American journal of epidemiology
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Beta-galactosidase (lactase) allows the digestion of lactose as its component sugars, galactose and glucose. Considerable variation exists worldwide in the prevalence of adults who lose the ability to digest lactose after infancy (hypolactasia) as well as in the amount of milk products they consume. ⋯ The authors found significant correlations among these variables such that fertility at older ages is lower and the decline in fertility with aging is steeper in populations with high per capita consumption of milk and greater ability to digest its lactose component. These demographic data add to existing evidence that dietary galactose may deleteriously affect ovarian function.