Chromium supplementation and resistance training: effects on body composition, strength, and trace element status of...

The effects of 8 wk of daily chromium supplementation (3.3-3.5 mumol as chromium chloride or chromium picolinate) or placebo (0.1 mumol Cr) and weight training were examined in 36 men in a double-blind design. Strength, mesomorphy, fat-free mass, and muscle mass increased with resistance training independently of chromium supplementation (P < 0.0001). Protein, magnesium, zinc, copper, and iron intakes equalled or exceeded the recommended dietary allowance (RDA) or estimated safe and adequate daily dietary intake (ESADDI) during training and did not change significantly from pretraining intakes (P > 0.05). Chromium supplementation increased the serum chromium concentration and urinary chromium excretion without a difference as a result of the chemical form of chromium (P < 0.05). Resistance training was associated with a significant decrease (P < 0.05) in serum ferritin, total-iron-binding capacity, transferrin saturation, the ratio of enzymatic to immunoreactive ceruloplasmin, and plasma copper, independently of chromium supplementation. However, transferrin saturation was decreased more with chromium picolinate supplementation (24%) than with chromium chloride or placebo (10-13%). Compared with pretraining values, urinary magnesium excretion increased (P < 0.05) and urinary zinc output tended to decrease during the first 4 wk of resistance training and then returned to baseline values for the final 4 wk, which suggests an adaptation in mineral excretion in response to weight training. These findings suggest that routine chromium supplementation has no beneficial effects on body- composition change or strength gain in men. Whether chromium supplementation of individuals with diminished chromium nutriture facilitates propitious changes in body structure and function remains to be determined.