Humans as cucinivores: comparisons with other species.

We discuss the relations of processed foods, especially cooked foods, in the human diet to digestive tract form and function. The modern consumption of over 70% of foods and beverages in highly refined form favours the diet-related classification of humans as cucinivores, rather than omnivores. Archaeological evidence indicates that humans have consumed cooked food for at least 300-400,000 years, and divergence in genes associated with human subpopulations that utilise different foods has been shown to occur over periods of 10-30,000 years. One such divergence is the greater presence of adult lactase persistence in communities that have consumed dairy products, over periods of about 8,000 years, compared to communities not consuming dairy products. We postulate that 300-400,000 years, or 10,000-14,000 generations, is sufficient time for food processing to have influenced the form and function of the human digestive tract. It is difficult to determine how long humans have prepared foods in other ways, such as pounding, grinding, drying or fermenting, but this appears to be for at least 20,000 years, which has been sufficient time to influence gene expression for digestive enzymes. Cooking and food processing expands the range of food that can be eaten, extends food availability into lean times and enhances digestibility. Cooking also detoxifies food to some extent, destroys infective agents, decreases eating time and slightly increases the efficiency of assimilation of energy substrates. On the other hand, cooking can destroy some nutrients and produce toxic products. The human digestive system is suited to a processed food diet because of its smaller volume, notably smaller colonic volume, relative to the intestines of other species, and because of differences from other primates in dentition and facial muscles that result in lower bite strength. There is no known group of humans which does not consume cooked foods, and the modern diet is dominated by processed foods. We conclude that humans are well adapted as consumers of processed, including cooked, foods.