D-aspartic acid doesn’t seem to be quite as popular these days, but it has gone through phases where it was the hot new ingredient claimed to boost testosterone levels. I was surprised and wanted to review today’s study when I saw that in some cases it might actually reduce testosterone levels. John always reviews the full-text of every article, but you may view the free abstract by clicking here: http://www.jissn.com/content/pdf/s12970-015-0078-7.pdf .