Yatkincitaddosamasadya, Na

 Yatkincitaddosamasadya, Na Nirharati Kayatah |
Aharajatam Tatsarvamahitayopapadyate
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We give below excerpts of what the Charak Sanhita describes as unsuitability of different types of foods or medicines under different circumstances:

Non-compatibility w. r. t. Place: Rugged or arid food and herbs are harmful or unsuitable in a wild land or in a desert, while cold and greasy-smooth, oily or fatty substances or preparations (including medicines) are bad for health (or have negative effects) in a wet (highly humid) or swampy area.

Non-compatibility w. r. t. Season:
Cold eatables and drinks and foods having chilling tendency are avoidable in winter; whereas the use of hot and spicy foods and substances having tendency to increase body-heat should be avoided during summer and spring.

Non-compatibility w. r. t. Appetite: Eating without having proper appetite is harmful. Similarly, not eating nourishing food in appropriate quantity even while feeling hungry is also harmful to health and has negative effect on appetite and metabolism.

Non-compatibility w. r. t. Combination:
Eating a combination of ghee (clarified butter) and honey in equal proportion causes severe toxic effect (while individually each has important nourishing and medicinal effects if taken in appropriate quantity with respect to other factors). Similar is the case with several other non-compatible combinations.

Non-compatibility w. r. t. Body's Adaptability:
If one's body has got accustomed to acrid, spicy and hot (in tendency) foods then sweet and cold (in tendency) foods would be generally unsuitable to his body's adaptability.

Non-compatibility w. r. t. Tridosas: The food or medicine, that might have properties similar to those inducing the tendencies of any of the three dosas (vata, pitta and kaph) but, that causes contrary effects because of disharmony (with one's natural constitution, habits and physical or mental work pattern) in practice is said to be non-compatible w.r.t. the tridosas. Non-compatibility w. r. t. Utensils: Boiling milk in pure copper pot makes it poisonous in its effects. These or some other types of metallic utensils are highly unsuitable for cooking meals; while several types of substances are unsuitable for preparation of chilled drinks, desserts, etc.

Non-compatibility w. r. t. Eating Habits: Eating hot (in tendency) food with cold (in tendency) substances or vice-versa, simultaneously or without substantial time gap causes harmful effects.

Non-compatibility w. r. t. Digestive System:
Giving laxatives or strong medicines or foods to someone having a delicate digestive system or intra-body structure is harmful. Non-compatibility w. r. t. Sleeping Habits: Food or medicine which intensifies kaph tendency is not suitable for people who are generally slow and sluggard in their routine or who sleep heavily; it further induces lethargy or drowsiness.

Non-compatibility w. r. t. Routine : Eating without proper excretion of urine and stools is harmful. Those desirous of good natural health should never eat food without really feeling hungry.

Non-compatibility w. r. t. Sequence of Eatables: Having water, cooling food or any medicines after drinking or eating smooth oily stuff causes negative effects. (One might even vomit instantly or have sour throat in such cases.)

Non-compatibility w. r. t. Cooking: Eating half-cooked or overcooked or over-fried food is un health y. Similar is the case with food cooked using polluting fuel.

Non-compatibility w. r. t. Composition: Drinking any preparation of mixing acidic substances (including fruits) with milk is harmful for health . Curd (unless well set and fresh) and desserts prepared with fruits kept in milk for some time  are also prohibited in Ayurveda .
The Twelve Categories of Nourishing Eatables: Charak Sanhita (likewise some other Ayurvedic scriptures) discusses a great deal about the impact of food on physical, mental and spiritual health . It broadly classifies the nourishing substances into twelve categories as highlighted in the following shloka. This description is based on the common crops and vegetation available in ancient times. What other cereals, plants etc are available today could also be added into the corresponding categories.