Evolutionary Biology and Pathology of Vitamin D

Abstract

The link between exposure to sunlight and the imparting of antirachitic properties to animals and humans led Saleeby to speculate that vitamin D in cod liver oil was probably made by sunlight falling on the green plankton in far waters of North Atlantic which was assimulated into the food chain and eaten by cod [1]. Phytoplankton produce over 120 billion tons of organic carbon each year compared to 20 billion tons produced by terrestrial plants. The concentrating ability of the food chain is obvious when one considers that a single fish consumes approximately 1.2% of its body weight every 24 hours and it has been estimated that it takes 0.5 tons of diatoms to make a pound of seal while a pound of killer whale, a predator of seals, requires 5 tons of diatoms [2, 3]. In 1927, Leigh-Clare [4] exposed the diatom Nitzschia closterium to sunlight and tried to isolate from the lipid extract antirachitic activity. However, she was unable to identify such a factor in her extract. Similarly, Drummond and Gunther [5] reported no significant content of vitamin D in phytoplankton and only very little in zooplankton and small fish that cod ate. In 1934, Copping [6] recovered copepods with fine fish net in the North Atlantic and found that these materials, when dry, possessed antirachitic activity. © 1992, Center for Academic Publications Japan. All rights reserved.