INTRODUCTION

Chapter 12 introduced dietary analysis and discussed physical aspects of potential foods as they might influence feeding behaviour. Here, we deal with chemical aspects of potential foods. Attempts to explain the influence of chemical factors on primate nutrition, and the dietary factors that promote or deter the uptake of nutrients, are limited by our understanding of how the primate gut operates. We are still not sure what the optimal dietary requirements are for humans (Challem, 1999). Research is developing both on theoretical (e.g. Jumars, 2000a, b) and practical levels (Minekus et al., 1999), but the effective rate of uptake is not simply a question of enzymatic action. The quantity of plant fibre that a primate ingests is a major influence on the rate of passage of food through the gut and thus digestibility. A variable gut population of micro-organisms and parasites also play a large positive or negative role, as do specialisations in the stomach or large intestine. The situation is even less clear when it comes to chemical compounds that act as feeding deterrents, toxins or anti-nutritional factors. These have largely been bred or processed out of the agricultural products on which humans feed, so they have received relatively little attention in food science. Currently, these chemicals are assessed by crude measures, such as total phenolics, which, of necessity, ignore the wide range of variation within each class of chemicals in the nature and intensity of the biological effect.