抗生素治療可能對情緒有長期負面影響

現已有證據顯示：抗生素治療可能對情緒有長期負面影響。There is now evidence to suggest that antibiotic treatments may have long term negative effects upon mood.

腸道細菌會如何影響大腦健康？How do gut bugs affect brain health?

http://blog.oup.com/2015/06/gut-bugs-brain-health/

                                          我們的大腦和我們的腸道細菌以一種共生關係在生活。our brain lives in a symbiotic relationship with the bugs in our gut. 無論我們吃甚麼，腸道細菌也吃。Whatever we eat, they eat.腸道細菌會以各種方式來幫助優化我們的大腦功能，作為回報。In return, they help our brain function optimally in a variety of ways.

在過去的幾年中，腸道細菌日益明顯的是，人體內缺乏腸道細菌，我們的大腦認知功能就無法發展到目前水平。During the past few years, it has become increasingly apparent that in the absence of bacteria humans would never have evolved to our current level of cognitive performance

我們的大腦是深刻依賴這些腸道細菌製造大範圍的化學物質。Our brains are profoundly dependent upon a wide range of chemicals produced by these gut bugs. 例如，如果沒有這些腸道微生物，我們大腦扮演調控情感關鍵角色的血清素神經元，會失控發揮。 For example, without these gut microbes our brains don’t correctly develop the serotonin neurons that play a key role in the control of emotion.

每一個人體的大細胞，大約有100到1000個的微生物在您體內、體表一起共生。For every one of your big human cells, roughly 100 to 1000 little bugs live alongside and inside of you. 如果你要計算您體內、體表所有的細胞一起共生的微生物， If you were to count all of the cells on and inside of you that are not actually you,會有數百萬億數字的微生物，they would number in the hundreds of trillions, 大約每平方厘米內的皮膚表面有一百萬微生物一起共生。with approximately one million of these microbes living within every square centimeter of your skin.

這些腸道微生物不是單純來湊熱鬧，腸道微生物可能讓人類成為地球上的優勢物種。These bugs were not simply along for the ride as we became the dominant species on this planet; they made the journey possible.在約500萬年前的寒武世紀，當生物從單細胞進化成全多細胞生物個體，這些細菌和病毒很快就發現完全和生物個體整合一起共生。As soon as individual cells evolved into fully multicellular organisms during the Cambrian period about 500 million years ago these bacteria and viruses quickly discovered the fantastic survival benefits of fully integrating themselves. 這些和生物個體整合一起共生的細菌和病毒一旦出現，他們從來就未離開過。 Once there, they never left.

這些很多萬億駐留在腸道細菌的總重量超過兩磅，由於人體不斷提供食物給這些腸道細菌持續繁殖後代。The total weight of the many trillions of bugs that reside in your gut is over two pounds and they are multiplying constantly thanks to all of the food you are providing them. 這些腸道細菌會不斷和腸道病毒戰鬥求生存。They are also in a constant battle for survival. 在腸道病毒會殺死很多腸道細菌，腸道細菌屍體在乾糞便中約佔60％（現在知道腸道細菌屍體經糞便排出）。The viruses in your gut kill so many bacteria every minute that their carcasses account for about 60% of the dry mass of your feces (now you know what is in there).

腸道細菌製造許多不同的化學物質，會影響大腦功能。Gut bacteria produce many different chemicals that can influence brain function. 這些腸道細菌製造的不同化學物質，會將我們的飲食中的碳水複合物轉換成脂肪酸、丁酸，醋酸，丙酸。They convert the complex carbohydrates in our diet to the fatty acids butyrate, acetate, and propionate. 丁酸(Butyrate)可以輕易地離開腸道進入大腦，丁酸(Butyrate)在大腦會影響大腦衍生神經營養因子（BDNF）的濃度。 Butyrate can easily leave the gut and enter the brain, where it can influence the levels of the brain-derived neurotrophic factor (BDNF). 大腦衍生神經營養因子（BDNF）扮演神經元的複製和存活及大腦學習和記憶能力的重要角色。BDNF plays a critical role in the birth and survival of neurons and the ability of the brain to learn and remember. 體內大腦衍生神經營養因子(BDNF)濃度降低與認知功能受損和憂鬱沮喪有關。 Reduced levels of BDNF are correlated with impaired cognitive function and depression.

腸道細菌也製造神經傳遞物質：正腎上腺素(norepinephrine)，多巴胺(Dpoamine)，乙醯膽鹼(Acetylcholine)，和伽馬氨基丁酸（GABA）。Gut bacteria also produce the neurotransmitters norepinephrine, dopamine, acetylcholine, and GABA. 雖然這些神經傳遞物質不能穿過血腦屏障，但這些神經傳遞物質透過迷走神經的反應作用，間接影響大腦功能。Although these molecules cannot cross the blood brain barrier, they indirectly affect brain function via their actions at the vagus nerve. 益生菌嬰兒雙歧桿菌(比菲德氏菌)35624對帶憂鬱症動物具有抗憂鬱作用，因為嬰兒雙歧桿菌(比菲德氏菌)35624能夠以釋放色氨酸，製造血清素(serotonin)的前驅物。 The presence of the bacterium Bifidobacerium infantis 35624 has an antidepressant effect in animal models of depression due to its ability to release tryptophan, a precursor to the production of serotonin. 累積的證據顯示，腸道細菌在神經系統的發育和成熟中扮演關鍵角色，並可能與情緒和行為異常及眾多的退行性神經疾病有關。 Accumulating evidence suggests that gut bugs play key roles in both the developing and mature nervous system, and may contribute to emotional and behavioral disorders as well as numerous neurodegenerative diseases.