Increased levels of vitamins and iron linked with better physical fitness during adolescence Tuesday, August 14, 2012. In an article published online in the Journal of Applied Physiology on June 21, 2012, European researchers report better performance on tests of physical fitness among male and female adolescents who had higher blood levels of several nutrients. Luis Gracia-Marco of the University of Zaragoza, Spain and his colleagues analyzed data from 1,089 participants in the long-term Healthy Lifestyle in Europe by Nutrition in Adolescents Cross-Sectional Study (HELENA-CSS). Blood samples were evaluated for hemoglobin, soluble transferrin receptor and serum ferritin (which reflect iron status), as well as retinol (vitamin A), vitamin C, beta-carotene, alpha-tocopherol, vitamin B6, cobalamin and holo-transcobalamin (vitamin B12 assessments), plasma folate, red blood cell folate and vitamin D. Lower body muscle strength was tested via a standing long jump test and cardiovascular fitness was evaluated by assessment of maximal oxygen consumption (VO2max) in conjunction with a 20 meter shuttle run test. Among male participants, higher levels of hemoglobin, beta-carotene, and retinol were significantly associated with increased muscle fitness, and elevations of hemoglobin, retinol and vitamin C were associated with greater cardiorespiratory fitness. For females, higher levels of beta-carotene and vitamin D were associated with both fitness measures. The authors acknowledge the role of iron in carrying oxygen to muscles via hemoglobin, and they note that vitamin D has been demonstrated to affect skeletal function and strength via several mechanisms. "This is the first study reporting the association between different physical fitness components (i.e. cardiorespiratory fitness and muscular fitness) and a large number of micronutrient biomarkers in a large sample of European adolescents," Dr Gracia-Marco and his associates announce. "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." |
 |  | | In an article published online on March 5, 2012 in the American Medical Association journal Archives of Pediatrics & Adolescent Medicine, Boston researchers report an association between higher intake of vitamin D and a lower risk of stress fractures in preadolescent and adolescent girls. The fractures are common among individuals who engage in sports, and occur when stress on a bone is greater than its ability to withstand it. Kendrin R. Sonneville, ScD, RD of Children's Hospital Boston and colleagues analyzed data from 6,712 girls aged nine to fifteen upon enrollment in the Growing Up Today Study. Questionnaires completed every one to two years from 1996 to 2001 provided information concerning the intake of calcium, dairy products and vitamin D, as well as physical activity levels and other information. Over the seven year follow-up period, stress fractures occurred in 3.9 percent of the girls. Ninety percent of these occurred in girls who engaged in one hour or more of daily high impact activity. Although no benefit for dairy products or calcium was observed, girls whose vitamin D intake from food and supplements was among the top 20 percent of participants had half the risk of stress fracture in comparison with those whose intake was among the lowest 20 percent. Subjects who participated in high impact activity experienced an even greater protective effect from vitamin D. Restricting the analysis to the intake of vitamin D and calcium from food failed to modify the associations. "To our knowledge, no previous longitudinal studies have examined the influence of dietary intake on the risk of developing a stress fracture among a general population of female adolescents," the authors announce. They conclude that "Future studies are needed to ascertain whether vitamin D intake from supplements confers a similarly protective effect as vitamin D consumed through dietary intake." | Request Your Free Product Directory 
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