Women battling uterine fibroids keep showing up in study after study with one thing in common: low vitamin D.
Quick Take
- National Institutes of Health (NIH) research found women with enough vitamin D were 32% less likely to develop fibroids.
- A 2022 review of 14 studies found every single one linked low vitamin D to more fibroids.
- Lab studies on rats showed vitamin D shrank fibroid tumors by about 75%.
- Human trials show promise for slowing fibroid growth, but results on shrinking existing fibroids are mixed.
A Government Study Sparked The Vitamin D Fibroid Question
The National Institute of Environmental Health Sciences ran a major study tracking more than 1,000 women between the ages of 35 and 49. Researchers used ultrasounds to confirm fibroid status and blood tests to measure vitamin D levels. Women with sufficient vitamin D were 32% less likely to have fibroids than women who were low on the vitamin.
That same study uncovered something harder to ignore. Only 10% of Black women in the study had sufficient vitamin D levels, compared to 50% of white women. Fibroids are also far more common and more severe in Black women. The overlap between the two patterns raised an obvious question for researchers to chase further.
Multiple Studies Keep Pointing The Same Direction
A 2022 systematic review pulled together 14 separate clinical studies covering more than 3,500 women. Every one of them found the same basic pattern: women with higher vitamin D in their blood had fewer fibroids than women with lower levels. That kind of consistency across independent research teams is rare and hard to dismiss as coincidence.
Animal research backs up the biology behind the pattern. In a 2012 NIH-funded study, rats treated with vitamin D developed fibroid tumors that were about 75% smaller than untreated rats. Researchers said the vitamin appeared to interfere with how fibroid cells grow at a cellular level, giving scientists a plausible reason for what the human data was showing.
Clinical Trials In Women Show A Mixed But Real Signal
A 2024 analysis combined five randomized clinical trials involving 511 women. The pooled results showed vitamin D supplementation measurably reduced fibroid size compared to placebo, especially in trials that lasted longer than eight weeks. It marked one of the first times trial data, not just observation, pointed toward a treatment effect.
Not every trial found dramatic results. One randomized study comparing vitamin D against placebo found the treated group’s fibroids did not shrink in a statistically meaningful way. But the placebo group’s fibroids grew significantly larger during the same period. Researchers took that as a sign vitamin D may slow fibroid growth even without shrinking existing ones.
Genetic Research Adds Weight To The Vitamin D Theory
A 2022 genetic study used a method called mendelian randomization, which looks at inherited traits tied to vitamin D levels to test for cause and effect rather than mere correlation. The researchers reported that higher genetically-predicted vitamin D levels were linked to a real drop in fibroid risk, strengthening the case that vitamin D itself plays a direct role rather than just tagging along with some other factor.
Vitamin D supplementation is beneficial for women living with uterine fibroids and prediabetes patients. Check it out!
Prediabetic range –
HbA1c: 5.7% to 6.4%
Fasting blood sugar: 100 to 125 mg/dL.
2-hour oral glucose tolerance result: 140 to 199 mg/dL.https://t.co/xu5WaPMcGW https://t.co/gu1rIFJkIE pic.twitter.com/a6kblGaxxL— Radio Cobalamin (@nob12deficiency) September 20, 2026
A separate cohort study tracking women over time found those with vitamin D levels of 30 nanograms per milliliter or higher had about a 22% lower chance of developing new fibroids, along with slower growth in fibroids they already had. Researchers still caution that larger, longer trials are needed before vitamin D testing becomes standard fibroid care, since existing trials remain small.
Why This Matters For Women Right Now
Fibroids affect a huge share of women during their reproductive years, often causing heavy bleeding, pain, and fertility trouble. A cheap, low-risk vitamin showing up as a consistent factor across genetics, lab research, and clinical trials is worth paying attention to. Women concerned about fibroid risk have every reason to ask their doctor for a simple vitamin D blood test.
Sources:
mindbodygreen.com, pubmed.ncbi.nlm.nih.gov, pmc.ncbi.nlm.nih.gov, tandfonline.com, ijrcog.org
