A framework to understand diet, physical activity, body weight, and cancer risk

Excerpt

In 1981, Doll and Peto attributed about 35% of cancers in the United States to diet and nutrition [1]. Belief in this estimate stands largely intact [2]. However, there has been some frustration in linking the precise causes [3], especially following many disappointing randomized trials that focused mostly on single factors such as fat, folic acid, beta-carotene, and vitamin E. Yet, 35% is a large proportion and seemingly should have a more obvious explanation. Some individual nutrients may play a role for specific cancers—for example, carotenoids may protect against estrogen receptor-negative breast cancer and calcium against colon cancer [4, 5]. Recent evidence indicates that early-life diet may be important [6]—such factors may have been missed in the many studies that have assessed intake mostly in middle-age and older persons. Yet, it seems unlikely that a single or several nutrients would account for a sizable proportion of the 35%. In the past several decades, obesity and physical inactivity have emerged as risk factors for a number of cancers, especially those of the digestive system and female reproductive organs [7‐9]. In this brief paper, I will propose an integrative framework to describe how diet, physical activity, and body weight, in an interactive manner, may exert their major influences on cancer risk. …