November 2017 Blog: Vitamin D Deficiency and Health
Vitamin D Deficiency and Health
National statistics show that increased prescribing of vitamin D, namely Colecalciferol, is a growing trend.
In England there were almost 20 million Colecalciferol prescriptions in 2015 at a cost of around £90 million pounds, putting it in the #1 position of the BNF 9.6 Vitamins Top 10. The next nearest competitor was Thiamine, prescribed 2.5 million times.
With a four-fold increase in the number of prescriptions for Cholecalciferol between 2005 and 2015, you could be forgiven for thinking there is an epidemic of deficiency.
So why do we all need vitamin D and why aren’t most people getting enough of it?
Vitamin D promotes calcium absorption in the gut and helps regulate the amount of calcium and phosphate in the body. This ensures normal mineralisation of the bones and prevents hypocalcaemia tetany. It is also needed for bone growth and bone remodelling by osteoblasts and osteoclasts.
A lack of vitamin D can lead to bone deformities such as rickets in children and osteomalacia in adults. Also, together with calcium, vitamin D helps protect older adults from osteoporosis.
Vitamin D is a fat-soluble vitamin which is naturally present in only a few foods making it hard to get hold of. There are however a number of options, but typical portion size could be an issue and needs to be taken into account. There may be some people, who would enjoy eating 10 rump steaks, or six whole boiled eggs or 8 bowels of cereal, but there can’t be that many and it certainly doesn’t look to have the makings of a healthy diet.
See below for an indication of vitamin D content of foods in relation to a typical portion:
• Oily fish – salmon (steamed 9.9µg), mackerel (grilled 13.6µg) and tuna (baked 4.7µg)
• Red meat – liver (lamb, fried 0.9µg) and beef (rump steak, fried 1µg)
• Eggs – whole boiled (1.7µg) and yolks (2.3µg)
• Fortified foods – bran flakes/corn flakes/rice cereal (1.3µg) and fat spreads (0.75µg)
It looks like eating more oily fish could be the best option as this comes closest to providing an adequate amount of vitamin D without having to consume an excess amount of food.
Vitamin D is also known as the “sunshine vitamin”, because it is produced endogenously when ultraviolet rays (UVB) from sunlight strike the skin and trigger vitamin D synthesis. The substance itself whether from food, supplements or sun exposure is actually biologically inert and must undergo two hydroxylations in the body for activation.
Unfortunately, vitamin D synthesis in the skin only really works for part of the year and then there’s a risk of sunburn and skin cancer if you really ‘go for it’! From late March until the end of September most people can make enough vitamin D from being out in the sun as follows:
• Go outside every day for at least a short period – sitting indoors by a sunny window doesn’t work as the UVB rays can’t get through the glass
• Expose forearms, hands or lower legs uncovered and without sunscreen
• Length of exposure required will vary with skin colour and how much skin is exposed
What happens in winter? In the UK, there just isn’t enough UVB radiation to promote vitamin D synthesis in the skin. Therefore, from October to early March there is no chance of making your own vitamin D, which means that you will need to ensure adequate dietary intake (see above) or take vitamin D supplements. The latter are readily available and the Department of Health recommends that some groups of the population definitely make sure that they get enough. As detailed on the NHS Choices website, these groups are:
• All babies from birth to one year of age (including breastfed babies and formula fed babies who have less than 500ml a day of infant formula)
• All children aged one to four years old
• People who are not often exposed to the sun – for example, people who are frail or housebound, or are in an institution such as a care home, or if they usually wear clothes that cover up most of their skin when outdoors
In 2007 the Scientific Advisory Committee on Nutrition (SACN) considered the evidence on vitamin D and health and concluded there was insufficient data to reconsider the Dietary Reference Values (DRVs) for vitamin D. However, in 2016 SACN produced a 304-page report: “Vitamin D and Health”, which changed their previous advice and they recommended that everyone in the general UK population, aged 4yrs and above, should have 10µg/day (400IU/day).
For those not included in the specified groups above the recommendation is that, everyone over the age of five years (including pregnant and breastfeeding women) is advised to consider taking a daily supplement containing 10µg of vitamin D. But, you can have too much vitamin D and for most people 10µg will be enough as a daily supplement. The advice is not to have more than 100µg a day for an adult, children 1-10 years it’s no more than 50µg per day, and babies under 12 months the maximum is 25µg.
The current recommendations are based on bone health. Vitamin D may also have a role in other health outcomes, which include reducing the risk of Type 1 and 2 diabetes, cancers, cardiovascular disease, infectious diseases and autoimmune diseases. There’s a lot more research to be done, but the evidence for improved bone health alone is enough to convince me that vitamin D supplementation is vital during the winter months for most people.