Eating a healthy, balanced diet can help you keep a healthy body weight. Maintaining a healthy weight is important because obesity is the second biggest preventable cause of cancer after smoking.
Diet can also directly affect cancer risk. Some foods, such as salt-preserved foods and processed and red meat, can increase the risk of developing cancer. While others, such as fruits, vegetables, and foods high in fiber, can reduce the risk of cancer.
Substantial evidence shows that eating lots of processed and red meat can increase the risk of bowel cancer, and possibly stomach and pancreatic cancer.
Processed meat includes ham, bacon, salami, and sausages. Red meat includes all fresh, minced and frozen beef, pork and lamb. Fresh white meat (such as chicken) and fish are not linked with an increased risk of cancer.
Scientists think there are some ways in which processed and red meat can increase the risk of cancer – they involve the chemicals found in these meats. Some chemicals are a natural part of the meat, and others are made when the meat is preserved or cooked at high temperatures.
Red meat (including processed red meat) contains a naturally occurring red pigment called haem. Haem could irritate or damage cells in the body or fuel the production of harmful chemicals by bacteria, which could lead to a higher risk of cancer. Almost all red meats contain much higher amounts of haem than white meats. This may partly explain why red meats increase cancer risk while fresh white meats don’t.
Chemicals called nitrates and nitrites are often used to preserve processed meat. In the body, nitrites can be converted into cancer-causing chemicals called N-nitroso compounds (NOCs). The presence of these chemicals may explain why many studies have found that processed meat increases the risk of cancer more than red meat.
Cooking meat at high temperatures such as grilling or barbecuing can produce cancer-causing chemicals called heterocyclic amines (HCAs) and polycyclic amines (PCAs).
More than two dozen studies have shown that women who exercise have a 30 % to 40 % lower risk of breast cancer than their sedentary peers. The female hormone estrogen seems to play a vital role. Women with high estrogen levels in their blood have increased the risk for breast cancer. Since exercise lowers blood estrogen, it helps lower a woman’s breast-cancer risk. Exercise also reduces other cancer-growth factors such as insulin. Even older women need to be concerned about estrogen because after menopause the hormone is produced by fat cells. Women who exercise have less fat and therefore produce less estrogen. With more than 150,000 new breast-cancer cases reported in the United States each year, preventing cancer through exercise is one of the best ways a woman can take charge of her health.
Salt-preserved foods could increase the risk of stomach cancer. Salt-preserved foods include some pickled vegetables, salted fish, and cured meats.
Salt could increase stomach cancer risk by damaging the stomach lining, which causes inflammation, or by making the stomach lining more sensitive to cancer-causing chemicals. Salt could also interact with a stomach bug called Helicobacter pylori that is linked to both stomach ulcers and stomach cancer.