This week the papers have been full of the latest Public Health England warnings about vitamin D deficiency and it's recommendations. Roughly one in five people have low vitamin D levels. Given that we're an outdoor walking club, I thought I'd look into it from our perspective. Why is vitamin D so important, do we get enough of it from our walks alone and, if not, what should we be doing?
What does vitamin D do and how much do we need?
Vitamin D is important because our bodies use it to control the amount of calcium and phosphate in our bodies. Both are needed for healthy bones, teeth and muscles. Without it young children are at risk from rickets and us adults can develop osteomalacia, which can make bones painful and tender, as well as osteoporosis (fragile bones).
It is also seems that vitamin D has other roles in the body including neuromuscular and immune function plus other health benefits such as an anti-depressant, although there hasn't yet been sufficient research to substantiate this claim.
The PHE guidance, published last Thursday, is that everyone over the age of one needs to have about 10 micrograms (400 IU) of vitamin D each day to stay healthy. This advice is based on recommendations from the government's Scientific Advisory Committee on Nutrition (SACN) following its review of the evidence on vitamin D and health (PDF, 4.2Mb).
How we get our vitamin D - sunlight, food and supplements
Probably the best known source of vitamin D is sunlight and vitamin D is often referred to as the 'sunshine vitamin'. The vitamin forms under our skin in reaction to the sun. This is good news for us walkers as we are exposed to the sunlight when we go out walking. The bad news is that in the UK the sun is only strong enough for us to make vitamin D from April to September. Whilst it is possible for our bodies to store vitamin D for up to a couple of months, in this country during the winter months (and all year round for some people) we need to obtain vitamin D from other sources.
Vitamin D is found naturally in a small number of foods, including oily fish (such as salmon, sardines and tuna), red meat, liver and egg yolks. It's also found in fortified foods like breakfast cereals and fat spreads. However, it's difficult for us to get the recommended amount of vitamin D from food alone. 10mcg amounts to the equivalent of one salmon fillet or ten egg yolks!
This is why PHE is recommending that everyone should consider taking a daily supplement containing 10 micrograms of vitamin D in autumn and winter. People whose skin has little or no exposure to the sun, like those in institutions such as care homes, or who always cover their skin when outside, risk vitamin D deficiency and need to take a supplement throughout the year. Dr Louis Levy, Head of Nutrition Science at PHE, said:
"A healthy, balanced diet and short bursts of sunshine will mean most people get all the vitamin D they need in spring and summer. However, everyone will need to consider taking a supplement in the autumn and winter if you don’t eat enough foods that naturally contain vitamin D or are fortified with it. And those who don’t get out in the sun or always cover their skin when they do, should take a vitamin D supplement throughout the year."
- From April to September, we can make enough vitamin D from sunlight by walking with our forearms, hands or lower legs uncovered and without sunscreen for a short period.
- It's not known exactly how much time is needed in the sun to make enough vitamin D to meet the body's requirements. This is because there are a number of factors that can affect how vitamin D is made, such as your skin colour or how much skin you have exposed. Several commentaries say that about 10 minutes would be sufficient.
- Although exposing our skin to the sun is important for vitamin D, we should be careful not to burn in the sun. There’s a balance to be had and there are skin cancer risks if our skin starts to turn red or burn through sun exposure.
- Our bodies can't make vitamin D if we are sitting indoors by a sunny window because ultraviolet B (UVB) rays, the ones our bodies needs to make vitamin D, can't get through the glass.
- During the months of October to March we need to ensure we are getting our vitamin D through the foods we eat and/or through vitamin supplements.
I'm off on my summer holidays next week and am taking a stack of books with me (a kindle's on my birthday list). Top of my list is Bill Bryson's A walk in the woods, which I've read great reviews about. Here's a few walking-related books I've already enjoyed.
The unlikely pilgrimage of Harold Fry by Rachael Joyce - A delightful and gentle novel of one man's 600 mile journey to deliver a letter to a dying person he hasn't seen for over 20 years.
Wanderlust A history of walking by Rebecca Solnit - I'm a fan of Solnit and Wanderlust is an excellent mix of historical, philosophical and personal reflection on walking and all it stands for. I could quote extensively from it - but will limit myself to this by Rousseau: " I can only meditate when I am walking. When I stop, I cease to think; my mind only works with my legs."
While wandering A walking companion by Duncan Minshull - An anthology of poetry and prose excerpts on all things connected with walking - the why and the how; in nature and in cities; processions and marches; and final steps. It's a great companion to Wanderlust.
On a final note, I just want to say thanks in advance to my guest blog contributors whose missives you'll be reading over the next few weeks.