Effect of zinc and magnesium supplementation on testosterone and insulin-like growth factor-1 in resistance-trained men
Koehler K, Parr MK, Geyer H, Mester J, Schänzer W
Evidence is still limited and needs further study
Summary
An RCT in 42 resistance-trained men taking ZMA (zinc, magnesium, vitamin B6) for 8 weeks. Although blood zinc and magnesium rose, there were no significant changes in testosterone or IGF-1, and no evidence that ZMA directly enhances strength or hypertrophy. An independent study that contradicts the 'testosterone-boosting' marketing claim for ZMA.
Key findings
- 1
Blood zinc and magnesium levels increased, but no significant difference in testosterone
- 2
No significant changes in IGF-1 observed
- 3
No evidence that ZMA directly enhances strength or muscle hypertrophy
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