What role does HDL play in fertility?

The role of HDL (high-density lipoprotein) in fertility is not clearly established by current evidence. HDL is best known for reverse cholesterol transport and has anti-inflammatory and antioxidant properties. Some observational studies suggest associations between HDL levels and fertility outcomes—such as ovarian reserve in women or sperm quality in men. However, these are correlations, not causal links. Critically, intervention trials that raise HDL pharmacologically (e.g., with niacin) have failed to improve clinical endpoints for cardiovascular disease, and no robust trials exist for fertility. HDL appears to be a marker rather than a therapeutic target. The evidence for a direct role in fertility is weak, relying mostly on mechanistic reasoning and small-scale studies. For individuals seeking to optimize HDL, lifestyle measures (exercise, Mediterranean diet, smoking cessation) are effective and safe. Genetic tests for HDL-related variants (e.g., CETP, LIPC) currently offer no actionable guidance for fertility. Be cautious of marketing claims that label HDL as 'good cholesterol' for fertility—the evidence base is insufficient to support such recommendations.