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The Physiology of Nutrition and Optimum Diet

From physiological rationality, the diet had to supply the necessary substances for the growth and repair of the organism, as well as energy for the production of animal heat and organic work. Experimental science was to be the necessary basis of any practical action.[1] Experiments with animals seemed to be useful to clarify fundamental aspects of human nutrition, but only the screening of humans and the analysis of clinical data could contribute to establishing specific standards for humans. During World War II human experiments were made, not only in the camps but also in some reputed laboratories.[2]

There were, however, a number of facts that were firmly established. The organism needed to be supplied daily with a certain quantity of food energy that could be evaluated in terms of calories and, from the

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beginning of the experimental science of nutrition, a considerable amount of information on calorie requirements was increasingly available. It was accepted that food factors such as vitamins and mineral salts were essential to health but, at the same time, it was also clear that they did not affect the fundamental problem of energy needs. The daily diet had to yield protein, fat and carbohydrates, with their proportion varying according to circumstances. On the other hand, small amounts of minerals were also considered necessary, the most important being phosphorus, calcium, iron and iodine, as well as vitamins and other essential factors.[3] Energy needs are met by fats, carbohydrates and proteins, the latter having the additional function of building new tissue for the growing animal and of repairing tissue wastage in the adult.[4] In addition, experimental research on the physiology of nutrition had stressed the great importance of other essential elements, such as vitamins and minerals, which were also deemed indispensable. The lack of those elements or their defective presence in dietaries was related to deficiency diseases and children’s organic development.

Physiologists in previous decades had generally devoted their attention to the establishment of minimum dietary requirements.[5] Such was also the usual standpoint of governments and administrations when called upon to fix the rations for workers, feed large numbers of soldiers and civilians in wartime, assist the unemployed and their families and establish school meals and public canteens. Minimum dietary requirements were the keystone. Nevertheless, the idea of an optimum diet was developed during the Interwar period and brought into preeminence as a more meaningful concept. An optimum diet was one that provided for the full development of the individual for efficiency without exhaustion and resistance to disease.[6]

Diseases such as scurvy, rickets, beriberi or pellagra were identified as being associated with deficient nutrition. Therefore, nutrition was to become an essential factor to enjoy optimum health, a condition necessary to fight infectious diseases. Since the late 1920s malnutrition, poverty, children’s diseases and economic crisis paved the way for a new field of action, and the idea of a standard for adequate nutrition was widely accepted as a starting point for future policies.[7]

According to the London Report, a dietary standard had to take into account energy demands, the proportion of protective foods and mineral and vitamin requirements.[8] Once those general aspects were clearly determined, further research was to focus on specific problems such as nutritive needs during the first year of life and infancy. Since a common methodology was needed in order to allow comparisons, the Technical Commission on Nutrition of the League of Nations shaped some guiding principles for experimental research and social surveys.[9]

The notion of optimum diet had been introduced at the beginning of the 20th century, based on physiological research into calorie intake and expenditure, and protein, fat, mineral and vitamin requirements. Foodstuffs were classified into two main groups: protective foods, such as milk, eggs, meat, cheese, vegetables, potatoes and cod liver oil; and supplementary energy-yielding foods, such as cereals, fats and sugar. A new calorie method was then introduced to calculate individual needs according to tables based on energetic quotients so that calorie requirements could be assessed to ensure the healthy development of the human organism. The calorie represented a universal value to measure nutrition.[10]

The Mixed Technical Commission on Nutrition of the League of Nations, the International Labour Organisation and the International Institute of Agriculture convened in London in November 1935. A preliminary “Report on the Physiological Basis of Nutrition” (1936) was published, including an interim report with their suggestions.[11] Edward Mellanby presided over the Technical Commission and R. Cathcart, an expert on quantitative methods in nutrition, chaired the sessions. Participants included physiologists, clinicians and statisticians. Evidence on vitamin deficiency diseases (scurvy, rickets, beriberi, pellagra) reinforced the scientific project of reaching a universal standard for an optimum and minimum diet. The London Report made room for the concept of dietary standards that took into account protective foods, energy, mineral and vitamin requirements, and their proportion in the main foodstuffs, although it seemed impossible to establish exact

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From Hunger to Malnutrition normal standards of health and physical development in order to stake the boundaries of the pathological. Empirical research and clinical observation showed that borderline conditions between health and pathology existed and they were hard to detect and define. The same applied to discussions about the validity of the so-called indices of nutrition, which mainly applied to children and were used to determine underdevelopment, insufficient nutrition and those pre-clinical states traditionally conceptualised as weakness and consumption.

The League of Nations’ Technical Commission on Nutrition submitted a report to the Health Committee in April-May 1936 and to the General Council in May 1936. The Health Committee suggested further work to attain practical effects in different countries, with specific research on food requirements during the first year of life and the implementation of social policies to scientifically assess the nutritional state of children, pregnant women, workers and, ideally, the whole population.[12] Technical aspects of research had to be covered and conceptual agreements reached, such as coefficients for calculating calories and proteins according to age and sex, particularly regarding maternity, infancy and periods of organic growth and convalescence.

The information sent by national boards was studied by the Technical Commission in its 2nd session held in Geneva between June 4 and 8, 1936.[13] The main point on the agenda was a critical review of the London Report on the physiological bases of nutrition, to oversee the progress of studies on the problems recommended in it, followed by some specific topics, such as milk consumption, physiological properties of milk, assessment of children’s nutritional condition, as well as the means to prevent, identify and cure malnutrition. The main difficulties emerged from the need to establish fixed standards for the optimum diet. Since health and nutrition were closely related, a distinction could be made between primary malnutrition due to a defective diet and secondary malnutrition resulting from illness.

When meeting in March 1937, the Technical Commission on Nutrition of the League of Nations was composed of 16 members, with E. Mellanby as President. Some specific commissions devoted to technical studies were integrated with national representatives.[14] The

Spanish representation was entrusted to the Real Academia de Medicina in Madrid.[15] Two main topics drew attention; the first one was related to energy, protein and fat requirements associated with calorie production and consumption in the light of the influence of climate on dietary requirements, and the second one focused on mineral and vitamin requirements. Physiological conditions such as pregnancy and lactation, and age groups - childhood and adulthood - were specifically discussed.

What constitutes a balanced diet? Answering this general question meant specifying the human requirements of calories, fat, proteins, vitamins and minerals, and establishing the right proportions in which the various nutritional factors had to be combined. The nutritive value of food was to be the basis for dietary standards as the starting point for further practical action; they allowed experts to gauge the value of the diet of individuals or social groups, making it possible to draw up dietary schedules for those communities or social groups that had no choice, such as armies, people in institutions, schoolchildren and prisoners. They were also used as the basis of large-scale wartime rationing schemes and as a starting point for future agricultural policies.

Human calorie requirements were investigated by direct and indirect calorimetric methods to determine the energy output of subjects at rest or performing various kinds of work. Experimental conditions provided data for the establishment of quantitative standards of food intake. Another method consisted of assessing dietary requirements by means of the observation of what healthy individuals consumed under various conditions and performing different kinds of work.

The basal metabolic rate of an average European citizen was considered to range from 65 to 75 calories per hour, the energy exchange being lower during sleep and considerably higher during physical activities. The increase in energy exchange in relation to the basal metabolism, which takes place during the execution of different tasks, was carefully investigated in the laboratory. As a result, it was possible to put together an energy budget for an average individual for an average day, which was found to be about 3,000 calories per day. This figure was widely used in practical dietetics, put forward as a standard by the Advisory Committee on Nutrition of the British Ministry of Health, and accepted by V. Tyzska, one of the most influential German specialists.

A crucial point was the acknowledgement that energy requirements varied enormously according to the type of work done, from about 6,000

From Hunger to Malnutrition or 7,000 calories in the case of a lumberman to 2,200 for a sedentary worker.[16] The energy requirements of children and women were considered to be lower than those of an adult man. Both statistical and calorimetric data regarding caloric intake and requirements were registered for both sexes and age groups as the basis of scales of family coefficients, which calculated the needs of children and women in terms of an average man, the latter being taken as the standard. More than 20 different scales of family coefficients were proposed. Such scales allowed the establishment of a consumption unit in terms of which the requirements of the entire group could be calculated. The scales of family coefficients were essential to finding out family dietary habits, comparing the total food intake with other families.[17]

The Expert Committee on Nutrition convened by the League of Nations in 1932 produced the following scale:[18]

Calorie Coefficient by Age and Sex

Age

Male

Both sexes

Female

0-2

0.2

2-3

0.3

4-5

0.4

6-7

0.5

8-9

0.6

10-11

0.7

12-13

0.8

14-59

1.0

0.8

Over

0.8

1.0 = 3,000 calories

This international proposal was widely employed to make results easily comparable. The first serious attempt to set up a dietary standard was made by Carl von Voit in his book Food and the Principles of Dietetics (London, 1927). Using a calorimeter, he calculated that a man weighing about 70 kg and doing moderate work needs 3,055 calories, 118 g of protein, 58 g of fat and 500 g of carbohydrates every day. Other standards proposed by experts on physiology of nutrition, such as Atwater, Rubner and Hutchinson, did not differ significantly.[19]

Heated discussions on the optimum protein intake took place during the 1930s. Even among experimental scientists, some advocated a high intake while others emphasised restricted consumption. To some extent, contradictory clinical evidence about the effects of high-protein diets on the kidneys heated the debate. Some experiments had shown that diets containing 30% of protein produced signs of kidney damage in rabbits and human beings. But those results had been criticised, with allegations that experimental diets were incomplete regarding dietary components other than protein. In most of such experiments, the proportion of protein in the diet greatly exceeded that in the ordinary, freely chosen diets of Western societies.[20] Physiologists, on the whole, agreed on the fact that societies with a high protein intake have a better organic development than those with a lower one, but no inference could be drawn as to the optimum protein consumption.[21]

In their report, Burnet and Aykroyd (1935) proposed the following

standards:[22]

Standard dietaries put forward by various authorities as being suitable for the average individual:

Protein

Fat (g)

Carbohydrates

Calories

Voit

118

56

500

3,055

Rubner

127

52

509

3,092

Atwater

125

125

450

3,520

Advisory Committee (British Ministry)

100

100

400

3,000

Playfair

119

51

531

3,140

Tyszka

80-100

60-80

500

3,000

As a general principle, no diet was deemed adequate by physiologists unless it contained enough mineral elements present in human tissues, those minerals taking part in metabolic actions and needing to be replaced by nutrition. Mineral deficiencies could also produce diseases. Calcium and iron were soon identified as a causal factor for diseases such as anaemia, osteoporosis and other deficiencies, and iodine deficiency was associated with goitre and cretinism. The consequences of phosphorus, calcium, iron and iodine deficits were immediately investigated and the dietary amounts of those minerals estimated. A diet rich in cereals was considered poor in phosphorus, while the absence of vitamin D was a complementary factor for rickets. The estimated amount of phosphorus in the diet was around 1.30 g per day for the average adult, the needs of growing children being relatively higher. Most Western dietaries contained sufficient amounts of phosphorus. Calcium was considered to be the inorganic element, which contributed the most to body weight, since over 99% of organic calcium is in the bones.

Experts on the physiology of nutrition linked vitamin D with the metabolic use of calcium and they therefore argued that calcium intake was especially important when the intake of vitamin D was very small, as was the case in wintertime or in countries where the sun seldom shone. The physiological effects of iron had been less investigated than the previously cited minerals although its deficiency was associated with some types of anaemia. Public health campaigns to prevent goitre were carried out in Las Hurdes, a depressed rural area in Spain, Switzerland and some areas of the United States: iodine compounds were administered to schoolchildren and sodium iodine was added to table salt.

An International Vitamin Conference, attended by a wide group of experts in the physiology of nutrition, was held in London in June 1931 under the auspices of the Standing Commission on Biological Standardisation of the League of Nations’ Health Organisation.[23] A further report was published in 1934 on the international adoption of standards and units for vitamins A, B1, C and D. The conference was chaired by E. Mellanby (League of Nations) and the participants were: J.C. Drummond (League of Nations); H.von Euler (Stockholm); L.S. Fridericia (Copenhagen); B.C.P. Jansen (Amsterdam); P. de Mattei (Pavia); E.M. Nelson (Washington); E. Poulsson (Oslo); Randoin (Paris); Steenbock (Madison); Szent-Gyorgyi (Szeged); Chick (League of Nations); and Aykroyd (LoN, Geneva). Other delegates were: H. Brorw (Toronto); K.H. Coward (League of Nations); H.H. Dale (League of Nations); P. Hartley (League of Nations); E.M. Hume (League of Nations); A. Jung (Basel); Ch. Lormand (Paris); Rafael Mendez (Madrid); A. Morton (Liverpool); R.A. Peters (Oxford); O. Rosenheim (League of Nations); M. Tsurumi (LoN, Japan); T.A. Webster (League of Nations); and S.S. Zilva (League of Nations).

A report published in 1937 by the Technical Commission on Nutrition of the League of Nations summarised the available knowledge regarding mineral and vitamin requirements, proteins, fats and nutritional requirements in the first year of life. The report also touched upon the nutritive value of milk and referred to some nutrition surveys on food consumption and some methods to assess the nutritional condition of infants and adolescents.[24] A table on the nutritive value of foods included milk, cheese, eggs, liver, fatty fish, green vegetables, raw fruits, butter, cod-liver oil, yeast, meat, root vegetables, legumes, cereals (bread, rice, nuts), sugar, jam, honey, margarine, olive and vegetable oil.

In August 1938 the Technical Commission on Nutrition of the League of Nations met in Geneva.[25] The experts convened under the chairmanship of Sir E. Mellanby, Secretary-General of the Medical Research Council, London.[26] In an extremely critical period, due to the economic slump and international tensions, the experts discussed the nutritive value of different cereals according to the degree of milling, the influence of climate on food requirements and the extent to which diets in common use fell below the standards recommended in the Report on the Physiological Bases of Nutrition. As bread played a prominent part in nutrition, particularly in rural areas, and since its composition widely varied across European regions, a special study on the composition and preparation of bread was considered indispensable. This research was formerly conducted by E.J. McDougall, a member of the Imperial

From Hunger to Malnutrition

Bureau of Animal Nutrition at the Rowett Institute (Aberdeen) and the Basle Institute of Physiology.

The Committee also requested an advisory opinion concerning the feeding of refugees in countries where whole population groups were threatened with acute malnutrition, or with actual famine. Considering all these important topics, a summary of the meeting’s agenda was drafted. Food requirements for infants and those on small incomes represented a particular source of concern. When considering special dietary needs for different social classes and age groups, expectant and nursing mothers occupied a central place for “although it is true that our knowledge of feeding in pregnancy and lactation is elementary, it can be said with some assurance that, in regard to the health of both mother and offspring, an increase in the protective foodstuffs would have a large effect in eliminating many of the ills of pregnancy”.[27]

Most paediatricians agreed that breastfeeding was the best option for nourishing an infant, but its health, diet and development had to be supervised because “the causes of infant mortality... made it clear that the pernicious combination of poverty and ignorance was largely responsible for the malnutrition of infancy, as, indeed, for that seen in other stages of human life”.[28] Gastrointestinal disturbances and other diseases in mothers during lactation could induce vitamin deficiency, affecting the child’s health. Concerning early childhood and preschool and nursery age: “There is a great need to maintain the resistance of children at the highest possible level against the ravages of the infectious diseases to which they will be exposed.”[29] For the poorer social groups, who could not easily afford fresh cow’s milk or dried milk preparations, breastfeeding had many advantages and minimised the risk of infection, but attention had to be paid to the fact that the quality of the mother’s milk depended on the quality of her diet to a certain extent.

In the 1930s artificial feeding and the so-called humanised dried milks had improved, a growing industry was expanded and those substitutive products were well accepted both by physicians and mothers as a way to complement or replace breastfeeding without risks to the infant’s health.[30] Some research on mortality and morbidity was conducted on a large sample of infants under care at the Infant Welfare Society of Chicago. A total of 48.5% received breast milk only until month nine, 43% were partially breastfed and 8.5% were fed on cow’s milk mixtures. All the groups received accessory food including orange juice, cod-liver oil and cereals at certain ages. These are the mortality and morbidity results for the three groups:[31]

Breastfed

Partially breastfed

Artificially fed

Percent total

48.5

43.0

8.5

Morbidity

37.4

53.8

63.6

Total mortality

6.7

27.2

66.7

Breastfeeding was associated with higher standards of health in this group of 20,000 children, although other factors could have influenced the figures.

As a result of the 1929 economic crash, a great deal of the population in most European countries saw their income fall. The situation affected the availability of foodstuffs.[32] The relationship between income, expenditure and adequate nutrition in poor families, whether employed or unemployed, became of interest for public health experts, social workers and politicians.[33] Subsequently, with the new international situation and the rise in social problems related to diet, community feeding became a reality. The Spanish Civil War was an exceptionally critical domain, soon followed by World War II.[34] Community feeding developed an essential social task, since a meaningful part of the population received their meals in residential institutions, armies, hospitals, sanatoria, prisons, asylums, schools and similar institutions. Health authorities became engaged in ensuring satisfactory diets and public health officers assumed the supervision of institutional diets. An increasing section of the population asked for food relief. Several systems for the provision of cheap meals appeared or extended previous experiences in most countries. In France, the soups populaires and the fourneaux economiques were extended. In Germany, Caritas

Association lent its kitchens to volunteers in 1932 in cities such as Cologne, to provide meals for thousands of people. In Britain, the provision of meals through central city kitchens, traditionally used for school meals and nursing mothers, was extended. In some cities like Birmingham the Citizens’ Society founded a number of canteens in occupational centres run by the unemployed.

Community feeding was conceived as one of the great public services when based on scientific grounds by national institutes of nutrition. Nevertheless, industrial and mass food production was considered by the experts to be a real risk for the quality of foodstuffs and the preservation of their physiological properties. Food industries were held responsible for the partial, total elimination or destruction of vitamins.

  • [1] Burnet, Aykroyd, 1935, p. 334.
  • [2] We shall comment upon those experiments in a further chapter.
  • [3] Burnet, Aykroyd, 1935, pp. 323-474.
  • [4] The Problem of Nutrition, 1936, p. 32.
  • [5] Livi-Bacci, M., Population and Nutrition: An Essay on European DemographicHistory Cambridge, Cambridge University Press, 1991.
  • [6] The Problem of Nutrition, 1936, p. 53.
  • [7] Burnet, Aykroyd, 1935; Caplan, P. (ed.), Food, Health and Identity, London,Routledge, 1997.
  • [8] The Problem of Nutrition, 1936.
  • [9] Bigwood, 1939.
  • [10] Ibidem.
  • [11] Archive of the League of Nations, Document C.H.1197.
  • [12] “Report on the Physiological Bases”, 1936, pp. 391-415.
  • [13] “Report by the Technical Commission on Nutrition on the work of its second sessionheld in Geneva, June 4th to 8th, 1936”, League of Nations Quarterly Bulletin of theHealth Organisation, 1936, Vol. 5, No. 3, pp. 416-426.
  • [14] League of Nations, Health General, R. 6133, Registry No. 8A, 21287, 20883. 19331939. Nutrition. Technical Commission on Nutrition. Reports, printing. Archives ofthe League of Nations.
  • [15] It consisted of three members: Teofilo Hernando, E. Suner and J. Murillo, director ofthe Institute for the Control of Food and Medicines.
  • [16] Burnet, Aykroyd, 1935, p. 339.
  • [17] Bigwood, E.J., Roost, G., L’alimentation rationnelle et les besoins energetiquesd’une population ouvriere, Bruxelles, Universite Libre de Bruxelles, Institute Solvay,1934, 256 p.
  • [18] Quarterly Bulletin of the Health Organisation of the League of Nations, Vol. 1, 1932,p. 480.
  • [19] Aykroyd, W.R., “Diet in relation to small incomes”, League of Nations QuarterlyBulletin of the Health Organisation, 1933, Vol. 1, pp.130-153.
  • [20] Burnet, Aykroyd, 1935, pp. 342-343.
  • [21] A wider discussion about the optimum protein intake in Barona, 2010, pp. 67-70.
  • [22] Burnet, Aykroyd, 1935, p. 348.
  • [23] “Second Conference on Vitamin Standardisation”, League of Nations QuarterlyBulletin of the Health Organisation, Vol. 3, 1934, pp. 428-440.
  • [24] “Report by the Technical Commission on Nutrition on the Work of its third session,held in London from November 15th to 20th, 1937”, Bulletin of the HealthOrganisation, Vol. 7, 1938, pp. 460-502.
  • [25] “Technical Commission on Nutrition. Report by a Special Committee which met inGeneva from August 22nd to 24th, 1938”, Bulletin of the Health Organisation, Vol. 7,1938, pp. 667-678
  • [26] The participants were: W.R. Aykroyd, Director of the Nutrition ResearchLaboratories, Conoor, India; E.J. Bigwood, Professor of Physiology, University ofBrussels; L.E. Booher, Chief Food and Nutrition Division Bureau of HomeEconomics, US Department of Agriculture, Washington; H. Chick, Head of theDivision of Nutrition, Lister Institute, League of Nations; L.S. Fridericia, Professorof Hygiene at the University of Copenhagen; A. Mayer, Professor at the College deFrance, Paris; J.B. Orr, Director of the Rowett Institute of Animal Nutrition,Aberdeen; participating also as observer: W.Ph. Kennedy, Professor of Physiology atthe Royal College of Medicine, Baghdad.
  • [27] The Problem of Nutrition, 1936, p. 39.
  • [28] Ibidem, p. 43.
  • [29] Ibidem, 1936, p. 44.
  • [30] Burnet, Aykroyd, 1935, pp. 401-402.
  • [31] Ibidem, p. 402.
  • [32] Rotberg, R.I., Raab, T.K., Hunger and History. The Impact of Changing FoodProduction and Consumption Patterns of Society, Cambridge University Press,Cambridge, 1985.
  • [33] Aykroyd, 1933.
  • [34] Cura, M.I. del, Huertas, R., Alimentacion y enfermedad en tiempos de hambre.Espana, 1937-1947, Madrid, CSIC, 2007; Barona, J.L., Perdiguero E., “Health andthe War. Changing schemes and health conditions during the Spanish Civil War”,Dynamis, 2008, Vol. 28, pp. 103-126.
 
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