The effects of a high-animal- and a high-vegetable-protein diet on mineral balance and bowel function of young men.

1. Twelve young men were given for periods of 20 d, each of three mixed diets, namely a low-protein (LP) diet (9% total energy as protein, 67% of animal origin), a high-animal-protein (HA) diet (16% total energy as protein, 67% of animal origin) and a high-vegetable-protein (HV) diet (16% total energy as protein, 67% of vegetable origin). Retention of calcium, magnesium, iron, zinc and copper as well as various bowel function indices were investigated during each dietary period. 2. Neither the HA diet nor the HV diet changed the retention of the minerals considerably. Only Fe balance decreased significantly on the HV diet. 3. Substituting the HV diet for the HA diet resulted in significant increases in faecal wet weight (17 g/d), defaecation frequency (0.12 stools/d), faecal volatile fatty acids (2.6 mmol/d) and a decrease in faecal bile acids (128 mumol/d). 4. It is concluded that a HV diet, rather than a HA diet is to be recommended with respect to bowel function, whereas the HV diet does not necessarily have a significant influence on mineral retention.