Vitamin D is essential for bone and muscle health. We get some vitamin D through our diet, but much of what we need is produced in the skin where the protein 7-dehydrocholesterol is converted into vitamin D3 under the influence of sunlight. During the spring and summer our bodies are normally able to make all the vitamin D that we need, but in the autumn and winter levels of vitamin D can fall. As it can be difficult to obtain a sufficient amount of vitamin D from food alone, the NHS recommends that people consider taking a daily 10 microgram (µg) vitamin D supplement in the autumn and winter months.