The Bhagavad Gita refers to the quality of prana in different foods by categorizing them as sattwic, rajasic and tamasic (17:8–10).

In recent times, a method was developed by André Simonéton in France for establishing the pranic value of food. He used a simple pendulum on a piece of string, like that used by water diviners for dowsing, for this purpose.

The subtle radiations emitted by organic matter affect the motion of a pendulum, causing it to swing and spin. By measuring the distance of a pendulum’s arc, and the speed of its spin, Simonéton was able to measure specific wavelengths, which indicate the intrinsic vitality and relative freshness of different foods. He published his research in Radiation des Aliments, Ondes Humaines, et Santé.

Based on his findings, Simonéton divided food into four general classes. On a scale of zero to 10,000 angstroms, he found the basic human wavelength to be about 6.5 thousand.

In this first class are fruits, fresh vegetables, whole grains, olive oil, ocean fish and shellfish.

In the next class, with radiations 6.5 thousand to 3,000 angstroms are eggs, peanut oil, wine, boiled vegetables, cane sugar and cooked fish.

The third category, with very weak radiations below 3,000 angstroms, is comprised of cooked meats, sausages, coffee, tea, chocolate, jams, processed cheeses, and white bread. The fourth category exhibits practically no life force and includes margarine, conserves, alcoholic spirits, refined white sugar and bleached flour.

Simonéton also found that food with a vital radiance of 8,000 to 10,000 angstroms caused the pendulum to rotate at the amazing speed of 400–500 revolutions per minute over a radius of 80 millimetres.

Those between 6,000 and 8,000 angstroms spin at 300–400 revolutions per minute over a radius of 60 millimetres. However, meats, pasteurized milk, and overcooked vegetables, which have a value of less than 2,000, are too low in energy to cause the pendulum to revolve at all.

This substantiates the recurrent yogic advice to maintain purity of diet, especially while practising pranayama.