Fecal flora of volunteers on controlled diets.

Ten volunteers completed a 4-month diet series consisting of a control diet, a meatless diet, a high-beef diet, and the same control diet, each lasting 1 month. Fat and fiber contents were essentially the same in all four diets, but protein content was doubled during the high-beef diet. High-beef protein consumption had little effect on the composition of the intestinal flora of the volunteers. There were no significant differences detween the high-beef and meatless diets in total numbers of anaerobic, facultative, or aerobic organisms isolated, nor were there major differences in the counts of the individual genera and species of bacteria encountered. The data indicate that animal protein consumption has little effect on the fecal bacterial profile in humans. The possible influence of animal fat consumption on the metabolic activities of intestinal bacteria is discussed.