It is important to realize that a University of California San Diego study group found how gut bacteria interact with vitamin D blood levels. Usually clinicians rely on 25-hydroxy vitamin D (25(OH)D) levels to assess whether patients are vitamin D deficient. However, this study found that this is only the storage form of vitamin D. It must be remembered what is crucial for the metabolism in the body, namely the active form of vitamin D, which is 1,25(OH)2D. There was a correlation in the study between healthy gut bacteria that produce butyrate and the active form of vitamin D. The investigators concluded that the active vitamin D, not 25-hydroxy vitamin D, stimulates the vitamin D receptor. Notably, the gut bacteria appear to have an important function in the activation process of vitamin D.
Details of how gut bacteria interact with vitamin D blood levels
Here are the details of the study published in nature communications. The researchers published this on Nov. 26, 2020. 567 older men (mean age 84 years) living in the community were the study’s participants. To emphasize, the researchers took stool and blood samples to measure the gut flora and vitamin D metabolites. To clArify, only 7.2% of men were vitamin D deficient.
The subjects came from 6 cities in the US. (San Diego, Minneapolis, Palo Alto, Pittsburgh, Portland, and Birmingham). Certainly, the effect of sun exposure on the 25-hydroxy vitamin D level was evident in the San Diego group, but not in the other cities. But there was no difference across sites between the 1,25(OH)2D levels, which is the active form of vitamin D.
Diverse gut bacteria produce butyrate and increase active vitamin D
Next the researchers determined how diverse the gut bacteria were in the stool samples. They found that the more diverse the gut bacteria were, the higher the active vitamin D levels were (1,25(OH)2D). The researchers analyzed the specific gut bacteria and correlated this to the active vitamin D levels in the blood. Senior men who had gut bacteria that were producers of butyrate increased their active vitamin D levels. In contrast, seniors who had gut bacteria that did not produce butyrate had low active vitamin D levels.
92% of men had gut bacteria that belong to the Firmicutes phylum class of bacteria that produce butyrate. Most of these correlated positively with increased levels of 1,25(OH)2D, the active form of vitamin D.
Exclusion of covariate factors
The researchers analysed covariates like age, body mass index, race, smoking status and alcohol intake. In addition, they also considered self-rated health, self-reported physical activity, season of sample collection and medication use.
Clinical medicine uses the vitamin D level (25(OH)D) as the standard test for determining whether a person is deficient for vitamin D or not. This is the storage form of vitamin D. The body metabolizes this into the active form of vitamin D (1,25(OH)2D). In a study with 567 older men (mean age 84 years) the researchers found a few surprises. First, sun exposure did not matter for the active vitamin D level, only for the storage form of vitamin D, 25(OH)D. Second, the gut bacteria diversity including bacteria that produced butyrate was what determined the level of active vitamin D, (1,25(OH)2D). It is this form of vitamin D that stimulates vitamin D receptors throughout the body.
Life styles determine the active level of vitamin D
We need to pay attention to our gut flora., as it takes a healthy gut flora for us to stay well. We can take probiotics and avoid unnecessary antibiotics. Avoid tobacco consumption and do not overindulge in alcoholic drinks. These steps are necessary for our health that starts in the gut.