A 1.3M-Woman Study Tied One Deficiency To Cancer Risk
Vitamin D is best known for supporting bone health and immunity, but it may play another important role: helping control how cells grow.
Cells in the ovaries, uterus, and cervix all respond to vitamin D, which has led researchers to ask whether low levels could be linked to cancer in these areas.
About the study
The study drew on health records from more than 150 organizations worldwide.
Researchers compared 675,079 women with vitamin D deficiency (levels below 20 ng/mL) with an equally sized group whose levels were in the normal range (30 ng/mL or higher).
The two groups were matched for factors such as age, health conditions, and medications.
To keep cancers that may have already been developing out of the count, the researchers only included cancers diagnosed at least two years after the vitamin D test.
Women with low vitamin D had a 47% higher cancer risk
Compared with women whose vitamin D levels were in the normal range, those with low levels were 47% more likely to develop a gynecologic cancer.
In absolute terms, that was 0.45% of women with low vitamin D versus 0.28% of women with normal levels.
Looking at each cancer separately, low vitamin D was linked to a 30% higher risk of ovarian cancer, a 31% higher risk of cervical cancer, and a 55% higher risk of uterine cancer.
The overall pattern was similar in women ages 30 to 65 and those over 65, although the link between low vitamin D and cervical cancer was much stronger in the older group.
Why this doesn't mean low vitamin D causes cancer
Because this was an observational study, it can show a link between low vitamin D and cancer but can't prove cause and effect.
The researchers didn't have data on several cancer risk factors, including HPV, body weight, diet, sun exposure, and physical activity, and women with a known family history of cancer were excluded.
The researchers also found that women with mildly low vitamin D still had a 41% higher cancer risk, compared with 47% in the main analysis. That small difference makes it harder to argue that lower vitamin D itself is driving the risk.
There are still biological reasons vitamin D could play a role. Its active form helps regulate immune responses and may help damaged cells die off before they become cancerous.
What to do with your own vitamin D number
If you're wondering whether you're running low, ask your doctor whether a blood test makes sense for you. Spotting low vitamin D is straightforward, and bringing a low level back into range has value on its own, separate from anything to do with cancer.
What this research doesn't support is taking vitamin D specifically to prevent gynecologic cancer. The strategies with the strongest track record are still the familiar ones:
- Staying current on cervical cancer screenings
- Getting the HPV vaccine if you're eligible
- Tending to weight and metabolic health, since this study's own analysis flagged overweight and obesity as an independent risk factor
The takeaway
Vitamin D deficiency has joined the list of factors that show up alongside gynecologic cancer without explaining it. Finding out where your own level sits takes one line on a lab order.
The moves with proven prevention value remain screening, the HPV vaccine, and metabolic health.