The concept of Pathya-Apathya in relation to Ritucharya is a cornerstone of Ayurvedic preventive medicine. It provides a systematic guide to diet (Ahara) and lifestyle (Vihara) modifications tailored to the specific Indian seasons (Ritu) to maintain health and prevent disease. Pathya refers to that which is wholesome and beneficial for the body's channels (Srotas), while Apathya refers to that which is unwholesome and obstructive. Ritucharya is the seasonal regimen that harmonizes the body's internal environment with the external climatic changes, preventing imbalances in the three fundamental bio-energies, or Doshas (Vata, Pitta, Kapha).
Lakshmi Mahajan (Fri,) studied this question.