Nutritional regulation of gastrointestinal growth.

Nutrition can control gastrointestinal (GI) tract growth at many stages of development. Fetal growth of the GI tract can be inhibited by restriction of the maternal diet, decrease of blood supply to the placenta, or partial obstruction of amniotic fluid swallowing. In most species there is an immature appearance of the GI mucosa that is characterized by large, long villi extending into the proximal colon. This pattern usually changes around the time of weaning and can be modified by manipulation of the diet. While total nutrition has a profound effect on GI development, there are specific nutrients that influence the epithelium during adult life. In the small intestine, glutamine has the most important effects and this amino acid is now considered conditionally essential. In the colon, dietary fiber has the strongest influence on mucosal structure and turnover. While it has been assumed that concentrations of bile acids and/or short chain fatty acids are the mediating factors, there is substantial evidence that mitigates against this conclusion. A better understanding of the molecular changes accompanying alterations in GI growth may lead to more comprehensive strategies for improving intestinal function and decreasing the risk of colon cancer.