Cholesterol And Plant Sterols

Cholesterol, the chief reason for writing this book, is a greasy or waxy substance, essentially tasteless and odourless, insoluble in water but easily dissolved in fat solvents such as ether and petrol. Cholesterol is not a fat at all but is found associated with the true fats in the animal body. Chemically, cholesterol is an unsaturated monohydric alcohol belonging to the family of sterols which includes such biologically diverse but chemically related compounds as the sex and adrenal hormones, one form of vitamin D, the poison of toad skin, the active ingredient in the heart stimulant, digitalis, and the bile acids.

Cholesterol amounts to 5 or more per cent of solids in the brain and nervous tissue where it is thought it may act as an electrical insulator and where, in any case, it is effectively isolated from the cholesterol in the blood and in the arteries. Cholesterol is also prominent in the adrenal glands, where it may be a supply of material for the manufacture of the adrenal hormones, and it is a main ingredient of gallstones. All in all, cholesterol is an important and remarkable substance quite apart from its unfortunate tendency to be deposited in the walls of arteries, thereby producing atherosclerosis.

Cholesterol is produced in the human body, chiefly in the liver, and by all animal species, apparently, but it does not occur at all in the vegetable kingdom. Plants, however, produce some chemically related sterols, the phytosterols, which include sitosterol and stigmasterol. These phytosterols can be concentrated from various sources, including soybean oil, and several preparations of them are sold for the purpose of controlling the cholesterol level in the blood.

If large amounts (15 to 30 grammes or 4- to 1 ounce) of these plant sterols are ingested daily the blood cholesterol frequently falls slightly. But is this useful? The preparations are expensive, any effect they may have requires uninterrupted dosage, and the cholesterol change is generally trivial.

All in all we are unhappy about daily phytosterol dosage in the hope it will prevent coronary heart disease. Research with such substances and with other possible competitors to cholesterol should continue. In the meantime, we think commercial propaganda should be curbed.

Heating Of Fats

When fats are subjected to very prolonged heating at a high temperature they tend to oxidize and break down. They become offensive to both mouth and nose and would not be eaten voluntarily. But at this inedible stage they can be fed to growing rats, and the result, not so surprising, is that the rats fail to grow well. These experiments, using large amounts of oils super-heated for several days with oxygen blowing through them, have given rise to loose talk and speculation about the dangers of fats subjected to heating in ordinary cooking. The fact is that there is not the slightest evidence that such cooking damage can occur without being immediately and disgustingly perceptible to the taste unless all odours and flavours are drowned by strong spices or condiments. When a fat becomes rancid or otherwise distasteful, it should be discarded, of course. This will happen long before reaching anything like the stage of spoilage of the oils fed to the poor rats.