Link between gut bacteria and vitamin D levels – sciencedaily

Researchers and collaborators at the University of California, San Diego recently demonstrated in older men that the makeup of a person’s gut microbiome is related to their levels of active vitamin D, a hormone important for bone health and skin. ‘immunity.

The study, published on November 26, 2020 in Nature communications, also revealed a new understanding of vitamin D and how it is typically measured.

Vitamin D can take many different forms, but standard blood tests detect only one, an inactive precursor that can be stored by the body. To use vitamin D, the body must metabolize the precursor into an active form.

“We were surprised to find that the diversity of the microbiome – the variety of types of bacteria in a person’s gut – was strongly associated with active vitamin D, but not with the precursor form,” the author said. Principal Deborah Kado, MD, Director of the Osteoporosis Clinic. at UC San Diego Health. “It is believed that greater diversity of the gut microbiome is associated with better overall health.”

Kado led the study for the National Institute on Aging-funded Osteoporotic Fractures in Men (MrOS) Research Group, a large multi-site effort that began in 2000. She teamed up with Rob Knight , PhD, professor and director of the Center for Microbiome Innovation at UC San Diego, and co-lead authors Robert L. Thomas, MD, PhD, fellow in the division of endocrinology at UC San Diego School of Medicine, and Serene Lingjing Jiang, graduate student of the biostatistics program at Herbert Wertheim School of Public Health and Human Longevity Sciences.

Many studies have suggested that people with low levels of vitamin D are at higher risk for cancer, heart disease, worse COVID-19 infections, and other illnesses. Yet the largest randomized clinical trial to date, with over 25,000 adults, concluded that taking vitamin D supplements had no effect on health, including heart disease, cancer, or even health. bones.

“Our study suggests that this could be because these studies only measured the precursor form of vitamin D, rather than the active hormone,” said Kado, also a professor at UC San Diego School of Medicine. and the Herbert Wertheim School of Public Health. “Measures of vitamin D formation and breakdown may be better indicators of underlying health problems and which may respond better to vitamin D supplementation.

The team analyzed stool and blood samples provided by 567 men participating in MrOS. Participants live in six cities in the United States, their average age was 84, and most reported being in good or excellent health. The researchers used a technique called 16s rRNA sequencing to identify and quantify the types of bacteria in each stool sample based on unique genetic identifiers. They used a method known as LC-MSMS to quantify the metabolites of vitamin D (the precursor, the active hormone, and the breakdown product) in each participant’s blood serum.

In addition to finding a link between active vitamin D and overall microbiome diversity, the researchers also noted that 12 particular types of bacteria appeared more often in the gut microbiomes of men with a lot of vitamin D. Most of these 12 bacteria produce butyrate, a beneficial fatty acid that helps maintain the health of the intestinal lining.

“Gut microbiomes are really complex and vary a lot from person to person,” Jiang said. “When we find associations, they are usually not as distinct as the ones we found here.”

Because they live in different parts of the United States, the men in the study were exposed to different amounts of sunlight, a source of vitamin D. As expected, the men who lived in San Diego, California, had got the most sun, and they also had the most vitamin D precursors.

But the team unexpectedly found no correlation between where the men lived and their levels of active vitamin D hormone.

“It seems it doesn’t matter how much vitamin D you get from sunlight or supplementation, or how much your body can store,” Kado said. “Your body’s ability to metabolize it to active vitamin D matters, and that may be what clinical trials need to measure to get a more accurate picture of the vitamin’s role in health.

“We often find in medicine that more is not necessarily better,” Thomas added. “So in this case, it might not be how much vitamin D you add, but how you encourage your body to use it.”

Kado pointed out that the study relied on a single snapshot over time of microbes and vitamin D found in participants’ blood and stools, and that these factors can fluctuate over time depending on the environment, diet, sleep patterns, medications, etc. According to the team, more studies are needed to better understand the role of bacteria in vitamin D metabolism and to determine whether a microbiome-level intervention could be used to augment current treatments to improve bones and possibly d ‘other health outcomes.