Darmflora research UV-B radiation has a positive effect on your intestines

gut flora A stimulus is also given to the composition of your microbiome via your skin, according to a brand new, albeit still small study. And people who take vitamin D supplements already have a head start, according to a surprising study

Intestinal inflammation and disturbances in the intestinal flora balance

Most studies are currently about the influences of your intestinal system on the skin. Inflammation and imbalance of various intestinal flora (dysbiosis) are associated with intestinal barrier disruption and have been linked to a number of diseases.

The passage of so-called antigens that alarm the immune system

It is thought that impaired intestinal barrier function allows the passage of antigens (substance that activates the immune system) from the gut, and stimulates the immune system to produce an inflammatory response in humans.

The positive influence of sunlight

A very recent study from Canada showed that the skin changes your intestinal flora under the influence of sunlight. The other way instead of gut influences on the skin.

Influence Of Sunlight On Intestinal Flora

What about sunlight and ultraviolet radiation?

The light from the sun consists of a number of elements: Ultraviolet A (UVA), Ultraviolet B (UVB), visible light and infrared (IR).

UVA rays are present with relatively equal intensity during all daylight hours throughout the year, and can penetrate clouds and glass. UVA rays make up the largest part of the ultraviolet radiation, so more than UVB. No vitamin D production.

Although the intensity of UVA rays is less than UVB, it penetrates deeper into the skin, even into the dermis.

They penetrate deeper into the skin

Free radicals are formed in the dermis by UV rays. This causes damage to elastin and collagen fibers in the dermis, which provide the elasticity of the skin and skin fibroblasts. Skin fibroblasts are responsible, among other things, for the synthesis of collagen and elastin

To clarify: UVA – A stands for aging, uva does not indicate spf filter.

UVB rays penetrates into the superficial epidermis and is responsible for our vitamin D production and for a slow and longer-lasting tan.

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Vitamin D production, but also sunburn

Too much UVB causes redness, sunburn and eventually also skin aging and skin cancer. Unlike UVA, UVB does not penetrate glass. Unlike UVA, UVB radiation can be up to 1000x stronger than UVA rays and does not penetrate glass to cause damage to our hereditary material, DNA.VB. Sun Protection Factor (SPF) only protects against UVB and not against UVA.

To clarify, UVB – B stands for burn or sunburn, but also for tanning of the skin. The spf is linked to UV-B radiation.

Dermatologist Francis Wu writes a lot on BeautyJournaal about the role of our intestines in skin health

Canadian study: UV-B and intestinal flora

This study investigated whether exposure of the skin to Narrow Band Ultraviolet B (NB-UVB) light (311 nm) increases the vitamin D value in the blood and whether this can also change the composition of the human intestinal flora.

This study involved 21 healthy female volunteers. They each received three one-minute sessions of full UV-B exposure over a week.

The participants were divided into two groups: those who already took vitamin D supplements (VDS) before the start of the study (VDS with) and those who did not (VDS without).

After three NB-UVB light exposures within the same week, vitamin D levels in the blood increased. The composition of the intestinal bacteria was examined by means of faeces.

Increase in microbiome in those who did not take supplements

The results revealed a significant increase in alpha and beta microbiome diversity only in individuals who had not taken vitamin D supplements.

Diversity increased in those who previously had a less balanced intestinal flora

Prior to UV-B exposure, these women had less diverse and balanced gut bacteria than those taking regular vitamin D supplements.

At the level of the supplement users

UV-B exposure increased the diversity and evenness of their gut bacteria to levels indistinguishable from the vitamin D supplement group. The intestinal bacteria of the supplement users had not changed significantly under the influence of UV-B.

At least 1 good family of bacteria increased

The largest effect in the non-supplement group was an increase in the relative abundance of at least one “healthy” family of bacteria, Lachnospiraceae. This is associated with improved health status. Lachnospiraceae are less abundant in people with inflammatory diseases.

New Year New Resolutions Intestinal Flora

Through the skin to healthier intestines

It is likely that exposure to UV-B light somehow modifies the immune system locally in the skin, then in the blood and finally in turn favorably influences the biodiversity of gut bacteria.

So far, this is the first human study to discover a direct link between UV-B exposure in the skin and microbiome alternations in the gut. Bring on the winter sun!!


Bosman ES, Albert AY, Lui H, Dutz JP, Vallance BA. Skin Exposure to Narrow Band Ultraviolet (UVB) Light Modulates the Human Intestinal Microbiome. Front Microbiol. 2019;10:2410

While you are here

The importance of your gut bacteria. A new way of looking is to look at the skin-gut axis. The influence of intestinal bacteria and the skin is receiving increasing attention. Gut bacteria react to your diet and an imbalance of good bacteria due to bad eating habits affects the immune system. This has consequences for your skin and intestines. More on skin diseases and leaky gut

Picture of Dr. Francis Wu

Dr. Francis Wu

Dr. Francis Wu, een vooraanstaande dermatoloog, is de drijvende kracht achter Iconic Elements. Hij heeft sinds 2004 zijn expertise ingezet om een veilige en effectieve huidverzorgingslijn te creëren, geschikt voor zowel gezonde huid als huidproblemen. Iconic Elements, opgericht in 2016, is de eerste brede skincare lijn in Nederland ontwikkeld door een dermatoloog. Als medisch specialist streeft Dr. Wu naar het bevorderen van het welzijn van mensen door hoogwaardige en effectieve huidverzorgingsproducten te bieden. De proefdiervrije en vegan producten vermijden schadelijke chemicaliën en bevatten natuurlijke ingrediënten.
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