Cancer prevention guidelines may lower risk of obesity-linked cancers

"Our research aims to clarify associations between diet and physical activity in relation to cancer to encourage at-risk individuals to make lifestyle modifications that may reduce their risk of certain cancers," said Nour Makarem, a nutrition doctoral student at NYU Steinhardt and the study's lead author.

A third of cancers are estimated to be related to excess body fat, and are therefore considered preventable through lifestyle changes. Obesity-related cancers include cancers of the gastrointestinal tract, reproductive organs, urinary tract, blood, bone, spleen, and thyroid.

In 1997, the World Cancer Research Fund and the American Institute for Cancer Research released cancer prevention guidelines advising on weight management, diet, and physical activity. These guidelines, updated in 2007, provide an integrated approach for establishing healthy habits that reduce cancer incidence.

In their study, Makarem and her colleagues sought to evaluate whether healthy behaviors aligning with the diet and physical activity cancer prevention guidelines are in fact associated with reduced risk for obesity-related cancers and the most common site-specific cancers (breast, prostate, and colorectal cancers).

The researchers analyzed medical and dietary data for 2,983 men and women who were part of the Framingham Heart Study, a 60-year population study tracking factors related to cardiovascular disease as well as cancer. Focusing on data from 1991 through 2008, they identified 480 obesity-related cancers among the participants.

In order to calculate the relationship between the cancer prevention recommendations and cancer incidence, the researchers created a seven-point score based on the recommendations for body fat, physical activity, foods that promote weight gain, plant foods, animal foods, alcohol consumption, and food preparation and processing.

After adjusting for other factors that could contribute to cancer risk, including age, smoking, and pre-existing conditions, the researchers found that the overall score, as a proxy for overall concordance to the guidelines, was not associated with obesity-related cancer risk. However, when score components were evaluated separately, two different measures emerged as strong predictors of cancer risk.

In the current study, adherence to alcohol recommendations -- limiting alcoholic drinks to two for men and one for women a day -- was protective against obesity-related cancers combined and against breast, prostate, and colorectal cancers. In addition, among participants who consume starchy vegetables, eating sufficient non-starchy plant foods (fruits, vegetables, and legumes) was associated with a lower risk of colorectal cancer.

"Based on the study's results, dietary advice on preventing cancer should emphasize the importance of eating a plant-based diet and restricting alcohol consumption," said Niyati Parekh, associate professor of nutrition and public health at NYU Steinhardt and the study's senior author.