24Drs好健康報:迷上曬黑了嗎？
好健康熱頭條 ─ 迷上曬黑了嗎？ Hooked on Tanning?
好健康小單字─紫外線輻射（Ultraviolet radiation；UV）
好健康熱頭條 ─ 迷上曬黑了嗎？
不能曬黑會讓你不舒服嗎？那你可能曬黑上癮了。
去年有篇針對常去海灘的人所做的研究顯示，這些曬許多太陽的人很像喝太多酒或是吃太多藥的人，也就是說，太常曬黑的人就像上癮了一樣；現在研究人員表示，經常曬黑並不只是「很像」上了癮，而是「真的」成癮了。
研究人員們觀察這些一個月曬8至15次的人，結果發現，如果給這些經常曬黑的人naltrexone（一種能限制麻醉劑類的藥物），他們曬黑時皮膚會產生戒斷症狀；但是不常曬黑的人服用naltrexone則不會有戒斷症狀。
Wake Forest大學Baptist醫學中心的皮膚科醫生Mandeep Kaur表示，開始時他們給常曬黑的人50毫克標準劑量的naltrexone，所有人都出現符合生理性的戒斷症狀：噁心、頭昏眼花、以及搖晃，所以他們必須停止那個研究。
Kaur醫師與同事們在最近的研究中找了8位經常曬黑的人，以及8位已經曬黑但不常這麼做的人進行研究，他們開始時都只給5毫克的naltrexone，再慢慢的增加劑量；當他們達到15毫克時，有四位經常曬黑的人有明顯的戒斷症狀。
Kaur醫師表示，有四位在結束時表示噁心或是緊張不安，其中有兩位在服用15毫克naltrexone後退出研究；不常曬黑的人則沒有任何戒斷症狀，而且沒有對麻醉劑上癮的人很少會對這麼低劑量的naltrexone產生這些副作用。
所以，Kaur醫師表示，他不認為這是naltrexone的副作用，他認為這是因為曬黑產生的生理性推縮。
研究結果刊載在2006四月號的美國皮膚醫學協會期刊（Journal of the American Academy of Dermatology）上。
【迷上曬黑者的快感？】
皮膚科醫生發現，曬黑會讓皮膚散發腦啡，這些類嗎啡的成分讓人覺得很好，它們就是讓馬拉松選手會有「跑者的快感」的原因，而這會是讓曬黑者有快感的原因嗎？
提出2005年報告的作者Richard Wagner Jr.醫師指出，經常曬黑可能是一種物質濫用，他是位於蓋文斯頓的德州大學醫學院皮膚外科主任兼皮膚系副主任；Wagner醫師表示，這個想法是從不想停止曬黑的皮膚癌患者而來。
Wagner醫師向WebMD表示，每一位皮膚科醫生都會告訴你，有些病患他們很關心，我們知道紫外線會導致皮膚癌，然而，我們看到皮膚癌患者還是一直在曬太陽，我們會告訴他們不要為了曬黑而去曬，有些人會說「但是醫生，我非常愛曬黑，它讓我覺得放鬆，我知道我已經有皮膚癌，但是我停不了。」
因此，Wagner醫師去海灘，對那些在做日光浴的人做上癮的問卷調查，有半數的人符合物質濫用障礙的心理標準，而這個物質就是曬太陽。
【所選的毒品：紫外線】
Wagner醫師與Kaur醫師懷疑經常曬黑的人是迷上因為在紫外光下曬黑所產生的腦啡，當皮膚接觸同樣會造成皮膚癌的紫外線時，就會產生腦啡。
Wagner醫師表示，曬黑的問題在於因為照紫外線而黑的生理反應，紫外線是腫瘤助長者，這也就是皮膚科醫生試著限制病患接觸紫外線的原因。
Kaur醫師的研究小組在研究中有兩張看起來一樣的曬黑機，其中一張用紫外線，另一張則沒有紫外線；研究人員找了8位經常曬黑的人與8位不常曬黑的人參與研究，他們要求參與者使用這兩張曬黑機，並要求他們比較偏好哪一張，接著他們給每一位參與者逐步增加劑量的naltrexone，或是沒有作用的安慰劑。
結果顯示，不常曬黑的人在產生腦啡的紫外線之下稍微偏好曬黑，naltrexone稍微降低了這種偏好；經常曬黑的人在紫外線之下非常喜歡曬黑，當他們用15毫克或25毫克劑量的naltrexone時，這種偏好會明顯的降低；而且就如同之前所述，有四位參與者顯示有生理性的戒斷徵兆。
你如何判斷是否有曬黑癮？Kaur醫師表示，要看你多常做日光浴或是去做曬黑美容，如果你無法不去做曬黑美容，而且一個月去8次以上的人要小心了，她也警告曬黑是有危害的。
Kaur醫師表示，如果你一個月要曬8次以上，又在早上10點至下午4點之間曬的話是會受到影響的，而且用曬黑機也一樣，雖然他們表示機器很安全，但是曬黑其實並不安全。
紫外線也不是都不好，皮膚接觸紫外線能製造維他命D，正常的接觸陽光能產生大量的維他命D，Kaur醫師表示，避免陽光的人要確定他們能有足夠的維他命D。
Hooked on Tanning?
Do you feel bad when you can't tan? You may be a tanning addict.
Last year, a study of beachgoers showed that people who tan a lot are much like people who drink or drug too much. That is, too-frequent tanners act a lot like addicts.
Now researchers report that frequent tanning isn't just like an addiction. It really may be an addiction.
The researchers looked at frequent tanners -- those who tan eight to 15 times a month. Their study shows that frequent tanners get withdrawal symptoms when given naltrexone, a drug that blocks a narcotic-like substance produced in the skin during tanning. But infrequent tanners who take naltrexone don't get withdrawal symptoms.
"In the beginning, we gave standard 50-milligram doses of naltrexone to frequent tanners," says researcher Mandeep Kaur, MD, a dermatologist at Wake Forest University Baptist Medical Center. "All of them developed symptoms consistent with physiological withdrawal: nausea, dizziness, and shaking. So we had to stop that study."
In their most recent study, Kaur and colleagues enrolled eight frequent tanners and eight people who tanned, but did so infrequently. They started them all on just 5 milligrams of naltrexone and gradually increased the dose. When they got to 15 milligrams, four of the frequent tanners got telltale withdrawal symptoms.
"Four of the eight frequent tanners ended up reporting nausea or jitteriness," Kaur says. "Two of them dropped out of the study after taking the 15-milligram dose of naltrexone."
None of the infrequent tanners got any withdrawal symptoms. And people who aren't addicted to narcotics rarely get these kinds of side effects from such a low dose of naltrexone.
"So I don't think it is a side effect of naltrexone. I think it is physiological withdrawal from tanning," Kaur says.
The findings appear in the April 2006 issue of the Journal of the American Academy of Dermatology.
Hooked on Tanner's High?
Tanning, dermatologists have found, makes the skin give off endorphins. These opioid compounds make a person feel good. They are the reason endurance runners report "runner's high." Could there really be such a thing as tanner's high?
The author of the 2005 report suggesting that frequent tanning may be a type of substance abuse is Richard Wagner Jr., MD, deputy chairman of dermatology and director of dermatologic surgery at the University of Texas Medical Branch at Galveston. Wagner says the idea came from skin cancer patients who couldn't stop tanning.
"Every dermatologist will tell you there are some patients we are concerned about," Wagner tells WebMD. "We know ultraviolet (UV) light can lead to skin cancer. Yet we all see patients with skin cancer who are always tan. We tell them not to tan on purpose, and some say, 'But doc, I like it too much. It makes me feel relaxed. I know I am getting skin cancer, but I can't stop.'"
So Wagner went down to the beach and gave addiction questionnaires to people who were sunning themselves. As many as half met the psychological criteria for substance-related disorder. That substance: sun tanning.
Drug of Choice: UV Light
Wagner and Kaur suspect that frequent tanners get hooked on the endorphins produced by tanning under ultraviolet light. The skin makes endorphins when it's exposed to UV light -- the same light that causes skin cancer.
"The problem with tanning is that the physiologic response of tanning is due to UV light," Wagner says. "UV light is a tumor promoter. That is why dermatologists try to limit their patients' exposure."
At their tanning research lab, Kaur's team has two identical-looking tanning beds. One uses UV light. The other does not.
The researchers enrolled eight frequent tanners and eight infrequent tanners in their study. They had them use both tanning beds and had them rate their preference. Then they gave each participant escalating doses of naltrexone or an inactive placebo pill.
The infrequent tanners slightly preferred tanning under the endorphin-producing UV light. Naltrexone slightly reduced this preference.
The frequent tanners greatly preferred tanning under UV light. This preference was markedly reduced when they were on 15-milligram or 25-milligram doses of naltrexone. And as noted above, four of these participants showed physical signs of withdrawal.
How can you tell if you're a tanning addict? Kaur says to look at how often you are sunbathing or visiting a tanning salon. Kaur says if you have an unlimited pass to a tanning salon and are going eight or more times a month, watch out. She also cautions about the hazards of tanning.
"If you are tanning yourself eight or more times a month, between the hours of 10 a.m. and 4 p.m. -- if you are baking yourself, this is going to affect you," Kaur says. "And that goes for tanning beds, too. They say they are safe, but there is no such thing as safe tanning."
UV light isn't all bad. Skin exposed to UV light makes vitamin D. Normal sun exposure generates plenty of vitamin D. Kaur says that people who avoid sunlight should make sure they get plenty of vitamin D.
SOURCES: Kaur, M. Journal of the American Academy of Dermatology, April 2006; vol 54: pp 709-711. Warthan, M.M. Archives of Dermatology, August 2005; vol 141: pp 963-966. Mandeep Kaur, MD, instructor in dermatology, Wake Forest University Baptist Medical Center. Richard Wagner Jr., MD, professor and deputy chairman of dermatology; director of dermatologic surgery, University of Texas Medical Branch, Galveston.
WebMD Medical News
by Daniel DeNoon
好健康小單字─紫外線輻射（Ultraviolet radiation；UV）
紫外線輻射（Ultraviolet radiation；UV）是許多太陽能量其中的一種，而一般我們常常說的紫外線有三種類型：紫外線A(UV-A)、紫外線B(UV-B)、和紫外線C (UV-C)，它們分別穿透肌膚的不同深度。
UV-A-波長介於320~400nm，可自由穿透大氣層不受臭氧層的影響；UV-B-波長介於280~320nm，臭氧在此波段有很強的吸收帶，若大氣中臭氧減少，則到達地面的UV-B將會增加；UV-C-波長小於280nm，此段波長完全被大氣吸收，因此無法在地面監測到。
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