(FoxNews) - Doctors attribute longevity to a combination of diet, genetics, and environment, but they are yet to discover any one single factor that guarantees a long life, or even, for that matter, an early death. Substantial evidence exists that certain vices like cigarettes, alcohol, and sugar-sweetened beverages are dangerous and have adverse health effects, but some of the world’s oldest people consume them regularly and live into their 100s.

While there are exceptions to every rule, there is more proof supporting the idea that a balanced diet, daily exercise routine, and strong social structures are the key to living a long life. The inhabitants of the so-called Blue Zones, as defined by Dan Buettner in his 2005 National Geographic cover piece, “Secrets of Long Life,” live in geographic areas with a population that has above-average life expectancies and one of world’s highest percentages of centenarians. Residents of Blue Zones often live well into their 90s and suffer fewer incidences of dementia, cancer, and heart disease than those in other areas.

But as mentioned, there are exceptions to every rule, and some of the oldest people in the world, whether in or out of Blue Zones, attribute their longevity to some rather bizarre and unexpected eating and drinking habits — ranging from a shot of whiskey in their morning coffee to a daily breakfast of raw eggs.