Diet and cancer: possible explanations for the higher risk of cancer in the poor

Humans have always had to eat; diets have always contained the same nutrients and bioactive constituents. Therefore, some have argued, the present pattern of diseases and changes in that pattern cannot be causally linked to dietary intake. This argument, its naivety notwithstanding, raises some important issues for the way we think about the epidemiology of nutrition and disease. Current research on diet and specific diseases is based, obviously, on the premise that this argument is false. This chapter uses a broad brush to present the evidence for a significant and causal association between eating patterns and cancer. It shows that, far from being an implausible link, the relationship between dietary patterns and cancer is largely explained by the dependence of humans on their food supply--dependence not merely in the sense of providing energy to sustain life, but more related to evolutionarily adaptive patterns of food intake and contemporary aberrations in those patterns. The chapter also shows that it is plausible that at least part of the explanation for the higher risk of cancer among the poor in both rich countries and poor countries relates to the extent of the aberrations in food supply and eating patterns.