High protein-PUFA supplementation, red blood cell membranes, and plasma antioxidant activity in volleyball athletes

The authors evaluated the role of a hyperproteic, hypocaloric, polyunsaturated fatty acid (PUFA) supplemented diet on anthropometric parameters, erythrocyte membrane fatty acid composition and plasma antioxidant defences of non professional volleyball athletes. The athletes were divided in two groups: One (n=5) followed the Mediterranean diet, and the other (n=6) followed a high protein, low calorie diet with a 3g/day fish oil supplementation. All the athletes had anthropometric measurements taken, both at the beginning and at the end of the study, which lasted for 2 months. Body mass index and total body fat were significantly diminished in the second group, while they remained unchanged in the first. Plasma total antioxidant activity (TAA) was significantly increased in the plasma of both groups, with no differences between the groups, suggesting that physical activity, not the different diets, is the main contributor to the increase of plasma TAA. The second group showed a significant increase in erythrocyte membrane PUFA content and in the unsaturation index value (UI), due to the fish oil supplementation. A high protein, low carbohydrate, fish oil supplemented diet seems to be useful only when the aim of the diet is to obtain weight loss in short term period. The significant increase in the UI of erythrocyte membranes indicates the potential for harm, because a high intake of PUFA may increase susceptibility to lipid peroxidation not counterbalanced by a higher increase in TAA. Adherence to the Mediterranean diet seems to be the better choice.