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It seems like everything can make us addicted these days. Our iPhones. The internet. Oreos. But just because something is pleasurable and causes a relevant reward area of your brain to light up does not mean that it is addictive. An addiction is like a compulsion, where you continue performing a behaviour even though it has resulted in negative consequences – like continuing to drink even though it's lost you your driving licence, your job and even your partner. Addiction also involves complex changes in your brain in areas where you process reward and self-control. These changes can result in feelings of craving and withdrawal, where your body has adapted to rely on the drug to feel normal. In some cases, withdrawal can be so severe that your body may actually shut down and you can die if you don't have another hit. No matter how many Oreos you eat, this will not happen to you. The idea of food addiction is not a new one, but a study released last week takes this claim to a whole other (and unsubstantiated) level, claiming that Oreos – and especially that all-enticing creamy centre – is as addicting as cocaine. Unfortunately, the researchers from Connecticut College who ran this study, led by Professor Joseph Schroeder, never actually tested this hypothesis. They used a standard conditioned place-preference test, giving rats either an Oreo or a rice cake on one side of a maze or another and then watched to see where the animals later chose to spend their time. This type of task is typically used to measure associations between a stimulus (like cookies or cocaine) and the environment in which it was experienced, with the idea being that the more pleasurable an experience is, the more likely you will want to repeat it, and thus the more time you will spend in the place where you first received it. Stemming from this logic, as might be expected, the rats preferred the side of the maze where they received the Oreo. Fine, great, we all like Oreos more than rice cakes. No surprise there. Then the researchers repeated the experiment, but this time they injected rats with a dose of cocaine or morphine on one side and with a neutral saline solution on the other. Once again, as you might anticipate, the rats kept going back to the side where they had received the drugs, hoping for more. Now here's where it gets sketchy. The researchers measured the amount of time the rats spent in each half of the chamber and claim that because the two groups of mice spent equal amount of time in the Oreo and in the cocaine area, these two stimuli are equally rewarding, or "addicting". However, they never actually compared the cocaine with the cookies! These were two completely separate groups of animals that took part in two different experiments – one testing Oreos with rice cakes and another comparing cocaine and saline. Yes the animals showed similar behaviours in response to the drugs and to the high-fat/high-sugar food, but these things cannot be equated if they are not directly compared. To be fair, the researchers didn't just rely on behavioural tests, but also measured the amount of chemical activity that was seen in a reward region of the brain, the nucleus accumbens, in response to each of the two vices. Here they report that there was greater evidence of activation in the Oreo-eating rats than in the cocaine-consuming ones. However, again, they haven't directly compared the amount of activity seen within an animal after receiving cocaine and Oreos. Many previous studies have directly compared cocaine with food rewards and the results are conflicting. One study measured cell firing in the nucleus accumbens in primates directly after receiving a sip of juice or a dose of cocaine. In these animals, there was significantly greater activity in response to the drugs than the juice. Now, this isn't to say that the idea of "food addiction", particularly to foods high in fat and sugar, is complete nonsense. For over the past 10 years Dr Nicole Avena and others have been conducting elegant experiments where they let rats binge on chocolate pellets and then measure changes in their brain and behaviour. These researchers quite frequently see similar effects in rats that have been gorging on chocolate as those given cocaine. This includes physical changes in the brain (including in that crucial reward centre), as well as behaviours reminiscent of craving and even withdrawal. The idea that junk foods can create addictive-like tendencies is not new, nor is it wrong. But the claims that this particular study makes are. As for whether the eating the middle of an Oreo first really is better, well I guess I'll let that one slide. |
最近，好像所有事物都能讓我們上癮。iPhone、互聯(lián)網(wǎng)、奧利奧。但是，僅因為一些事物使你感到愉悅，并刺激大腦引起相關(guān)反應(yīng)，這不意味著上癮。 上癮就像一種強迫力，迫使你重復作出一種行為，即使它已產(chǎn)生了負面結(jié)果——就象即使已讓你的駕駛證吊銷，父母甚至愛人離你而去，你還要繼續(xù)喝酒。上癮包括你大腦中處理反應(yīng)和自控力的部分的一系列變化。這些變化導致你渴望和抵制情緒的產(chǎn)生，而你已依賴于藥品來保持正常的感覺。一些情況下，嚴重的抵制情緒會是你身體停止運轉(zhuǎn)，如果不繼續(xù)吸食藥品的話，可能會死亡。 但不管你吃了多少奧利奧，這種事情都不會發(fā)生。 食物上癮的觀點并不是個新觀點，但上周的研究結(jié)果卻把這一結(jié)論提到了另一個完全不同的，未經(jīng)證實的層面。結(jié)果表明，奧利奧——尤其是中間誘人的夾心——和可卡因一樣能使人上癮。 糟糕的是，由約瑟夫·施羅德教授主持，研究人員都來自康涅狄格學院的一項研究從來沒有證實過這個假設(shè)。他們做了一項位置偏愛的標準條件測試，把奧利奧或年糕給小白鼠，放在迷宮的兩頭，觀察動物會選擇哪一邊的食物。這種類型的測試是典型的測試刺激（餅干或可卡因）與環(huán)境的聯(lián)系的，如果你經(jīng)歷的感覺越愉快，你就越傾向于重復它，你就會在你第一次感受到的地方花更多時間。根據(jù)理論，可以想象出小白鼠更喜歡能得到奧利奧的一邊。 很好，相對于年糕，我們都喜歡奧利奧，沒什么驚訝的。 然后，研究人員重復這項實驗，但是這次他們給一邊的小白鼠注射小劑量的可卡因或嗎啡，而另一邊注射中性鹽水。你能想象的到，小白鼠仍舊跑到能得到毒品的那一邊，希望得到更多。 現(xiàn)在，到了總結(jié)實驗結(jié)果的時候了。研究人員測量了小白鼠在籠子兩邊所用時間，并宣稱兩組老鼠在有奧利奧和可卡因的一邊多用時間相同，所以這兩種刺激能引起大腦相同的反應(yīng)或“令人上癮”。但是他們卻從來沒有真正比較過可卡因和餅干！這是完全不同的兩組動物在做兩種不同的實驗——一組對比奧利奧和年糕，另一組對比可卡因和鹽水。是的，動物們對毒品和高脂肪、高糖食物的反應(yīng)類似，但如果沒有直接的比較，兩者不能劃等號。 公平的說，研究人員沒有進行行為測試，但測量了大腦中反應(yīng)區(qū)域中化學反應(yīng)量—伏核。他們聲稱在吃了奧利奧的小白鼠比注射了可卡因的小白鼠有更多受到興奮刺激的證據(jù)。然而，他們沒有直接比較吃完奧利奧和可卡因的小白鼠的活動量。 許多以前的研究都直接比較了吃了還有可卡因食物的反應(yīng)，但二者結(jié)果矛盾。一研究結(jié)果測出，靈長類動物在喝完一小口橘汁或可卡因后，伏核內(nèi)的細胞都會燃燒。在這一類動物中，對于毒品的反應(yīng)要明顯大于對橘汁的反應(yīng)。 現(xiàn)在就提出“食物上癮”的觀點，尤其是高脂肪，高糖的食物純屬無稽之談。在過去的十年中，尼克爾·艾薇娜博士和其他人做了小型試驗，她讓小白鼠吃巧克力球，然后測量它們大腦和行為的變化。研究人員經(jīng)常發(fā)現(xiàn)吃巧克力和可卡因?qū)π“资笥邢嗨频淖饔?。這包括大腦里的物理變化（包括重要的反應(yīng)中心），也包括渴望與抵制行為。 垃圾食品會使人上癮也不是新觀點，但也不是錯誤觀點。但確實是需要特殊研究的領(lǐng)域。 至于先吃奧利奧的夾心是不是更好，我想我會先舔著吃完的。 相關(guān)閱讀 （譯者 肖瀟-BUAA 編輯 丹妮） |
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