciferous and allium vegetables; vegetable juice could meet part of this goal.
• 4 or more servings of fruits a day.
• Low in total fat, but containing necessary essential fatty acids.
• No or less red meat.
• Supplemented with ~200 μg/day selenium,
• Supplemented with 1,000 μg/day methylcobalamin (vitamin B12).
• Very rich in folic acid (from dark green vegetables).
• Adequate sunshine to get vitamin D, or use 1,000 IU/day supplement.
• Very rich in antioxidants and phytochemicals from fruits and vegetables, including α-carotene, β-carotene, β-cryptoxanthin, vitamin C (from foods), vitamin E (from foods). Maintaining regular exercise, balanced diet and avoiding excessive bodyweight are the key elements for fighting cancer.