More Evidence on Side Effects of a High-Protein Diet

WAGENINGEN, Netherlands--Research conducted at Wageningen Center for Food Sciences and Wageningen University concluded a diet high in protein can increase postprandial levels of homocysteine, which may contribute to cardiovascular disease. Published in the September issue of the American Journal of Clinical Nutrition (82, 3:553-8, 2005), the randomized, dietary controlled, crossover trial involved 20 healthy men, aged 18 to 44, who consumed a low-protein controlled diet along with either a protein supplement (21 percent of energy from protein) or an isocaloric amount of short-chain glucose polymers (9 percent of energy from protein).

Following eight days of the diet treatment, as well as a 13-day washout period, the treatments were reversed. Researchers took blood samples from each man on days one and eight, before breakfast (fasting) and throughout the day. Blood tests revealed fasting total homocysteine (tHcy) levels did not differ between the high-protein and low-protein diets after one week of treatment. However, the daily homocysteine levels were higher from the high-protein diet on both day one and eight. The scientists concluded a high-protein diet raised homocysteine levels postprandially, but did not increase fasting homocysteine levels. They noted the extent of tHcy increase was modified by the amino acid composition of the diet. Furthermore, they conceded the relevance of the results depends on whether high concentrations of homocysteine, especially postprandial levels, contribute to cardiovascular disease.