The Coonoor Diet Experiments: Indian and British Diets Compared in Rats

Between 1918 and his retirement in 1935, Robert McCarrison ran a small laboratory at Coonoor, a hill station in the Nilgiri Hills of southern India. What made his work unusual was the food he gave his animals. Instead of the purified, laboratory-made mixtures that most vitamin researchers of the day used, he fed rats, pigeons and monkeys on the real diets eaten by the peoples of India, cooked the way those peoples cooked them, and then watched what happened to the animals’ growth, organs and health. He later set out the results for a British audience in his 1936 Cantor Lectures to the Royal Society of Arts, Nutrition and National Health, republished by Faber & Faber in 1953.

This page follows the experiments in the order he described them: the “faulty food” method, the monkeys of 1918, the organ studies of the Beriberi Inquiry, his work with pigeons and polished rice, the comparison of seven Indian diets, the large rat colony kept on a Sikh-type diet, what happened when milk and vegetables were taken away, a good diet set against a poor English one, white flour against whole-wheat flour, and peptic ulcer on the rice and tapioca diets of the south. Every number below is McCarrison’s own, as he reported it; his life story, the Hunza and goitre science, and what became of his laboratory each have their own page in this wing.

Table of Contents

  1. Faulty Food Instead of Purified Diets
  2. The Madras Monkeys (1918)
  3. Organs Under the Microscope: the Beriberi Inquiry
  4. Pigeons, Polished Rice and Beriberi
  5. Seven Peoples’ Diets, Seven Groups of Rats
  6. The Sikh-Diet Rat Colony
  7. Take Away the Milk and Vegetables
  8. A Good Diet and a Bad One
  9. White Flour and Whole Wheat Flour
  10. Peptic Ulcer and the Travancore Diet
  11. Key Research Papers
  12. Connections

1. Faulty Food Instead of Purified Diets

In the years after the First World War, vitamin science was young. The usual way to discover a vitamin was to build an artificial diet out of purified starch, purified protein, fat and salts, leave out one ingredient, and see which disease appeared. That approach isolated single missing factors with great clarity. McCarrison asked a different question. He wanted to know what the food actually eaten by the people of India did to the body — and so, in his own description, he made up his animals’ diets “from foodstuffs in common use by the people of India.”

His view, set out in his 1937 Lloyd Roberts Lecture Adventures in Research and quoted by his successor W.R. Aykroyd, was that real diets almost never lack one thing alone. Their faults, he wrote, were “usually those of multiple deficiencies combined with carbohydrate excess.” A diet of polished rice, for example, might be short of several vitamins, of good-quality protein and of minerals all at once, while being heavy in starch. A purified laboratory diet could not reproduce that tangle; a real one could.

Over the years he applied the method to many species: rats, pigeons, fowls, rabbits, guinea-pigs and monkeys. The rat became his main animal. It eats much the same range of foods as people, grows quickly and lives out its whole life in a few years, so a feeding experiment of some months covers a large share of its lifespan — McCarrison equated 140 days of a rat’s life with nearly twelve human years.

Aykroyd, writing his obituary memoir in the British Journal of Nutrition in 1960, summed up McCarrison’s first contribution to science as exactly this: he showed that faulty diets made from natural foods damage the body in numerous ways, and he was the first to use the method on a large scale.

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2. The Madras Monkeys (1918)

McCarrison arrived at Coonoor in 1918, convalescing from an illness contracted on war service, and began work almost at once. One of his first experiments, which he described again eighteen years later in the Cantor Lectures, used “some dozens of healthy monkeys from the jungles of Madras.”

Some of the monkeys were fed well; others were given faulty food of the kind he had come to study. According to his account, the monkeys on the faulty diets developed a whole series of digestive diseases — from gastritis and ulcer to colitis and dysentery — and in one animal he found a stomach cancer in its early stage. The well-fed monkeys, kept under the same conditions, stayed healthy.

He published the work in the British Medical Journal in 1920 as “The Effects of Deficient Dietaries on Monkeys.” In this experiment the damage appeared first in the digestive tract, and the stomach and bowel stayed at the centre of his later rat work.

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3. Organs Under the Microscope: the Beriberi Inquiry

The government post that brought McCarrison to Coonoor was called the Beriberi Inquiry. In its first years it was, as the National Institute of Nutrition’s centenary history records, a one-room laboratory inside the Pasteur Institute at Coonoor, staffed by McCarrison and a single assistant. His Sikh assistant Mula Singh, trained at Oxford to cut and stain tissue sections, prepared thousands of slides at Coonoor (his story is told on the Life and Career page).

Those slides allowed McCarrison to study, in Aykroyd’s words, almost every organ of animals kept on faulty diets. His reports from these years appeared as a long series in the Indian Journal of Medical Research titled “The Pathogenesis of Deficiency Disease,” running to seventeen parts, and in a 1919 British Medical Journal paper of the same title.

Enlarged adrenal glands

The finding Aykroyd singled out was the state of the adrenal glands, the small hormone-making glands that sit on top of the kidneys. McCarrison found them enlarged in a range of deficiency states. Aykroyd noted that this observation was “subsequently confirmed by numerous workers.”

A long list of damaged organs

By the time of the Cantor Lectures, McCarrison could list the disorders he had seen in improperly fed animals organ by organ: the skin; the eye, ear and nose; the lungs; the stomach and bowel, including two stomach cancers; the urinary tract; the reproductive organs; the blood, including an anaemia caused by the blood parasite Bartonella muris; the endocrine glands, with goitre, enlarged adrenals and a shrunken thymus; the heart; the nerves, with polyneuritis and beriberi; and the bones. He noted that he had not worked on rickets.

Infection and parasites as triggers

Aykroyd also credited him with drawing attention to the part played by infection and parasitism in tipping a marginal diet into open disease. An animal, or a person, living on the edge of deficiency might show nothing until an infection or a heavy load of parasites pushed it over.

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4. Pigeons, Polished Rice and Beriberi

Beriberi, the nerve and heart disease now known to result from a lack of vitamin B1 (thiamine), was the disease his post was named after. Since the work of Christiaan Eijkman in Java in the 1890s, birds fed on polished white rice had been the standard model for it: they developed a paralysis that could be cured by the rice polishings.

McCarrison used pigeons in the same way, with a twist that fitted his method. According to Aykroyd, he reported producing “true beriberi” in pigeons on diets that were deficient in vitamin B1 but not entirely lacking it — closer to what people actually ate than a diet with none at all.

How rice was eaten in the south

In the Cantor Lectures he described the rice diets of the poorer people of the Madras region. The rice was parboiled, milled or polished, then washed in many changes of water before being boiled, and eaten with little milk, little protein and few fresh vegetables. Each step, in his account, stripped away more of the grain’s value. That diet would become the poor end of every comparison he made.

His view of beriberi in India

McCarrison set out his thinking in a 1924 paper to the Royal Society of Medicine, “Rice in Relation to Beri-beri in India.” The historian David Arnold, in a 2010 history of beriberi in British India, reads him as holding that beriberi in India was older than mechanised rice milling and was concentrated largely in one coastal region, the Northern Circars.

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5. Seven Peoples’ Diets, Seven Groups of Rats

The experiment McCarrison placed first in his Cantor Lectures was the comparison of national diets. He took seven groups of twenty young rats, matched for age, sex and weight, and fed each group on the diet of one people of India, “as prepared and cooked” by that people. The seven diets were those of the Sikh, Pathan, Mahratta, Goorkha, Kanarese, Bengali and Madrassi communities.

The rats were kept on their diets for 140 days, a span McCarrison equated with nearly twelve years of human life. At the end, he reported, the diets ranked by their effect on growth and health in exactly the order listed above: the Sikh diet best, the Madrassi diet worst. He photographed the average rat of each group side by side, a large animal at one end of the row and a small one at the other. Arnold later wrote that such photographs gave “clear ocular testimony” that ordinary diets made a visible difference.

The best diet, in his description

The diets at the top of the scale, in McCarrison’s description, were built on whole wheat freshly ground into flour (atta) and made into chapattis; milk and milk products such as ghee, curds and buttermilk; dhal, the cooked pulses; vegetables and fruit; and meat eaten sparingly, or by the Pathans in larger amounts.

The poorest diet

The diets at the bottom were based on the processed rice described in the previous section: parboiled, milled or polished, washed and boiled, with little milk, low protein and few fresh vegetables.

Why the order mattered to him

The design is what gave the experiment its force: the rats were matched at the start, lived under the same care and differed only in what they ate, so differences in climate, work or way of life among the peoples themselves played no part in the result.

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6. The Sikh-Diet Rat Colony

The Sikh-type diet, best in his comparison, became the standard food of McCarrison’s breeding stock. Aykroyd linked the choice to McCarrison’s years in the Himalayan valleys of Hunza and Gilgit, describing the Sikh diet as “resembling that of the Hunzas whom he never forgot.”

What the stock rats ate

In the Cantor Lectures he listed the colony’s diet: chapattis made from whole-wheat flour, spread with fresh butter; sprouted Bengal gram (a chickpea); raw cabbage and raw carrots; milk; crusts of bread; meat with its bone once a week; and water to drink.

The five-year record he reported

By his later years at Coonoor the colony numbered about 1,000 rats. McCarrison stated that in the five years before he left India there was in this stock “no case of illness, no death from natural causes, no maternal mortality, no infantile mortality.” He offered the colony as his picture of what a well-fed animal community looked like, against which every faulty diet could be measured.

The statement is his, made in a public lecture, and he gave it as an observation of his own colony rather than as the outcome of a controlled trial.

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7. Take Away the Milk and Vegetables

Having found a diet that kept his rats well, McCarrison began taking it apart to see which parts mattered. In one series he removed the milk from the Sikh-type diet and cut back the fresh vegetables, leaving the whole-wheat chapattis and pulses.

The result, in his account, was a return of disease. Many rats on the reduced diet developed “stone” — hard deposits in the bladder and urinary tract. They developed, he added, “a wide variety of other ailments” as well. When milk or butter was put back into the diet, he reported, the stone was prevented.

He published the work in two short British Medical Journal papers in 1927: “The Experimental Production of Stone in the Bladder” and, a few months later, “The Experimental Prevention of Stone in the Bladder in Rats.” He connected the stone to a shortage of the fat-soluble factor in milk and butter that was then being identified as vitamin A, and he returned to the surgical side of faulty nutrition in a 1931 lecture.

For McCarrison the experiment showed the value of the foods the Sikhs themselves called takatwar khurak, “foods that give strength” — milk, milk products and fresh vegetables. “Nowadays,” he told his 1936 audience, “we speak of them as ‘the protective foods’.”

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8. A Good Diet and a Bad One: Sikh vs Poor English Fare

The experiment that brought the comparison closest to home for a British audience was this one. McCarrison set the Sikh-type diet against a diet modelled on that of the poorer classes in England, as he described it: white bread, margarine, sweetened tea with a little milk, boiled cabbage and boiled potatoes, tinned meat and jam.

Twenty rats were placed on each diet, and the experiment ran for 187 days. In his account:

A short report titled “A Good Diet and a Bad One: An Experimental Contrast” appeared in the British Medical Journal in 1926, as an abstract of a fuller paper in the Indian Journal of Medical Research in 1927. He described the experiment again to a British audience in the 1936 Cantor Lectures.

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9. White Flour and Whole Wheat Flour

Bread was the centre of both the best Indian diet and the poor English one, but they used very different flour. The Sikh chapatti was made from whole wheat freshly ground, with its bran and germ; the English loaf was made from white flour, from which the bran and germ had been milled away.

McCarrison tested the difference directly. In a chart he showed in the Cantor Lectures, young rats on diets based on white flour had a mortality of 30 per cent, usually from pneumonia, while young rats on comparable diets based on whole-wheat flour had a mortality of 4 per cent.

He discussed the question in a 1929 British Medical Journal paper, “White and Brown Bread,” and in a 1930 paper in the Indian Journal of Medical Research on whole-wheat bread and white bread. Aykroyd recalled that McCarrison followed his own findings at table: “remembering the Hunzas he breakfasted on whole wheat chappatis.”

What white flour lacks compared with whole wheat — the B vitamins, minerals and fibre of the bran and germ — is described on this site’s whole-grain pages, linked under Connections.

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10. Peptic Ulcer and the Travancore Diet

The last experiment in this series grew out of a surgeon’s observation. T.H. Somervell, a missionary surgeon in Travancore in the far south-west of India, drew McCarrison’s attention, according to Aykroyd, to the high incidence of gastric and duodenal ulcer there. McCarrison himself described peptic ulcer in the Cantor Lectures as very common in the south of India and rare in the north.

McCarrison set up three groups of rats and kept them on their diets for close on 700 days — a large part of a rat’s life:

The incidence of peptic ulcer he reported was 0 per cent on the Sikh-type diet, 11 per cent on the Madras diet and 29 per cent on the Travancore diet. He presented the result as showing that a disease common in certain parts of India could be produced in rats by feeding them on the faulty diets in use there.

The thread through the experiments

Taken together, McCarrison read his Coonoor experiments as saying one thing in many ways: a diet of whole grain, milk and fresh vegetables kept animals well, and the further a diet moved from it — towards polished rice, tapioca, white flour, sugar and tinned food — the more disease appeared, in the lungs, the gut, the urinary tract and beyond. What later historians and nutrition scientists made of that message is the subject of the Legacy page in this wing.

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Key Research Papers

  1. McCarrison R. The Pathogenesis of Deficiency Disease. Br Med J. 1919;1(3033):177-178. PubMed PMID: 20769368
  2. McCarrison R. The Effects of Deficient Dietaries on Monkeys. Br Med J. 1920;1(3086):249-53. PubMed PMID: 20769796
  3. McCarrison R. Rice in Relation to Beri-beri in India. Proc R Soc Med. 1924;17(Sect Trop Dis Parasitol):65-82. PubMed PMID: 19984111
  4. McCarrison R. A Good Diet and a Bad One: An Experimental Contrast. Br Med J. 1926;2(3433):724-732. PubMed PMID: 20772829
  5. McCarrison R. The Experimental Production of Stone in the Bladder. Br Med J. 1927;1(3458):717-8. PubMed PMID: 20773132
  6. McCarrison R. The Experimental Prevention of Stone in the Bladder in Rats. Br Med J. 1927;2(3473):159-60. PubMed PMID: 20773319
  7. McCarrison R. White and Brown Bread. Br Med J. 1929;2(3593):913-4. PubMed PMID: 20775068
  8. McCarrison R. A Lecture on Some Surgical Aspects of Faulty Nutrition. Br Med J. 1931;1(3674):966-71. PubMed PMID: 20776211
  9. Aykroyd WR. Major-General Robert McCarrison, Kt, C.I.E., M.A., M.D., D.Sc., LL.D., F.R.C.P. (15 March 1878–18 May 1960). Br J Nutr. 1960;14:413-418. DOI: 10.1079/bjn19600055
  10. Walker AR. The assessment and remedying of inadequate diets in India, as appreciated by Sir Robert McCarrison. Nutrition. 2002;18(1):106-9. PubMed PMID: 11827781
  11. Arnold D. British India and the “beriberi problem”, 1798-1942. Med Hist. 2010;54(3):295-314. PubMed PMID: 20592882
  12. Gavaravarapu SM, Hemalatha R. National Institute of Nutrition: 100 years of empowering the nation through nutrition. Indian J Med Res. 2018;148(5):477-487. PubMed PMID: 30666974

PubMed Topic Searches

  1. https://pubmed.ncbi.nlm.nih.gov/?term=McCarrison+R%5Bau%5D
  2. https://pubmed.ncbi.nlm.nih.gov/?term=McCarrison+history
  3. https://pubmed.ncbi.nlm.nih.gov/?term=beriberi+history+India
  4. https://pubmed.ncbi.nlm.nih.gov/?term=whole+wheat+white+flour+rats

Further Reading

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Connections

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