Scientific studies on endometriosis have shown that both environment and genetics play a role in disease development. Researchers have continued to study additional factors that could be related to the onset and progression of endometriosis. One area of focus examines the relationship between a person having low levels of vitamin D and how that might factor into the development of endometriosis.

What Exactly Is Vitamin D?

Vitamin D is a fat-soluble micronutrient. It is involved in several processes in your body. Some of those can include:

• Helping the body absorb calcium and phosphorous, which are essential for building and repairing bones
• Reducing cancer cell growth
• Keeping infections in check
• Reducing inflammation

Vitamin D is also an immunomodulator. That means it can intensify or suppress parts of the immune system. In other words, immunomodulators can increase your body’s defense against a pathogen or they can tame your body’s inflammatory response.

There are two main forms of vitamin D. The first, D2 (or ergocalciferol) comes from plants and synthetic supplements. The second, D3 (or cholecalciferol), comes from ingesting animals and their byproducts, and also from exposure to sunlight. About 10 percent of your body’s vitamin D comes by eating food and dietary supplements, or by exposure to the sun. (Your body makes the remaining 90 percent.)

When you get Vitamin D via ingestion or exposure, it is not “active” and must undergo two chemical processes for your body to use it. One such process happens in your liver and the other happens in your kidneys. When Vitamin D is made active, it is called 25-hydroxyvitamin D (or 25(OH)D). Health care professionals assess your vitamin D status by testing your level of 25(OH)D.

What Connection Does Vitamin D Have to Endometriosis?

Endometriosis is both an inflammatory condition and an immune system disorder. An immune system disorder happens when the body’s immune system gets confused about what to attack and what to defend. With endometriosis, the body doesn’t recognize the endometrium-like tissue that grows outside the uterus. Because of this, your body does not initiate the process to destroy the “foreign” cells.

The connection between low vitamin D levels and immune system dysfunction has been established by research. Given that, some scientists also suspect vitamin D deficiency might be a contributing factor for endometriosis.

Several studies have been conducted to evaluate the possible link between vitamin D and the development of endometriosis. Overall, research results have been mixed. A 2014 literature review asked if a body’s dysfunction with vitamin D processing could be associated with infertility related to endometriosis. There was not enough conclusive evidence to confirm the association.

Two years later, an observational study discovered a relatively high rate of endometriosis among people with low levels of vitamin D. However, a 2019 case-control study (which measured 25(OH)D serum levels in reproductive-age women with and without endometriosis) found otherwise. That study showed no statistically significant difference in their vitamin D levels.

In 2020, a team analysis of nine studies looked at vitamin D levels and endometriosis. It concluded the disease — and its severity — were associated with low levels of vitamin D. That same year, another observational study researched the link between ovarian endometriosis and the levels of 25(OH)D in a person’s blood serum and their peritoneal fluid. (Peritoneal fluid coats the lining of your abdomen.) This study found that women with a vitamin D deficiency were at higher risk of developing endometriosis.

Endometriosis and Vitamin D Supplementation

If you’re living with endometriosis, you may be wondering whether vitamin D supplementation might help relieve your symptoms.

One research study found that boosting vitamin D levels with supplements could help relieve moderate endometrial pain. In 2021, a randomized, double-blind, placebo-controlled trial showed vitamin D supplementation significantly cut down on the pelvic pain a person with endometriosis might have. It also acted as an anti-inflammatory. Further, the results also showed a robust increase in total antioxidant capacity (TAC). TAC is a biomarker that measures the body’s ability to rid itself of harmful free radicals.

How Much Vitamin D Is Enough?

Your need for vitamin D changes as you go through life. Different stages of growth and development require different levels of this nutrient. The National Institutes of Health recommends the following daily amounts in micrograms (mcg) and international units (IU).

• Birth to 12 months: 10 mcg (400 IU)
• Children 1 to 13 years: 15 mcg (600 IU)
• Teens 14 to 18 years: 15 mcg (600 IU)
• Adults 19 to 70 years: 15 mcg (600 IU)
• Adults 71 years and older: 20 mcg (800 IU)
• Pregnant and breastfeeding individuals: 15 mcg (600 IU)

Because vitamin D is fat-soluble, its absorption is linked to how well your gut is able to absorb fat. Certain medical conditions like Crohn’s disease, ulcerative colitis, and celiac disease can affect how much vitamin D is actually taken in by your body. Other medical conditions can also influence the amount of vitamin D you absorb. Because of that, check with your doctor to see what your specific needs are before trying any supplements.

What Do Members of MyEndometriosisTeam Say About Vitamin D?

Several members of MyEndometriosisTeam report they were diagnosed as deficient in vitamin D and were advised to take supplements. Here are a few of their comments.

• “My vitamin D levels were completely insufficient. My doctor put me on prescription vitamin D that I take once a week. It helps.”
• “I am not sure if it is endometriosis-related or an autoimmune correlation. I do know that I am extremely deficient and have been on very high levels of D3 for years. I am still low and have been unable to absorb and build up my levels.”
• “I'm vitamin D deficient as well. The doctor has me taking 6,000 IU a day.”

Other members wrote that their doctors spoke to them about the importance of vitamin D and its relationship to hormone levels and endometriosis.

One said, “My doctor informed me that vitamin D affects your hormone levels. If you do not have enough vitamin D, your hormones will be out of whack.” Yet another added, “With hormones being a big factor in endometriosis, my doctor said it was important to figure out if you are vitamin D deficient. I hope there will be more research and information related to this.”

While it is clear that more precise research is needed, the results from scientific studies so far show that the effects of vitamin D levels could be a determining factor in the manner in which endometriosis originates and the progression of its severity.

Talk With Others Who Understand

On MyEndometriosisTeam, the social network for people with endometriosis, more than 123,000 members come together to ask questions, give advice, and share their stories with others who understand life with endometriosis.

Are you living with endometriosis and wondering if low levels of vitamin D are a risk factor? Share your experience in the comments below, or start a conversation with a post on your Activities page.