Vitamin D, also known as the sunshine vitamin, is very important for maintaining the health of the bones, muscles, heart, lungs, brain, and maybe other parts of the body, including the skin. Scientists also believe it may play a role in the immune system.
This article will look at the relationship between psoriasis and vitamin D, how to get more vitamin D, and whether or not an extra dose of this vitamin can help people with psoriasis.
What is vitamin D?
Sunshine is a key source of vitamin D, which may help with the symptoms of psoriasis.
Vitamin D is a unique vitamin for two reasons:
- When the skin is exposed to sunlight, the body can make its own store of this vitamin. People need to consume other vitamins in food.
- Unlike other vitamins, the body turns vitamin D into a hormone. The name of this hormone is "activated vitamin D" or calcitriol.
There is evidence that vitamin D helps to maintain and support the health of:
- bones and teeth
- the immune system
- the brain
- the nervous system
- insulin levels
- lung function
- cardiovascular health
Scientists have also found links between vitamin D and some skin conditions, including psoriasis.
When sunlight falls on the skin, the body produces vitamin D. The skin appears to play a role in the synthesis of vitamin D.
Scientists describe this interaction as "complex." They still do not understand the relationship fully.
Learn more here about vitamin D and its benefits.
Effect on psoriasis
Low vitamin D levels are common among people with long-term psoriasis.
People with psoriasis go through times of remission, when symptoms recede or disappear, and flares, when they get worse.
Scientists have found that a person with psoriasis is more likely to experience low levels of vitamin D.
Experts believe that having a vitamin D deficiency does not cause psoriasis, but it might limit the body's ability to keep skin healthy.
One study looked at the vitamin D levels of people in Ireland with psoriasis. The investigators found that, when there was less sunlight, people's vitamin D levels fell, and their psoriasis symptoms tended to worsen.
The researchers proposed that, during the wintertime, people with psoriasis might benefit from either UVB therapy or vitamin D supplementation.
In fact, doctors often prescribe ultraviolet B (UVB) light therapy to treat psoriasis. It seems to work, but whether or not this is due to increased vitamin D remains unclear.
Vitamin D also features in some oral and topical psoriasis treatments.
UVB light therapy and vitamin D
Researchers have noted that UVB is effective at reducing psoriasis symptoms.
One effect of the treatment is that it mimics the sun's UVB rays, and these rays trigger the production of vitamin D in the skin.
However, some scientists have suggested that, while UVB treatment improves symptoms of psoriasis, this may be due to other factors, rather than the creation of additional vitamin D.
Sources: How to get more vitamin D
There are four ways for people with psoriasis to boost their vitamin D levels.
Fortified dairy produce can provide vitamin D.
Good dietary sources of vitamin D are:
- cod liver oil
- oily fish, such as salmon
- fortified cereals, juices, and dairy produce
- egg yolk
- beef liver
The Office of Dietary Supplements (ODS) recommend that most people get enough vitamin D through a healthful diet and careful exposure to the sun's UVB rays.
Vitamin D2 and D3 are available as supplements, and doctors recommend them for infants and others who are at risk of a deficiency.
There is no specific recommendation for adults to use vitamin D supplements. Anyone with psoriasis who is considering supplements should speak to a doctor first.
The Institute of Medicine recommend an upper limit of 4,000 IU of vitamin D a day to prevent the risk of side effects.
The sun enables the body to make vitamin D, but sunlight consists of both UVA and UVB rays.
While UVB exposure does not increase the risk of cancer, UVA exposure does.
For this reason, people with psoriasis should ask a doctor for advice before increasing their exposure to sunlight. Find out more here about sun exposure and psoriasis.
A healthcare professional will provide UVB treatment at a doctor's office. It is not available in tanning salons.
Tanning beds are not suitable for treating for psoriasis because they increase the risk of skin cancer and other skin problems. People with psoriasis should not use a tanning bed.
A doctor may prescribe creams and other topical applications containing a form of vitamin D to treat the symptoms of psoriasis.
Some studies have found that applying vitamin D to the skin, especially combined with corticosteroids, might be an effective treatment. There are concerns about the side effects of corticosteroids, and researchers say that this could help to solve this problem.
In a Cochrane review, published in 2016, researchers concluded that vitamin D may be beneficial.
However, they found that it can also have adverse effects, especially when used alone and in high doses, and appears to be less effective than corticosteroids.
For this reason, authors concluded that it is safer and more effective to use vitamin D in combination with a high-quality topical steroid.
Creams for psoriasis containing vitamin D are available for purchase online.
Vitamin D deficiency
Some creams for psoriasis contain vitamin D.
Low levels of vitamin D can result from:
- poor diet
- low absorption or high excretion, due, for example, to inflammatory bowel disease
- lack of exposure to sunlight
- certain medical conditions
People with psoriasis often have low levels of vitamin D, but exactly why is unclear.
In addition, people are more likely to have a deficiency if they:
- are older in age
- have a high BMI
- are breastfed infants
- have dark skin
- have little exposure to the sun, due, for example, to winter cloud cover, an indoor lifestyle, or wearing clothing that covers all the body
If there is a chance that a person has low vitamin D levels, a doctor can use a blood test to check. If the levels are low, they may advise the person to take oral supplements to increase their levels.
However, there is little evidence to suggest that supplements will help to improve psoriasis symptoms.
Clinical trials are under way to find out whether vitamin D might have a role to play in treatment. One Norwegian study is due for completion in May 2019.
Vitamin D side effects
According to the ODS, taking too high a dose of a vitamin D supplement can lead to:
- anorexia and weight loss
- excessive urination
- irregular heart beat
- high calcium levels in the blood, increasing the risk of kidney stones and cardiovascular problems
The ODS suggest that an intake of 10,000 IU a day or more could be toxic. They warn that both low and high levels of vitamin D could cause health problems in the long term.
In studies where people with psoriasis used vitamin D as a topical treatment, some people experienced adverse effects in the area where they applied the cream.
- skin pain
- red, inflamed, dry skin
The National Psoriasis Foundation note that there is little evidence to confirm that using vitamin D supplements will help people with psoriasis, and they also warn that vitamin D supplementation can lead to side effects.
They advise people to check with their doctor before taking supplements, to prevent adverse effects and interactions with other drugs.
Other vitamins and supplements for psoriasis
There is not much evidence to suggest that vitamins or dietary supplements help reduce symptoms of psoriasis.
However, oily fish are a good source of vitamin D, and some people with psoriasis believe that omega-3 fatty acid supplements help ease their psoriasis.
Omega-3 fatty acids may reduce inflammation, and psoriasis is an inflammatory disease.
However, there are not enough long-term clinical trials to show whether these supplements are effective for treating psoriasis.
Scientists believe there is a link between vitamin D and psoriasis, and they have often found low levels of vitamin D in people with the condition.
However, they do not yet understand how the two interact. Nor is it clear whether vitamin D supplements will help people with psoriasis.
Topical creams combining corticosteroids and vitamin D may help. In addition, UVB treatment, an established therapy for psoriasis, can help the body to create more vitamin D and also appears to relieve symptoms.
As researchers find out more about the links between psoriasis and vitamin D, their findings could lead to new treatments in the future.
For now, however, people should speak to their doctor before trying either UVB treatment or vitamin D supplementation.
Any supplement could interfere with other medications the person is taking.