Researchers discovered that two natural substances in our bodies—vitamin D and the female hormone estrogen—may help protect cells from COVID-19 infection. Scientists tested these substances in laboratory cells and found that when cells were treated with either vitamin D or estrogen (or both), they were better able to resist the virus. This is interesting because men tend to get sicker from COVID-19 than women, and this study suggests that female hormones might play a protective role. While these results are promising, they come from lab experiments, not from testing in actual people, so more research is needed before we know if this could help treat COVID-19 in humans.

The Quick Take

  • What they studied: Whether vitamin D and the female hormone estrogen could reduce how much COVID-19 virus infects cells in a laboratory setting
  • Who participated: This was a laboratory study using specially prepared cells (Vero E6 cells) grown in dishes, not human subjects or animals
  • Key finding: When cells were treated with vitamin D or estrogen before being exposed to COVID-19, the virus had a harder time infecting them. The protective effect was strongest when cells received the treatment both before and after viral exposure.
  • What it means for you: This research suggests vitamin D and estrogen may have protective properties against COVID-19, which could eventually lead to new treatments. However, this is early-stage laboratory work, and it doesn’t yet mean you should change your vitamin D intake or expect these substances to prevent COVID-19 in real life.

The Research Details

Scientists conducted an experiment in laboratory dishes using special cells that can be infected with COVID-19. They treated these cells with either vitamin D (a form called calcitriol), estrogen (called 17β-estradiol), both together, or neither. Then they exposed the cells to COVID-19 virus in two different ways: treating the cells before the virus arrived, or treating them both before and after viral exposure. They measured how much virus was able to infect the cells by counting viral particles and looking at how much virus was produced.

The researchers used two types of test viruses: a modified virus that mimics COVID-19 (called a pseudovirus) and actual COVID-19 virus. This allowed them to see if the protective effects worked against both types. They also checked whether the treatments changed the levels of two important proteins (ACE2 and VDR) that the virus uses to enter cells, though they found no changes in these proteins.

This research approach is important because it helps scientists understand the basic mechanisms of how our bodies might naturally fight COVID-19. By testing in controlled laboratory conditions, researchers can identify promising substances before testing them in animals or humans. Understanding why men get sicker from COVID-19 than women could lead to better treatments for everyone.

This is a laboratory study, which is the first step in scientific research but has limitations. The study was conducted in cells grown in dishes, not in living organisms, so results may not translate directly to how these substances work in human bodies. The sample size is not specified in the available information. The study appears to be published in a peer-reviewed journal, which means other scientists reviewed the work before publication. However, laboratory findings often don’t produce the same results when tested in humans, so these results should be considered preliminary.

What the Results Show

When cells were treated with vitamin D or estrogen before being exposed to COVID-19, both substances significantly reduced how much virus could infect the cells. The combination of both substances together also showed protective effects in this pre-treatment scenario. Interestingly, when cells were treated both before and after viral exposure, estrogen alone continued to show protection, but vitamin D alone did not show the same level of protection in the actual COVID-19 virus test.

The researchers found that the protective effect was most consistent when cells received treatment before the virus arrived. This suggests that these substances may work best as a preventive measure rather than as a treatment after infection has already started. The fact that estrogen showed stronger protective effects in the pre-post-treatment model suggests it may work through different mechanisms than vitamin D.

The study found that neither vitamin D nor estrogen changed the levels of ACE2 and VDR proteins, which are the main entry points the virus uses to infect cells. This suggests that these substances protect cells through different pathways than simply blocking the virus’s entry points. This finding is important because it indicates these hormones may work by boosting the cell’s natural immune defenses rather than by creating physical barriers to viral entry.

Previous research has shown that both vitamin D and estrogen play important roles in immune function and have protective effects against various respiratory infections. This study builds on that knowledge by specifically testing these substances against COVID-19. The finding that sex hormones may explain why men and women have different COVID-19 outcomes aligns with observations from the pandemic that men tend to develop more severe illness. This research provides a potential biological explanation for those real-world observations.

This study has several important limitations to consider. First, it was conducted entirely in laboratory cells, not in living organisms or humans, so the results may not work the same way in actual bodies. Second, the study doesn’t specify how many experiments were conducted or provide detailed statistical analysis of the results. Third, the researchers didn’t test whether these substances would work in combination with other treatments. Fourth, the study doesn’t address whether the doses used in the lab would be achievable or safe in humans. Finally, laboratory conditions are very different from the complex environment inside a living body, where many other factors could affect how these substances work.

The Bottom Line

Based on this laboratory research, there is not yet enough evidence to recommend changing your vitamin D intake or hormone levels specifically to prevent COVID-19. However, maintaining adequate vitamin D levels through diet, sunlight exposure, or supplements is already recommended for overall health by health authorities. If you’re interested in vitamin D supplementation, discuss appropriate doses with your healthcare provider. This research should be considered preliminary and interesting, but not yet actionable for COVID-19 prevention.

This research is most relevant to scientists and medical researchers working on COVID-19 treatments and vaccines. It may eventually be of interest to people at high risk for severe COVID-19, particularly men (since the research suggests sex hormones may play a protective role). Healthcare providers may find this research useful for understanding biological differences in COVID-19 severity. The general public should be aware of this research but should not change their behavior based on these preliminary laboratory findings alone.

Since this is laboratory research, there is no realistic timeline for seeing benefits in humans. If these findings prove promising in future animal studies and clinical trials, it could take several years before any new treatments based on this research become available. Vitamin D’s effects on immune function, if you choose to supplement, typically take weeks to months to become apparent, but this research doesn’t yet support using vitamin D specifically for COVID-19 prevention.

Want to Apply This Research?

  • Track daily vitamin D intake (from food, supplements, and sun exposure) and correlate with overall immune health markers like frequency of respiratory infections. Record estimated daily sun exposure time and dietary sources of vitamin D (fatty fish, fortified milk, egg yolks).
  • Users could set a daily reminder to track vitamin D sources and maintain consistent intake at levels recommended by their healthcare provider. The app could provide education about natural vitamin D sources and help users understand their current intake levels compared to recommended amounts.
  • Establish a baseline of current vitamin D intake and sources, then monitor consistency over 8-12 weeks. Track any changes in respiratory health or illness frequency. Users should also note any changes in sun exposure, diet, or supplementation. This long-term tracking helps identify patterns between vitamin D status and overall wellness, though it should not be used as a substitute for medical advice about COVID-19 prevention.

This research is preliminary laboratory work and has not been tested in humans. These findings should not be used as a basis for treating, preventing, or diagnosing COVID-19. Vitamin D and hormone supplementation should only be undertaken under the guidance of a qualified healthcare provider. If you have concerns about COVID-19 prevention or treatment, consult with your doctor or public health authorities for evidence-based recommendations. This article is for educational purposes only and does not constitute medical advice.