Iron, vitamins could affect physical fitness in adolescents

The article is entitled "Iron and Vitamin Status Biomarkers and its Association with Physical Fitness in Adolescents. The HELENA Study." and is online at http://bit.ly/Q2j6lJ. It appears in the online edition of the Journal of Applied Physiology, a publication of the American Physiological Society.

Researcher Luis Gracia-Marco of the University of Zaragoza, Spain and his colleagues relied on data from a larger, long-term research project known as the Healthy Lifestyle in Europe by Nutrition in Adolescents Cross-Sectional Study, or HELENA-CSS. Part of this study, which involved thousands of volunteers between the ages of 12.5 and 17.5 in cities scattered across Europe, gathered nutrition and physical fitness data. Blood samples taken in one third of the volunteers (n=1089) were tested for a variety of micronutrients, including hemoglobin, indicative of iron intake, soluble transferrin receptor, serum ferritin, retinol, vitamin C, beta-carotene, alpha-tocopherol, vitamin B6, cobalamin, holo-transcobalamin, plasma folate, RCB folate and vitamin D. The volunteers' physical fitness was also assessed through a standing long jump test, which assesses lower-body muscular strength, and a 20 meter shuttle run test, which assesses cardiovascular fitness through maximal oxygen consumption (VO2max). When looking for correlations between the micronutrient levels and physical fitness, they took into account the adolescents' age, time of year, latitude of the city they lived in, body mass index, age of menarche in females, and amount of regular physical activity (using accelerometers).

The researchers found that blood levels of certain micronutrients were intimately connected with the volunteers' performance on the physical fitness tests. For cardiorespiratory fitness, concentrations of hemoglobin, retinol, and vitamin C in males and beta-carotene and vitamin D in females was associated with VO2max. For muscular fitness, concentrations of hemoglobin, beta-carotene, retinol, and alpha-tocopherol in males and beta-carotene and vitamin D in females was associated with performing better on the standing long jump test.

The authors suggest that studies connecting micronutrients, such as the ones they measured, with physical fitness in any population has been controversial and limited. This is especially true for adolescents, a group that's often difficult to gather information on. This new study, they say, is one of the first to find connections between micronutrients and physical fitness in this age group, with the strength of controlling the results for a complete set of relevant confounders. Yet, they note that more research still needs to be done.

"The associations between physical fitness and iron or vitamin status observed in this cross-sectional study in adolescents should be followed up by a study specifically designed to evaluate causal relationships," the authors write.

Journal reference: Journal of Applied Physiology

Provided by American Physiological Society