MNT：晒太阳对心脏好处胜过患皮肤癌的风险

　　英国爱丁堡大学科学家表示，晒太阳对心脏的好处会大于患皮肤癌的风险。

　　在富有里程碑意义的研究中，研究人员发现，当阳光照射我们的皮肤时，释放一种有助于降低血压名叫一氧化氮的复合物到我们的血管。

　　皮肤学高级讲师Richard Weller 和同事说，此效果是全面的，晒太阳可以改善健康甚至可以延年益寿，因为降低血压减少了心脏病和中风的发生，这益处远远高于得皮肤癌的风险。

　　研究人员注意到，冬季高血压和心血管疾病的发病率与地理纬度有关（如在北欧的人高血压和心血管疾病发病率高于南欧）。

　　同时，估计显示，在北欧，在所有死于皮肤癌的病例中，约60 至100 人死于与高血压相关的中风和心脏病。

　　此新研究非常重要，因为直到现在人们认为晒太阳有利于维生素D 的产生，晒后维生素D 增长，阳光对人类健康有益无害。

　　以往的研究已发现，增加了与降低心血管病相关的维生素D的水平时，口服补充对此并没有影响。

　　Weller 和同事们发现，体内一氧化氮的产生独立于维生素D 的产生。

　　为了研究，他们邀请了24 位志愿者，让他们坐在太阳灯下20 分钟（两个过程），同时检查血压。

　　在第一个过程中，他们让志愿者身处紫外线(UV) 照射和灯加热的环境中。在另一个过程中，他们阻挡紫外线，只让志愿者身处灯加热的环境中。

　　结果表明，志愿者身处紫外线照射和加热的环境中时血压下降且心率上升，但是当他们只在灯加热的环境中时并没发生此变化。血压下降持续了约50 分钟。

　　人的皮肤中储存了大量的亚硝酸盐(NO2) 和硝酸盐(NO3)。研究人员注意到，硝酸盐有“生物惰性”，而阳光的作用可减少活性亚硝酸盐和一氧化氮(NO) 的惰性。

　　他们发现，同时身处紫外线照射和加热环境（非仅身处加热环境）期间，循环的硝酸盐下降，亚硝酸盐上升，而维生素D 的水平并无差异。

　　Weller 在一份报告书中说：

　　“我们推测阳光对心脏健康的益处将大于患皮肤癌的风险。我们所做的工作提供了一个可以解释这一点的机理，同时还解释了为什么单独饮食补充维生素D 并不能补偿阳光缺乏。”

　　他和他的成员现在想看看在已接受不同程度阳光照射的人身上，皮肤癌和心脏病的相关风险。

　　“如果确定阳光减少所有病例的死亡率，则我们将需要重新考虑有关晒太阳的建议。”Weller 说。

　　还有这样的建议，晒太阳有助于预防传染病。例如，在2011 年，伦敦大学圣乔治医院病毒学家Phil Rice 提出，太阳紫外线灭活皮肤水痘病毒。

与皮肤癌相关的拓展阅读：

• JNCI：HIV阳性者非黑色素瘤皮肤癌发病率高
• CANCER RES：致命的皮肤癌如何全身扩散
• J INVEST DERMATOL：美甲灯？皮肤癌？
• Cancer Cell：胸腺基质淋巴生成素（TSLP）或抵御皮肤癌
• JID：蛋白Wnt1抑制皮肤癌转移 更多信息请点击：有关皮肤癌更多资讯

Sun Exposure Benefits May Outweigh Risks Say Scientists
Scientists at the UnIversity of Edinburgh in the UK suggest that the heart-health benefits of sun exposure may outweigh the risk of developing skin cancer.
In the landmark study, the researchers found that when sunlight touches our skin, a compound called nitric oxide that helps lower blood pressure, is released into our blood vessels.
Richard Weller, Senior Lecturer in Dermatology, and colleagues, say the effect is such that overall, sun exposure could improve health and even prolong life, because the benefits of reducing blood pressure, cutting heart attacks and strokes, far outweigh the risk of getting skin cancer.
The proof-of-principle study is being presented this week in Edinburgh at International Investigative Dermatology 2013, the world's largest gathering of skin experts.
The abstract was published online in the Journal of Investigative Dermatology on 15 April.
The researchers note that rates of high blood pressure and cardiovascular disease rise in winter and are tied to geographic latitude (for instance they are higher in northern Europe than in southern Europe)
Also, estimates show that in northern Europe, for every death from skin cancer, about 60 to 100 people die of stroke and heart disease linked to high blood pressure.
This new study is important because until now it was thought that sunlight's only benefit to human health was production of vitamin D, which rises after exposure to the sun.
Previous studies have found that while increased vitamin D levels link to lower cardiovascular disease, oral supplements do not have an effect on this.
Weller and colleagues found that the body's production of nitric oxide is separate from production of vitamin D.
For their study they invited 24 volunteers to sit under sunlamps for two 20 minute sessions while they examined their blood pressure.
In one session, they exposed the volunteers to both ultra-violet (UV) rays and heat from the lamps. In the other session, they only exposed them to the lamps' heat and blocked the UV rays.
The results showed that the volunteers' blood pressure fell and their heart rate rose in the session where they were exposed to both UV and heat, but not when they were exposed to heat only. The reduction in blood pressure lasted for about 50 minutes.
Human skin contains large stores of nitrite (NO2) and nitrate (NO3). The researchers note that while nitrate is "biologically inert", the action of sunlight can reduce it to active nitrite and nitric oxide (NO).
They found that circulatory nitrate fell and nitrite rose during UV and heat exposure, but not during exposure to heat only. There was no difference in vitamin D levels.
Weller says in a statement that:
"We suspect that the benefits to heart health of sunlight will outweigh the risk of skin cancer. {nextpage} The work we have done provides a mechanism that might account for this, and also explains why dietary vitamin D supplements alone will not be able to compensate for lack of sunlight."
He and his team now want to look at the relative risks of skin cancer and heart disease in people who have received different amounts of exposure to sunlight.
"If this confirms that sunlight reduces the death rate from all causes, we will need to reconsider our advice on sun exposure," says Weller.
There have also been suggestions that exposure to the sun can help prevent infectious disease. For example, in 2011, Phil Rice, a virologist at St George's Hospital, University of London, suggested that the sun's UV rays inactivate the chickenpox virus on the skin.