The recent Million Women breast cancer study, which found that having children and breastfeeding protected against the disease, confirmed the findings of the 17th-century Italian physician Bernardino Ramazzini, who came to the same conclusion after discovering nuns were more likely to develop breast cancer than the general female population.

Nun-testing may sound old-fashioned, but in fact it's still rather common. The Nun Study, an ongoing investigation into Alzheimer's disease, involves 678 School Sisters of Notre Dame, originally ranging in age from 75 to 102, all of whom agreed to leave their brains to science. Spain's Centre for Information on Beer and Health fed beer to 50 nuns, half a litre a day for 45 days, in order to establish a link between beer consumption and lower cholesterol rates. Between 1967 and 2000, 200 nuns participated in a study about the benefits of calcium in preventing osteoporosis, which required, among other things, a hospital stay of eight days every five years. Two years ago 15 cloistered Carmelite nuns underwent scans in order to determine if there was a spiritual centre or "God spot" in the brain (there isn't, apparently).

Why pester the nuns? One obvious reason is that the strictures of convent lifestyle make for an ideal control group. "Many factors that confound (or confuse) the findings of other studies are either eliminated or minimised because of the relatively homogeneous adult lifestyles and environments of these women," reads the website of the Alzheimer's study. "Participants in this study are non-smokers, drink little if any alcohol, have the same marital status and reproductive history, have lived in similar housing, held similar jobs and had similar access to preventive and medical care."

They're also altruistic, which means they're willing to participate without complaining or expecting payment, simply in order to advance medical science. Their record-keeping tends to be scrupulous and their archives often go way back. And because they have no families, it is usually less problematic to take their organs for analysis when they die. If you've ever asked yourself, "What have the nuns done for me lately?", now you know. They proved beer is good for you.