Unlike other vitamins, vitamin D functions like a hormone and every cell in your body has a receptor for it. It's found in certain foods such as fatty fish (salmon, tuna, sardines), eggs & liver, but it is hard to get enough just from your diet. Our bodies can also produce vitamin D from cholesterol when skin is exposed to sunlight. However, because of the risks of sunburn and skin cancer, we need to be careful how much sun we get.

Vitamin D deficiency is fairly common and ~ 5% of adults in New Zealand are deficient. A further ~ 27% are below the recommended blood level of vitamin D. This can be due to having dark skin, being elderly, being overweight or obese, not eating much fish or dairy, always using sunscreen when going outside, skin not being regularly exposed to sunlight, living in the South Island, if you have liver or kidney disease, or are on certain medications that affect vitamin D levels.

Vitamin D deficiency can:
- increase risk of developing colds/infections, particularly respiratory infections
- cause slow wound healing & increased inflammation
- cause fatigue/tiredness
- cause bone/back pain & can cause rickets in children - vitamin D assists with the absorption of calcium
- can effect mood & increase symptoms of depression

Different people need different amounts of sun exposure to make enough vitamin D. How much sun you should get depends on your skin colour, your age, weight and mobility, your risk of skin cancer, how much vit D you get from your food, if you are taking medications (eg photosensitising meds), the season & certain medical conditions.

You can increase the amount of vitamin D you are getting by eating foods rich in vitamin D and making sure you get outside. This is particularly important during lockdown as we head towards winter. Getting outside for some exercise in the sun in the early morning or late afternoon between September & April is recommended by the Ministry of Health if it is safe for you to do so. During May-August this can be done in the middle of the day. Some medical professionals may also prescribe taking vitamin D supplements, especially in the winter for those at risk of having low vitamin D.