A deficiency in Vitamin D is known to cause various diseases due to insufficient calcium or phosphate in the bones. Vitamin D is actually an umbrella term that covers a group of steroid molecules. Of these, only Vitamin D3 requires sunlight to synthesize. It is formed in the skin of all mammals when light energy is absorbed by a precursor molecule called 7- dehydrocholesterol. A recent study found that at the height of summer, two minutes’ exposure of the face and arms to the sun, three to four times a week, could supply enough Vitamin D3. This rose to 15 minutes in the winter. Ironically, Vitamin D deficiency, which may also lead to skin cancer, is actually very common in some of the sunniest but most underdeveloped countries in the world. This is not because of malnutrition or a lack of dietary supplements, as most people mistakenly think. In fact, it is because very dark skin colour slows the rate of Vitamin D3 production by a factor of six, and people in these countries are usually heavily veiled when outside, as well. In addition, wearing sunscreen with a sun protection factor greater than eight will also block Vitamin D3 production.