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Donkey milk knowledge archive · Historical source
Galen on donkey milk: advice on the way of life in old age
Around AD 175, the physician Galen advised older people to drink goat’s and donkey milk alternately: donkey milk, he said, was thin and rich in whey, goat’s milk of medium consistency.
- Author
- Galen of Pergamon (Galen)
- Work
- De sanitate tuenda (On the Preservation of Health)
- Passage
- Book V, ch. 7; Kühn edition, vol. VI, p. 346
- Time & place
- c. AD 175 · Roman Empire (Rome)
- Type of source
- Ancient medical text
In the original words
What the original says
Satiusque fuerit alterum capram, alterum asinam esse, earumque lacte alternis vicibus uti; quippe asinae lac tenue serosumque est, caprae mediocris substantiae est.
It would be better if one animal were a goat and the other a she-ass, and their milk were used alternately; for donkey milk is thin and rich in whey, goat’s milk of medium consistency.
τὸ δ᾽ ὄνειον ἀσφαλέστερον πάντη.
Donkey milk, however, is in every respect the more cautious choice.
English rendering: our own translation by the DON DONKEY’S editorial team, following the sense of the text.
Background
Who, when, what kind of text
Galen of Pergamon (AD 129 – c. 216) was personal physician to several Roman emperors and one of the influential physicians of antiquity. His writings shaped medicine in Europe and the Arab world until the early modern period.
“De sanitate tuenda”, in six books, is a doctrine of healthy living. The fifth book deals with the way of life of older people. In it, Galen discusses foods according to their digestibility, including milk at length.
We quote from the complete edition by Carl Gottlob Kühn (Leipzig 1821–1833), which prints an older Latin translation alongside the Greek text. Volume VI is freely available as a scan.
Content
What the source reports about donkey milk
Galen begins with examples: a countryman had lived to an advanced age of over a hundred years mainly on milk; others who imitated him, by contrast, had tolerated the milk poorly and complained of pressure in the upper abdomen. Milk was therefore not suitable for everyone.
Anyone wishing to use milk should pay attention to the animal: it had to be in its prime and well fed and must not eat sharp or bitter fodder. Galen advised keeping a goat and a she-ass and drinking their milk alternately.
To justify this, Galen compares the two types of milk: donkey milk is thinner and richer in whey, goat’s milk of medium thickness. Goat’s milk therefore nourishes more, while donkey milk is in every respect the more cautious choice: it passes through the body more quickly, causes hardly any flatulence and does not curdle in the stomach, especially if a little salt and honey is added.
In another work in the same volume (De probis pravisque alimentorum succis, Kühn VI 765), Galen classifies camel’s and donkey milk as the types of milk with the highest watery content.
At a glance
Figures & facts from the source
Critical assessment
How reliable is this source?
Weighing up rather than generalising
Galen does not recommend milk in general. He expressly names cases in which it was poorly tolerated and ties his advice to the animal, the feed and the individual person.
Agreement with Aristotle
Galen’s description of donkey milk as thin and rich in whey agrees with Aristotle. Today’s analyses examine the composition of donkey milk in more detail (see archive studies 71 and 97).
Medical framework
Galen’s judgements are based on humoral theory and experiential knowledge. They have not been tested by today’s standards.
Today’s assessment
No health effects of donkey milk can be derived from this passage. It shows how a leading ancient physician distinguished types of milk by their digestibility.
Our assessment
We like Galen because he differentiates: he compares goat’s and donkey milk soberly and does not conceal that milk does not agree with everyone. We read this as medical history, not as nutritional advice.
References
Sources to check
- Primary sourceGreek text with Latin translation, C. G. Kühn edition, vol. VI, p. 346 (Internet Archive)
https://archive.org/details/b29339339_0006
More sources and studies in the research archive. Summarised by the DON DONKEY’S editorial team, as of November 2026.