Vitamin D and gut health: what the research shows
What it found
Vitamin D helps the gut absorb calcium and also affects gut stem cells, gut barrier strength and gut inflammation, mostly in lab and animal studies.
The authors say the challenge is turning these findings into better human gut health.
What they found
Studies in people
Human gut conditions
People with gut diseases that cause fat malabsorption also tend to be vitamin D deficient. This suggests that vitamin D absorption depends on fat being absorbed properly.
Animal and lab studies
Calcium absorption
Vitamin D controls how much calcium the gut absorbs. In growing mice without the vitamin D receptor, calcium absorption dropped by 70%, and mice with the receptor removed only in the intestine had the same problems.
Gut barrier strength
In lab tests on human gut cells, active vitamin D strengthened the tight junctions between cells and reduced leakiness. Mice without the vitamin D receptor had worse gut damage from a chemical that causes colitis.
Gut stem cells
Mice fed a low vitamin D diet had about 30% fewer Lgr5+ gut stem cells after 3 months. In cell cultures, active vitamin D pushed stem cells to become more specialized cell types and reduced their growth.
Gut immune cells
Studies in mice give mixed results on how vitamin D affects gut immune cells called ILC3. Some found that removing the vitamin D receptor increased these cells and protected against infection, while others found the opposite.
Vitamin D absorption
The gut absorbs vitamin D from food and supplements, mostly by following fat. There is no evidence that the body adjusts how much vitamin D it absorbs when levels are low.
What the authors conclude
“While research demonstrates that there are both classical, calcium-regulating and non-calcium regulating roles for vitamin D in the intestine, the challenge facing biomedical researchers is how to translate these findings in ways that optimize human intestinal health.”
Also in their conclusions
- They conclude that vitamin D has broad actions in the intestine beyond calcium absorption, including protecting stem cells from cancer, limiting gut leakiness, and reducing inflammation.
- They say the challenge facing biomedical researchers is how to translate these findings in ways that optimize human intestinal health.
How it was done
The authors wanted to explain how vitamin D acts on the intestine beyond its known role in calcium absorption, because the intestine is the most responsive vitamin D target tissue.
The paper reviews molecular and cellular studies of vitamin D in the intestine, including mouse models with vitamin D receptor changes, human gut cell cultures, and some human observations. It covers calcium absorption, gut stem cells, barrier function and gut immune cells.
What it can’t tell you
- Most of the detailed findings come from mice and lab-grown cells, so they cannot show exactly what happens in people.
- The human evidence in this paper is limited to observations, which can show a link but not cause and effect.
- The studies on gut immune cells in mice gave conflicting results, so the role of vitamin D there is still unclear.
Who paid
- Funding
- Funded by NIDDK NIH HHS (from the PubMed record).
- Conflicts
- Dr. Fleet has no conflicts to report
- Authors work at
- University of Texas, USA
The paper
- Title
- Vitamin D and Gut Health
- Type
- Study
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Fleet JC (2022). Vitamin D and Gut Health. Advances in experimental medicine and biology. doi:10.1007/978-3-031-11836-4_9Free full textPubMed 36107318DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error