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晒太阳的好处远不止补维生素D：科学家发现阳光还能降血压、抑制过度免疫反应｜科学60秒

环领研网约 11 分钟
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我们防晒过度了吗

现代人的防晒装备越来越齐全：防晒霜、防晒衣、防晒帽、冰袖、口罩、遮阳伞……夏日出门前的每一步准备，都是为了对抗太阳的“袭击”。但与此同时，“晒太阳能补钙”是我们从小听到大的常识；社交媒体上，“晒背养生”的风潮也在兴起。阳光似乎又成了身体离不开的东西。

作为同一件事的两面，无论是防晒还是晒太阳，我们到底应该做到什么程度？

防晒在中国曾经是件不需要认真对待的事，最多戴顶帽子、打把伞。但过去十年间，“硬核防晒”迅速成为大众共识：SPF50+成了日常出门的标配，防晒服市场规模突破800亿元，社交平台上“补涂提醒”的帖子比比皆是。而在大洋彼岸，防晒技术本身也在迭代。2026年6月初，美国食品和药品管理局（FDA）批准了一种名为双-乙基己氧苯酚甲氧苯基三嗪（bemotrizinol，BEMT）的全新防晒活性成分——这是该机构二十多年来首次扩充防晒成分名录。这种成分在欧洲和亚洲已经使用了近三十年，以光稳定性强、皮肤吸收率低著称。

但与此同时，另一种声音也开始冒头：这些年反复告诫我们“别晒太阳、当心皮肤癌”的健康建议，是否有点矫枉过正？当然，科学并不支持毫无节制的暴晒或使用晒黑床，但“到底该晒多少太阳才合适”，问题的答案远比我们想象中更复杂。

长期关注科学、自然与环境议题的记者兼作家罗温·雅各布森（Rowan Jacobsen）在最近出版的新书《为阳光辩护：日晒背后令人惊讶的科学》（In Defense of Sunlight: The Surprising Science of Sun Exposure）中深入探讨了这一议题，系统梳理有关日晒风险与获益的研究进展。

罗温表示，针对美国目前对待阳光的两极态度，他写这本书并不是想揭开“反防晒阴谋”，也并非号召读者扔掉所有防晒装备、放开了晒。

原因是他注意到，大约十年前，学术界陆续发表数项研究，揭示了阳光此前被忽视的健康益处。这让罗温开始反思：过去主流防晒建议的出发点极为单一，即阳光会导致皮肤癌，但当越来越多阳光有益的证据浮出水面，我们与阳光的关系是否也应当被重新评估？

首先，“防晒至上”的主流建议究竟是如何形成的？罗温表示，在长达约一百年的时间里，阳光能促进维生素D合成是人们对它唯一确切的正面认识。而从20世纪20年代至40年代起，科学家们相继发现，太阳光谱中的紫外线（UV）具有致癌性，可诱发皮肤癌。

这一发现让人们第一次重新审视自己与太阳的关系。过度暴晒确实会显著提高罹患皮肤癌的风险，到1940年代后期，美国的皮肤癌发病率开始迅速攀升，一时之间仿佛“新型流行病”蔓延，“防晒“相关的公共卫生警告也随之愈发严厉。

口服维生素D补充剂问世后，人们似乎找到了完美的替代方案。如今“应尽量避免一切日晒”的主流建议，正是建立在这样一条逻辑之上：阳光的好处无非就是维生素D，而维生素D可以靠吃补回来。但事实上，这一逻辑的两个环节都站不住脚——维生素D药丸并不能替代阳光，而促进维生素D合成也仅是阳光对人体作用的一小部分。

过去的一系列大规模人群观察显示，无论在世界哪个地区，接受日晒更多的人群，罹患多种疾病的比例更低、寿命也更长。英国爱丁堡大学皮肤病学教授理查德·韦勒（Richard Weller）团队基于英国生物样本库（UK Biobank）超过39万人的分析验证了这一趋势：更高的阳光暴露与更低的全因、心血管及癌症死亡率相关。

这项观察性研究虽然不能证明因果关系，但至少提示我们：躲避阳光对健康可能存在负面影响。与此同时，科学家还发现阳光对人体的益处远不止合成维生素 D 这一项。

其中几项重要发现是：阳光照射皮肤时会促使皮肤释放一氧化氮，这是一种能够扩张血管、降低血压的信号分子。心血管疾病是全球头号致死原因，因此，血压的小幅下降对整体公共卫生的意义非同小可。此外，阳光似乎还能抑制过度活跃的免疫系统（背后的机制学界仍在探索），并对新陈代谢产生轻度改善作用。

但具体到机制层面，解释这些好处的过程更为复杂。

首先，阳光照射皮肤后合成的维生素D会在全身层面引起多种效应，这无法被口服D药丸完全复制。其中，一氧化氮的产生是最有趣的一种……[查看全文]


Are we too afraid of the sun? Scientists rethink sun exposure risks and benefits

Rachel Feltman: Hey listeners, it’s Rachel here. Before we get into today’s episode, I just wanted to acknowledge our unexplained absence from your feed over the last few weeks. To make a long story short, Scientific American was sold to a new parent company in June, which caught our team by surprise. There were lots of things to sort out during the transition from Springer Nature to LabX, but now we’re back at work on the pod. We’re sorry for the hiatus was so abrupt, but the good news is that Science Quickly isn’t going anywhere! Thanks for your patience as we get back up to speed. Without further ado, here’s a new episode for you to enjoy.

For Scientific American’s Science Quickly, I’m Rachel Feltman.
I’ve always had a love-hate relationship with the sun. As the sole alabaster-skinned outlier in an otherwise solidly Mediterranean family, photographic evidence can confirm that, despite my parents’ good-faith efforts, I spent most of my childhood very, very sunburned. On one infamous trip to Aruba, I got second-degree burns across my shoulders that were so bad, I spent a week covered in zinc diaper cream for extra protection.
While my SPF needs may have been considered offbeat and a little bit fussy back in the mid-1990s, we’ve since come a long way when it comes to societal attitudes around sun protection. The popularity of tanning lotions and baby oil have given way to cutting-edge sunscreen formulas, including plenty intended for everyday use. In fact, earlier this month, the U.S. Food and Drug Administration approved the first new sunscreen ingredient in 27 years.
At the same time, we’re starting to see a backlash to that wave of skin cancer prevention messaging about sun exposure—including from people in the White House. And while science definitely doesn’t support the use of tanning beds or endless, unprotected sun exposure, it is true that there could be a bit more nuance to the question of how much sunshine to seek out than you’ve been told.
Today’s guest is writer Rowan Jacobsen. He’s the author of a new book called In Defense of Sunlight: The Surprising Science of Sun Exposure. He’s here to unpack the latest research on the risks and benefits of unadulterated sunshine.
Thanks so much for coming on to chat with us today.
Rowan Jacobsen: Thanks. I’m excited to be here.
Feltman: So we’re in a pretty weird place right now with sun exposure in the U.S. You know, we have the mainstream medical guidelines on one end, and then we do have people in the White House trying to make it easier for teens to use tanning beds. So with that in mind, I would love to start at the top by making it clear what your book is not saying. You’re not busting open an antisun conspiracy and telling us that the science says we should throw away all sun protection forever and tan with abandon. Is that correct?
Jacobsen: Yeah, that gang is doing me no favors right now.
Feltman: But how did you get interested in the topic of the sun and, you know, in defending it? Because it turns out there is nuance to some of these recommendations that we have.
Jacobsen: There is a lot of nuance, which is why I decided a book was the right format so that you can actually get into all the nuance of it. But for me, it started about 10 years ago, when a few studies hit the scientific literature showing that sunlight actually had some beneficial qualities that we hadn’t previously taken into account.
So then, you know, you start asking, “Well, we know that sun has these negative qualities related to skin cancer, and the recommendations that existed, that you referred to, were based purely on that. But if suddenly we have these benefits, then does that mean we need to reevaluate the relationship there?” And so my book asks that question and tries to dive in and do that at some level.
Feltman: So how did we come to our current mainstream recommendations when it comes to sunlight?
Jacobsen: So basically, for a really long time, like 100 years, the one thing we knew that sunlight did that was good for you was vitamin D. When sunlight hits skin, it makes vitamin D. And we learned that, yeah, in, like, the 1920s, [in the] 1930s, 1940s, scientists started to discover that the ultraviolet light in the solar spectrum can cause skin cancer.
So suddenly, everybody had been very prosun up to that point. Suddenly, you know, they went, “Well, we gotta reconsider this ’cause it looks like too much sun exposure will raise your risk of skin cancer.” We learned more and more from there about those dangers, and at the same time, skin cancer rates in the U.S. started to explode after World War II, basically.
So it started to look like we had kind of an epidemic on our hand. So the warnings got more and more strident that you better be careful with sunlight. We still had the issue of vitamin D; we didn’t want people to be deficient in vitamin D, but you can also make a pill, and people could get vitamin D through their pills.
So basically, the current recommendations to avoid all sun exposure were based on the concept that you could make up for that by taking a vitamin D pill, and that would give you all the good stuff that you weren’t getting from the sunlight. And it has turned out that neither one of those—that calculus was not right. It turns out the vitamin D pills don’t do what the sun does and that vitamin D is only part of the story for what the sun actually does.
Feltman: Yeah. So tell me more about the growing body of evidence that maybe this total avoidance of the sun when possible is not ideal.
Jacobsen: So it kind of starts with these big observational studies. Like, you just look at populations, and you can estimate how much sunlight those different groups are getting, and what we always see across the board, no matter where those studies are done, is that the people exposed to more light on average tend to have lower rates of a whole lot of diseases and better longevity than the people who don’t get much sun exposure.
So you know, like, observational studies, they don’t prove causation, but we do have quite a bit of evidence that shows, like, sun avoidance seems to be bad for people for ways that we’re still trying to figure out. So we knew about vitamin D, but then, since then, we’ve also discovered some other good things that the sun does.
The sunlight hitting skin also produces nitric oxide, which can lower blood pressure, and because cardiovascular disease is the number one killer around the world, lowering blood pressure can make a big difference in terms of overall public health.
Feltman: Right.
Jacobsen: Sun also seems to sort of dampen an overactive immune system for reasons we’re still trying to figure out, and it seems to, like, improve metabolism a little bit. Those are kind of the big ones.
Feltman: And what do we know, if anything, about the mechanisms that might be at play here, both, you know, with the literal sun exposure itself and with maybe, you know, some other potential correlating factors?
Jacobsen: Right. It’s so fascinating, and it gets really complicated really fast. So sun hits skin, it makes vitamin D. That actually has a ton of effects on the body that don’t seem to be replicated by a vitamin D pill. Nitric oxide...[full transcript]

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