The Relationship of Dietary Intakes of Calcium, Magnesium, and Zinc on Body Composition in Female and Male Athletes of Various Sports
Authors:   , Terry Maria Sylvester , Volpe Stella L. 
Published: July 2021

Because athletes often seek to enhance their performance and body composition through nutrition, researchers must continue to investigate the current dietary consumption and the relationship of diet to body composition to best individualize nutrition guidance for athletes. Exploration of sex differences and sport specific differences in dietary intake provides insight on possible nutrition trends in specific athlete populations and risks for deficiencies. Calcium, magnesium, and zinc affect physiological mechanisms and systems needed for athletic performance, such as calcium for bone health; magnesium for energy production; and, zinc for the function of hundreds of enzymes and proteins. One purpose of our research was to determine the dietary intake of calcium, magnesium, and zinc in female and male athletes, including runners, triathletes, rowers, CrossFit athletes, and General athletes, 18 years of age and older. We also investigated the presence of sex differences and sport specific differences in dietary intake of these minerals. Finally, we examined possible correlations among these mineral intakes and body composition (bone mineral density [BMD] and percent body fat) to determine the strongest predictors of body composition. We evaluated the dietary intake and body composition of 247 athletes, 129 women and 118 men, with a mean age of 34.86±11.38 years. The population included runners (n=90), General athletes (n=59), triathletes (n=43), rowers (n=34), and CrossFit athletes (n=21). Dietary intake was assessed via a 2005 Block Food Frequency Questionnaire (FFQ), which analyzes one's annual macronutrient and micronutrient intake. Bone mineral density (total body, lumbar spine, and dual femoral neck) and percent body fat were measured using dual-energy x-ray absorptiometry (DXA). One sample T-tests were used to compare the dietary intake of calcium, magnesium, and zinc to the Recommended Dietary Allowances (RDA) in female and male athletes. A one-way analysis of variance (ANOVA) was used to determine differences in dietary intake between the sexes and among various sports. Multiple regression analyses were utilized to identify the strongest predictors for BMD and percent body fat. All data were analyzed using standard SPSS version 25 software, with the alpha a priori set at 0.05. We found that across all female athletes, dietary intake of calcium was significantly below the RDA of 1000 mg/day (801.3 mg/day ± 264.9, p < 0.001). In addition, we found that General athletes (753.5 mg/day ± 262.9, p < 0.001), female runners (860.1 mg/day ± 262.3, p = 0.001), female CrossFit athletes (690.9 mg/day ± 207.1, p = 0.001), and female rowers (748.1 mg/day ± 224.1, p < 0.001) all consumed significantly lower calcium intakes below the RDA. Magnesium intake in all female athletes was significantly above the RDA of 310-320 mg/day (358.7 mg/day ± 110.9, p < 0.001). Zinc intake in all female athletes was significantly above the RDA of 8 mg/day (10.3 mg/day ± 4.1, p < 0.001), which was observed in female General athletes (9.7 mg/day ± 3, p = 0.001), female runners (11.5 mg/day ± 5.1, p < 0.001), and female triathletes (10.9 mg/day ± 4.4, p < 0.05). In male CrossFit athletes, we observed dietary intakes of calcium (680.9 mg/day ± 411.8, p < 0.05) and magnesium (285.9 mg/day ± 78.9, p < 0.001) below the RDAs of 1000 mg/day and 420 mg/day, respectively. We also found that zinc intake in all male athletes were significantly higher than the RDA of 11 mg/day (13.2 ± 5.7, p < 0.001). Zinc intake above the RDA was observed in male triathletes (14.2 mg/day ± 5.8, p < 0.01), and male rowers (16.3 mg/day ± 7.1, p < 0.05). Male athletes in other specific sports (runners, general athletes, and rowers) were at or slightly above the RDA for calcium, magnesium, and zinc. We found a significant difference in dietary calcium (p<0.01), magnesium (p<0.05), and zinc (p<0.001) intakes between sexes, with Bonferroni adjustment applied. We utilized a factorial ANOVA to determine significant correlations between sex and dietary intake, and sport type and dietary intake. Sport type had the strongest correlation to calcium intake (p=0.021), followed by sex (p = 0.03). Sex was also significantly correlated with magnesium intake (p = 0.039) and zinc intake (p <0.001). Sex was significantly negatively correlated with total body BMD. Through multiple regression analysis, we determined sex, zinc intake, and magnesium intake (p<0.001) were the three greatest predictors in that order for total body BMD in all athletes. Sex (p<0.01) and sport type (p<0.05) were significantly correlated to lumbar spine BMD. The greatest predictors of lumbar spine BMD were, in order, magnesium intake, sex, and zinc intake (p<0.01). Sex was significantly negatively correlated with dual femur BMD. Magnesium intake, sex, and zinc intake (p<0.001) in this order were the three strongest predictors for dual femoral neck BMD. Sex was positively correlated with percent body fat, while calcium, magnesium, and zinc intakes were all negatively correlated with percent body fat (p<0.001). In female athletes, the strongest predictor of percent body fat was the combination of calcium, magnesium, and zinc intakes (p<0.04). In male athletes, the strongest predictor of percent body fat was calcium intake (p<0.01), followed by magnesium intake and sport type. Dietary intakes of calcium, magnesium, and zinc varied significantly between sexes and across sport types. In the female athlete population and some sports, such as CrossFit, more research is required to evaluate the effects of dietary intake on body composition in athletes.