According to Ayurveda, there is a substance called 'ojas', which is extracted from food once it had been perfectly digested.  This is the basis of an Ayurvedic approach to understanding nutrition which is different from Western nutritional science.

Ayurvedic Science pays more attention to the
1.  state of the food
2.  flow of food energy through the body’s seven tissue layers
3.  effect of the food on the body. 
The State of the food
Foods generally have three states or stages. These states are called Sattavic, Rajasic and Tamasic.
For example an apple when it is just ripe and plucked from the tree it will be in the Sattavic state. When it lies on the counter or grocery shelf for a few days its state turns to Rajasic and when it starts to get soft and brown it has entered the Tamasic stage.
- Eating fresh foods and in moderation is considered sattavic and helps to preserve youth, such a person is alert, and in harmony with nature.
- Eating highly salty, oily, fast foods are considered rajasic. Eating your meal quickly and under stress is also rajasic. The person consuming such food loses the capacity to distinguish subtle stimuli and can be prone to disease.
- Food that is stale, overcooked, cooked eight hours earlier than consumption, liquor, drugs and overeating are considered tamasic.. Tamasic foods robs the person of the capacity to think clearly and disease and lethargy set in.

Flow of food energy through the body’s seven tissue layers
The seven tissue layers in the body in order are plasma, muscle, fat, bone, nerves, marrow and reproductive tissues. Good cuisine and nutrition will aid in the proper flow of energy through these channels.
Effect of food on the body is in the following 3 ways
1.  We must eat according to the elemental structure (doshas) of our body and food according to Ayurveda. Some have more of the earth and water element in us, some of us have the air and ether element in us and some of us have the fire and heat elements in us. We can use food to create balance in us so we mimic the universal balance around us. Thus a person with a higher earth and water element can balance themselves with foods that have more fire and air elements in them.
- Secondly the food itself has a potency or veerya and has either a cold or hot effect on the body
- Thirdly the food has a personality or prabhav can also have a certain action on the body like purgative or binding quality to it.

© Kavita Mehta