In 'The Core of an Onion' Mark Kurlansky peels back the layers of the ubiquitous allium

For thousands of years learned people have argued whether onions were a healthy or unhealthy food. A 600 B.C.E. medical text recommends that religious people such as Brahmins and Hindu widows avoid onions in their quest for deeper spirituality. Onions and garlic, like pork, mushrooms, and a few other foods, were said to be tama, literally containing the quality of darkness. Such tama foods were said to lead to ignorance, sloth, lewdness, and fear in those who ate them. And yet Susruta also writes in the Susruta Sushruta that onions are healthy for digestion, eyesight, joints, and a healthy heart. The manuscript suggested that religious people feed onions to cows and drink the milk and in that way they could enjoy the health benefits of forbidden alliums without ingesting them.