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May I join the debate between Drs Ness1 and Segall2 on the above subject?
The suspicion that excessive milk consumption was associated with increased coronary mortality arose in the 1950s when it was customary to treat peptic ulcer with large quantities of milk. The practice was discontinued when it was found that many of the so treated patients died of coronary heart disease. Extensive investigations at the time in American and British hospitals seem to have confirmed the suspicion.
Naturally, it would be interesting to see whether in the long run the consumption of non-excessive quantities of milk was also connected with heart disease. One method of finding out, as Ness and colleague have done, is to recruit a number of volunteers, establish their milk consumption and wait 20 years to see whether the high consumer fared worse than he low consumers.
Apart from the long wait a disadvantage is that a significant part of milk consumption is hidden in milk products, like chocolate, ice cream, etc, tends to be discounted and make the results unreliable.
An alternative method is to take advantage of the fact that developed countries have published both mortality and food consumption statistics for the best part of the century. It is, therefore, possible to correlate coronary mortality in various countries with their very different average milk consumption.
I carried out several such studies in the 1980s3 invariably showing a strong correlation between them.
Statistical studies also produce evidence regarding the critical constituent of milk. There is no connection between fermented milk products, like cheese, and coronary disease. When milk is fermented, milk sugar, lactose, is converted into lactic acid, strongly in favour of Dr Segall’s discovery of the crucial importance of lactose.
Statistical studies also show another important variable, climate. Mortality is high in cold countries, like Russia and its neighbours, very low in the tropics.
This calls attention to another component of milk, calcium, sweat glands being an important calcium excretor. In cold climates the amount of calcium excreted by sweating is small, in the tropics it can be several times the quantity excreted by the kidneys.
A little appreciated biological fact is that the calcium requirements of the body vary greatly in various age groups. Ninety nine per cent of the calcium content of the body is in the skeleton and teeth, which reach their full size by the age of 32. Nature’s solution of this problem is to make the walls of the intestines impenetrable for calcium. A special substance, 1,25 dihydroxy-cholecalciferol, is needed to transfer calcium through the intestines. For the other extreme case, when the calcification of the infant skeleton needs comparatively large quantities of calcium, nature produced a special nutrient, milk. Milk is not only high in calcium, but milk sugar, lactose, assists in its transfer through the intestinal wall, essentially the same way as cholecalciferol.
The human habit of consuming the milk of another species as food for all age groups invalidates the natural expedient for ensuring calcium intake according to needs. The lactose of cow’s milk causes the absorption of its calcium content whether it is needed or not. Briefly, the intake of excess calcium in old age results in the hardening of the arteries, hence its connection with mortality from coronary heart disease.