Updated: Oct 30, 2019
Vitamin D - what is it and why we need it
Vitamin D is often called the Sunshine Vitamin as it is mostly made in the skin from exposure to sunlight. It is a fat soluble vitamin and hormone that is essential for calcium absorption, bone development  and plays a role in immune function. Vitamin D insufficiency can lead to Rickets, a condition that was an epidemic in the 1940’s but is becoming more common in UK children today. 
D2 vitamin D is produced by plants (found in mushrooms, fortified foods and supplements). D3 vitamin D is produced by sunshine and animals foods (found in oily fish & fish oil, liver, egg yolk, butter, and supplements.
Am I getting enough?
We live in the UK and sunshine is not guaranteed! Food sources provide us with some vitamin D but not enough to meet the recommended levels.
What can I do?
Government guidelines were updated in 2016 to recommend that all UK infants, children and adults now take a year-round vitamin D supplement to ensure the recommended levels are met.
The Recommended Nutrient Intake (RNI) for vitamin D for everyone in the UK population aged 4y and above is 10 μg/d (400 IU/d) throughout the year.
For children under the age of 4y a safe intake of 8.5-10 μg/340-400 IU per day for all infants aged under 1y and 10 μg/400 IU per day for ages 1 up to 4y.
Those at risk
o Those who follow a vegan diet
o Those living in northern latitudes including the UK
o The elderly or overweight
o Those who have dark skin: the pigment melanin reduces the skin’s ability to make vitamin D in response to sunlight exposure 
o Breast fed infants: vitamin D content in breast milk is typically low and so guidelines recommend as a precaution that breast fed babies from birth to one year of age should supplement .
Where can I buy suitable vitamin D supplements?
o Local pharmacy’s and chemists
o Healthfood shops
o Healthystart campaign
N.b Always check the doseage against the above Supplement guidelines.
 Christakos, S., Dhawan, P., Porta, A. et al., 2011. Vitamin D and Intestinal Calcium Absorption. Molecular and cellular endocrinology. Vol. 347. Pg. 25-29.
 Christodoulou, S., Goula, T., Ververidis, A., et al., 2012. Vitamin D and Bone Disease. BioMed Research International.
 Prietl, B., Treiber, G., Pieber, T., et al., 2013. Vitamin D and Immune function. Nutrients. Vol. 5. Pg. 2502-2521.
 Holick, M., 2006. Resurrection of vitamin D deficiency and rickets. The Journal of Clinical Investigation. Vol. 116. Pg. 2062-2072.
 SACN: Scientific Advisory Committee on Nutrition, 2016. Vitamin D and Health [online]. Available at: https://www.gov.uk/government/groups/scientific-advisory-committee-on-nutrition [Accessed 1/6/19].
 Nair, R. & Maseeh, A., 2012. Vitamin D “The sunshine” vitamin. Journal of Pharmacology & Pharmacotherapeutics. Vol. 3. Pg. 118-126.
 Unicef, 2017. Statement on Vitamin D supplementation for breastfed babies [online]. Available at: https://www.unicef.org.uk/babyfriendly/wp-content/uploads/sites/2/2017/01/Vitamin-D-supplementation-for-breastfed-babies-Unicef-UK-Statement.pdf [Accessed 2/6/19].