Scurvy observed in any organism apart from humans and had been considered an exclusively human disease. Certain birds, mammals, and fish are susceptible to scurvy, but pigeons are unaffected, since they can synthesize ascorbic acid internally. Holst and Frølich found they could cure scurvy in guinea pigs with the addition of various fresh foods and extracts. This discovery of an animal experimental model for scurvy, which was made even before the essential idea of "vitamins" in foods had been put forward, has been called the single most important piece of vitamin C research. In 1915, New Zealand troops in the Gallipoli
Vitamin D deficiency D levels falling within this normal range prevent clinical manifestations of vitamin D insufficiency as well as vitamin D toxicity from taking in too much vitamin D. Vitamin D deficiency can be asymptomatic, but may also cause several problems including: Vitamin D deficiencies are often caused by decreased exposure of the skin to sunlight. People with a darker pigment of skin or increased amounts of melanin in their skin may have decreased production of Vitamin D. Melanin absorbs ultraviolet B radiation from the sun and reduces vitamin D production. Sunscreen can also reduce vitamin D production. Medications may speed up