When one observes the actual consumption of the average man of a society, one sees that the most constant factor is the percentage of protein calories.
The percentage of lipid calories varies from 10 to 40%; that of the protein calories in relation to the average calorie intake taken as index 100, varies generally by &+-;20%.
- the cereals comprise 11 to 13% of protein calories,
- the meat and fish comprise 30 to 65% thereof,
- the fats, sugar, starch are consumed in greater quantites when the meat consumption rises.
1 - The specific endogenous nitrogen expenditure is in steady relation with the basic calorie expenditures of one kind or another (Terroine and sorg-matter)
2 - Experimentally, it is the quantity and quality of the proteins consumed separately that determine the level of the spontaneous calorie intakes (Jacquot and Peretianu).
3 - The level of the nitrogen expenditure is in relation with the speed of renewal and the size of certain fractions of the protein pool (Waterlow).
4 - Studies on the consequences of differences in relation to the percentage of habitual protein calories would have to be developed. There are some experimental ones on the shortening of longevity with the high levels.
5 - The percentage of proteic calories has a steadiness in the adult which makes it the most spontaneously steady nutritional criterion.
To each society is left the choice of the absolute level of proteins that corresponds to it, and that is to be determined according to the surveys for each type of society, that is to say for each "Reference Man". In the industrial societies it is 80 g.
On the other hand in the suckling this percentage depends on the methods of feeding. It is 7.2% with woman's milk and 23% with cow's milk.
1) The percentage of protein calories (11 to 13%) appears as the most steady index of the nutritional behaviour of man; it is proposed to take this index into consideration in determining the nitrogen-caloric rates to be recommended.
2) The protein rate effectively consumed by the Men of Reference being 4-5 times higher than the minimum rate capable of equalizing the balance, it is proposed to discard this basis as an element for fixing the protein rate recommended.
3) At a time when the use of foods without protein is becoming general and the dangers of their excess are being put forward, the underlining of the importance of an overall protein rate in accordance with habits, and of the percentage of protein calories, appears to bring out clearly two major indexes of the nutritional behaviour of man.
4) The fact that the protein rate of woman's milk is two times lower than that of cow's milk, compared with the experimental facts concerning the relations of the increases in the speeds of growth and the shortening of longevity, calls for a thorough re-examination of the criteria of artificial feeding, and in particular of its percentage of protein calories.