Is Vitamin D 25-OH useful for gut health?

The question of whether vitamin D (25-OH) is useful for gut health is not yet clearly answered by science. Vitamin D is well known for its role in bone metabolism and immune function. There is mechanistic evidence that vitamin D may strengthen the gut barrier and exert anti-inflammatory effects, which could theoretically benefit gut health. A link between vitamin D deficiency and inflammatory bowel disease (IBD) has also been discussed. However, robust randomized controlled trials demonstrating a causal benefit of vitamin D supplementation for gut health in healthy individuals are lacking. Measuring 25-OH vitamin D in blood is useful to detect deficiency, but it cannot be considered a direct 'gut health test.' The evidence level is therefore unclear to mechanistic. Consumers should be cautious of exaggerated marketing claims. Maintaining a normal vitamin D level is generally advisable, but specific gut health benefits are not well supported.