Monkeys and Vitamin D. Pioneering science successfully applied to wild animal husbandry in the 1920s and 30s by Miss Hume, Miss Smith and Dr Lucas

The story of the discovery of Vitamin D in the early decades of the 20th century as part of an effort to cure rickets is well known to historians of endocrinology and nutrition. What I did not know until I looked in some editions of Zoo Life magazine was the rôle that monkeys kept as pets, at London Zoo and at the Lister Institute played in the early days of the story.

The article written in 1951 by Margaret Hume and Hannah Henderson Smith under the title ‘Monkeys and Sunshine’ began:

Twenty-five years ago monkeys in captivity used to suffer from cage paralysis. They lost the use of their limbs, sat about listlessly and gradually faded away. We know now that the disease was really the same as human rickets and that what the monkeys lacked was sunshine.

Eleanor Muriel Margaret Hume (1887-1968) and Hannah Henderson Smith (1885-1972) were nutritionists working at the Lister Institute in London. Hannah Henderson Smith served in Queen Alexandra’s Imperial Military Nursing Service during the 1914-18 War; she became Acting Matron of the military hospital at Fovant in Wiltshire. After the end of the First World War they were sent as half of a team led by Hariette (later Dame Hariette) Chick (1875-1977) to Vienna to investigate nutritional diseases which were then rife in the city. They established in their two-year stay at the children’s hospital that cod liver oil or exposure to ultraviolet light could cure and prevent rickets in children.

The article continued: 

Having seen miracles of healing and of relief from pain achieved in Vienna with the aid of light and cod-liver oil, and being monkey lovers, convinced that monkeys in confinement in Britain were the sun-starved victims of the colder climate which kept them indoors, we decided on our return to England to test our belief.

There was no lack of subjects for experiment. Many people, from publican to peer, were monkey lovers too. They heard about our work from the pet shops and brought their bent and crippled pets to us at the Lister Institute for treatment with ultra-violet light. There was no doubt about its success. The crippled creatures began to walk again, even though on deformed limbs. In spite of difficulty we had X-ray photographs taken of a few and were able to demonstrate the restoration of bone which was the basis of the cure. Our experience in curing these invalids and our success in advising their owners how to keep them in health made it clear to us that, once the supply of vitamin D was in some way assured, the major obstacle to keeping many of these creatures healthy in captivity was removed.

They acquired monkeys for themselves to see if they could get them to breed. The first they chose were a pair of Common Marmosets (Callithrix jacchus but then known as Hapale jacchus). They were commonly available in British pet shops, particularly in London, and had a short lifespan in captivity. Each day the marmosets were exposed to ultraviolet radiation from a mercury-vapour lamp. Not only did that pair breed, the first successful breeding of this species in Britain, but another pair produced 25 young over the years and a number of grandchildren. They then went on to see if they could keep Squirrel Monkeys (Saimiri sciureus, then S. sciurea) since London Zoo failed to keep them successfully. Initially so did Hume and Smith but after one of their’s died, an autopsy revealed rosary of the ribs, a characteristic of rickets. Therefore they upped the length of daily exposure to ultraviolet for the next Squirrel Monkeys they obtained. That pair lived together at the Lister Institute for ten years, every day being exposed to ultraviolet for half an hour. They thrived but did not breed. Then their lab was evacuated to Cambridge (to occupy the house of the Lister’s Director) and the monkeys had to live in a glazed conservatory (glass blocks ultraviolet radiation from the sun) with no means of running the mercury-vapour lamp. The monkeys began to deteriorate and the male died within a couple of months. I have told the story of ‘Vitaglass’ and its pioneering use at London Zoo previously; it did not block the sun’s ultraviolet rays. Two panes were obtained and installed instead of glass in the conservatory. The remaining monkey’s cage was moved close to the panes of Vitaglass. She responded to the winter sun shining directly into her cage: ‘She curled up in it, making a happy noise like sleigh bells with which she ever afterwards welcomed the coming of the sun’.

Photograph from Zoo Life showing 'Olive' on the
shoulder of 'her best friend'. I suspect this is Hannah
Henderson Smith

In 1946, lab and monkey moved back to London but there was no mercury-vapour lamp or Vitaglass. She was therefore given milk containing Vitamin D (the form is not stated, see below). In 1949 at the age of 21 the female Squirrel Monkey (called ‘Olive’) died of old age. Olive had been entertained by the comings and goings of a busy lab; in turn she, and the marmosets, had informed her fellow primates something of the of the habits of New World Monkeys and of the necessity of Vitamin D.

The authors concluded:

In summing up the whole story, one must say that the application to the care of all these monkeys, of scientific knowledge about the supply to them of vitamin D, made it possible to study the domestic habits and life history of the marmosets, and to maintain the squirrel monkey for so long that she developed, in an intimate relationship, a psychology of interest and charm and exhibited an intelligence quite unexpected in these little monkeys.

The link to London Zoo and its experiences and evidence on keeping monkeys was provided by Nathaniel Sampson Lucas (1884-1968). He had qualified in medicine with an Oxford M.B. and was on the Medical Register from 1912. He served in the Royal Army Medical Corps in 1917-19 and then joined London Zoo as pathologist. Chalmers Mitchell in his history of the Zoological Society of London noted that he retired in 1924 (at the age of 40!) but he actually joined the Lister Institute as a voluntary worker. He worked on all sorts of things, from vitamins to trying to isolate oxytocin from the pituitary. His work often involved light, from analytical spectroscopy to the effect of different wavelengths on biological processes. Having examined many dead monkeys at the Zoo and been involved in efforts to prevent vitamin deficiencies he  noted that cod liver oil had been tried but that marmosets found it distasteful and usually rejected it.

The team of Hume, Smith and Lucas was an ideal one to tackle the problem and as the authors of the article in Zoo Life stated, the results of their work were reported in Proceedings of the Zoological Society of London in 1927 and then in 1937 as a ten-year follow-up. There were also papers in Veterinary Journal.

But that was far from the end of the story because what Hume and Smith set off was a continuing interest in Vitamin D and bone metabolism in New World monkeys in particular against a background of a spectacular increase in knowledge of Vitamin D in the following decades of the 20th century and against a continuing debate on the provision of Vitamin D and its physiological rôle in human health and wellbeing. There  have been many bumps in the road to the present state of knowledge. There were, for example, claims that depriving monkeys of Vitamin D had no effect on their bones, without the realisation dawning that animals store the fat-soluble Vitamin D in body fat and signs of deficiency only become evident when the stores are exhausted. 

The biologically active form of Vitamin D acts as a steroid hormone and has effects on a number of tissues and organs. For the purpose of the present discussion I will restrict its function as stimulating the absorption of calcium and phosphorus from the intestine. The chemical precursor of the active form, which is produced by the kidneys, is synthesised in the skin by the action of ultraviolet rays. However, precursors of the biologically active form of Vitamin D are also present in some foods that some animals eat. Plants and fungi produce one form of precursor, ergocalciferol (Vitamin D₂), while animals produce and store cholecalciferol (Vitamin D₃). In the absence of natural sunlight or ultraviolet rays from an artificial source, an animal becomes entirely dependent on Vitamin D provided in the food. Because Vitamin D given in large amounts is toxic, there has been endless argument on how much should be in the diet of the human population as well as of animals in captivity.

Factors also known to be important in rickets and its adult equivalent are the calcium:phosphorus ratio of the diet and the provision of Vitamin B₁₂. The use of ultraviolet sources fell out of favour when Vitamin D additives became available for fear of damage to the eyes. However, while Old World monkeys responded to the provision of vitamins and the correct Ca:P ratio, there remained a problem with New World Monkeys, both adults and young. First, the seemed to require D₃ rather than D₂. Even with daily intakes of D₃ sufficient for Old World Monkeys serious problems remained. Further research showed that they need Vitamin D₃ in far greater quantities. Marmosets and tamarins—the ones that responded to ultraviolet rays in the hands of Hume and Smith—need a specially formulated complete food that if eaten by other mammals would cause Vitamin D toxicity. Even then, animals not kept with access to sunlight run into problems, especially the young since primate milk has low concentrations of Vitamin D even when the mother has an ample sufficiency.

Clearly, just using a mercury-vapour quartz-walled lamp, Hume and Smith did provide sufficient Vitamin D for their marmosets to thrive and breed for several generations. Modern lamps which produce a targeted spectrum are said to be in use for South American monkeys not exposed to sunlight.

The reason why—in the mechanistic sense— most but not all Old World Monkeys need more Vitamin D₃, from synthesis in the skin and/or the diet has been studied since the 1980s but are beyond the scope of this article. The reason why—in the evolutionary sense—has not been, to my knowledge, yet considered. 

The need for sunlight or dietary sources of Vitamin D₃ of marmosets and tamarins reminded me of our only visit to Jersey Zoo in the mid-1990s (there is still discussion about who forgot the camera). A large troupe of Golden Lion Tamarins was being kept outside and many were congregated on an earth bank. There many of them were clearly sun-bathing, exposing as large a surface area as possible to the sun. On a similar note we saw Guianan Red Howler Monkeys (Alouatta macconnelli) just sitting on the top of the forest canopy in the full sun. The Harpy Eagles that live nearby must sometimes strike lucky. I therefore end with a question: Do New World monkeys get sufficient exposure to sunlight as part of their daily activity or do they need to spend time out of the forest canopy exposing themselves to the sun, and is there a trade-off in a greater exposure to predation?

Margaret Hume
from obituary in British Journal of Nutrition

The article in Zoo Life magazine:

Hume EM, Smith HH. 1951. Monkeys and sunshine. Zoo Life 6 (1, Spring 1951), 3-5.

The original publications:

Hume EM, Smith HH. 1927. The value of ultra-violet rays in the prophylaxis and cure of rickets in

monkeys. Veterinary Journal 83, 368-372.

Hume EM, Lucas NS, Smith HH. 1929. Further Notes on the Prevention and Cure of Rickets in Monkeys. Veterinary Journal 85, 490-492.

Lucas NS, Hume EM, Smith HH. 1927. On the breeding of the Common Marmoset (Hapale jacchus Linn.) in captivity when irradiated with ultra-violet rays. Proceedings of the Zoological Society of London 97, 447-451.

Lucas NS, Hume EM, Smith HH. 1937. On the breeding of the Common Marmoset (Hapale jacchus Linn.) in captivity when irradiated with ultra-violet rays. - Il. A ten years' family history. Proceedings of the Zoological Society of London A107, 205-210.

Other publications:

Copping AM. 1970. Eleanor Margaret Hume (27 May 1887-1 April 1968). British Journal of Nutrition 24, I. 

Power ML, Oftedal OT, Tardif SD, Allen ME. 1995. Vitamin D and primates: recurring problems on a familiar theme. In Proceedings of the First Conference on Zoo and Wildlife Nutrition, AZA Nutrition Advisory Group, Scarborough, OT.