Journal of Advances in Medicine and Medical Research

Both D-aspartic acid (DAA) and nitrate have received considerable attention in recent years. Vitamin D₃ is also considered important for overall physical health and has been associated with elevated blood testosterone. The present study evaluated the impact of a DAA-nitrate-vitamin D₃ containing dietary supplement on anaerobic exercise performance, blood testosterone and nitrate/nitrite in men.

Methods: 24 resistance-trained men (mean age: 23 years) were assigned to ingest a DAA-nitrate-vitamin D₃ supplement or a placebo for 28 days. Exercise performance (upper body muscle power, force, and endurance; Wingate cycle sprints), in addition to blood total and free testosterone and nitrate/nitrite was measured before and after 14 and 28 days of supplementation.

Results: No increase in total or free testosterone was noted at either measurement time (p>0.05), with values remaining stable or decreasing slightly following intake of the supplement. Nitrate/nitrite was increased significantly following intake of the supplement (p<0.05), from 19.1±2.1 µmol∙L^-1 (pre) to 70.0±12.4 µmol∙L^-1 at 14 days and 68.6±7.7 µmol∙L^-1 at 28 days. Despite this increase in nitrate/nitrite, no performance variable was impacted in a statistically significant manner by supplementation (p>0.05). However, the cumulative number of repetitions performed during a five-set bench press challenge was 11.3% higher after 28 days of supplementation, as compared to 3.6% higher for placebo.

Conclusion: Twenty-eight days of treatment with a DAA-nitrate-vitamin D₃ supplement increases blood nitrate/nitrite and can moderately improve repetitive bench press performance. However, this supplement does not result in an increase in total or free testosterone or any other performance measure.