The cause of the disease is multifactorial. One in three cancer cases can be prevented through simple lifestyle changes – increase nutrient intake of non-starchy fruits and vegetables to at least 400gm/day, reduce red and processed meat to less than 500gm/week, lower salt intake to less than 6gm/day, reduce alcohol intake, avoid sugary drinks and reduce fast food intake, reduce body weight, increase physical activity, and breastfeeding for women. This course does not focus on tobacco and lung cancer. Diet is recommended to include 1/3 or less of animal protein, 2/3 or more of vegetables, fruits, whole grains and beans.
Although much research is being conducted on antioxidant and phytochemical properties inherent in fruits and vegetables, not a lot of information is available to support that they prevent cancer. What is known is that these nutrients do possess some beneficial effects in the fight against cancer. So far hundreds of these nutrients have been identified.
Colorectal cancer: Convincing evidence to support that increased red and processed meat diet, increased body fat, increased alcohol intake in males, and reduced physical activity are risk factors. Probable excess alcohol intake in females is a risk factor.
Prostrate cancer: Family history, (limited evidence that) increased red and processed meat intake, (probable evidence that) increased high-fat dairy and calcium intake, and obesity, are risk factors. Overall evidence suggests that selenium, vitamin E supplements do not lower the risks nor prevent prostrate cancer.
Breast cancer: Age, alcohol, family history, inactivity, and excess weight are risk factors. Breastfeeding appears to be protective. For breast cancer survivors, current recommendations are to reduce reliance on animal foods and increasing amounts of plant foods, with a moderate level of soy foods. General guidelines are to avoid soy supplements. Recommended level of calcium intake for postmenopausal women to prevent osteoporosis is 1,500mg/day, with 400-800 IU vitamin D/day.
Alcohol and cancer: High intake increases risk of cancer of the esophagus, mouth and throat, breast, bowel liver and colorectal. Alcohol is a toxin and when broken down in the body, it damages DNA cells, produces carcinogenic compounds, and raises the levels of some hormones, like estrogen. What is an allowable standard drink? One drink for women and two for men per day (see chart by the National Institute of Alcohol Abuse & Alcoholism). This association is purely observational and has not been proven as cause and effect as it is unethical to experiment with humans. So the risk threshold for a person can vary.