Food is the primary means by which sustenance is gathered for most people.
According to the hindu physicians of old, the body could be considered to be composed of three elements i.e Ojas,Tejas and Vayu.Ojas was derived primarily from food which in turn was convereted into the other two.Sufficient Ojas has long been considered to be a prerequisite for succesful completion of sadhana. Ojas derived from vegetables and organic food stuff was considered the best as it did very little to affect the quality of one's conciouseness.
Ojas is to be understood as the physical matter from which all other processes start. But the ancient regeim that ojas could be gathered only from food is no longer a valid supposition.today's food supplements like multi-mineral,multi-vitamin tablets, calcium & iron supplements, selenium supplements,tonics like five phos with alfalfa,cobalmin syrups,vitamin E capusules,cod liver oil capsules etc have literally elevated this segment into a multi million dollar industry.That most of them have a very good impact on the human system is beyond doubt but even there moderation..ie the budhha's recommendation of the middle path needs to be observed.Further it has been observed that using the 22 sticks of sound fire i.e. homoeopathic remedies ..potencies also has a positive effect on all the koshas.
The old system of being unable to clearly define these chemicals was the reason for the blanket term 'OJAS'.But the recommendation on preserving semen and using it only when absolutely necessary is still a very valid point.
A lot of people eat at all odd hours and then complain of various problems.Eating during the four twilights i.e the transition points sunrise,zenith,sunset and nadir of the sun will really promote proper nutrition of the body and all the higher vahanas. Eating a little less then actually,physically required is another good habit to form.Eating during twilights is a very pleasant phenomena and it will be noticed that a small quantity of good quality food is deeply satisfying and nourishing.
Eating tonns and tonns and the filling up the sewage tank is just another way of wasting life's precious gift!. Cleaning the entire digestive track regularly by fasting is a good way to maintain health.Keeping the fire in manipura chakra burning bright and not over burdened with all sorts of oils and fats is also needed for clear perception.
Fruits,nuts, milk particularly goat's milk, curds without cream and butter milk are very usefull for maintaining the ph value of the system in range.Blood being one of the dominant constituents of the body tends to affect consciousness with its ph value and maintaining it within range is necessary for a neutral flame i.e neutral consciousness.
Again let me emphasis: there is nothing like impure_food,impure thoughts,impure practices etc. A well maintained neutral flame slowly but surely neutralizes karma leading first to net zero and then over a period of time to gross zero.