In our gut lies our enteric nervous system and it’s often called our second brain.

腸道位於腸神經系統，它通常被稱為我們的第二個大腦。

We have the same number of neurons lining our long tube of gut as we do in our spinal cord.

腸道擁有的神經元數量和脊髓相同。

And our gut is capable of reacting, like causing cravings for a taco, without even communicating with our first brain.

而且腸道可以讓我們不需要和大腦溝通就能立即反應，就像對墨西哥夾餅產生渴望一樣。

We have a community of bacteria living in our gut called our microbiome.

有一群細菌住在我們的腸道裡，它們叫做微生物基因組群。

It’s influenced by what you eat, your genes, age, stress levels and even where you live.

它們會被你吃的食物、你的基因、年齡、壓力層級，甚至是住在哪裡影響。

Certain bacteria thrive depending on what you eat, and we’re just starting to realise what it can do.

有些細菌會因為你吃的東西而成長得更繁盛，而現在我們正要開始了解這會有什麼影響。

Our microbiome can communicate with our Central Nervous System and influence our behaviour.

微生物會和中央神經系統溝通、傳遞，進而影響我們的行為。

In one study, germ-free mice, who aren't exposed to any bacteria since birth and don’t develop a microbiome, were compared to their germ-carrying counterparts in a maze test.

在一項研究中，自出生以來就沒有暴露在任何細菌環境裡，也沒有產生微生物的無菌老鼠，和其他有攜帶細菌的對照組進行迷宮測驗，並加以比較。

The germ-free mice showed a reduction in anxiety-like behaviors in response to the maze.

對於迷宮，無菌老鼠表現出較少的焦慮行為。

They were then housed with the other mice, and exposed to their germs.

接下來，無菌老鼠和其他老鼠安置在一起，並暴露於牠們的細菌之中。

But when they did the maze test again, they still showed a reduction in anxious behaviour.

但當無菌老鼠再次參與迷宮測驗時，牠們仍然表現出較少焦慮行為。

The researchers suggested gut-brain interactions are important to the development of stress systems, and the germ-free mice missed their window to develop one.

學者推測腸道和腦的相互作用是發展應力系統很重要的一環，而無菌老鼠錯失了發展系統的管道。

A recent study found that prebiotics, little fibre compounds that stimulate the growth of gut bacteria, have an anti-anxiety effect in people.

近期研究指出，益生元 (一種會刺激腸道細菌生長的膳食纖維化合物) 會對人體產生抗焦慮效果。

Participants were split into two groups, one that took prebiotics every day, and one that took a placebo.

參與實驗者被分成兩組，其中一組天天都吃益生元，另一組則是吃安慰劑。

After three weeks, those who took prebiotics had lower levels of the stress hormone cortisol,

三週過後，吃益生元的組別有較低的應激激素皮質醇，

and in tests they paid less attention to negative information and more attention to positive information.

而且在實驗中，他們較不關注負面訊息，比較關心正面資訊。

And other studies have shown that giving people fermented milk products containing probiotics, or healthy bacteria, twice a day for four weeks, altered brain activity in regions linked to emotion.

另外一項研究顯示，給人喝含有益生菌或是益菌的發酵乳製品，一天喝兩次並持續四週，會改變大腦中情感區域的活動表現。

The function of our gastro-intestinal tract goes far beyond just processing what we eat.

胃腸道的功能不只有消化食物。

Of course our second brain, our enteric nervous system, isn’t capable of conscious thought.

我們的第二大腦，也就是腸神經系統，當然不能夠有意識的思考。

But our microbiome can influence our behavior, our stress levels and even our mood.

但是微生物可以影響人類的行為、壓力水平，甚至我們的心情。

So the next time you have that feeling of butterflies in your stomach, remember there’s a whole lot more happening down there than you may realise.

所以下次當你忐忑不安時，記得其背後的作用遠遠比你想像到的還多。

For more awesome facts about yourself, head over to my friends Alltime Numbers, where they’ll take you through the human body in numbers.

若是想知道更多關於自己的超酷事實，請去 Alltime Numbers 的專頁看看，他們會用數字帶領你穿梭於人體的奧妙世界。

And if you don’t already, subscribe to BrainCraft for a new, brainy video every Thursday.

如果你還沒有訂閱 BrainCraft，我們每個星期四都會有新的知識影片，快訂閱吧！