Scurvy believed to be more effective because they were more acidic. It was the acid, not the (then-unknown) Vitamin C that was believed to cure scurvy. In fact, the West Indian limes were significantly lower in Vitamin C than the previous lemons and further were not served fresh but rather as lime juice, which had been exposed to light and air, and piped through copper tubing, all of which significantly reduced the Vitamin C. Indeed, a 1918 animal experiment using representative samples of the Navy and Merchant Marine's lime juice showed that it had virtually no antiscorbutic power at all. The
Vitamin D deficiency deficiency has been associated with urbanisation in terms of both air pollution, which blocks UV light, and an increase in the number of people working indoors. The elderly are generally exposed to less UV light due to hospitalisation, immobility, institutionalisation, and being housebound, leading to decreased levels of vitamin D. The reduced pigmentation of light-skinned individuals may result in higher vitamin D levels and that, because melanin acts like a sun-block, dark-skinned individuals, in particular, may require extra vitamin D to avoid deficiency at higher latitudes. The natural selection hypothesis suggests that lighter skin color evolved to optimise vitamin D