Until recently, there has been relatively little scientific research investigating the influence of food or nutrient intake on longevity. This is partly due to the fact that most investigators have been interested in the relationship of food or nutrient intake to specific diseases i.e. communicable diseases, coronary heart disease and cancer of specific sites, rather than to overall mortality or longevity. Another significant factor is the difficulty of comparing the nutritional intake of populations, owing to the wide variability in individual intake and poor individual recall of specific food items in epidemiological studies.