Rickets in lion cubs at the London Zoo in 1889: some new insights.

In 1889, when Dr John Bland-Sutton, a prominent surgeon in London, England, was consulted concerning fatal rickets in more than 20 successive litters of lion cubs at the London Zoo, he evaluated the role of diet relative to the development of rickets. He prescribed goat meat and bones and cod-liver oil to be added to the lean horse-meat diet of the cubs and their mothers. Rickets reversed, the cubs survived, and litters were reared successfully. In classic controlled studies conducted in puppies and young rats 3 decades later, the crucial role of calcium, phosphate, and vitamin D in both prevention and therapy of rickets was elucidated. Later studies led to the identification of the structural features of vitamin D. Although the Bland-Sutton interventional diet obviously provides calcium and phosphate from bones and vitamin D from cod-liver oil, other benefits of this diet were not initially recognized. Chewing bones promotes tooth and gum health and removes bacteria-laden tartar. Cod-liver oil also contains vitamin A, which is essential for the prevention of infection and for epithelial cell health. Taurine-conjugated bile salts are also necessary for the intestinal absorption of fat-soluble vitamins, including A and D. Moreover, unlike dogs and rats, all feline species are unable to synthesize taurine yet can only conjugate bile acids with taurine. This sulfur-containing beta-amino acid must be provided in the carnivorous diet of a large cat. Taurine-conjugated bile salts were provided in the oil cold-pressed from cod liver. The now famous Bland-Sutton "experiment of nature," namely, fatal rickets in lion cubs, was cured by the addition of minerals and vitamin D. However, gum health and the presence of taurine-conjugated bile salts undoubtedly permitted absorption of vitamin A and D, the latter promoting the cure of rickets.