We know from government population studies that most people don’t spend enough time outdoors. This is significant as sunlight is needed for production of vitamin D in the skin. When exposed to sun, the skin produces 7-dehydrocholesterol from cholesterol in the body. After going through some complex processes in the liver and then kidneys, the active from of vitamin D, calcitriol, is produced. So, if you’re spending less than about 10 or 15 minutes outside in the sun daily, you’re relying more on your diet to keep your body levels up. Plus, skin colour and other factors such as sun cream affect how much vitamin D the body is actually producing.