Proper nutrition reduces the risk of numerous diseases, including certain cancers. According to the American Cancer Society (ACS), there is a direct link between dietary choices and 30 to 40 percent of cancers.

Good nutrition involves eating a variety of healthful foods – especially fruits and vegetables, which are rich in antioxidants. These nutrients protect the body against the tissue damage that results from normal metabolism. Because this tissue damage is linked to increased cancer risk, antioxidant nutrients may play an important role in cancer prevention.

Poor nutrition and inactivity typically contribute to excess body weight and obesity, which, in turn, increases an individual’s risk of developing many types of cancer. The National Cancer Institute (NCI) has extensively studied cancer development and its association with weight and physical activity. According to NCI's 2005 Cancer Trends Update, an estimated 20 to 30 percent of some of the most common cancers in the United States may be linked to overweight and/or physical inactivity. In addition, studies have indicated that being overweight and obese may increase the risk of death of many cancers. These factors may account for up to 14 percent of cancer deaths in men and 20 percent in women.

The relationship between obesity and cancer is not yet fully understood. However, studies have shown that obesity increases an individual’s risk of developing the following types of cancer:

• Breast cancer (in postmenopausal women)
• Colorectal cancer
• Endometrial cancer
• Esophageal cancer
• Gallbladder cancer
• Kidney cancer
• Pancreatic cancer
• Prostate cancer

In addition, obesity may contribute to a greater risk of recurrence of certain cancers after treatment.

Scientists suspect that poor nutrition may increase the risk of other cancers as well, and that good nutrition may limit the risk. Many research studies are investigating the possible links between diet and the following cancers:

• Bladder cancer
• Lung cancer
• Ovarian cancer
• Stomach cancer
• Secondary cancers

Studies of particular foods and their associations with cancer risks are ongoing. For example, research has suggested that a diet high in red meat may increase the risk of colon cancer and prostate cancer. In contrast, research has found that diets that are high in fruits and vegetables may lower the risk of lung and breast cancer. Scientists continue to examine these foods as well as other dietary factors to determine their effect on cancer development.

There are several common misconceptions about diet and cancer risk. For instance, many people believe that aspartame, a low-calorie sugar substitute, causes cancer in humans. However, no evidence suggests a link between the artificial sweetener and elevated cancer risk. There is also no evidence that the following foods and substances increase cancer risk:

• Bioengineered foods. Foods that are genetically altered or modified to achieve various benefits (e.g., improved flavor, better resistance to pests).
  
  
• Coffee
  
  
• Fluorides
  
  
• Food additives
  
  
• Irradiated foods. Foods treated with radiation to eliminate harmful organisms.
  
  
• Phytochemicals. A group of plant compounds.
  
  
• Saccharin. An artificial sweetener.
  
  
• Salt

Eating a balanced diet that is rich in nutrients is especially important for people with cancer. Consuming insufficient calories and protein is the most common nutrition problem that many cancer patients face, according to the NCI. There is no proof that eating well can slow, cure or prevent the recurrence of cancer. However, cancer patients typically benefit from additional nutrients that can help their bodies more effectively combat the disease and recover from the effects of treatment.