2: Meat makes meat: the first protein fashion

Liebig and Mulder’s work on protein and the chemistry of nutrition was not taking place in a vacuum. In France in the 1830s and 40s, administrators and scholars like Jean-Baptiste Boussingault and Jean-Baptiste Dumas worked on the science of nutrition not solely out of scientific interest but motivated by social, economic and political concerns.³³ Boussingault and Dumas framed nutrition in terms of the slow combustion of food carbon and the expenditure of bodily tissue through activity. Some scholars were motivated by the problem of feeding an expanding labour force: in a situation of scarcity, what must the worker eat (and, consequently, be paid) in order that labour be able to reproduce itself?³⁴ Here, the question was both that of identifying how much tissue was ‘used up’ through work (and so needed to be replaced with food), and what resources were needed to raise children to replace the labourer himself — although more emphasis was put on the first of these two. This frame was of interest to industrialists wanting to identify the floor to which wages could be lowered. For social reformers, on the other hand, nutritional science promised both explanations and solutions — what might the relationship be between problems of poverty, disease and ill-health, and inadequate diets? Did poverty cause poor dietary health, or did poor dietary choices cause enfeeblement and therefore poverty? Social surveys mapping out incomes and dietary habits offered the tools to probe these questions.³⁵ For administrators, an interest in nutrition arose from the challenges of managing institutions, particularly prisons and schools, whether with an eye to the humane treatment of inmates or simply to efficiency. In many of these cases, a growing idea of state responsibility for public welfare helped to make nutrition and agriculture areas of scientific interest.

Another important context for the precipitous rise and fall of protein theory was ongoing work on fertiliser and nitrogen in agriculture. There are striking parallels with the work on human nutrition: here too was a search for a singular, crucial nutrient; here too nitrogen compounds played a special role in the debate; some of the same scholars (Liebig, Boussingault, Dumas) were important figures in both fields.

Since the mid-18th century, understanding of plant nutrition had been dominated by the retrospectively-named ‘humus theory’. In this theory, all nutrients came from the soil: plants took in water and humus (decayed plant and animal matter) through their roots. This supplied carbon, oxygen, nitrogen and hydrogen, which could then be transformed into the full range of substances found in plant tissues by means of ‘vital force’ (German Lebenskraft).³⁶ However, experimental work around the turn of the century (particularly an 1804 book by Nicolas-Théodore de Saussure³⁷) had suggested that at least carbon dioxide was instead absorbed from the atmosphere.³⁸ 

Two important contributions towards the end of this period were German agronomist Albrecht Thaer’s 1809 ‘Grundsätze der rationellen Landwirthschaft’ (translated into English as ‘The Principles of Agriculture’) and a hugely popular 1813 lecture series by Cornish chemist Humphry Davy. Both were deeply practical works, exploring organic chemistry with a focus on the advice that could be derived for farmers. Both put forward versions of humus theory that allowed that some carbon might be acquired by the plant from the air, but which focused nevertheless on maintaining healthy soil as the primary source of plant nutrition. Davy dedicated a lecture to the efficacy and mode of action of many different organic substances as fertilisers, and the importance of water-solubility in making these substances available to roots; Thaer (whose methods have been recognised as a precursor of organic farming) recommended rotating cash crops with forage crops, fallowing, and fertilising the soil with manure to maintain the right nutrient balance.³⁹

In the 1820s, a student of Thaer, Carl Sprengel, demonstrated that soil contained many mineral salts which could be taken up by plant roots — obviating the need for vital force to create phosphorus, sulphur, and so on by transmutation. He proposed that plant growth was limited by whichever of these nutrients was least available in the soil—the ‘Law of the Minimum’. Sprengel received little recognition for this work, but his observations were taken up by Liebig in an 1840 book which established ‘mineral theory’. This broke with humus theory by asserting that plants got all of their carbon and oxygen from the atmosphere, and only the mineral nutrients from the soil. An important practical implication was that fertilisers need not be organic substances: instead, it should be possible to identify the limiting missing minerals in a given soil and synthesise an artificial fertiliser to supply them.⁴⁰

In the early 1840s international trade had already opened up new agricultural technologies. Indigenous peoples of the Andes had traditionally mined deposits of seabird droppings — guano — for use as fertiliser. This had been known in the west for some time — indeed, Davy’s lectures had mentioned the efficacy of guano in 1813 ⁴¹ — and by the 1830s and 40s huge quantities of guano were being imported from Peru to Great Britain and on from there. Liebig saw an entrepreneurial opportunity in designing a targeted fertiliser that could be produced cheaply and locally. In the book which laid out mineral theory, he had explained the power of guano as a fertiliser on the basis that it supplied nitrogen needed for plant growth in the form of ammonia.⁴² However, shortly after publication he changed his mind and argued that enough nitrogen reached the soil through precipitation of atmospheric ammonia to supply the plant’s needs.⁴³ So confident was he in this new theoretical work that he saw no need to perform field tests when he designed a mineral fertiliser for commercial production. This product, which was composed primarily of water-insoluble calcium phosphate⁴⁴ and contained no ammonia, was launched in 1845 and proved to be completely ineffective; ⁴⁵ Liebig would later acknowledge that he had hugely underestimated the importance of nitrogen—and also of practical experimentation.⁴⁶ English agriculturalist John Lawes’ similar chemical fertiliser — informed by Liebig’s mineral theory but actually tested in the field before its commercial release in 1843 — was far more successful.⁴⁷

There are both direct connections and important parallels between this work on plant nutrition and the debates around human nutrition. As journalist and nutritional scholar Geoffrey Cannon has pointed out, both projects involved the use of organic chemistry to search for a substance that would promote growth: a plant fertiliser and a human ‘fertiliser’.⁴⁸ In both cases, nitrogen compounds played a major role in the debate and were sometimes seen as the singular nutrient — nitrogen in the form of ammonia as a limiting nutrient in fertiliser, and the nitrogenous substances as the key component of food needed for growth and health in humans. And, as we shall see, both fields were shaped by entrepreneurial as well as scientific goals.

Although he quickly abandoned protein theory per se, Liebig’s Animal Chemistry and subsequent Researches on the Chemistry of Food established a theory of nutrition and energy that he, his students and his students’ students would continue to develop for much of the rest of the 19th century — a theory which owed something to the work of Boussingault, Dumas and their predecessor Antoine Lavoisier, and much to Mulder’s protein theory. In it, foodstuffs were divided into two types with different functions: nitrogenous foods, used to build tissue which was then expended in muscle movement and had to be replaced; and all other foods that merely fuelled ‘respiration’ — the combustion of carbon to maintain body heat.⁴⁹ The latter is roughly the Dumas- Boussingault conception of nutrition, the former is Mulder’s protein.

Crucially, where Dumas and Boussingault thought that animal bodies could not transform one nutritional substance into another (for example, sugar⇿fat), Liebig thought this constraint applied only to nitrogenous substances.⁵⁰ This gave the nitrogenous substances a special dietary importance: they were the only parts of food that were truly necessary, since they could not be created by the body from other things. A body fed only nitrogenous substances would use some for tissue formation (and so muscle movement) and transform the remainder for respiration to keep warm; by contrast, if no nitrogenous substances were supplied, tissue would gradually be used up and the body would waste away.

In this framework, Liebig extolled the importance of meat.⁵¹ Raw meat, he reasoned, was the only foodstuff that must contain all the substances required to recreate flesh. This had implications for cookery: “if flesh, employed as food, is again to become flesh in the body,” he wrote, it was of crucial importance not to remove or totally transform any components of it.⁵² Water in which meat had been boiled should be retained and consumed, since many important nitrogenous substances were water-soluble (his English editor helpfully pointed out in a footnote that this described the existing process of making stock⁵³).

Liebig’s celebrity over his long career helped to ensure that his ideas about nutrition exerted significant influence on cookery books and housekeeping books: his name alone was felt to be a selling point when advertising ostensibly healthful foods.⁵⁴ He founded Liebig’s Extract of Meat Company (or Lemco, which created the brands Fray Bentos and OXO) to process the meat that could now be imported cost-efficiently (though controversially⁵⁵) from Uruguay, Australia and elsewhere into a concentrated liquid which purportedly retained all the important dietary components of meat. This extract was later criticised for containing little of nutritional value, prompting Liebig to reframe it as a stimulant and shift to selling tinned corned beef (still under the Fray Bentos brand), itself an invention that was transforming the global food system. Via Lemco’s success and his own celebrity, Liebig’s influence on the meat industry and advertising, on culinary culture, and on societal beliefs about meat long outlasted his scientific theories themselves.⁵⁶

From about 1870, the use of the word protein as catch-all for nitrogenous substances began to rise in frequency in texts on human and animal nutrition (cf. Figure 1). No-one was arguing as Mulder had that there was a single chemical from which all animal tissue was formed and the exchange of which was the sole basis of the food chain. Instead, it seems that the word protein had lost its association with Mulder’s debunked theory of chemistry while still retaining the connotation of being the ‘primary substance of nutrition’.⁵⁷ By this point, Adolf Fick and others had experimentally demonstrated that more energy was expended in muscular work than could be accounted for by protein nutrition alone.⁵⁸ This should have ruled out Liebig’s theory of nutrition — if protein intake couldn’t account for muscular work, then movement could not be driven by ‘burning’ muscle tissue and protein could not have the unique dietary function Liebig had assigned it. What is more, an important prediction of the theory had been that physical work should result in increased nitrogen content in urine as the proteinous substance of flesh was expended — and this prediction was repeatedly disproven in both dogs and humans. Instead, such exertion was found to be associated with increased carbon in urine. Nevertheless Liebig and his students such as Carl Voit continued to emphasise the idea that muscular work relied solely on protein and could not be powered by carbohydrate or fat, even when serious intellectual gymnastics were required to ignore the mounting evidence to the contrary.⁵⁹

Figure 1. Use of protein and related forms in Google Books by date

The German school of nutrition was not monolithic and nutritional science did not stay still. Voit, in a bitter break with Liebig, argued that starch and fat could serve nutrition and that Liebig’s “erroneous view” that these nutrients contributed only to ‘respiration’ (the maintenance of body heat) had mistakenly brought protein to be regarded as a uniquely important nutrient.⁶⁰ Yet Voit continued to argue for a high bodily requirement for protein that increased with muscular work. Voit’s student Max Rubner, taking advantage of the developing science of thermodynamics as well as improved calorimeter designs, partially broke with Voit and Liebig to frame bodily requirements not in terms of carbon and nitrogen but in terms of energy. Nutritional needs could now be completely expressed in terms of calories and protein,⁶¹ and the first estimates of daily dietary requirements in this form appeared in Germany, the Netherlands, the UK and the US.

Rubner also broke with Liebig and Voit on the specifics of dietary need for protein. Estimates of daily requirements for protein had been a part of the discourse on nutrition since Mulder estimated in 1847 that a typical labourer needed to consume 100g of protein per day⁶² (to compare this to other recommendations from the time and to modern estimates, see Figure 4). Numbers such as this were derived in two ways. Firstly simply by observing the actual diets of particular segments of the population and calculating how much protein they were consuming.⁶³ The second, more exacting method was to place subjects on a controlled diet and measure the amount of nitrogen in their excreta. This worked on the assumption that the diet should contain at least enough protein to compensate for the amount of nitrogen lost each day⁶⁴ — ‘nitrogen balance’ methods descended from these early experiments are still central to the calculation of protein requirements today.

There was a risk of circularity with both of these methods. Much of the impetus for this work came from conflict and concern around industrial labour in cities, and so there were strong biases towards certain sorts of bodies and livelihoods. The greatest interest (coming from industrialists, social reformers, unionists and Marxists alike — though for different reasons) was in the needs of men doing demanding physical labour. Scholars offered gradated estimates for different types of labourer, and more rarely also for women; however, these estimates tended to have less prominence than the headline figure for highly active men. For example, in 1876, Voit proposed that a man undertaking moderate work required 118g of protein per day and a man undertaking hard work 145g of protein per day.⁶⁵ Although Voit emphasised that he had a particular population in mind and that other demographics would have lower requirements, among the researchers who cited him the figure of 118g/ day became the gold standard for a good diet —  anything less than this was Armenkost, a poverty diet.⁶⁶ Since it would be hard to achieve such a high protein intake without eating a lot of meat, by the 1880s it was generally accepted among German scientists that meat was a key element of a ‘rational diet’.⁶⁷

The influence of these ideas went far beyond the German-speaking world. It was common in the late 19th century for US scholars wanting to gain expertise in nutrition or chemistry to train in German laboratories; one such scholar was Wilbur Atwater, the first head of the USDA’s Office of Experiment Stations, among other accolades.^68,69 Atwater studied under Voit and built on his beliefs — including concerning the unique importance of dietary protein — and on his methods — including the estimation of dietary needs through observational studies. One study offers us a particularly clear picture of the circularity of such work: Atwater investigated the diets of undergraduate boat crews. His interest in this group was based on the logic that they undertook demanding physical work while facing little financial constraint on their diets, and so could be expected to gravitate to the best diet to keep themselves fit. He found that they had very high protein intakes (155g/day) and saw this as confirmation that protein was required for high muscular activity, just as Voit, Liebig, and others had argued. In retrospect, it has been pointed out that these athletes sat at a special table and were encouraged to eat extra meat by their coaches — who believed (in no small part because of the work of a generation of German nutritionists,⁷⁰ cf. Figure 2) that meat-heavy diets were necessary to build strength.^71,72 A few years later Atwater was to publish the USDA’s first dietary recommendations, suggesting an intake of 125g protein per day⁷³ (more than double the USDA’s recommendation today⁷⁴).

The problem of poor nutrition among the urban poor was not only of interest to those engaged with industry and labour, but also to militaries—and thus there was also a military impetus behind the project of identifying protein requirements. During the Boer War of 1899-1902 the British military had struggled to find sufficiently tall and healthy recruits: 40-60% of would-be soldiers failed to meet the statutory height requirement (compared with around 10% in 1845⁷⁵) and this was suspected to be the result of poor nutrition in situations of urban poverty.⁷⁶ A committee was set up to investigate, and the nutritional scientists they interviewed were confidently able to pinpoint the root of the problem: too little protein, especially meat and milk (although excessive drinking of overly-stewed tea was also considered a major worry⁷⁷). At the same time, it was feared that problems of public health might be a symptom of the “deterioration of the British race” instead of the result of poverty.⁷⁸

The two explanations were intimately connected, since meat-eating in particular was increasingly understood as a site of racial difference and imperial superiority. Meat was believed to be necessary for bodily strength and was at least connotatively linked with desirable psychological traits like bravery and rationality; when it was found that certain populations (particularly in the US, Australia and Germany) had particularly high intakes of meat and that many Asian and African populations particularly low, this offered 19th century thinkers one possible explanation of imperial power and domination as a consequence of natural law (“the effeminate rice- eaters of India and China have again and again yielded to the superior moral courage of an infinitely smaller number of meat-eating Englishmen”⁷⁹). In India, distinctions were made between colonial subjects according to whether their traditional diets promoted ‘courage’ and ‘strength’. Rice in particular was condemned for its low protein content and wheat and lentils identified as preferable — but vegetarian diets of beans and grains were still fundamentally poverty diets compared with meat and milk.⁸⁰ The ‘ability’ to go without eating meat became a racialised symbol that could be weaponised in conflicts over labour and Asian immigration in the US (“you cannot work a man who must have beef and bread alongside of a man who can live on rice”⁸¹).⁸² Institutions in the colonies offered European scientists opportunities to undertake nutritional experiments on populations “limited neither by unwillingness nor small numbers”^83,84 which identified increased protein (meat, dairy, and possibly wheat) consumption as a means of improving the yield of colonial labour:⁸⁵ thus the development of nutritional science was both informed and facilitated by racist-colonial beliefs. That said, it is hard to untangle racial from nationalist motivations here, as meat-eating also played a role in competition between western nations: the USDA saw evidence of US national superiority not just in the “starvation diets” of India and China but also in the fact that US protein recommendations were higher than those issued by European scientists.⁸⁶

Ideas about protein increasingly filtered out of the domains of science and governance and into popular thought. This could take place more or less directly, through popular summaries of research⁸⁷ and through public health messaging.⁸⁸ But commercial advertising also played a major role. Nutritional scientists like Liebig had profited from lending their names to ostensibly healthy foods, but by the turn of the century the public was sufficiently familiar with ideas about protein that claims about protein content could be used to sell food directly (cf. Figure 2). This can be seen in the light of ‘nutritionism’, the name popularised by academic Gyorgy Scrinis and food writer Michael Pollan for the shift towards thinking of food solely in terms of nutritional content.⁸⁹ Where nutritional science began as a descriptive enterprise that looked at food culture from the outside, it increasingly played a role in creating it. The term ‘protein’ (or ‘proteid’) had first functioned to try to explain why people chose to eat what they did; increasingly, it was itself a reason for their food choices.

Figure 2. Feedback loop linking nutritional work on protein requirements to existing practice

Bournemouth Graphic - Thursday 30 October 1902

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