Box 12.3 Recommended Adequate Intake of n-3 Fatty Acids138


• 4 to 8 y: 0.9 g/d • 9 to 13 y (boys): 1.2 g/d • 9 to 13 y (girls): 1.0 g/d • 14 to 18 y (boys): 1.6 g/d • 14 to 18 y (girls): 1.1 g/d • Adult women: 1.1 g/d • Adult men: 1.6 g/d


optimum levels, the IOM, the American Academy of Pediatrics, and the Pediatric Endocrine Society define the parameters for vitamin 25(OH)D adequacy as follows: • Sufficient: > 20 ng/mL • Insufficient: 15 to 20 ng/mL • Deficient: < 15 ng/mL134,135


However, other studies, most notably from the orthopedic literature on adults, suggest the following param- eters for vitamin 25(OH)D: • Sufficient: ≥ 32 ng/mL • Insufficient: 20 to 32 ng/mL • Deficient:< 20 ng/mL136,137


Tese values are based on cutoffs believed to optimize intestinal calcium absorption and prevent hyper- parathyroidism. Te role of vitamin D and bone mineral accrual is well established and beyond the scope of this chapter. Bone formation peaks during puberty, and the establishment of adequate bone density in childhood is critical for long-term bone health throughout adulthood. Pubertal girls with hypovitaminosis D seem to be at risk of not reaching maximum peak bone mass, particularly at the lumbar spine.139


Main-


taining vitamin D blood levels at or above 20 ng/mL throughout the year may be needed to improve the bone markers in adolescents.140 Research investigating the relationship of vitamin D deficiency and muscular status in the pediat-


ric population is sparse. Ward and colleagues assessed serum 25(OH)D in girls age 12 to 14 years and measured muscle power. Vitamin D levels were significantly associated with muscle power and force in adolescent girls. Vitamin D myopathy is associated with fatigue and lack of participation in physical education.141


sequently negatively affecting muscle strength and causing weakness.142


Inadequate vitamin D status may result in fatigue and diminished muscle oxygenation, con- Sport performance criteria, such


as higher jump velocities and jump heights, are significantly improved with adequate levels of vitamin D.143


Muscle biopsies from adult athletes with low vitamin D levels have demonstrated atrophic changes in fast-twitch type II muscle fibers, which are crucial to most athletes.144


However, the supplementa-


tion of adolescents with vitamin D in a randomized controlled trial indicated that despite improvements in 25(OH)D status, treatment with vitamin D was not shown to increase bone mineral accretion, bone geometry or strength, muscle force, or power. Improvements were found in jump velocity in girls with the lowest baseline 25(OH)D concentrations.141


Research showing the lack of effect of vitamin D intervention


aſter the period of peak mineral and muscle mass accretion suggests that supplementation with vitamin D earlier in pediatrics may be required. Accumulating data suggests that a deficiency of vitamin D may also contribute to iron deficiency ane-


mia. Research by Sim and colleagues has established the link between vitamin D deficiency and increased prevalence of anemia in adults, likely due to the role of vitamin D in erythropoiesis.145


Atkinson and col-


leagues demonstrated among white children that 25(OH)D levels in the upper quartiles (≥ 20 ng/mL) were associated with a nearly 0.2 g/dL higher hemoglobin compared with those less than 20 ng/mL.146 In African American children, hemoglobin was higher among those with 25(OH)D levels above 11 ng/


mL, highlighting ethnic differences. It is clear that sports dietitians should consider vitamin D status when working with child and adolescent athletes.


CHAPTER 12: CHILD AND ADOLESCENT ATHLETES 253


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