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 A deficiency to the liver, maximising the VAD. Treatment of VAD can be undertaken with both oral Vitamin A and injectable forms, generally as vitamin A palmitate. The richest animal sources of vitamin A (retinol) are livers (beef liver - one ounce provides around 8,000 IUs ) and cod liver oil - one teaspoon provides around 4,500 IUs ). Researchers at the U. S. Agricultural Research Service have been able to identify genetic sequences in corn that are associated with higher levels of beta-carotene, the precursor to vitamin A. They found that breeders can cross certain variations of corn to produce a