Changes In Urinary Arsenic In Collegiate Athletes Encouraged To Ingest Muscle Milk™ Post-exercise

Abstract

Protein ingestion post-exercise may promote muscle repair and recovery. However, Consumer Reports (July 2010) suggested that protein shakes, like Muscle Milk™ (MM), contain over the maximum U.S. Pharmacopeia (USP) limit for heavy metals. PURPOSE: 1) To measure urinary arsenic, lead and cadmium in collegiate athletes before and after a 16-week competitive season and 2) compare changes in body composition and aerobic fitness in athletes who ingested >50% (+MM) versus <50% (-MM) of the recommended daily dosage of MM supplied by the training staff. METHODS: Fall sports teams (men’s soccer, women’s volleyball, men’s and women’s cross country and swimming teams) were tested before collegiate training began (pre-season) and 16-weeks later (post-season). Body composition (DXA scan); 2) aerobic fitness (VO2 peak treadmill test); and 3) urinary arsenic, lead and cadmium levels were measured in 24-hour urine samples (ICP-OES). MM ingestion assessed by weekly logs and data categorized into +MM vs. -MM groups. Statistical significance set at p<0.05. RESULTS: 33 (58% male) athletes were in the +MM group while 42 (40% male) athletes were categorized into the -MM group. No significant differences in the pre-to post-season change (Δ) in body composition, aerobic fitness or urinary metals between MM groups. Urinary Arsenic (U-As) was the only heavy metal detectable, with non-significant pre- to post-season increases in U-As in both the +MM (13.4±34.8μg/L) and -MM (13.3±51.9μg/L) groups. Non-significant increases in U-As Δ noted in male (10.7±39.6μg/L;71%+MM) and female (28.0±60.8μg/L;26%+MM) swimmers and male soccer players (26.3±46.5μg/L;53%+MM). U-As Δ positively correlated with total lean mass Δ (r=0.31;p<0.05) while pre-season U-As negatively correlated with VO2 peak (r=-0.25;p<0.05) and urine volume (r=-0.62;p<0.05) and positively correlated with pre-season T-score (r=0.27;p<0.05). Reconstituted MM and Gatorade powders, freely available in the training room, contained As levels above USP recommendations (15μg/L consumed). CONCLUSION: No relationships noted between MM ingestion and urinary arsenic levels. No differences in body composition or aerobic fitness parameters in collegiate athletes supplemented with higher versus lower doses of MM during a 16-week competitive cycle.