What’s on the menu?
December 18, 2014
Does an apple a day keep the oncologist away? While eating more fruit is certainly part of a healthy lifestyle, the research remains inconclusive on whether eating apples, or any one specific food for that matter, can reduce the risk of cancer.
So-called “superfoods,” such as blueberries, kale and garlic, are often promoted because they are rich in antioxidants or reduce inflammation.
It is certainly beneficial to add healthy fruits and vegetables to the diet, but solely focusing on certain foods can make you miss out on other important nutrients.
“In green tea, for example, there are many potentially cancer protective nutrients, but those are not exclusively existing in tea. You can get those nutrients from other dietary sources,” Shu said.
Zheng and Shu lead the Shanghai Women’s and Men’s Health Studies, with more than 136,000 research subjects enrolled. Using such a large cohort, they are working to determine how lifestyle and environmental factors contribute to cancer development and prognosis and to develop new prevention strategies.
Unlike counting how many cigarettes someone smokes per day, it is difficult to accurately measure a subject’s diet. Plus there are many confounding factors—people who eat lots of fruits and vegetables also generally exercise more and get more sleep. How do you determine exactly which habit protected them from cancer?
“To determine a causal association, consistency of research findings is very important. We want to see if the results can be replicated in studies conducted in different places. We need to have a large sample size to control for variations and obtain reliable findings,” Zheng said.
The Shanghai studies have revealed several dietary factors that may be related to a reduced risk of cancer, although Zheng cautions that they are just associations at this point. He expects that with more future research, some of these will move from associations to definite causes of cancer protection.
Women who get adequate amounts of folate—a water-soluble B vitamin that occurs naturally in foods such as leafy green vegetables, fruits and dried beans and peas—have a reduced risk of developing breast cancer, although the benefit appears linked to a woman’s menopausal status. The Shanghai Study found that women who had not yet reached menopause and who had the highest average intake of folate had a 40 percent reduced risk of developing breast cancer.
High consumption of vitamin E either from diet or supplements may lower the risk of liver cancer. Vitamin E is a fat-soluble vitamin which is considered an antioxidant, and numerous experimental studies have suggested that vitamin E may prevent DNA damage. Foods rich in vitamin E include nuts, sunflower seeds and greens.
Research shows women who eat more soy food have a lower risk of developing pre-menopausal breast cancer. High soy food consumption after diagnosis of breast cancer is related to a reduced risk of recurrence and mortality. Women who eat more soy food prior to a diagnosis of lung cancer live longer than those who consume less. The association of soy food intake with lung cancer survival appears to follow a dose-response pattern until soy food intake reaches the 4-ounce tofu equivalent per day. No additional benefits were observed for women who ate more soy food than the 4-ounce tofu equivalent.
A diet rich in cruciferous vegetables—like broccoli, kale, cauliflower, Chinese cabbage, bok choi and turnips—may lead to decreased risk for breast cancer in women. In one study, while there was only a weak association between a diet high in these vegetables and a reduction in breast cancer risk for the overall study population, there was a striking risk reduction (50 percent) among women with a certain genetic profile. This indicates an individual’s genetic makeup may influence the effect of diet on cancer risk.
Drinking green tea may lower a woman’s risk of developing some digestive system cancers, especially cancers of the stomach, esophagus and colorectum. The researchers found that regular tea consumption, defined as tea consumption at least three times a week for more than 6 months, was associated with a 17 percent reduced risk of all digestive cancers combined. Those who consumed about two to three cups per day had a 21 percent reduced risk of digestive system cancers.