More research needed to determine if vitamin D helps treat fibroids

Social media has become a popular avenue for people to discuss medical issues and seek health advice. But it’s also become fertile ground for promoting a range of unproven treatments for chronic and complex medical conditions, including urine therapy, nicotine patches, and supplements.

More recently, Science Feedback came across TikTok videos encouraging women to take vitamin D supplements to treat uterine fibroids. Some of these videos have received tens of thousands of views to date.

In one video viewed nearly a million times, chiropractor Eric Berg recommended taking 50,000 international units (IUs) of vitamin D every day to help “shrink fibroids”. He also advised viewers to take a variety of “co-factors”, namely vitamin K2, magnesium, and zinc, to protect themselves from the side effects of such a high dose of vitamin D.

Although Berg uses the title “Dr.” to refer to himself on social media, he doesn’t have medical qualifications. He also spread misinformation about vaccine safety and cholesterol; in 2008, he was disciplined by the Virginia Board of Medicine for making unproven therapeutic claims.

As we will explain below, claims that vitamin D is an effective treatment for fibroids aren’t substantiated by clinical evidence. Furthermore, the dose of vitamin D that Berg recommends is unsafe and increases the risk of side effects like kidney stones.

Multiple factors associated with fibroid risk

Uterine fibroids, also called leiomyomas or myomas, are growths that develop in or around the uterus. Most are benign (non-cancerous), although a rare form known as leiomyosarcoma is cancerous.

Many women have fibroids without showing symptoms. For others, however, fibroids are a constant source of discomfort and pain that, in more severe cases, interfere with daily life. Some symptoms of fibroids include the frequent need to urinate, pelvic pain, and heavy bleeding during menstruation.

Various treatments are available for women who experience symptoms. These include pain medication and hormone therapy, such as the contraceptive pill and progestogen. For severe cases, surgery may be necessary to remove fibroids.

Exactly what causes fibroids is still unclear, but there are several factors related to an increased risk of fibroids. For instance, women in their childbearing years are more likely to be affected by fibroids compared to women in menopause. This is possibly related to the higher estrogen and progesterone levels during a woman’s reproductive years. Both estrogen and progesterone are associated with fibroid growth.

Other factors that can increase the risk of fibroids are family history, obesity, high blood pressure, and a diet rich in red meat.

Ethnicity is another key factor, as Black women are more likely to be affected by fibroids compared to white women. A Mayo Clinic Press article from 2024 reported:

“By age 50, up to 90% of Black people with a uterus have fibroids, which means that among every 10 people you know in this group, nine of them may have fibroids! Furthermore, Black people develop fibroids at younger ages and have larger, faster growing fibroids.”

No evidence Vitamin D dose recommended by Berg is effective, can cause side effects instead

Another potential risk factor of interest is vitamin D. Research in several countries has shown that lower vitamin D levels are associated with a higher risk of uterine fibroids^[1-3], leading some to hypothesize that increasing vitamin D levels could help reduce the risk of fibroids.

A systematic review of the scientific literature, published in 2022, sheds some light on the effectiveness of vitamin D as an intervention for fibroids^[4]. The review found some encouraging results, with a few randomized clinical trials (see here, here, and here) reporting that fibroids ceased to worsen or even shrunk in women who received vitamin D supplementation.

However, these trials came with significant limitations: they were relatively small, with the largest trial including a little over 200 women. On top of that, the quality of these trials was variable.

Science Feedback reached out to the Royal College of Obstetricians and Gynecologists (RCOG) regarding the credibility of vitamin D as a fibroid treatment. In an email, Ranee Thakar, RCOG president and consultant obstetrician and urogynecologist, stated:

“Fibroids affect around two in three women during their lifetime, most commonly between the ages of 30 and 50.

Evidence around using vitamin D to treat fibroids is limited and unclear. While increased vitamin D levels may be linked to slowing fibroid growth, there’s no proven cause-and-effect relationship. More research is needed to understand whether vitamin D has any real treatment benefit. We strongly encourage women to seek reliable, evidence-based health information through trusted sources such as the NHS website, or to speak directly with their GP or another healthcare professional.

The RCOG is working with clinical experts and women to develop recommendations for improved screening, diagnosis and treatment of fibroids in England. With over half a million women across the UK still waiting for gynaecological care for conditions such as fibroids, timely detection and access to treatment are vital.”

In summary, there’s some evidence that vitamin D levels influence fibroid risk and that vitamin D supplementation might have some therapeutic value for fibroids. However, larger and better-quality studies are still needed to determine whether vitamin D is effective.

Furthermore, it remains unclear whether vitamin D supplementation would change the risk of developing fibroids in people with normal levels of vitamin D. The Endocrine Society’s guideline doesn’t recommend routine vitamin D supplementation in non-pregnant women under 50 years of age^[5], although it must also be acknowledged that uterine fibroids weren’t among the clinical outcomes studied.

More is not always better: taking 50,000 IUs of vitamin D daily is unsafe

Berg provided no evidence to support his dosage recommendation (50,000 IUs of vitamin D per day). But we did find a few published studies looking at the effect of 50,000 IUs of vitamin D supplementation in women who had fibroids and vitamin D deficiency^[6].

These studies might be the basis for Berg’s claim. However, the dose of vitamin D used in these studies wasn’t administered every day, but on a weekly basis.

Science Feedback reached out to Robert Scragg, a vitamin D researcher who recently retired from his position as professor of epidemiology at the University of Auckland, regarding Berg’s claims.

In an email, Scragg pointed out that a daily dose of 50,000 IUs of vitamin D is “unsafe”, adding that this would lead to “side effects over time, the main ones being high blood calcium levels and high calcium levels in urine increasing the risk of renal stones”.

In the video, Berg told viewers to take several compounds that he called “co-factors”, namely vitamin K2, magnesium, zinc, boron, and vitamin B6, to protect them from the side effects of high levels of vitamin D. This seems to suggest that Berg was aware the dose he recommended could cause problems. But he presented no evidence to support his recommendation to take these compounds. Scragg told Science Feedback that he was “not aware of evidence” showing that these alleged “co-factors” protected against vitamin D toxicity.

We reached out to Berg’s company The Health & Wellness Center, Inc. for comment and will update this review if new information becomes available.

Conclusion

Researchers have observed that lower vitamin D levels are associated with a higher risk of fibroids, leading some scientists to hypothesize that vitamin D supplementation could be beneficial for people with fibroids.

However, it’s also important to keep in mind that association alone isn’t sufficient evidence of cause and effect. Larger and better-quality trials are needed to establish vitamin D’s effectiveness in treating fibroids. In the meantime, women affected by fibroids should discuss their condition with their healthcare provider to determine which treatment options would work best for them.

Finally, while vitamin D is essential to health, there can be too much of a good thing. Excessive vitamin D intake can lead to side effects like kidney stones. People taking vitamin D supplements should talk to their healthcare provider to make sure that they only take safe amounts.

References:

1. Paffoni et al. (2013) Vitamin D status in women with uterine leiomyomas. Journal of Clinical Endocrinology and Metabolism.
2. Sabry et al. (2013) Serum vitamin D3 level inversely correlates with uterine fibroid volume in different ethnic groups: a cross-sectional observational study. International Journal of Women’s Health.
3. Xu et al. (2021) Vitamin D as a risk factor for the presence of asymptomatic uterine fibroids in premenopausal Han Chinese women. Fertility and Sterility.
4. Combs et al. (2022) A Systematic Review of Vitamin D and Fibroids: Pathophysiology, Prevention, and Treatment. Reproductive Sciences.
5. Shah et al. (2024) A Systematic Review Supporting the Endocrine Society Clinical Practice Guidelines on Vitamin D. Journal of Clinical Endocrinology and Metabolism.
6. Arjeh et al. (2020) Effect of oral consumption of vitamin D on uterine fibroids: A randomized clinical trial. Complementary Therapies in Clinical Practice.