Nearly all of us have dealt with dental caries — better known as cavities — at some point in our lives. According to the World Health Organization, “the disease affects nearly 100% of the population in the majority of countries.”1 Although cavities are common, dentists agree that fluoride dosing, a comprehensive oral hygiene regimen, and nutritious diet can reduce the risk. However, in the 1920s and 1930s, many dentists scoffed at the idea that a healthy, vitamin-rich diet could avert tooth decay. With the causes of cavities hotly contested, Lady May Mellanby, a Cambridge-trained physiologist, campaigned to convince the naysayers that diet mattered. By the 1940s she had succeeded, in part, by correlating years of experimental data with observational studies of the dentally perfect population of Tristan da Cunha, a tiny, British-held island in the remote South Atlantic Ocean.
The Early Life and Work of Lady Mellanby
In 1902, twenty-year-old May Mellanby started flaunting Edwardian gender expectations when she chose to study science, rather than the arts, at Girton College, the women’s college at the University of Cambridge. She finished her studies in 1905, but could not qualify for a degree since the University of Cambridge had yet to confer them on women. Despite this setback, Lady Mellanby still pursued a career in science, first as a researcher and then as a lecturer in physiology at the Bedford College for Women, University of London. It was there that she met Sir Edward Mellanby, a promising researcher and Chair of Physiology of the King’s College of Women. After marrying in 1914, Lady Mellanby, a seemingly “devoted wife,” prioritized Sir Mellanby’s career.2 In 1920 Lady Mellanby vacated her position as lecturer in physiology to follow Sir Mellanby to the University of Sheffield, where he took up a post as professor of pharmacology.
The Mellanbys forged a romantic and scientific partnership. From the outset, Lady Mellanby became “a more-than-full-time but unpaid laboratory assistant to her husband.”3 Sir Mellanby readily conceded that his wife independently undertook much of the laboratory analysis for his pioneering work on rickets. Throughout Sir Mellanby’s long tenure as Secretary of Britain’s Medical Research Council (MRC) from 1933 to 1949, Lady Mellanby faithfully managed the day-to-day operations of his Mill Hill laboratory.
Inspired by their work on the nutritional causes of rickets, Lady Mellanby started considering the links between diet and dental health. With the backing of the MRC, she commenced in-depth studies on canine subjects in the early 1920s. This research indicated that adequate levels of vitamin D and low cereal consumption produced “perfect teeth” in dogs.4 Encouraged by these findings, Lady Mellanby began trials on institutionalized English children. Mirroring the results of the canine studies, Lady Mellanby found that she could induce a higher incidence of cavities by manipulating diet.
This dietary research reflected changing perceptions of caries. Dentists now accept that caries form when oral bacteria, which thrive in dental plaque, convert dietary sugars into acids. These acids, in turn, damage the teeth by stripping them of protective minerals. Deprived of restorative minerals, teeth become permeable and, if not remineralized, decay. First substantiated by Willoughby D. Miller, the contention that invisible microbes caused caries revolutionized late nineteenth-century dentistry. Nonetheless, the so-called “chemico-parasitic” theory failed to explain decay fully. With cavities still menacing mouths around the globe, interwar dentists like Lady Mellanby focused on the role of diet.
Lady Mellanby’s findings sparked a dispute with the “Glasgow School” and its sympathizers. Drawing its name from Glasgow University, then a dynamic site for research into nutrition and the causes of rickets, the Glasgow School rejected the theory that vitamin intake impacted dental health. Critics like James Sim Wallace, the eminent dental surgeon and researcher, deemed oral hygiene of greater importance than dietary nutrients in preventing caries. Locked in a bitter dispute, Lady Mellanby turned to Tristan da Cunha for evidence.
The Dental Utopia of Tristan da Cunha
Marooned in the South Atlantic Ocean, between the African and South American continents, Tristan da Cunha seems an unlikely site for dental research. Lacking any indigenous population, this speck of volcanic rock remained unknown until 1506, when the Portuguese navigator Tristão da Cunha first sighted it. In 1816 the British annexed Tristan da Cunha and stationed a garrison on the island to prevent Napoleon Bonaparte’s rescue from nearby Saint Helena, where the vanquished emperor languished in exile. When the garrison withdrew a year later, several settlers elected to stay.
Over time, a multiethnic, multiracial community of shipwrecked mariners and immigrants from Europe, the United States, South Africa, and Saint Helena coalesced. Long hailed as the most remote inhabited island in the world, the Tristan islanders eked out a meager living from seabirds, fish, and potatoes. Today, Tristan da Cunha boasts a population of fewer than 300 English-speaking islanders descended from just a handful of settlers.
Along with the islanders’ monotonous diet and relatively high degree of inbreeding, Tristan da Cunha’s isolation and microscopic size enticed dentists to visit the island. The island sojourns of these dentists had important implications for our understanding of cavities. Indeed, after several investigations during the 1920s and 1930s, the dental community embraced Tristan da Cunha as an island whose inhabitants enjoyed “dental perfection.”5
In a 1926 dental survey, Lieutenant-Colonel E.H. Marshall, a Royal Navy surgeon, determined that Tristan islanders had among the lowest incidence of carious teeth in the world.6 Marshall’s data indicated that Tristan children were between 20 and 64 times less likely to develop cavities than their English and Welsh peers.7 Subsequent studies confirmed these remarkable findings.8
The revelation that the Tristan islanders had better teeth than most Britons astonished dentists because it contradicted the dental axiom that “a clean tooth never decays.” After all, W.E.A. Sampson reported in 1932 “that not one of them has ever cleaned his or her teeth.” Since the islanders did not practice dental hygiene, clearly something else produced the excellent condition of their teeth. Sampson’s observation that the islanders subsisted almost exclusively on fish, potatoes, and milk renewed interest in the relationship between diet and cavities.9
The evidence gathered from Tristan da Cunha became fodder in the feud between Lady Mellanby and the proponents of the Glasgow School. At the centenary meeting of the British Medical Association in July 1932, Wilfred Fish, assistant dental surgeon, Royal Dental Hospital and St. Mary’s Hospital, and Lady Mellanby debated the dental significance of Tristan da Cunha. Fish argued that caries occurred not from nutritional deficiencies, but from inborn faults in the enamel that rendered the tooth susceptible to bacteria and eventual decay.
Given the high degree of genetic interrelation on the island, Fish thought that the Tristan islanders supported the hypothesis that “caries appear to be definitely racial and hereditary in character.”10 In her reply, Mellanby downplayed the importance of inheritance and dental hygiene. She reiterated that data from Tristan da Cunha suggested that adequate vitamin D intake produced perfect teeth.11
This exchange between Fish and Lady Mellanby hints at why Tristan da Cunha mattered to dentistry. Throughout the interwar period, the dental profession regarded cavities as a disease of “civilization” because Europeans and their descendants in North America, Australia, and New Zealand suffered higher rates of dental decay than “the primitive native living in his natural conditions.” Mellanby argued that Tristan da Cunha refuted the assumption that “civilization” and healthy teeth were mutually exclusive.
As the denizens of the most remote inhabited island in the world, the Tristan islanders lived a unique existence. Yet Tristan da Cunha’s temperate climate and the potato-laden diet of its inhabitants resembled conditions throughout much of Europe, North America, Australia, and New Zealand. For Mellanby, this proved that the supposedly “civilized” peoples living in temperate regions, regardless of genetic endowment or hygienic practices, could improve their dental condition with dietary modifications.12
Lady Mellanby’s theory owed much to Tristan da Cunha. Although Lady Mellanby considered evidence from sub-Saharan Africa, the Arctic, Australasia, and the Western Hebrides, Tristan da Cunha was special because of its geography. Tristan da Cunha’s extreme remoteness made the island an ideal laboratory for what Lady Mellanby called “a test in dietetics.”13 With the islanders’ diet restricted by physical isolation, Lady Mellanby found a natural experiment that validated years of laboratory data.
A Female Pioneer
By the 1940s, the dental profession had accepted that dietary nutrients influence cavity development because of the research of Lady Mellanby and her exponents. As a result, she made an enduring and often underappreciated contribution to nutrition and dentistry. Sir Mellanby’s work earned him prestigious honors, most notably appointments as a fellow at the Royal Society and the Royal College of Physicians. Lady Mellanby, on the other hand, received some honorary degrees and a Science Award from the International Association for Dental Research. The male-dominated scientific community overlooked or diminished Lady Mellanby’s many achievements because of her gender.
In 1978, The Times published an obituary for Lady Mellanby, who died on March 5th, aged 95. “May Mellanby sacrificed much of her scientific energies to help her husband,” it read, “but nevertheless she made a substantial contribution to research on diet and teeth.”14 Lady Mellanby’s scientific accomplishments deserve parity with those of her husband. Lady Mellanby not only helped Sir Mellanby achieve critical breakthroughs, but her own research forever transformed how we look at our teeth.
As for Tristan da Cunha, its status as a dental utopia proved short lived. With the advent of a commercial canning factory for crayfish following the Second World War, Tristan da Cunha’s links with the outside world multiplied. As Tristan da Cunha became better integrated into the international system and income levels rose, the islanders’ consumption of processed foods soared. By 1966, over half of the islanders’ calories derived from imported foods.15 As the consumption of sugary, processed foods increased, so too did the incidence of cavities. By the end of the 1960s, Tristan da Cunha had earned the distinction of being “probably the best example of dental deterioration associated with the consumption of sophisticated foodstuffs enjoyed by populations with an improved standard of living.”16 But that is a story for another day.
- Poul E. Petersen et al., “The Global Burden of Oral Diseases and Risks to Oral Health,” Bulletin of the World Health Organization, 83, no. 9 (September 2005), 662. Return to text.
- “Edward Mellanby, 1884-1955,” Biographical Memoirs of the Fellows of the Royal Society, 1 (November 1955), 193. Return to text.
- “Lady Mellanby: Research on Diet and Teeth,” Obituary, The Times, Thursday, March 9, 1978, 18. Return to text.
- May Mellanby, Diet and the Teeth: An Experimental Study: Part II: A. Diet and Dental Disease (London: His Majesty’s Stationery Office, 1930), 7. Return to text.
- “The Riddle of Tristan da Cunha,” The Dental Magazine and Oral Topics, 49 (1932), 387. Return to text.
- On the incidence of caries among Tristan islanders in 1926, see E.H. Marshall, “Report on a Visit to Tristan da Cunha,” British Dental Journal, 47 (October 1926), 1101-1102. Return to text.
- On the rates of dental decay among English and Welsh schoolchildren, see Table IX and X in MRC, Reports of the Committee for the Investigation of Dental Disease: II: The Incidence of Dental Disease in Children, (London: His Majesty’s Stationery Office, 1925), 41-42. Return to text.
- For the results of these surveys, see W.E.A. Sampson, “Tristan da Cunha: Dental Conditions of the Islanders,” The British Medical Journal, 1, no. 3715 (March 19, 1932), 538-539; Reidar Fauske Sognnaes, Results of the Norwegian Scientific Expedition to Tristan da Cunha, 1937-1938: Oral Health Survey of Tristan da Cunha, 24 (Oslo: Det Norske Videnskaps-Akademi, 1954). Return to text.
- Sampson, “Tristan da Cunha” The British Medical Journal, 539. Return to text.
- E.W. Fish, “The Aetiology of Dental Caries,” The British Medical Journal, 2, no. 3746 (October 22, 1932), 749. Return to text.
- For Mellanby’s response, see May Mellanby, “The Aetiology of Dental Caries,” The British Medical Journal, 2, no. 3746 (October 22, 1932), 749-751. Return to text.
- May Mellanby, Diet and the Teeth: An Experimental Study: Part III: The Effect of Diet on Dental Structure and Disease in Man (London: His Majesty’s Stationery Office, 1934), 158. Return to text.
- Mellanby, Diet and the Teeth, 165. Return to text.
- “Lady Mellanby,” The Times, 18. Return to text.
- On the diet of the Tristan islanders in 1966, see Margaret Chambers and H.E. Lewis, “Nutritional Study of the Islanders of Tristan da Cunha, 1966: The Energy Expenditure and Food Intake of Tristan Islanders,” British Journal of Nutrition, 23, no. 2 (1969), 244-245. Return to text.
- F.J. Fisher, “A Field Survey of Dental Caries, Periodontal Disease and Enamel Defects in Tristan da Cunha,” British Dental Journal, 125, no. 10 (Nov. 19, 1968), 450. Return to text.