巧克力控看過來:巧克力有益健康的新證據大綱

In recent years, large-scale epidemiological studies have found that people whose diets include dark chocolate have a lower risk of heart disease than those whose diets do not. Other research has shown that chocolate includes flavonols, natural substances that can reduce the risk of disease. But it hasn't been clear how these flavonols could be affecting the human body, especially the heart. New findings from Virginia Tech and Louisiana State University, however, suggest an odd explanation for chocolate's goodness: It improves health largely by being indigestible.

近年來，大規模流行病學研究發現常吃黑巧克力者心臟病發病率比不吃黑巧克力的人要低。還有研究發現巧克力中含有黃醇酮，這是一種天然物質，可以降低疾病發病率。但黃醇酮是如何影響人體，特別是心臟，原理仍不分明。不過，弗吉尼亞理工大學與路易斯安那州立大學的新發現爲巧克力的益處提供了一種奇異的解釋：它因爲難以消化，所以對健康格外有益。

Researchers at Louisiana State reached this conclusion after simulating the human digestive system in glass vessels. One represented the stomach and the small intestine, with their digestive enzymes, and a second reproduced a large-intestine-like environment, with gut microbes from human volunteers. The scientists then added cocoa powder to the stomach vessel.

路易斯安那州立大學的研究者在玻璃容器中模擬人類的消化系統後得到了這個結論。其中一個器具用來模擬胃和小腸，內有消化酶，另一個器具用來模擬類似大腸的環境，內有從志願者體內提取的腸道微生物。之後科學家把可可粉放入這些模擬腸胃的容器中。

The "stomach" and "small intestine" broke down and absorbed some of the cocoa. But while many of the flavonols previously identified in chocolate were digested in this way, there was still plenty of undigested cocoa matter. Gut bacteria in the simulated colon then broke that down further into metabolites, small enough to be absorbed into the bloodstream and known to reduce cardiac inflammation. Finally, the last undigested cocoa matter, now mostly fiber, began to ferment, releasing substances that improve cholesterol levels. And there was another health-giving twist to this entire process: The gut microbes that digested the cocoa were desirable probiotics like lactobacillus. Their numbers appeared to increase after the introduction of the cocoa, while less-salutary microbes like staphylococcus declined in number.

“胃”和“小腸”系統分解並吸收了部分可可粉，但當許多巧克力內的黃醇酮被消化的同時，仍有大量可可粉末沒有被消化。模擬大腸中的腸道菌羣將黃醇酮進一步分解爲代謝物，小到足以被血液吸收，我們已知它能抑制心臟炎症發病率。最後，未被消化的可可粉，在這個階段主要是纖維，開始發酵，釋放出能提升膽固醇水平的物質。在這個過程中又出現一種能改善健康的變化：消化可可粉的腸道菌羣是非常有益的原生菌，諸如乳酸菌等。腸道攝入可可粉後，這些原生菌的數量開始增加，而葡萄球菌等不那麼有益健康的菌種開始減少。

These findings are broadly consistent with those from Virginia Tech, published in March in The Journal of Agricultural and Food Chemistry. Researchers there began by feeding healthy lab mice a high-fat diet. Some of the mice were also given unsweetened cocoa extract; others were fed various types of flavonols extracted from the cocoa. After 12 weeks, most of the mice had grown fat and unwell, characterized by insulin resistance, high blood sugar and incipient diabetes. A few, however, had not gained weight. These animals had ingested one of the flavonol groups whose chemical structure seems to be too large to be absorbed by the small intestine.

弗吉尼亞理工學院的研究於3月發表在《農業與食品化學期刊》(The Journal of Agricultural and Food Chemistry)上，其結果與路易斯安納州立大學的結果非常一致。弗吉尼亞理工學院的研究者給健康的試驗用鼠餵食高脂肪食物。並給其中一些老鼠餵食無糖的可可提取物；另一些則餵食各種從可可中提取的黃酮醇。12周後，大多數老鼠變得肥胖而不健康，表現出胰島素抵抗、高血糖和初期糖尿病症狀。但其中一些並沒有增重。這些沒有增重的老鼠得到的黃酮醇化學結構過大，無法在小腸內吸收。

What the results suggest, says Andrew Neilson, an assistant professor at Virginia Tech and the senior author of the mouse study, is that "there is something going on with cocoa in the colon," but what that means for chocolate lovers is not clear. Future experiments, he hopes, will tease out why one flavonol group impeded weight gain and the others did not. Do not hold your breath for a cocoa-based diet pill anytime soon, though. Cocoa's biochemical impacts are "extremely complex," he says.

弗吉尼亞理工大學助理教授和老鼠研究領域內的資深撰稿人安德魯·尼爾森(Andrew Neilson)說，這些實驗結果表明“腸道內部的可可粉發生了一些事情”，但這一結果對巧克力愛好者意味着什麼尚不分明。他希望在未來的試驗中可以發現爲什麼某一種黃酮醇可以阻止增重，另一種則不能。但是，不要馬上就去弄以可可爲原料的減肥藥丸。他說，可可的生物化學影響“非常複雜”。

Sadly, Dr. Neilson also points out that cocoa is not a chocolate bar, something whose added ingredients and processing reduce the number and type of flavonols, increase calories (cocoa itself has very few) and possibly change the response of gut bacteria to the cocoa. "The evidence does not show that you can eat a chocolate bar every day and expect to improve your health," he says. A few tablespoons of unsweetened cocoa powder sprinkled onto oatmeal or a handful of cocoa nibs — bits of the cacao bean, available at natural-food stores — would be better, he says less than sweetly.

不幸的是，尼爾森博士還指出，可可跟巧克力不是一回事。有時巧克力中添加的原料和加工工序會減少黃酮醇的含量和種類，增加卡路里（可可本身所含的卡路里很少），因此可能會改變腸道菌羣對可可的反應。“實驗結果並不表明你可以每天都吃一大塊巧克力，指望這樣能夠改善健康，”他說。在燕麥中加入幾湯匙無糖可可粉或一把可可豆碎粒（天然食品店可以買到）會比含糖的巧克力好些，他說。