Certain sugar alcohols (polyols), notably mannitol, sorbitol and xylitol have gained use in food manufacturing for sweetening and technical purposes. These compounds are natural polyols that occur in small amounts in animals and plants. Some sugar alcohols, like xylitol, appear as normal intermediates in the carbohydrate metabolism. Exogenous mannitol, sorbitol and xylitol are metabolized in the human body along pre-existing, physiological pathways. Moderate doses of least xylitol and sorbitol are almost totally absorbed and metabolized, chiefly in the liver cells, thereby eventually contributing to the formation of glucose and liver glycogen. Various slowly absorbed carbohydrates, including sugar alcohols, when taken in orally in large quantities, can give rise to osmotic diarrhea. The available data indicate that the severity of such gastro-intestinal disturbances, induced by large doses of polyols, decrease in the following order: mannitol, sorbitol, xylitol. This osmotic diarrhea resembles that caused by lactose in subjects with restricted or frank lactose intolerance. The quantities of xylitol, for example, required to elicit diarrhea are so high that the consumption of xylitol for dental purposes does not cause any problems in children or adults. Long-term feeding trials and peroral loading experiments on human subjects have been unable to show any clinically significant differences between chronic users of xylitol and comparative human material in factors related to various metabolic functions of the body. These subjects have not shown any delayed or acute reactions which could be distinguished from those caused by the consumption of a sucrose diet. The available clinical data generally suggest that moderate consumption of the above polyols is not harmful to human metabolism.