In Ayurveda, chaas is traditionally known as Takra.
Takra is not just diluted curd. It is a preparation made through proper churning, correct proportion of water, and suitable additions depending on the person, season, and digestive strength - Depending on the method, it may vary in thickness, fat content, taste, and effect.
With lemon juice, ginger, curry leaves, hing, cumin and mustard seeds - Takra (Buttermilk) is the ayurvedic solution to combating dehydration and an excellent source of vitamin D and calcium.
Yoghurt is heavier. Takra is lighter because it is churned and diluted. This is why traditional Ayurveda often gives importance to preparation method.
Churning changes the texture, lightness, and digestibility of the preparation. Ayurveda does not treat food only by ingredient, but also by processing.
Takra is traditionally appreciated for rekindling the Digestive fire, clears Ama (undigested food), balances Vata and Kapha Dosha, and nourishes Jatharagni — the very cornerstone of Ayurvedic health and longevity.
People with dairy intolerance, severe acidity, Pitta Prakriti, Acute fever, Injury, Debility, or Medical dietary restrictions should be cautious and seek professional advice.