Chapter twenty-five in the first book of the Caraka Samhita talks only about food. The chapter starts like most of the different sections, with the sages sitting around discussing Ayurvedic precepts. Ayurveda is not static, consequently teaching was in the form of disciples debating with each other and the teacher keeping things on track. This discussion starts out with the King of Kashi (modern day Varanasi, the oldest continually inhabited city in the world) asking if disease arises from the same source as we did or if it arises from some other external influence. After a debate and various views being given the teacher, Atreya tells them all to stop controversial debating as it perpetually goes around truth, but never arrives at it, something like modern politics.
That much being said, the sage goes on to say that the things in life that normally cause good health, when consumed in the wrong combination or the wrong season, cause disease. The King of Kashi then asks the critical question: "Oh! Lord, what are these factors whose wholesome and unwholesome combinations are responsible for the growth of living beings and their diseases.
Atreya said, 'wholesome causes the growth of living beings and unwholesome food the growth of disease.'
Now all the students want to know how to distinguish wholesome food from unwholesome food when there are so many different factors involved.
They are: dose, time, preparation, habitat, individual constitution, kind of disease, strength of the person and age.
No problem says Atreya, foods that maintain the balance of the seven tissues and the three humors are wholesome, and those that imbalance the humors and tissues are unwholesome.
This is the definition of a good, balanced diet in Ayurveda. But, hold on says the faithful author, Agnivesa, that is just too simplistic, we need a much more precise method of figuring out all this wholesome and unwholesome stuff.
Agnivesa is a little like us, we need real specific guidelines.
The teacher responds by saying that any good doctor can figure this stuff out. (Too bad for us!) His point is that if you know the properties of food—the combinations of the six tastes and their actions—then you will not have trouble knowing what to recommend to patients. He then says that once you understand the basic qualities of food, then the rest must be determined according to each individual situation. However, he also realizes that not every doctor is good, so he starts to give the various properties of the twenty best foods, and also what he considers to be the twenty worst foods for balancing the humors.
These twenty items are from twenty different categories of products: grains, beans, water, salt, vegetable, animal, bird, animal who lives in a hole, fish, ghee, milk, vegetable oil, fat of marshy animals, fat of fish, fat of aquatic birds, fat of domestic birds, fat of grazing animals, roots, fruits, and sugar. This is just an example to demonstrate the thorough classifications of Ayurvedic food categories.
Vedic culture was predominantly vegetarian in the higher levels of society, nevertheless the ruling and warrior classes would generally eat meat. The poorer classes would eat anything available, as is still the case today. The lowest classes eat the animals that no one else eats, like pork and other foods that Ayurveda considers unwholesome.
However, Ayurveda also understood the great nutritive value of animals and animal products. Normally, they used milk, butter, and ghee as the main source of animal proteins, but when the situation demanded, they prescribed animal products to quickly build back the strength of a person.
The whole point here is that by the careful selection of foods according to 1) category, 2) qualities, 3) actions, 4) tastes, 5) longterm effects, and 6) overall effect on the humors, you can either balance or imbalance your body.
