LOW FAT DIETS HAVE A DOWNSIDE FOR ACTIVE FEMALES
Tomten, S. E., & Hostmark, A. T. (2009). Is there a minimum requirement for fat intake in athletic nutrition? A paper presented at the 14th Annual Congress of the European College of Sport Science, Oslo, Norway, June 24-27.
"In contrast to extensive research on the significance of dietary carbohydrates and proteins for performance and health, the possible existence of a minimum requirement of fat in athletic nutrition has received little attention. The intake of important fat soluble vitamins may be limited when the nutritional content of fat is reduced, and increasing evidence of low dietary intake of vitamin E in modern Western societies has been presented within the general population. Additionally, a low fat diet is suspected to reduce the absorption and bioavailability of vitamin E, making dietary estimates an uncertain predictor for vitamin E status. Among the components of vitamin E in blood, alpha-tocopherol is the most potent antioxidant, protecting cell membranes from oxidative damage, and as athletic anemia has been frequently discussed, it was of interest to investigate if a low vitamin E bioavailability in athletes on a low fat diet could possibly cause damage to red blood cells."
Two groups of sub-elite female athletes were studied. One group had regular menstrual function and the other was irregular. The two groups had similar height, weight and athletic success. While intakes of protein and carbohydrates were similar and within the normal range in the two groups, the daily intake of fat was significantly lower in the irregular group than in the regular group. In order to determine the resistance of red blood cells to haemolysis, 13 Ss from both groups exercised for 20 minutes at the anaerobic threshold.
Normal serum levels of alpha-tocopherol were found in the regular menstruation group while the irregular menstruation group had a very low content. In blood sampled after the exercise, osmotic fragility of red blood cells (%haemolysis) was found to be significantly negatively related to serum levels of alpha-tocopherol.
Implication. A low fat content dietary intake may cause reduced alpha-tocopherol levels in blood which renders the red blood cells more susceptible to haemolysis in physical activity. This should be taken into account when nutritional guidelines are given to physically active females.
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