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.
近年来，大规模流行病学研究发现常吃黑巧克力者心脏病发病率比不吃黑巧克力的人要低。还有研究发现巧克力中含有黄醇酮，这是一种天然物质，可以降低疾病发病率。但黄醇酮是如何影响人体，特别是心脏，原理仍不分明。不过，弗吉尼亚理工大学与路易斯安那州立大学的新发现为巧克力的益处提供了一种奇异的解释：它因为难以消化，所以对健康格外有益。
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.
路易斯安那州立大学的研究者在玻璃容器中模拟人类的消化系统后得到了这个结论。其中一个器具用来模拟胃和小肠，内有消化酶，另一个器具用来模拟类似大肠的环境，内有从志愿者体内提取的肠道微生物。之后科学家把可可粉放入这些模拟肠胃的容器中。
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“小肠”系统分解并吸收了部分可可粉，但当许多巧克力内的黄醇酮被消化的同时，仍有大量可可粉末没有被消化。模拟大肠中的肠道菌群将黄醇酮进一步分解为代谢物，小到足以被血液吸收，我们已知它能抑制心脏炎症发病率。最后，未被消化的可可粉，在这个阶段主要是纤维，开始发酵，释放出能提升胆固醇水平的物质。在这个过程中又出现一种能改善健康的变化：消化可可粉的肠道菌群是非常有益的原生菌，诸如乳酸菌等。肠道摄入可可粉后，这些原生菌的数量开始增加，而葡萄球菌等不那么有益健康的菌种开始减少。
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.
弗吉尼亚理工学院的研究于3月发表在《农业与食品化学期刊》(The Journal of Agricultural and Food Chemistry)上，其结果与路易斯安纳州立大学的结果非常一致。弗吉尼亚理工学院的研究者给健康的试验用鼠喂食高脂肪食物。并给其中一些老鼠喂食无糖的可可提取物；另一些则喂食各种从可可中提取的黄酮醇。12周后，大多数老鼠变得肥胖而不健康，表现出胰岛素抵抗、高血糖和初期糖尿病症状。但其中一些并没有增重。这些没有增重的老鼠得到的黄酮醇化学结构过大，无法在小肠内吸收。
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.
弗吉尼亚理工大学助理教授和老鼠研究领域内的资深撰稿人安德鲁·尼尔森(Andrew Neilson)说，这些实验结果表明“肠道内部的可可粉发生了一些事情”，但这一结果对巧克力爱好者意味着什么尚不分明。他希望在未来的试验中可以发现为什么某一种黄酮醇可以阻止增重，另一种则不能。但是，不要马上就去弄以可可为原料的减肥药丸。他说，可可的生物化学影响“非常复杂”。
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，尼尔森博士还指出，可可跟巧克力不是一回事。有时巧克力中添加的原料和加工工序会减少黄酮醇的含量和种类，增加卡路里（可可本身所含的卡路里很少），因此可能会改变肠道菌群对可可的反应。“实验结果并不表明你可以每天都吃一大块巧克力，指望这样能够改善健康，”他说。在燕麦中加入几汤匙无糖可可粉或一把可可豆碎粒（天然食品店可以买到）会比含糖的巧克力好些，他说。
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