Scurvy on a diet devoid or nearly devoid of vitamin C, had blood levels of vitamin C too low to be accurately measured when they developed signs of scurvy, and in the Iowa study, at this time were estimated (by labeled vitamin C dilution) to have a body pool of less than 300 mg, with daily turnover of only 2.5 mg/day. The vast majority of animals and plants are able to synthesize vitamin C, through a sequence of enzyme-driven steps, which convert monosaccharides to vitamin C. However, some mammals have lost the ability to synthesize vitamin C, notably simians and tarsiers.
Vitamin D deficiency in Australia margarine and milk. Additionally, if you consume vitamin D through your diet, or make vitamin D in your skin from UVB exposure, it is processed through two organs before it becomes activated. Vitamin D is first processed in the liver, before heading to the kidneys where it becomes activated to the form 1-25 dihydroxy vitamin D or alternatively named chemical calcitriol. Vitamin D deficiency historically used to be identified through counting cases of rickets. The old theory was that if someone had enough vitamin D to prevent rickets and osteomalacia, two skeletal disorders, they were considered safe from a deficiency.