47. Physiological basis of nutrition
[The following are the findings of the International Commission of Experts appointed by the Health Committee of the League of Nations.]
Part 1 - ENERGY, PROTEIN AND FAT REQUIREMENTS
1. Calorie Requirements
An adult, male or female, living an ordinary everyday life in a temperate climate and not engaged in manual work is taken as the basis on which the needs of other age-groups are reckoned. An allowance of 2,400 calories net per day is considered adequate to meet the requirements of such an individual.
b) The following supplements for muscular activities should be added to the basic requirements in (a) :
Light work: upto 50 calories per hour of work
Moderate work: " 50-100 "
Hard work: " 100-200 "
Very hard work: " 200 calories and upwards per hour of work.
c) The energy requirements for other ages and for mothers can be obtained from the following table of co-efficients:
The requirements for babies under 1 year are difficult to specify except in terms of body-weight, but the following allowance are considered adequate:
Age (months) Calories per kilogramme of body-weight
The muscular activities characteristic of every healthy child and adolescent necessitate additions to the basic requirements shown in (c). It is suggested that the activities of children of both sexes from 7-11 years be considered as equivalent to light work, of boys from 11-15 years as moderate work, and of girls from 11-15 upwards as light work.
Allowance must also be made for women engaged in household duties, whether pregnant or not; these have to be reckoned as quivalent to light work for eight hours daily.
2. Protein Requirements
In practice, the protein intake for all adults should not fall below 1 gramme of protein per kilogramme of body- weight. The protein should be derived from a variety of sources, and it is desirable that a part of the protein should be of animal origin.
During growth, pregnancy and lactation, some animal protein is essential and in the growing period it should form a large proportion of the total protein.
The following allowances of total protein are recommended:
3. All the above figures on which the Commission has agreed are average values and it is essential that they should be interpreted in the light of this fact.
4. Fat Requirements
Fat must be a constituent of the normal diet, but the data at present available do not suffice to permit a precise statement of the quantity required.
5. The Influence of Climate on Dietary Requirements
In cold climates, the energy-content of the diet should be increased.
6. Mineral and Vitamin Requirements
The Commission recognizes the fact that the deficiencies of modern diets are usually in the protective foods (foods rich in minerals and vitamin) rather than in more strictly energy-bearing foods (rich in calories). Among the former are, first and most important, milk and milk products, eggs and glandular tissues; then green-leaf vegetables, fruit, fat, fish and meat (muscle). Among the energy-bearing foods of little or no protective power are sugar, milled cereals and certain fats.
Of energy-giving foods, unmilled cereals are not rich in protective nutrients and the more they are refined the less is their protective power. Many fats, especially when refined, possess little or no protective constituents. Refined sugar is of value only as a source of energy; it is entirely devoid of minerals and vitamins. The increasing habit of large sugar consumption tends to lessen the amount of protective foods in the diet and is to be regarded with concern.
7. Requirements of Pregnancy and lactation
The Commission has attempted to define the quantitative needs of protective foods for perfect nutrition in terms of the requirements for the pregnant and nursing woman. She should be regarded as the member of the population needing the greatest "protection" in order to ensure adequate physical endowment for the child at birth and optimum nutrition during infancy.
The greatest difficulty in arranging such a diet is to provide adequate calcium, phosphorus, iron and vitamins B1, B2, C & D.
8. Milk, whole or skimmed, is a rich source of calcium salts and phosphates and of vitamin B1, also a good source of vitamin B,; milk fat is an excellent source of vitamin A. Eggs contain vitamins A, B1 B2, and D and are rich in iron. The proteins of these foods are not only themselves of the highest nutritive value, but also improve the utilization of the protein contained in cereals and vegetables. Milk has an additional advantage in the abundance and availability of its calcium salts and phosphates; these enhance the effect of any vitamin D derived from other articles of diet or from sunshine. Milk, although itself poor in iron, renders more effective the iron contained in the diet.
9. Ordinary diets are usually inadequate in vitamin D and except in sunny seasons and sunny countries a small daily ration of cod-liver oil is to be recommended in the diet of the pregnant and nursing mother and in that of the growing child. Fish-liver oils are the richest known natural sources of vitamin A and are also important sources of iodine. In goitrous regions, where sea-fish are not available the provision of extra iodine in the form of iodized salt or in some other way is recommended.
10. An extended dietary use of the potato is recommended to replace part of the sugar and highly milled cereals in the ordinary diet. Potatoes provide extra vitamin C and more readily available calcium and phosphorus than are present in cereals. Potatoes also yield more iron and B vitamins than milled cereals.
The above paragraph applies to countries where potatoes are abundant, but it is of general application, due account being taken of local resources.
11. General Recommendations
A. Although a simplified diet may be so constituted from a few protective foods as to be satisfactory, it is a general principle that Variety in Diet tends to safety, provided it contains a sufficiency of the protective types of food materials.
B. White flour in the process of milling is deprived of important nutritive elements. Its use should be decreased and partial substitution by lightly milled cereals and especially by potatoes recommended. The consumption of an excessive amount of sugar is to be condemned and in this case also partial replacement by potatoes is urged.
C. Milk should form a conspicuous element of the diet at all ages. The Commission commends the tendency manifested in some countries to increase the daily intake up to one litre per day for pregnant and nursing women, as well as to provide an abundant supply for infants, children of all ages and adolescents. The practice of providing milk either free or at a reduced price to these is highly recommended.
The Commission desires to draw attention to the high nutritive value of skimmed and separated milk, which, although deprived of its vitamin A through removal of the fat, retains the protein, the B and C vitamins, the calcium and other mineral elements. The Commission deplores the large wastage in many countries of this valuable food.
D. Fresh vegetables and/or fruit should always be constituents of the normal mixed diet. Adequate provision of the vitamins other than vitamin D can be readily accomplished by inclusion in the diet of optimum amounts of protective foods. Where these are not available, only such vitamin preparations as are officially controlled and approved should be permitted.
E. The Commission emphasizes the need for provision of extra vitamin D, either as cod-liver oil or as irradiated products, wherever and whenever sunshine is not abundant, especially in the period of growth and during pregnancy.