Having spent 10 weeks on Parris Island in 1966, I can tell you for a fact,
I didn't have a single sexual desire the entire time I was there. Not one.
I had the same experience while at MCRD San Diego in 1984.
I don’t think it had anything to do with salt peter in the chow, I think it had a lot to do with the fact that you had four screaming Drill Instructors in your face 24/7 for 13 weeks!
I started at MCRD in 1969. The salt peter in food may have been true but even without it there wasn’t any time or inclination when you are surrounded by almost entirely men and the DIs are grinding your ass into the ground every moment. Your one mindset becomes making it through each day, graduation, and leaving the Recruit Depot on time. Carnal thoughts might only occur in the few moments before you slip into sleep from exhaustion. Now, ITR that immediately followed at that time was a different story.