3. Testing the lower limit: the end of the first protein fashion

Enthusiasm for protein in the latter half of the 19th century was a bubble — disconnected from the reality of research findings and driven by a series of feedback loops. The concept of protein as a single substance held such theoretical appeal that its influence was felt for decades after it was formally rejected. Research which established dietary requirements by measuring existing dietary habits took place in countries with cultural norms of high meat consumption. Beliefs about meat fitted neatly into ideologies of cultural, racial and national superiority — and the concept of protein established a seeming scientific basis for these beliefs. Scientists engaged in nutritional and agricultural research were often entrepreneurs, and findings that meat was healthsome and necessary offered the marketing tools to capitalise on a newly globalised and technologised meat market. In all of this, exaggerating the physiological importance of protein aligned with the interests of (commercial, social, national and racial) power.

All bubbles must burst in the end, and the seeds of protein doubt had been sown long before the end of the century. Max Rubner, as mentioned above, broke with his mentor Carl Voit and the reigning expert Liebig on protein requirements. He put more weight than they had on the experimental evidence against Liebig’s theory
of nutrition, and concluded that protein, fat and carbohydrate were largely interchangeable sources of dietary energy. By the early 20th century, he had suggested that the protein requirement for a male worker weighing 70kg might be as little as 30g of protein per day⁹⁹ — less than a quarter the value that he had given at an earlier point in his career, and far lower even than present-day estimates. This did not immediately result in a complete reassessment of the consensus, but it was part of a growing body of evidence complicating the earlier picture of protein. A gradually improving understanding of the chemistry of protein and new methods for exploring dietary requirements also contributed to this.

Since the mid-19th century, the growing vegetarian movement had offered an alternative narrative, both on protein and on meat. Prominent proponents of vegetarianism on religious grounds such as Presbyterian minister Sylvester Graham and later the Seventh Day Adventist J. H. Kellogg argued that consumption of meat led to overstimulation, bodily pollution and spiritual temptation. Kellogg (brother of W.K. Kellogg of breakfast cereal fame)¹⁰⁰ explained this as an effect of protein, and the idea that high protein consumption was dangerous developed in the discourse of a number of Christian denominations. In 1914, an advert for shredded wheat biscuits masquerading as an article on prison reform was published in a range of Christian publications in the US, and offers a telling example of the themes at play. The advert suggested that “an excess of high proteid foods” poisoned the blood, disturbed mental equilibrium, caused a “quarrelsome temperament” and might lead to “more heinous crimes”.^101,102

Such beliefs had little direct impact on the scientific consensus, with nutritionists rejecting such diets as protein- deficient.¹⁰³ Proponents of vegetarianism were generally seen as cranks, and parodied variously as enfeebled, effeminate, and living dull lives of indigence. Nevertheless, there was a clear discrepancy between mainstream beliefs about protein and the existence of many people living on vegetarian diets — vegetarian restaurants had multiplied in cities like London and Manchester in the late 19th century — and this prompted researchers like

Voit, Rubner, American biochemist Russel Henry Chittendon and Danish nutritionist Mikkel Hindhede to test whether bodily health could be maintained while eating less meat. Hindhede (whose work was also inspired by a desire to defend the potato-heavy but protein-light diet of his youth in rural Jutland)¹⁰⁴ published the results of experiments in which his lab assistant had been obliged to live on only potatoes, butter, and occasional fruit for a year — a diet, in other words, with no meat and no main source of protein. Although monotonous,¹⁰⁵ Hindhede claimed that this maintained him in “full vigor”.¹⁰⁶ Hindhede found that this work — together with his earlier finding that bovine dietary requirements for protein were much lower than previously thought — was highly controversial in Denmark, leading him to publish a 1913 monograph condemning the work of the German nutritional school and attacking generally accepted views of protein. The book (“somewhat polemical” by its own admission¹⁰⁷) concluded that “it would seem to be practically impossible to avoid getting protein enough”¹⁰⁸ and indeed that a high protein diet was “probably harmful”. Although he stressed that he was not a vegetarian on principle, he would go on to advocate ovo-lacto vegetarianism as the healthiest diet for the remainder of his career.¹⁰⁹

Perhaps the end of the fashion for protein was now an inevitability—or perhaps these arguments could have dragged on in the literature for many more years. However, the First World War created a dramatic break with the past.

The move to war economies in which states held monopsonies on food¹¹⁰ created a need for governments to determine how much protein the agricultural sector should produce; blockades and rationing created a need to determine the minimum diets that could keep populations healthy. This led to greater power in the hands of nutritional scientists and a reification of nutritional science in the context of concrete goals and the opportunity to undertake experiments at enormous scale.

Rubner, heading the Kaiser Wilhelm Institut für Arbeitsphysiologie, was given authority by the German Ministry of War to investigate the role of nutrition in the optimal use of military and industrial labour. Hindhede, head of Denmark’s Statens Laboratorium for Ernæringsundersøgelser, gained even greater authority. Thus two great critics of inflated demands for protein were given unprecedented platforms — but Rubner, who had vacillated on protein requirements over the course of his career, returned to the safe scholarly mainstream of assuming that diets should be high in protein¹¹¹ and so it was Hindhede’s work that was transformative.

Towards the end of the war, the Danish state was affected by the Allied blockade and faced the challenge of avoiding the same disastrous famine that had already affected Germany. Hindhede centred the idea of feed-food competition¹¹² and recommended that 30-90% of pigs be allowed to starve so that lower quality cereals and vegetables normally used for feed could be repurposed as food. This policy, carried out, actually saw a reduction in human mortality through the period of rationing in Denmark. By contrast, Germany saw a precipitous rise in civilian deaths from starvation and disease — a disparity that completely vindicated both the arguments against high protein requirements and against the specific necessity of meat.¹¹³ Hindhede wasted no time in highlighting this in international medical journals.¹¹⁴

Following the War these findings were cemented with new methods of testing specific nutrient requirements in the lab — but Hindhede’s views were becoming mainstream even earlier than this¹¹⁵ and estimates of daily protein requirements dropped precipitously (see Figure 4). Already in 1923, American nutritionist Lafayette Mendel was looking back on the 19th century obsession with protein,¹¹⁶ commenting that long-disproven scientific ideas had left behind a public misconception of “momentous consequence” that “the production of ‘flesh and blood’ requires a liberal consumption of protein, which in turn is commonly interpreted to mean meat”.¹¹⁷ Hindhede, too, was establishing the narrative that the mists of an ideologically-sustained fixation on protein had finally lifted; he described one 19th century nutritionist of the German school as having written “with the manner of a propagandist” in advocating for the importance of protein.¹¹⁸

Nutritional science had broadly reached a consensus that protein requirements were far lower than previously believed and that meat consumption was not a physiological necessity — but this reassessment was tempered by other new research. The identification of individual amino acids had progressed (cf. Figure 3), and the discovery of the distinction between essential and non-essential amino acids through experiments on rats and dogs offered a possible explanation of civilian and military experiences of starvation¹¹⁹ (particularly ‘war dropsy’ or ‘war oedema’, a condition involving swelling that was widespread in Europe — and would be again during the Second World War¹²⁰). This strengthened a belief in the dietary importance of at least some level of intake of animal proteins, particularly milk.¹²¹ What is more, the reassessment of protein and meat never consistently filtered out into other sciences or into public perception. In a 1939 American medical textbook we read that “the prowess and achievements of our early Anglo-Saxon ancestors have been attributed in part to the energy-giving effects of the meat which they consumed in liberal quantities [... and] if man would enjoy sustained vigor and would experience his normal expectancy, as well as contribute to the improvement of his race, he must eat a liberal quantity of good protein”.¹²² This quote clearly demonstrates the problem: all of the cognitive and cultural biases favouring protein and meat were still there. The power and influence of ‘scientific consensus’ is nothing against the power of a good story.

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The Scotsman - Monday 07 May 1917

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Figure 3: Timeline of identification of the amino acids

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Figure 4. Recommendations by institutions and individual researchers for daily protein intake by body weight by year; recommendations mentioned in the text are individually labelled; shaded areas show the two world wars.¹²³

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