Agricultural Productivity in relation to Population 
But is it not the case, many people may ask, that it is possible 
to have a diet adequate in calories, or “starchy foods”’, but 
still to suffer serious malnutrition through lack of adequate 
quantities of the “protective foods” ? When I was working 
with Lord Boyd Orr in the 1930’s this was clearly understood’. 
We required 100 grams of fat per head per day, 68 grams of 
protein, at least half of which had to be obtained from animal 
sources, 0:9 grams of calcium, which had to be obtained from 
dairy products and vegetables and not by enriching flour; and 
so on. Subsequent advances in physiological science have 
caused all these figures to be abandoned. Some recent work by 
Brock and Waterlow has indicated that true protein needs may 
be much less than was previously supposed (3 grams per kilo- 
gram body-weight per day for infants, falling progressively to 
0-5 gram for adults) and that very little of the protein need be of 
animal origin. 
An attempt to state baldly the average calorie requirements 
of any population, as is often done, may lead to serious error. 
Requirements of calories are functionally related, though not 
directly proportional to the weight of the body. Less food is 
required to maintain body temperature in a warm climate than 
in a cold one. Active physical work increases calorie require- 
ments, as also do pregnancy and lactation. 
The calculations which follow are based on Table 7, p.45, 
in the 1957 FAO report on calorie requirements* which relates 
to such a population, with both birth and death rates fairly 
high, and a high proportion of children and of pregnant and 
lactating women in the population. 
The objection sometimes raised, that these varying body 
weights themselves are the consequence of varying levels of 
nutrition, is best met by Table I. Between castes which have 
been living, probably for many generations, at violently con- 
trasted levels of nutrition, the differences in body-weight are 
- slight. 
Calorie requirements obtained’ from direct measurements 
of calorie requirements (computed per hour from the rate of 
Oxygen consumption as measured by the Douglas bag) of 
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