陽光照射會影響腸道細菌

陽光照射會影響腸道細菌

People living at higher latitudes may be safer from the dangers of too much sunlight, but they also face a greater risk of having too little vitamin D in their bodies, a deficiency that affects as many as 1 billion people around the world.

生活在高緯度地區(qū)的人們可能更安全，免受過多陽光的危害，但他們也面臨著體內(nèi)維生素D太少的更大風(fēng)險，這一缺陷影響著全世界多達10億人。

For the first time, scientists have directly linked sun exposure to changes in the gut microbiome. (Photo: Kanchana P/Shutterstock)

A vitamin D deficiency alone can lead to a variety of health problems. Along with other environmental factors like diet and antibiotic use, it's also seen as one reason why many developed countries have such high rates of chronic inflammatory diseases, including multiple sclerosis and inflammatory bowel disease (IBD).

單單缺乏維生素D就會導(dǎo)致各種健康問題。除了飲食和抗生素使用等其他環(huán)境因素外，它也被視為許多發(fā)達國家患有慢性炎癥疾病(包括多發(fā)性硬化癥和炎癥性腸病(IBD))的原因之一。

Research suggests our gut microbiomes — the bacteria and other tiny creatures living in our digestive tracts — might wield some influence over these conditions. And now, in a study published in the journal Frontiers in Microbiology, researchers reveal a potentially important way to boost our gut bacteria with sunlight.

研究表明，我們的腸道微生物群——生活在我們消化道中的細菌和其他微小生物——可能會對這些情況產(chǎn)生一些影響?，F(xiàn)在，在一項發(fā)表在《微生物學(xué)前沿》雜志上的研究中，研究人員揭示了一種利用陽光促進腸道細菌生長的潛在重要方式。

A 'novel skin-gut axis'

一個“新的皮膚-內(nèi)臟軸”

Even briefly shining ultraviolet B (UVB) light onto a person's skin can lead to a wider diversity of gut bacteria, the researchers found, as well as higher levels of vitamin D. This was a small study, and the effect was only seen in subjects with lower vitamin D levels. Still, this is the first study to find a direct effect from UVB light on the gut microbiome, the researchers write, suggesting "the existence of a novel skin-gut axis that could be used to promote intestinal homeostasis and health."

研究人員發(fā)現(xiàn)，即使只是短暫地將紫外線B照射在人的皮膚上，也會導(dǎo)致腸道細菌的多樣性增加，維生素D的含量也會增加。不過，研究人員寫道，這是首次發(fā)現(xiàn)UVB光對腸道微生物群有直接影響的研究，表明“存在一種新的皮膚-腸道軸，可以用來促進腸道內(nèi)環(huán)境平衡和健康。”

There are two basic types of ultraviolet light that reach Earth's surface, known as UVA and UVB. Both can be harmful, but UVB rays are the main rays responsible for sunburns and are thought to cause the most skin cancers, according to the American Cancer Society. At the same time, UVB rays from sunlight trigger our bodies to produce vitamin D. Low UVB exposure has been linked to the onset of inflammatory gut diseases, and since vitamin D can influence our gut bacteria, the researchers hoped to shed new light on the relationship among all three factors.

到達地球表面的紫外線有兩種基本類型，即UVA和UVB。這兩種射線都是有害的，但據(jù)美國癌癥協(xié)會稱，UVB是造成曬傷的主要射線，被認為是導(dǎo)致皮膚癌的主要原因。同時,從太陽光UVB引發(fā)人體產(chǎn)生維生素D低UVB照射與炎性腸道疾病的發(fā)病有關(guān),因為維生素D可以影響我們的腸道細菌,研究人員希望揭示所有三個因素之間的關(guān)系。

Levels of UV light from the sun tend to be naturally lower at higher latitudes, raising the risk of health problems from a vitamin D deficiency. (Photo: yanikap/Shutterstock)

Led by Else Bosman, a doctoral candidate in experimental medicine at the University of British Columbia, the researchers recruited 21 healthy women to participate in the study. All of the volunteers had fair skin and lived in Canada during winter for the three previous months, and thus were exposed to relatively low levels of UVB light. Before the study began, the researchers tested their vitamin D levels and took stool samples, which revealed the makeup of their gut microbiome.

在不列顛哥倫比亞大學(xué)實驗醫(yī)學(xué)博士生愛爾莎·博斯曼的帶領(lǐng)下，研究人員招募了21名健康女性參與研究。所有的志愿者都是白皮膚，前三個月都住在加拿大的冬季，因此暴露在相對較低水平的UVB光線下。在研究開始之前，研究人員測試了他們的維生素D水平，并采集了糞便樣本，這些樣本揭示了他們腸道菌群的組成。

Nine of the women had been taking vitamin D supplements for three months prior to the study, while 12 hadn't. Of those 12, most had insufficient levels of vitamin D. The researchers gave the volunteers three sessions of UVB light exposure in a week, then tested their vitamin D and stool again. Not only did the women with low vitamin D now have normal levels, but their gut microbiomes had also grown more diverse.

在研究之前，其中9名女性已經(jīng)服用了3個月的維生素D補充劑，12名沒有服用。在這12名志愿者中，大多數(shù)人體內(nèi)的維生素D含量不足。研究人員讓志愿者在一周內(nèi)接受三次紫外線照射，然后再次測試他們的維生素D和糞便。維生素D含量低的女性不僅體內(nèi)的維生素D含量正常，而且腸道菌群也變得更加多樣化。

More research needed

需要更多的研究

This study was small, and its findings are still "extremely preliminary," as Leslie Nemo writes for Discover Magazine. More research will be needed before we can draw firm conclusions or take action based on these findings. It's especially important to be careful with sunlight exposure given the potential risks, and the researchers note they didn't use actual sunlight in this study, just an isolated component of it.

正如萊斯利·尼莫為《發(fā)現(xiàn)》雜志所寫的那樣，這項研究的規(guī)模很小，其發(fā)現(xiàn)也“極其初步”。在我們得出確切的結(jié)論或根據(jù)這些發(fā)現(xiàn)采取行動之前，還需要進行更多的研究?？紤]到潛在的風(fēng)險，在陽光照射下要格外小心，這一點尤其重要。研究人員指出，他們在這項研究中并沒有使用實際的陽光，只是其中一個孤立的成分。

Still, this study fills in some blanks and offers intriguing hints in our quest to understand the human microbiome, showing a shift in gut bacteria that was apparently driven mainly by the body's production of vitamin D.

盡管如此，這項研究填補了一些空白，為我們探索人類微生物群落提供了有趣的線索，顯示腸道細菌的變化顯然主要是由人體維生素D的生產(chǎn)驅(qū)動的。

"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," Bosman says. While those facts were known individually, she adds, this is the first study linking them all together. This study should now be repeated with more volunteers, the researchers say, including both sexes and a wider range of skin types.

“眾所周知，UVB光會產(chǎn)生維生素D，現(xiàn)在我們開始明白維生素D對保持腸道健康很重要，”博斯曼說。她補充說，雖然這些事實是單獨知道的，但這是第一次把它們聯(lián)系在一起的研究。研究人員說，這項研究現(xiàn)在應(yīng)該在更多的志愿者身上重復(fù)進行，包括男性和女性，以及更廣泛的皮膚類型。