Fertility has been decreasing in the last 50 years, 50% of cases are due to male infertility

The key amino acids in fertility are:
1. arginine (building block of sperm cells/lots in head I think) & improves circulation & erection,
2. carnitine to supply energy etc; study: http://www.ncbi.nlm.nih.gov/pubmed/12568837
3. Cysteine to build glutathione, which protects DNA, study: http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD007411.pub2/abstract

Key study: http://www.nutraingredients-usa.com/Research/Micronutrient-combination-may-boost-male-fertility-Study