High protein diets. (Scientific update: a review of recent scientific papers related to vegetarianism).

High protein diets are often promoted for weight loss. The concern with this type of diet is that excess dietary protein can compromise kidney function over time in some individuals, and that excess animal protein may increase risk of heart disease. What if the high protein diet is high in vegetable protein? That's the question that Canadian investigators set out to answer. Twenty men and women with high blood cholesterol levels ate diets with either 16% of calories from protein or 27% of calories from protein (a good deal of this was wheat gluten--protein from wheat). The high protein diet led to lower serum triglyceride levels and lower levels of oxidized (harmful) LDL cholesterol. No change was seen in total or HDL cholesterol. Apparently the higher protein diet had no effect on kidney function, although the study period may have been too short to see a change. Diets with generous amounts of vegetable protein may have the same effect (reduced triglyceride levels), as is seen with using more monounsaturated fats and may even offer more benefits since oxidized LDL cholesterol was also lowered. The authors call for additional study of diets high in plant protein (more than 15-20% of calories) before recommending that this type of diet be used.

Jenkins DJA, Kendall CWC, Vidgen E, et al. 2001. High-protein diets in hyperlipidemia: effect of wheat gluten on serum lipids, uric acid, and renal function. Am J Clin Nutr 74:57-63.