A fascinating area of Ayurvedic science is the knowledge of rasa, the influence that a food’s taste has on digestion. Understanding the three categories of rasa can be very helpful in both the diagnosis and treatment of disease. That is why it is important to be able to distinguish between these three types of rasa or taste. As was mentioned earlier, the first type of rasa is the natural taste of food imparted by the combination of elements that make up that food substance. For example, a food that is high in both vayu and agni will taste sour and pungent, like chilis or peppers.
The second type of rasa is defined by the taste that is acquired by food when it undergoes distinct phases of prapaka digestion. As food moves through the G-I tract, it is temporarily converted into a sweet, a sour, and then a pungent taste, reflecting the specific zone or phase of transient metabolism that it is in.
Rasa’s third aspect relates to the influence of the food’s taste on the post-absorptive or vipaka metabolism (which we will be discussing shortly). After a nutrient has undergone prapaka digestion, it will often take on a taste that is different either from its original taste or from the taste it took on during any of the various phases of transient digestion. The knowledge of a food’s post-digestive taste is utilized by the Ayurvedic physician to influence vipaka or dhatu metabolism. This influence can be either nourishing or wasting.
For instance, if someone is suffering from emaciation, the physician will prescribe foods with a sweet vipaka effect, since the sweet taste is responsible for building tissue in the body. On the other hand, foods with a pungent post-digestive influence have a wasting effect on the dhatus. A food’s pungent vipaka influence can, of course, be very beneficial in situations such as obesity, where it is important to reduce bodily tissue. Knowledge of this third aspect of rasa is particularly useful in understanding how various herbal and mineral compounds help to regenerate the dhatus.
Ayurveda therefore classifies foods according to both their pre-digestive and post-digestive taste or influence on the body.