People living with endometriosis often wonder how their vitamin D levels affect their symptoms or whether a vitamin D deficiency is a risk factor for endometriosis. “I am low in vitamin D and I feel like that could slightly contribute to some of my problems,” one MyEndometriosisTeam member wrote.

Another member shared, “I am always low on iron, vitamin Bs, and vitamin D.”

Endometriosis is a chronic condition that occurs when tissue similar to the type that lines the uterus exists outside of the uterus. Research has been mixed as to whether or not there’s a connection between vitamin D levels and endometriosis. Nevertheless, vitamin D can play an important role in a person’s overall health, so it can be worthwhile to speak with your health care provider about ways to ensure you’re getting enough in your diet.

What Is Vitamin D?

Vitamin D is a nutrient that your body needs to make your muscles move, help your nerves send signals, and allow your immune system to fight off bacteria and viruses. Vitamin D plays an important role in helping bones absorb the calcium they need to be strong and healthy.

There are two kinds of vitamin D: vitamin D2 and vitamin D3. Vitamin D2 is mostly found in plants, mushrooms, and yeast. Vitamin D3 can be found in oily fish and is also made in the body during sun exposure. Additionally, vitamin D3 is later converted to 25-hydroxycholecalciferol, which helps turn on and off the genes that allow vitamin D to carry out its function in the body.

Studies have indicated that women of reproductive age are often deficient in vitamin D, with one clinical trial indicating that insufficient levels of vitamin D were seen in nearly 90 percent of women between the ages of 20 and 49.

Moderate exposure to sunlight can be a good source of vitamin D. Additionally, according to the Cleveland Clinic, foods that are good sources of vitamin D include:

• Beef liver
• Fortified cereal
• Fish (such as salmon, sardines, swordfish, and cod liver oil)
• Egg yolks
• Fortified milk and orange juice

Your body breaks vitamin D down into its active form, called 1,25-dihydroxyvitamin D — which is also known as calcitriol and can be found in supplements. This active form of vitamin D can affect the cells involved in the immune system.

Is Vitamin D Deficiency Linked to Endometriosis?

Researchers have studied potential connections between vitamin D levels and endometriosis, with mixed results.

In one study, researchers examined pain outcomes of 39 women who underwent laparoscopy — a type of surgery that checks for problems in the abdomen or a woman's reproductive system — for endometriosis. They found that increasing vitamin D intake did not significantly improve participants’ pelvic pain or dysmenorrhea (menstrual cramping).

But other research suggests there may be an association between vitamin D and endometriosis, though further studies are needed to confirm that. For example, a recent analysis found that overall, people with endometriosis had lower vitamin D levels than those in the general population. They also found that vitamin D deficiency was correlated with worse endometriosis symptoms. The researchers suggested that vitamin D insufficiency may be a risk factor for developing endometriosis.

Despite the mixed research on vitamin D’s effects on endometriosis symptoms, the nutrient may have other general health benefits. Among them, vitamin D in your blood helps regulate calcium levels, which is instrumental to your bone health. Research has also shown that in postmenopausal women, vitamin D supplementation may help increase bone density.

Vitamin D and Fertility

People living with endometriosis are often concerned that their condition may cause infertility. According to the USC Fertility, reproductive organs such as the ovaries, uterus, and placenta contain vitamin D receptors. Additionally, calcitriol helps produce estrogen and plays an important role in the genes that control embryo implantation. Studies also have found that among women undergoing in vitro fertilization, those with higher vitamin D levels were more likely to get pregnant.

Given vitamin D’s potential role in your overall health, you may consider taking supplements to ensure your body is getting enough. Before adding vitamin D supplements — or any others — to your diet, talk to your health care team. Taking too much of certain supplements, including vitamin D, can result in undesirable side effects.

Vitamin D Complications

The Office of Dietary Supplements warns that too much vitamin D can cause nausea and vomiting, muscle weakness, confusion, pain, dehydration, and kidney stones, among other side effects. Vitamin D can also interact with some medications, so don’t start any supplementation plan before speaking with your physician.

Talk With People Who Understand

On MyEndometriosisTeam, the social network and online support group for people with endometriosis and their loved ones, members discuss the chronic nature of the disease. Here, more than 118,000 members from across the world come together to ask questions, offer advice and support, and share stories with others who understand life with endometriosis.

Have you ever investigated your vitamin D levels? Share your experience in the comments below, or start a conversation on MyEndometriosisTeam.