The World Health Organization (WHO) estimates that approximately 30 percent of cancers in Western countries are related to dietary factors. This number rests at about 20 percent in developing countries, and is believed to be increasing. Obesity and being overweight immediately follow tobacco usage as being among the most avoidable causes of cancer. Those overweight and obese are thought to be at risk for cancers of the esophagus, colon, rectum, breast, endometrium, and kidney.

As nearly 30 percent of all cancers are related to nutritional and obesity issues, eating a variety of healthy foods can go a long way. The American Cancer Society provides the following diet recommendations:

• Consume 5 or more servings of fruits and vegetables daily

• Eat plant-based foods like whole grains and beans several times a day
• To reduce the risk of colon and stomach cancers, consume green and dark yellow vegetables, soybean products, broccoli, Brussels sprouts, and cabbage
• To protect against the risk of oral, esophageal, gastric, and colorectal cancers, consume more fruits and vegetables
• Lower the amount of fat you ingest, especially fat derived from animal sources, as it can increase the risk of prostate, colon, rectal, and uteral cancers
• Limit alcohol intake, as too much drinking increases the risk for oral, esophageal, pharynx, larynx, liver, and breast cancers.

The WHO also warns against the excessive consumption of red and preserved meats, which have been associated with an increased risk of colorectal cancer. It also recommends the avoidance of some forms of salting and fermenting fish, and very thermally hot salty drinks and food. Alfatoxins, or fungal contaminants, found in some grains, peanuts, tree nuts, and cottonseed meal, are also cautioned against.