Nicknamed the sunshine vitamin, Vitamin D is actually a hormone which is made in response to UVB light hitting our skin. Sunlight is our main source of vitamin D, although we consume small amounts from food, but this only accounts for around 5-10% of our needs.
Vitamin D’s main job is helping the body absorb calcium to create strong bones but the discovery of vitamin D receptors throughout the body shows that is it involved in many biological processes, including regulating immune function, skin cell growth and inflammation.
The amount of vitamin D your body makes is affected by clothing cover, pollution, skin pigmentation and even the time of day – in the morning and late afternoon, sun rays aren’t strong enough for us to make vitamin D.
- Vitamin D is produced via the action of sunlight on the skin. Studies show patients with psoriasis tend to have low levels of vitamin D, which is associated with an increase in inflammation and disease severity.
- Vitamin D may benefit psoriasis by reducing skin cell growth and inflammation.
- Both oral and topical vitamin D have been shown to be effective in reducing psoriasis severity.
What do we know about Vitamin D and psoriasis?
The discovery of vitamin D receptors on skin cells tells us that the hormone plays an important role in the health of our skin.
This is confirmed by studies which show people with psoriasis tend to have lower levels of D-vitamin than healthy controls and that psoriasis is more common in high latitudes7, where sun exposure is poor.
Low vitamin D levels have also been linked with an increase in psoriasis severity and raised levels of inflammatory proteins.
Research into the effects of vitamin D show that it can benefit psoriasis by;
- Slowing the rate at which skin cells grow, resulting in thinner and less scaly plaques.
- Reducing T-cell activity, lowering inflammation
- Studies have found that calcipotriol (a type of activated vitamin D) delivered topically onto the skin either alone or in combination with UVB treatment can improve psoriasis severity.
Oral supplements of vitamin D have also been found to be effective. In one study, 85 patients with plaque psoriasis covering at least 15% of their body were given calcitrol (the activated form of vitamin D), at an average of 2.5 micrograms per night. After 6 months, 88% had some improvement in their disease severity, with 26% experiencing complete improvement.
Are there any risks associated with taking vitamin D?
The main risk associated with supplementing with high doses of vitamin D over a long period is a raised calcium level, which can affect bone mineral density. This does not happen with normal sunlight exposure, as the body can ‘turn off’ vitamin D production when it has sufficient stores.
However, several studies have shown that calcipotriol as well as calcitriol and are safe and can be used on a long-term basis for psoriasis under medical supervision.
The American Academy of Dermatology recommends obtaining vitamin-D from nutritional sources and dietary supplements and not from sun exposure, due to the risk of skin cancer.
How much vitamin D do I need?
In the UK, there is no recommended ‘intake’ as under optimal conditions the body is able to make all the D vitamin it needs.
People who have limited sun exposure are advised to take a supplement containing 10 micrograms or 400 international units (IU) a day, but we don’t know if this is the right amount for people with psoriasis.
If your vitamin D levels are low, you may need a higher dose supplement from your doctor to bring your levels into the healthy range.
What the dietician says:
By Laura Tilt, Registered Dietitian, MSc Public Health Nutrition
“Because we don’t get much sun in the UK, it’s difficult to make enough vitamin D to keep our levels in the healthy range. Between April and October, the sunlight isn’t strong enough for us to produce any vitamin D and so we must make enough during the summer, or supplement through the winter. In one UK study, levels of vitamin D deficiency rose to 80.9% in patients with psoriasis during the winter, compared to 30% in a group of healthy controls.
Getting enough vitamin D from your diet isn’t possible, as egg yolks, butter and oily fish are the only natural sources of vitamin D in the UK diet. Some breakfast cereals and yoghurts are fortified with vitamin D, but these usually contain high levels of added sugars, which you may be trying to avoid.
Given the link between vitamin D and psoriasis, it’s a good idea to get your levels tested as deficiency is common, especially in winter. If you are carrying excess body weight, you’re even more likely to have low levels, as vitamin D gets tucked away in body fat, making it less available for the body to use. In one US report, psoriatic patients with a body mass index over 27 had a higher risk of deficiency.”