The human body naturally synthesis vitamin D in the skin through exposure to direct sunlight and through the diet from fish liver oils and saltwater fish, however it is rare that enough vitamin D is made for what is required. 

Vitamin D is essential to increase calcium and phosphate absorption, making it important in the health of muscles and bones. It also has a vital role in the functioning of the immune system, controls the growth of normal and cancerous cells, stimulates the production of insulin, regulates blood pressure, reduces inflammation in the blood vessel wall, helps skin conditions such as psoriasis, helps the body absorb calcium, good for the teeth and reduces the risk of neurological disorders such as MS, Parkinson's, autism and Alzheimer's.

Due to the lack of sun in the UK, or the increased use of sunscreen to protect against cancer, we unfortunately reduce the amount of Vitamin D our body can produce. Those with darker skin types also absorb less due as the pigment in their skin is designed to block the rays from the sun.

Supplements are often taken, and people assume they are taking their daily allowance. This is not the case- Vitamin D is fat soluble and gets trapped in fat meaning out body is not absorbing enough of what we need