vitamin d supplements

Do Vitamin D Supplements Help Psoriasis? We Asked a Dietitian

By Elena Donovan Mauer
Reviewed by Allison Truong, M.D.
April 11, 2022

Vitamin D is something we often hear people with psoriasis ask about. Sure, there are topical prescription vitamin D creams (such as calcipotriene or calcitriol) that can help soothe inflammation, but what about taking supplements orally or adding more vitamin D to your diet? We asked our nutrition expert, Elizabeth DeRobertis, a New-York based registered dietitian about vitamin D and whether it is worth the hype for improving psoriasis symptoms.

Why do we keep hearing about vitamin D for psoriasis and psoriatic arthritis?

Vitamin D has been a buzz vitamin for a few years now. Vitamin D is a nutrient that we eat, and also a hormone that our bodies produce. It is required for the body to absorb and retain calcium, so it’s long been known to be essential for bone health. A few years ago, there were some studies that found it may help to reduce cancer-cell growth; and then, more recently, some studies on COVID-19 found that taking vitamin D may be beneficial to boost immunity to the virus.

We know that we make vitamin D through exposure to the sun, and that the process happens through our skin. There are some studies that link vitamin D deficiencies to psoriasis. For example, one found a correlation between vitamin D deficiency and psoriasis, but it doesn’t look like the deficiency actually causes the psoriasis. (If low vitamin D levels always caused psoriasis, then many more people in the population would have psoriasis, but they do not.)

While more studies are needed, researchers say that someone with psoriasis should make sure they’re not vitamin D deficient. This is a factor someone can control that may help to improve their skin and reduce flare-ups.

What should someone with psoriasis or psoriatic arthritis consider when deciding whether to take vitamin D?

First, the person should find out if they are deficient in vitamin D. This is an easy blood test. If they’re deficient in vitamin D, then there are certainly benefits to eating foods rich in vitamin D, plus taking a supplement to achieve an optimal level of vitamin D. Being deficient in vitamin D doesn’t set your skin up to be able to maintain its best health.

It’s very easy to find out if you’re vitamin D deficient through a simple blood test that can be done by your primary care physician. In the blood, a form of vitamin D known as 25-hydroxyvitamin D [25(OH)D] is measured in either nanomoles per liter (nmol/L) or nanograms per milliliter (ng/mL). (One nmol/L equals 0.4 ng/mL.)

There is still some controversy surrounding the optimal serum 25(OH) concentrations. So, the definitions of sufficiency, insufficiency, and deficiency are only approximate. The majority of medical groups use these values to categorize vitamin D in adults.

Here’s a quick guide to what the levels mean:

  • Below 30nmol/L (<12 ng/mL): These levels are considered "deficient" and might weaken your bones and negatively affect your health.
  • 30-50 nmol/L (12-20 ng/mL): These levels are considered "insufficient" and supplementation is also recommended.
  • 50-100 nmol/L (20-250 ng/mL): These levels are adequate for most people for bone and overall health.
  • >Above 100 nmol/L (250 ng/mL): These levels are considered too high and might cause health problems.

It’s important to work with your doctor to help you interpret lab values, because different laboratories may report values differently making it difficult to compare.

Who’s most likely to be vitamin D deficient?

In the United States, almost one out of four people have vitamin D blood levels that are too low or inadequate for bone and overall health. So it’s fairly common.

The following groups of people are more likely to be deficient in vitamin D:

  • People with inflammatory bowel disease (ulcerative colitis or Crohn’s disease) or other conditions that disrupt the normal digestion of fat. Vitamin D is a fat-soluble vitamin and its absorption is increased with fatty foods.
  • People who are obese, since vitamin D accumulates in excess fat tissues but is not easily available for use by the body when needed.
  • People who have undergone gastric bypass surgery, which typically removes the upper part of the small intestine where vitamin D is absorbed.

What about people who aren’t vitamin D deficient—should they take vitamin D supplements?

It used to be thought that vitamin D may build up to levels that are too high in your blood. But in recent years, it has been found that the levels did not increase as quickly as once thought. But overconsuming vitamin D causes a condition called hypervitaminosis D or vitamin D toxicity.

This condition can cause a buildup of too much calcium in the blood, which can cause frequent urination, weakness, and eventually, kidney problems. It’s typically only caused by excessive doses of vitamin D supplements. And it almost never occurs from diet or sunlight exposure alone. This is why it’s important to check in with your doctor before supplementing; you want to know your level before taking more than you need.

What are the differences between getting vitamin D through sun exposure, supplements, and food?

Vitamin D production in the skin via sun exposure is the primary natural source of vitamin D, but many people have insufficient levels because they live in places where sunlight is limited in winter, or because they have limited sun exposure due to being inside much of the time. Also, people with darker skin tend to have lower blood levels of vitamin D because the pigment (melanin) acts like a shade, reducing production of vitamin D.

But to gain enough vitamin D via sun exposure alone may put someone at risk for skin cancer. It’s more important to wear sunscreen and protect your skin and to obtain the rest of the vitamin D from natural sources like foods and/or supplements, if necessary.

Food sources of vitamin D are beneficial because they may also contain other nutrients like protein, omega 3s, and calcium, which are all good for you.

If someone is very deficient in vitamin D, it may be hard to obtain enough through just diet and sun exposure initially. For some people who are deficient, their doctors may prescribe a therapeutic dosage, depending on their deficiency, to boost up the vitamin D level until it gets to a healthier number.

Data from The National Academy of Sciences shows the median intake of vitamin D from food and supplements in women ages 51 to 71 years was 308 IU daily, but only 140 IU from food alone. This demonstrates how hard it may be to achieve adequate vitamin D intake through food alone if someone is deficient.

So, depending on someone’s vitamin D level in their labs, they can work with their physician to determine the right combination of food, supplementation, and sun exposure.

How much vitamin D should someone take and how should they take it?

Vitamin D is a fat-soluble vitamin, meaning that it doesn’t dissolve in water and is best absorbed when paired with high-fat foods. For this reason, it’s a good idea to take vitamin D supplements with a meal. According to one study in 17 people, taking vitamin D with the largest meal of the day increased vitamin D blood levels by about 50 percent after just two to three months. Nuts, seeds, avocados, and eggs are nutritious sources of fat that can help boost your vitamin D absorption.

Look for vitamin D3, since this is the form of vitamin D already stored in your body. The dosage can range anywhere from 600 IU to 1,000 IU (15 to 20 micrograms) per day for adults, depending on the deficiency. Ask your doctor for a recommendation based on the vitamin D levels in your lab-work results. It isn’t recommended to take vitamin D without a doctor’s guidance. Work with your doctor to have your blood work done and see what the ideal amount is for you.

Know that U.S. Food and Drug Administration does not regulate supplements, so look for a supplement that has the USP verification from United States Pharmacopeia, a nonprofit that aims to verify the quality of the ingredients.

What foods can people eat to boost their vitamin D intake?

Few foods are naturally rich in vitamin D3. The best sources are the flesh of fatty fish, such as mackerel and salmon and fish-liver oils. Smaller amounts are found in egg yolks, cheese, and beef liver. Certain mushrooms contain some vitamin D2, and some commercially sold mushrooms contain higher amounts of vitamin D2 due to intentionally being exposed to high amounts of ultraviolet light.

Many foods, such as dairy products, plant milks, cereals, and orange juices are fortified with vitamin D.

All in all, there isn’t yet enough data to recommend vitamin D supplementation for psoriasis, unless the person has blood tests that show that they’re deficient. It’s definitely possible to overdo it, and that’s not something you should risk. Have your vitamin D level checked, and if it’s low, then it doesn’t hurt to boost your vitamin D level up to normal. Who knows? It might even help your psoriasis.

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