N-Acetyl-Cysteine (NAC)
NAC is the precursor to glutathione, which is your body's central intracellular antioxidant, the big one, and it also carries mucolytic and insulin-sensitizing properties on top of that. In reproductive tissue the logic runs two directions: it may cut oxidative stress in both oocytes and sperm, and in women with PCOS specifically, it may improve insulin signaling and ovulatory response. For men, the target is seminal oxidative stress, the kind that can drag down sperm parameters if it's left unchecked.
Evidence
Mixed, and genuinely mixed, not just a hedge word. Some randomized trials in PCOS show improved ovulation and pregnancy rates, occasionally rivaling metformin, which is a real claim to make. Some male-fertility trials report better sperm parameters. But plenty of other studies in both categories show no benefit at all, and the results don't line up cleanly from trial to trial. Promising in spots. Not proven yet.
Interactions
May add to the effects of nitroglycerin and other nitrates, potentially causing headache or low blood pressure; theoretical additive effects with anticoagulant or antiplatelet drugs. High doses can affect certain lab assays and may interact with some blood-sugar-lowering strategies.
Cautions
Generally well tolerated; can cause nausea, heartburn, or a sulfur-like taste or smell, and rarely allergic-type reactions. People with asthma, bleeding disorders, or on nitrates or anticoagulants, and anyone pregnant or breastfeeding, should confirm use with a clinician given the mixed and evolving evidence.
Food sources
NAC itself is not found in food, but its parent amino acid cysteine occurs in high-protein foods such as poultry, eggs, dairy, garlic, onions, and legumes.
