Dietary wheaten bran in baboons: long-term effect on the morphology of the digestive tract and aorta, and on tissue mineral concentrations.

Two groups of 13 young baboons, each consisting of 8 males and 8 females, were fed on either high- or low-bran diets (based on wheat of either high or low extraction rate) for a period of 26 months. All animals grew well and remained in good condition throughout. Male (but not female) baboons on the high-bran diet had lower (p less than 0.05) concentrations of zinc in serum and bone, despite a low phytate: zinc molar ratio and a high intake of zinc. Particle-induced X-ray emission analysis showed there to be lower concentrations of calcium, copper, zinc, sulphur, potassium and nickel in the livers of baboons on the high-bran diet (P less than 0.005). Baboons on the low-bran diet passed smaller quantities of softer faeces, they had fewer nodules of lymphoid tissue in the distal portion of the colon (P less than 0.05), and within mucosal microherniations of their ileo-caecal valves the epithelial cells showed a greater tendency to squamous transformation (P less than 0.05). Mucosal microherniations of the ileo-caecal valves tended to be more frequent and larger in size (P less than 0.05) in animals of the low-bran group. Morphometrical studies did not reveal any differences in the general structural development of the digestive tract. The high-bran diet had no effect on serum cholesterol concentrations, nor on the incidence or severity of atherosclerotic lesions of the aorta.