Macrobii

Indeed, there are even whole nations that are very long-lived, like the Seres, who are said to live three hundred years: some attribute their old age to the climate, others to the soil and still others to their diet, for they say that this entire nation drinks nothing but water. The people of Athos are also said to live a hundred and thirty years, and it is reported that the Chaldeans live more than a hundred, using barley bread to preserve the sharpness of their eyesight. They say, too, that on account of this diet their other faculties are more vigorous than those of the rest of mankind.

But this must suffice in regard to the long-lived castes and nations who are said to exist for a very long period either on account of their soil and climate, or of their diet, or of both. I can fittingly show you that your good hopes are of easy attainment by recounting that on every soil and in every clime men who observe the proper exercise and the diet most suitable for health have been long-lived.