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【TED】食物是如何影响肠道的

2023-03-07 19:16 作者:TED资源  | 我要投稿

中英文稿

数万亿细菌、病毒和真菌 生活在我们身上及体内, 和它们保持良好平衡的关系 是对我们有利的。 它们一起形成肠道微生物群, 这是一个丰富的生态系统, 在我们的身体中发挥各种作用。 肠道细菌可以分解 体内无法消化的食物, 产生重要的营养物质, 调节免疫系统, 防止有害细菌。 我们目前还无法明确 健康的肠道需要哪些有益细菌, 但我们确切地知道, 对于健康的微生物群来说, 拥有多种细菌非常重要。 影响微生物群的因素有很多, 包括环境、 药品,如抗生素, 以及我们是否生于剖腹产。

 饮食也渐渐变成了 影响肠道健康的 主要因素之一。 虽然无法控制所有因素, 但我们可以通过关注饮食 来控制体内微生物群的平衡。 来自水果、蔬菜、坚果、豆类 和全谷类食物的膳食纤维 是肠道菌群最好的补给。 当细菌分解纤维时, 它们会产生短链脂肪酸, 滋养肠道屏障, 改善免疫功能, 帮助预防炎症, 从而降低癌症风险。 摄入的纤维越多, 肠道中消化纤维的细菌就越多。 在最近的一项研究中, 科学家们将南非农村人 长期食用的高纤维饮食, 换成非洲裔美国人的高脂多肉饮食。 改用高脂肪、低纤维的 西式饮食仅仅两周后, 非洲农村人实验组出现结肠炎症增加、 丁酸盐减少的现象。 这种短链脂肪酸, 可以降低患结肠癌的风险。 与此同时,改用高纤维、 低脂肪饮食的实验组 则出现相反的结果。 

当我们摄入低纤维加工食品时, 肠道细菌出现了什么问题呢? 对于肠道细菌来说, 纤维越少意味着补给越少, 致使肠道细菌挨饿,直至死亡。 这会使细菌多样性减少, 并产生饥饿细菌。 事实上,有些细菌甚至 开始吃黏液层。 特定的食物也会影响肠道细菌。 在最近的一项微生物组研究中, 科学家发现水果、 蔬菜、 茶、 咖啡、 红酒、 以及黑巧克力 都可以增加细菌多样性。 这些食物含有多酚, 一种天然抗氧化剂。 另一方面, 乳脂含量高的食物, 如全脂牛奶,加糖的苏打水 则会使细菌多样性降低。 

如何烹制食物也很重要。 最低限度加工的新鲜食品 通常含有更多纤维, 可以提供更多营养。 所以清蒸的, 淡炒的, 或生的蔬菜 通常比油炸菜品更有益。 还有一些食物制作方法, 可以切实地将有益细菌, 也称为益生菌,引入肠道。 发酵的食物中含有大量有益的益生菌, 如乳酸杆菌 和双歧杆菌。 在制冷工艺发明之前, 本来是作为一种保存食物的方式。 发酵这种传统工艺 一直广泛流传于全世界。 韩国泡菜、 德国酸菜、 印尼豆豉 和红茶菌等食物 为我们的饮食提供了多样性和活力。

 酸奶是另一种可以为肠道 带来有益菌的发酵食品, 但这并不意味着所有的 酸奶对我们都是有益的。 那些糖分较多、 细菌较少的品牌 可能对我们没有好处。 这些只是一般指导原则。 要彻底了解食物与我们体内 微生物群之间的相互作用, 还需要很多研究。 我们看到了正向相关性, 但肠道内部很难进行直接观察。 例如,我们目前还不知道 是这些食物直接 改变了细菌多样性, 还是发生了更加复杂的过程。 仅仅是刚开始研究肠道世界内部, 我们就已经初窥微生物 对消化系统健康的重要性。 好消息是我们可以 调动肠道里的细菌。 补充纤维、 多吃新鲜和发酵食品, 剩下的事情放心交给肠道, 它会让你变得强壮。

Trillions of bacteria, viruses, and fungi live on or inside of us, and maintaining a good, balanced relationship with them is to our advantage. Together, they form the gut microbiome, a rich ecosystem that performs a variety of functions in our bodies. The bacteria in our guts can break down food the body can't digest, produce important nutrients, regulate the immune system, and protect against harmful germs. We don't yet have the blueprint for exactly which good bacteria a robust gut needs, but we do know that it's important for a healthy microbiome to have a variety of bacterial species. Many factors affect our microbiomes, including our environment, medications like antibiotics, and even whether we were delivered by C-section or not. Diet, too, is emerging as one of the leading influences on the health of our guts. And while we can't control all these factors, we can manipulate the balance of our microbes by paying attention to what we eat. Dietary fiber from foods like fruits, vegetables, nuts, legumes, and whole grains is the best fuel for gut bacteria. When bacteria digest fiber, they produce short chain fatty acids that nourish the gut barrier, improve immune function, and can help prevent inflammation, which reduces the risk of cancer. And the more fiber you ingest, the more fiber-digesting bacteria colonize your gut.In a recent study, scientists exchanged the regular high-fiber dietsof a group of rural South Africans with the high-fat, meat-heavy diets of a group of African-Americans. After just two weeks on the high-fat, low-fiber, Western-style diet, the rural African group showed increased inflammation of the colon,as well as a decrease of butyrate. That's a short chain fatty acid thought to lower risk of colon cancer. Meanwhile, the group that switched to a high-fiber, low-fat diet had the opposite result. So what goes wrong with our gut bacteria when we eat low-fiber processed foods? Lower fiber means less fuel for the gut bacteria, essentially starving them until they die off. This results in less diversity and hungry bacteria. In fact, some can even start to feed on the mucus lining. We also know that specific foods can affect gut bacteria. In one recent microbiome study, scientists found that fruits, vegetables, tea, coffee, red wine, and dark chocolate were correlated with increased bacterial diversity. These foods contain polyphenols, which are naturally occurring antioxidant compounds. On the other hand, foods high in dairy fat, like whole milk, and sugar-sweetened sodas were correlated with decreased diversity. How food is prepared also matters. Minimally processed, fresh foods generally have more fiber and provide better fuel. So lightly steamed, sautéed, or raw vegetables are typically more beneficial than fried dishes. There are also ways of preparing food that can actually introduce good bacteria, also known as probiotics, into your gut. Fermented foods are teeming with helpful probiotic bacteria, like lactobacillus and bifidobacteria. Originally used as a way of preserving foods before the invention of refrigeration, fermentation remains a traditional practice all over the world. Foods like kimchi, sauerkraut, tempeh, and kombucha provide variety and vitality to our diets. Yogurt is another fermented food that can introduce helpful bacteria into our guts. That doesn't necessarily mean that all yogurt is good for us, though. Brands with too much sugar and not enough bacteria may not actually help. These are just general guidelines. More research is needed before we fully understand exactly how any of these foods interact with our microbiomes. We see positive correlations, but the insides of our guts are difficult places to make direct observations. For instance, we don't currently know whether these foods are directly responsible for the changes in diversity, or if something more complicated is happening. While we're only beginning to explore the vast wilderness inside our guts, we already have a glimpse of how crucial our microbiomes are for digestive health. The great news is we have the power to fire up the bacteria in our bellies. Fill up on fibers, fresh and fermented foods, and you can trust your gut to keep you going strong.

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