The Influence of an Exclusive Meat Diet on the Flora of the Human Colon

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Abstract
A bacteriological study was made of the effect of an exclusive meat diet on the colonic flora of 3 normal men, 2 of whom continued the diet for 13 mo. and 1 for 10 days. The diet included both fat and lean cooked meats, providing a protein intake of 85-180 gm. and a carbohydrate fraction of 5-10 gm. per diem. Fecal specimens were characteristically composed of a finely divided compact material with a mild and aromatic odor and a pH of 6.0-7.0. Gram-stained fecal films prepared so as to permit comparative direct bacterial counts showed, on change to meat diet, an abrupt drop of about 50% in total bacteria, due mainly to suppression of lactic-acid-producing types and, to a less extent, of coliform types. Cultural procedures permitted quantitative and qualitative surveys of the entire flora. Cultural findings in their main features were much alike for all 3 subjects during the meat period, showing a general reduction in number of viable bacteria and suppression of obligate fermentative types, but, on the other hand, no overgrowth of putrefactive anaerobes, rarely any increase in proteolytic propensities of the flora as a whole, and no introduction of unusual types of intestinal organisms. The Bacillus coli count decreased for all subjects and in 1-1/4 that on the mixed diet. Also Lactobacillus acidophilus, entero-cocci and the group of microaerophil bacteria were strongly repressed. On the other hand, growth of B. welchii was greatly favored, particularly during the first 3-5 mo. of the meat period. On resumption of normal mixed diet, the intestinal flora reverted, as regards both types and numbers, to the original form.