說(shuō)起全球的健康飲食方式，種類可不在少數(shù)，我們耳熟能詳?shù)?strong>地中海飲食、DASH飲食、沖繩飲食等，都是名單上的“常駐嘉賓”。而近年來(lái)流行的無(wú)麩質(zhì)飲食，似乎又把一個(gè)新鮮的健康飲食方式擺到了我們面前。

無(wú)麩質(zhì)飲食是指僅攝入不含麩質(zhì)的食物，根據(jù)美國(guó)FDA的規(guī)定，只要食品中麩質(zhì)含量小于20mg/kg就能加上這樣的標(biāo)識(shí)[1]。

這種飲食方式最早可以追溯到20世紀(jì)40年代。二戰(zhàn)讓歐洲的民眾失去小麥來(lái)源，卻意外改善了乳糜瀉患者的健康狀況。之后，研究人員發(fā)現(xiàn)根源在于小麥中高含量的麩質(zhì)，并提倡在乳糜瀉高發(fā)的白人群體中推廣無(wú)麩質(zhì)飲食[2]。

那么，麩質(zhì)究竟是何物，于人類而言，它是敵還是友，所有人都該避免麩質(zhì)嗎？希望看完全文，你能得到答案。

麩質(zhì)：藏身谷物中的面粉魔法師

提到麩質(zhì)，第一反應(yīng)以為是谷物表層的麩皮。其實(shí)不然，麩質(zhì)并非碳水，而是天然存在于谷物中的多種蛋白質(zhì)，主要為麥膠蛋白和谷蛋白，又被統(tǒng)稱為醇溶谷蛋白[3]。

在不同來(lái)源作物中，麩質(zhì)的分子質(zhì)量相差數(shù)倍，但都具有較高比例的脯氨酸和谷氨酰胺，不易溶于水，與乙醇有更好的親和力[4]。

這種藏身在谷物中的神奇蛋白熱穩(wěn)定性強(qiáng)，并有很好的粘合與延展作用[5]，可以保持面團(tuán)的彈性和黏稠度，改善口感，增加面粉的“筋道”。原來(lái)身邊北方朋友常稱贊的“面好，有筋道”，實(shí)則是面粉中麩質(zhì)含量較高。

保護(hù)心血管，或觸發(fā)免疫反應(yīng)？

麩質(zhì)與人類愛(ài)恨糾葛

與人類生活息息相關(guān)的麩質(zhì)，一直都是個(gè)熱議話題，關(guān)于它與人類健康的關(guān)系，多年來(lái)，各方意見(jiàn)爭(zhēng)論不休，支持者與反對(duì)者都沒(méi)能說(shuō)服對(duì)方。

#No.1 寶藏！麩質(zhì)頂呱呱：

預(yù)防心血管、糖尿病全靠它

對(duì)于支持者而言，麩質(zhì)簡(jiǎn)直人間寶藏。超十萬(wàn)名健康男性與女性參與、25年長(zhǎng)期追蹤，這項(xiàng)研究終于在2017年公布了結(jié)果，研究人員發(fā)現(xiàn)在膳食中添加麩質(zhì)能降低15%的心臟發(fā)病率[6]。

健康人群刻意避免麩質(zhì)攝入，會(huì)影響有益全谷物的攝入，大大增加罹患心血管疾病的風(fēng)險(xiǎn)[7,8]。

此外，對(duì)于健康人群而言，攝入含麩質(zhì)的全谷物食物還能顯著預(yù)防2型糖尿病[9]，并降低全因及各類原因的死亡率[10]。

不過(guò)，關(guān)于麩質(zhì)功效背后的機(jī)制，目前還不太清楚，僅推測(cè)它可能有控制體重[11]、改善胰島素敏感性的作用，因?yàn)?strong>全谷物攝入帶來(lái)的益處無(wú)法被除麩質(zhì)外的其他特點(diǎn)，如富含膳食纖維、鎂及B族維生素及低升糖指數(shù)等完全解釋[12]。

#No.2 毒藥！麩質(zhì)伸魔爪：

炎癥、免疫反應(yīng)全引發(fā)，還能讓你精神分裂

再把話筒遞給麩質(zhì)的反對(duì)方，在他們口中，麩質(zhì)搖身一變，成了個(gè)徹徹底底的毒藥。

開(kāi)篇曾介紹，麩質(zhì)是一種脯氨酸和谷氨酰胺含量很高的蛋白混合物，正因如此，它在進(jìn)入人體后，無(wú)法被蛋白酶完全消化成小肽或氨基酸[13]。這些殘存的麩質(zhì)片段可能會(huì)在腸道菌的作用下，產(chǎn)生促炎底物[14]。

對(duì)于健康人群而言，麩質(zhì)殘片的影響幾乎可以忽略不計(jì)，然而對(duì)于小麥過(guò)敏、乳糜瀉和非乳糜瀉麩質(zhì)敏感的人群而言，那真是碰都不能碰。

在敏感人群中，攝入麩質(zhì)帶來(lái)的細(xì)胞毒性、免疫原性和腸道滲透性改變等負(fù)面作用被無(wú)限放大[15-17]。

敏感人群在意外攝入麩質(zhì)后，可能會(huì)出現(xiàn)呼吸道過(guò)敏（哮喘、鼻炎）、皮膚問(wèn)題（蕁麻疹）、胃腸道反應(yīng)（腹脹、腹瀉、腹痛）等，嚴(yán)重時(shí)可能會(huì)導(dǎo)致休克[17]。

圖注：麩質(zhì)過(guò)敏導(dǎo)致的副作用

借助前沿生物與醫(yī)學(xué)等手段，麩質(zhì)的蛋白質(zhì)基序（指保守序列，是構(gòu)成任一特征序列的基本結(jié)構(gòu)）被描繪出來(lái)，我們終于得見(jiàn)其隱藏在序列中的“暗殺密碼”[18]。

圖注：醇溶蛋白的基序結(jié)構(gòu)

麩質(zhì)的“黑暗序列”主要可分為四段（見(jiàn)上圖不同色區(qū)），對(duì)麩質(zhì)敏感的人可能會(huì)同時(shí)受到多個(gè)序列的影響。

• 紅色——發(fā)揮細(xì)胞毒性[19]

• 淺綠色——最具免疫原性，能與T細(xì)胞特異性結(jié)合，引發(fā)自身免疫反應(yīng)[20]

• 藍(lán)色——破壞腸道屏障，產(chǎn)生炎癥，觸發(fā)免疫反應(yīng)[21]

• 深綠色——促進(jìn)乳糜瀉患者的炎癥因子IL-8釋放[22]
  

值得一提的是，相當(dāng)數(shù)量的研究發(fā)現(xiàn)乳糜瀉患者存在與大腦和情緒相關(guān)的疾病，其中包括認(rèn)知障礙、自閉癥、精神分裂癥和注意力缺陷綜合征等[23-25]，并在無(wú)麩質(zhì)飲食干預(yù)后出現(xiàn)好轉(zhuǎn)[26]。

雖然還未能發(fā)現(xiàn)乳糜瀉患者這些神經(jīng)系統(tǒng)疾病的直接誘因，但鑒于當(dāng)前一眾臨床結(jié)果，學(xué)者們依舊把槍口對(duì)準(zhǔn)了麩質(zhì)。

人人都應(yīng)無(wú)麩質(zhì)？

不，麩質(zhì)也許能讓你活得更長(zhǎng)

說(shuō)到這里，若是硬要給麩質(zhì)貼上個(gè)“好”或“壞”的標(biāo)簽，派派客觀講，暫時(shí)真還做不到。

但現(xiàn)實(shí)中，總有些“非醫(yī)學(xué)力量”能走在科學(xué)前頭，搶先對(duì)科學(xué)問(wèn)題開(kāi)展“解釋”。在這種力量的推波助瀾下，無(wú)麩質(zhì)飲食走向了舞臺(tái)中央。

不少公眾人物也曾在節(jié)目或社交平臺(tái)上表示自己支持無(wú)麩質(zhì)飲食。

圖注：部分采用無(wú)麩質(zhì)飲食的明星

鐘擺去往一側(cè)，一邊倒的言論讓大家選擇性忽視麩質(zhì)的優(yōu)點(diǎn)，口耳相傳都是：麩質(zhì)是毒蛋白，所有食物都該排除麩質(zhì)。但事實(shí)果真如此嗎？

雖然對(duì)于敏感人群而言，無(wú)麩質(zhì)飲食的確能起到改善胃腸、骨骼健康與精神面貌等多方面作用[17]。

但放在機(jī)能正常、吃下麩質(zhì)也沒(méi)什么異常反應(yīng)的普通人身上，卻沒(méi)有證據(jù)說(shuō)明無(wú)麩質(zhì)飲食的益處[27]，且長(zhǎng)期攝入麩質(zhì)也沒(méi)讓結(jié)腸炎風(fēng)險(xiǎn)率[28]、重要的代謝指標(biāo)（如體脂率、膽固醇、甘油三酯、C反應(yīng)蛋白等）[29]、認(rèn)知能力[30]等走上下坡路。

不僅如此，麩質(zhì)的酶解物還可能具有延壽價(jià)值！

研究將模式動(dòng)物秀麗線蟲(chóng)暴露在不同濃度的麩質(zhì)酶解物環(huán)境中，發(fā)現(xiàn)線蟲(chóng)的腸道健康與行動(dòng)能力得到改善，最終擁有了更長(zhǎng)的健康壽命[31]。這些益處可能要?dú)w功于麩質(zhì)酶解物先前被證實(shí)的抗氧化[32]、修復(fù)肌肉損傷[33]及改善肝臟炎癥[34]的功效。

圖注：麩質(zhì)酶解物添加對(duì)秀麗線蟲(chóng)壽命的影響

所以，限制麩質(zhì)攝入不太可能為健康人群提供代謝益處，相反適量攝入或許有可能的延壽功效。

那為何我們又用了“可能延壽”這樣模糊的說(shuō)法？這是由于當(dāng)前麩質(zhì)與生物體壽命關(guān)聯(lián)的研究非常少，證據(jù)的邏輯鏈條確實(shí)有些單薄。

《麩質(zhì)食用指南》

寫到這里，我們可以初步下個(gè)結(jié)論：麩質(zhì)并非洪水猛獸，可以吃，但部分人卻真的碰不得。

那么，我如何知道自己是否能吃麩質(zhì)？日常生活中哪些食物富含麩質(zhì)？無(wú)麩質(zhì)飲食需求者又該吃什么？

如果你有上述困惑，那時(shí)光派精心總結(jié)的這份《麩質(zhì)食用指南》剛好適合你。

不盲目跟風(fēng)，選擇適合自己的飲食方式，才是積極對(duì)待生活的正確方式。

—— TIMEPIE ——

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