Ayurved lays a lot of emphasis on suitable diet and regimen for every season. According to seasons the year is divided into six parts. The northward movement
of the sun and its effect of dehydration brings about three seasons beginning from late winter to summer. The southward movement
has the effect of hydration and gives rise to three seasons beginning from monsoons to early winter.
The knowledge of diet and regimen is incomplete without the knowledge of seasons. The period of uttarayana or dehydration is called adana kaala and includes Shishira, Vasanta and Yushma
. Shishira begins in January and ends in March, Vasanta is March to May and Yushma is from May till July. The period of Dakshinayana or hydration is called Visaega kaala and includes Varsha, Sharat and Hemanta. Varsha, begins in July and lasts till September, Sharat is in September to November and Hemanta is from November till January.
In the period of Visaega, winds are not very dry as they are in the period of Adana. Visaega kaala predominantly shares the qualities of the moon. During this period, the moon with its unstrained cooling property has the delightful effect with its soothing rays. The period of Adana kaala is dominated by the qualities of agni or the sun. In Visaega kaala not only the sun with its rays but also winds with their sharp velocity and dryness absorb the moisture from the earth, progressively creating dryness in the atmosphere which enhance the bitter (Katu), astringent (Kashaya), and pungent (Tikta) rasas or tastes having drying effects on the body thereby causing weakness in the body.
During the rainy season, autumn and early winter the sun moves towards south and its power of heating because of time, its course and rains and storms is slackened but the moon is not affected. The earth is relieved of heat and drugs which are sour (amla), salty (lavana), and sweet (madhur) nature, cause unctuousness in the body grow in this season. These tastes have the effect of strengthening the body.
In the beginning of the period of Viseaga and the end of the period of Adana, weakness prevails in the body. In the middle of both, the body gains moderate strength. However, at the end of Viseaga and the beginning of Adana, the body gains considerable strength.
Diet and regimen for winter
During the winter, the digestive power is enhanced as a result of restraint caused by the cold wind so much so that it is capable of digesting foods which are heavy in nature irrespective of the quantity. When it does not get the proper fuel, the digestive fire affects the nutritive fluids and results in disturbing Vata which is cold in nature. Therefore, during winter one should take a diet consisting in good amount of fats and foods which are saltiest and sour in nature. Even moderate amount of wine is allowed in this season. One should include honey and nuts also in the diet along with seasonal vegetables and fruits. One who habitually takes preparations of cow's milk, cane juice, fats, oils, new rice, and hot water during winter is sure to gain strength and vitality.
In winter one should resort to massage and application of oil on the head and stay indoors. One should ensure that beddings, seats are well covered by heavy wrappers, silken cloth, blankets, etc. It is only in winter that excessive indulgence in sexual activities is allowed provided one is taking heavy and nutritious diet (Sutrasthana VI:17). One should avoid diet and drinks that are light in nature as they aggravate Vata, which is cool in nature.