Sunshine makes most of us feel better. Long warm sunny days of late spring and summer spent relaxing outdoors bring on the urge to uncover the barbeque and get into holiday mode. But how much time do we actually spend absorbing the sun’s rays and is it enough? Vitamin D is dubbed ‘the sunshine vitamin’ and around one quarter of the UK population is deficient.
Our bodies make vitamin D by converting UV-B rays from the sunshine into a cholesterol like substance which is then processed by the liver and kidneys before becoming available to the cells in the biologically active form.
The key function of Vitamin D is the regulation of calcium, magnesium and phosphate in the body.
It promotes calcium absorption in the gut which allows normal mineralisation of bones and is needed for bone growth and repair. In addition, vitamin D regulates normal cell functioning – including cell growth, proliferation and cell death; all essential functions to prevent the formation of cancers. It is also necessary for proper muscle and immune function and reduction of inflammation.
Vitamin D deficiency has been linked to a number of health disorders including arthritis, osteoporosis, depression, cancers and chronic fatigue.
How to boost your dose
The most effective way to increase your levels of vitamin D is to get regular doses of sunshine! Between 50 and 90 percent of most people’s vitamin D comes from everyday sunlight exposure, however it’s not always this simple.
As a society we’re spending more time indoors, with centrally heated houses. When we go out the cool air is likely to make us don a jacket or long sleeved top and on the few days that the sun does shine with any strength we cover up with sun screen and, sun hats.
Research shows that wearing just SPF 8 reduces the body’s ability to make vitamin D by up to 90 percent! Night shift workers are at an even greater risk of deficiency as are those with dark skin tones as their natural sun protection is higher.
Increasing the duration of sun exposure seems like an obvious solution, but, balancing the risks of skin damage must also be a consideration. Just 5 – 30 minutes of full sun exposure at least twice a week is usually enough to raise vitamin D to adequate levels. Even on cloudy days, when the sun’s radiation is reduced by around half, levels will still be boosted; just remember to pull up your sleeves and take a walk outside.
Two points to remember:
- Build your reserve of vitamin D on dry and sunny days and your body will store it in the liver and body fat to last through the winter.
- UVB rays do not pass through glass so you need to be outside to reap the benefits.
D3 or not D3?
New advice from the scientific advisory committee on nutrition stated that due to the low levels of sunshine from October to March of each year, everyone over the age of 5 will need to rely on dietary sources of vitamin D during this period.
Dietary sources are limited; oily fish provide the best levels with a 100g portion nearly meeting the daily requirement. Other foods with any notable content include egg yolks (one egg contains around 6 – 10% of the daily requirement), beef liver and mushrooms.
Vitamin D comes in two forms:
D3 is the type of vitamin D formed by the skin following exposure to sunlight and is the form present in foods of animal origin.
Vitamin D2 is formed by irradiating yeasts in the lab or allowing mushrooms to grow in the sunshine. It is D2 that is most commonly used for supplements and in foods fortified with vitamin D as it is the cheapest and easiest to make.
Unsurprisingly, research suggests that D3 is far more effective at raising vitamin D levels than its counterpart. One study found that it was 87% more potent in raising and maintaining vitamin D concentrations and that there was a two to threefold greater storage of vitamin D32.
Getting vitamin D in to the cells
Providing optimum levels of vitamin D doesn’t stop at sunshine and food sources! Once in the body it must be converted into the form that is used by the cells.
Step 1. The health of the gut is vital to the absorption of vitamin D from food or for those that choose to supplement. Gastric juices, pancreatic secretions, bile from the liver and the integrity of the intestinal wall all influence how much can be absorbed.
Steps 2 and 3. The liver and kidneys are the next steps in the conversion of vitamin D – even that which comes directly from sunshine. Levels of the bioactive form tend to mirror the health of these organs; when the liver or kidneys are performing well, levels of available vitamin D are low.
Signs of poor liver function include a yellowish colouring in the whites of the eyes, small lumps of fat in the skin (particularly around the eyelids), a coating on the tongue, itchy skin or excessive sweating.
Ensure your vitamin D is doing all it needs
- Ensure your gut, liver and kidneys are working effectively.
- Allow unprotected sun exposure on arms and legs whenever possible for 10 – 20 minutes (do not allow the skin to burn).
- Consume oily fish regularly.
The Herbal Clinic, 32 King Edward Road, Swansea SA1 4LL
2. Robert P. Heaney et al. Vitamin D3 Is More Potent Than Vitamin D2 in Humans The Journal of Clinical Endocrinology & Metabolism, Volume 96, Issue 3, 1 March 2011, Pages E447–E452