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cientists show that ultraviolet (UV) light exposure leads to
changes in the gut microbiome, but only in volunteers who were deficient in
vitamin D.
Share on PinterestCan sunlight
affect our gut microbiomes?
Living at higher latitudes, which means less exposure to UV
light and a greater chance of being vitamin D deficient, carries a higher risk
of developing diseases such as multiple
sclerosis (MS) and inflammatory
bowel disease (IBD).
Research into the gut
microbiome indicates that our microbial passengers may play a
significant part in these conditions.
But what links vitamin D to our intestinal microbiota?
A team of researchers, many from the University of British
Columbia, in Vancouver, Canada, set out to answer this question by studying how
the gut microbiome responds to UV light.
When volunteers who were deficient
in vitamin D received three sessions of UVB exposure, their gut microbiomes
changed and bore the same hallmarks as those of study participants who were not
vitamin D deficient.
The team published their findings in Frontiers in Microbiology.
UVB light
boosts 'richness' of microbiome
The study included nine female volunteers who took vitamin D
supplements in the 3 months leading up to the experiments and 12 who did not.
All participants had fair skin, specifically Fitzpatrick
skin types 1 to 3.
The volunteers who had taken the supplements had vitamin D
blood levels that are classed as adequate, while all but one of those who had
not taken the supplements were vitamin D deficient.
All participants then had three sessions of full body
exposure to UVB light. The research team saw increases in the vitamin D levels
in all of the volunteers, as a result.
They then compared the composition of each participant's gut
microbiome before and after the treatments.
The authors found significant changes in the microbial
compositions in the group that had been mostly vitamin D insufficient at the
start of the experiment.
"Prior to UVB exposure, these
women had a less diverse and balanced gut microbiome than those taking regular
vitamin D supplements," senior study author Prof. Bruce Vallance notes,
summarizing the teams' results. "UVB exposure boosted the richness and
evenness of their microbiome to levels indistinguishable from the supplemented
group, whose microbiome was not significantly changed."
Specifically, the vitamin D deficient volunteers experienced
an increase in Firmicutes and Proteobacteria and a decrease
in Bacteroidetes, to bring
their levels in line with the microbiomes of participants who had taken vitamin
D supplements.
Vitamin D
'main driver' of shift in microbiome
Medical News Today spoke to first study author Else Bosman about the
study.
"We found that vitamin D production was the main diver
of the shift in the microbiome," she explained. "It is well known
that UVB light produces vitamin D, and we now start to understand that vitamin
D is important to maintain a healthy gut."
"Although those facts were known individually, this is
the first study linking them up together," Bosman continued. "The
results were surprising in the way that there was a strong effect visible
within 1 week's time."
When asked how much time we should each be spending in the
sunshine to boost our vitamin D levels, Bosman urged caution.
"During the study, we made
use of specialized UVB lamps that don't cause burning. It was a therapeutically
used photobooth in a clinical setting," she explained. "From my
study, it is hard to conclude how much sun exposure is enough to produce vitamin
D."
This is down to our individual skin types and the amount of
UV radiation in the environment that we live in.
"Unfortunately, it is really hard to obtain enough
vitamin D from diet alone, so it is wise to supplement with vitamin D during
the winter," Bosman recommended. "Your body is very efficient in
making vitamin D from sunlight in the summer."
The extent to which variations in our microbiomes resulting
from fluctuating vitamin D levels affect our health is unclear at this point.
But Prof. Vallance suggests that this may be more important
for people with inflammatory diseases, such as MS and IBD.
Larger studies are needed and should include the full
spectrum of skin types, as well as male and female participants, the authors
suggest in their paper.
"This study made use of a very selective group of
participants, e.g., healthy, female, pale skin," Bosman told MNT. "It would be very
interesting to repeat the study with participants that have a lot more variety
in ages and with bigger study groups to confirm the results. It would also be
great if we can test if the phototherapy is useful for people with
intestinal inflammation to promote
their gut health."
"The
results of this study have implications for people who are undergoing UVB
phototherapy and identifies a novel skin-gut axis that may contribute to the
protective role of UVB light exposure in inflammatory diseases like MS and IBD."
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