Ayurveda, an ancient holistic science of healing, offers a logical and scientific approach for determining correct diet based upon an individual's constitution. Vata, pitta and kapha; the tri-dosha, are the elements which comprise individual constitution. This approach is quite different from the "traditional" view of a balanced diet; viz., eating daily from the basic food groups; meat, dairy, fruit, grains and vegetables. According to Ayurvedic literature, such a scheme is insufficient to lead us to the path of good health.

In the Ayurvedic literature there are five types of nutritional disorders:

1. Quantitative dietary deficiency. This includes under-nutrition due to insufficient food, and even starvation.
2. Qualitative dietary deficiency. This includes wrong food combination which results in malnutrition, toxic condition and lack of essential nutrients.
3. Qualitative and quantitative over-nutrition. This includes emotional overeating which can result in obesity and/or high cholesterol which can lead to hypertension, heart attacks or paralysis.
4. Toxins in food. Certain foods and food combinations lead to toxemia and to certain digestive disorders.
5. Foods not suitable to one's constitution may affect natural resistance and cause disease.

These five factors are closely connected to the strength of agni (the gastric fire). There are four types of agni:

1. VISHAMA AGNI. Due to vata dosha the gastric fire becomes vitiated, causing irregular appetite, indigestion and gases. Emotionally this can result in anxiety, insecurity, fear, and neurological or mental problems.
2. TIKSHNA AGNI. Pitta dosha is responsible for this type of agni disorder. It may cause hyper-metabolism, hyperacidity, heartburn and hypoglycemia leading to inflammatory diseases.
3. MANDA AGNI. This is due to an excess kapha condition, leading to slow metabolism, overweight, allergies and congestive diseases.
4. SAMA AGNI. This type of agni is the result of balanced tri-dosha. A person having this type of agni can eat almost any type of food without difficulty. Digestion, absorption and elimination are all normal.

The nutritionist should give consideration to these types of agni when making suggestions concerning diet.

According to Ayurveda, every food has its own taste (rasa), a heating or cooling energy (virya) and post-digestive effect (vipak). When two or three different food substances of different taste, energy and post-digestive effect are combined together agni can become overloaded inhibiting the enzyme system and resulting in production of toxins in the system. While it is true that an individual's agni largely determines how well or poorly food is digested, food combinations are also of great importance. When foods, (proteins, carbohydrates and fats) having different attributes, tastes, heating or cooling properties, and post-digestive effects are eaten together, agni will be slowed down. The foods can then remain in the stomach for seven to eight hours. These same foods, if eaten separately might well stimulate agni, be digested more quickly and even help to burn ama. Thus, according to Ayurveda, one should eat according to one's constitution and take fruits, starches, proteins and fats separately at different times of the day. Combining foods improperly can produce indigestion, fermentation, putrefaction and gas formation. This condition, if prolonged, can lead to toxemia and disease complex. For example, eating bananas with milk can diminish agni, change the intestinal flora producing toxins and may cause sinus congestion, cold, cough and allergies.