Clinical trials in nutrition

Trials of nutritional intervention in a wide range of health and disease states, preventive and therapeutic, are required. Not only has the emergence of chronic non-communicable disease (CNCD) with acknowledged nutritional pathogenesis created this imperative need, but so also have other conditions which, previously, had not been regarded as nutritionally based. Among the latter are health problems associated with ageing: the menopause, a decline in immune function, and a decline in cognitive function. At the same time, there is a new set of materno-foetal and infant nutrition issues for investigation which relate to new food exposures and the long-term effects of nutritionally mediated gene expression. The emergence of the new food science of phytochemicals with human biological importance also sets the scene for their evaluation in traditional diets and novel foods. Such trials are more complex than comparable pharmacotherapeutic studies because of the complexity of food chemistry, as well as the food behavioural changes which may accompany a nutritional intervention, and the general problem of there not being a 'gold standard' for food intake methodology. Choice of study population is also a key issue in relation to the extrapolation of findings from a particular trial, with population representativeness being an advantage. In order to obtain useful information on manageable sample sizes, either intermediate end-points (short of morbidity and mortality) need to be studied or high-risk groups (such as the aged) need to be recruited. There are some unique ethical issues which must inform clinical nutrition trials. These include certain preventive imperatives like the right to be fed, the risks in disruption of food cultures and the need for food security and sustainability. Rapid changes in the food supply do, however, make such trials more important, while the value of food-health knowledge that cannot be obtained by trial must still be appreciated.