说起全球的健康饮食方式,种类可不在少数,我们耳熟能详的地中海饮食、DASH饮食、冲绳饮食等,都是名单上的“常驻嘉宾”。而近年来流行的无麸质饮食,似乎又把一个新鲜的健康饮食方式摆到了我们面前。

麸质饮食是指仅摄入不含麸质的食物,根据美国FDA的规定,只要食品中麸质含量小于20mg/kg就能加上这样的标识[1]。

这种饮食方式最早可以追溯到20世纪40年代。二战让欧洲的民众失去小麦来源,却意外改善了乳糜泻患者的健康状况。之后,研究人员发现根源在于小麦中高含量的麸质,并提倡在乳糜泻高发的白人群体中推广无麸质饮食[2]。

那么,麸质究竟是何物,于人类而言,它是敌还是友,所有人都该避免麸质吗?希望看完全文,你能得到答案。

麸质:藏身谷物中的面粉魔法师

提到麸质,第一反应以为是谷物表层的麸皮。其实不然,麸质并非碳水,而是天然存在于谷物中的多种蛋白质,主要为麦胶蛋白谷蛋白,又被统称为醇溶谷蛋白[3]。

在不同来源作物中,麸质的分子质量相差数倍,但都具有较高比例的脯氨酸和谷氨酰胺,不易溶于水,与乙醇有更好的亲和力[4]。

这种藏身在谷物中的神奇蛋白热稳定性强,并有很好的粘合与延展作用[5],可以保持面团的弹性和黏稠度,改善口感,增加面粉的“筋道”。原来身边北方朋友常称赞的“面好,有筋道”,实则是面粉中麸质含量较高。

保护心血管,或触发免疫反应?

麸质与人类爱恨纠葛

与人类生活息息相关的麸质,一直都是个热议话题,关于它与人类健康的关系,多年来,各方意见争论不休,支持者与反对者都没能说服对方。

#No.1 宝藏!麸质顶呱呱:

预防心血管、糖尿病全靠它

对于支持者而言,麸质简直人间宝藏超十万名健康男性与女性参与、25年长期追踪,这项研究终于在2017年公布了结果,研究人员发现在膳食中添加麸质能降低15%的心脏发病率[6]。

健康人群刻意避免麸质摄入,会影响有益全谷物的摄入,大大增加罹患心血管疾病的风险[7,8]。

此外,对于健康人群而言,摄入含麸质的全谷物食物还能显著预防2型糖尿病[9],并降低全因及各类原因的死亡率[10]。

不过,关于麸质功效背后的机制,目前还不太清楚,仅推测它可能有控制体重[11]、改善胰岛素敏感性的作用,因为全谷物摄入带来的益处无法被除麸质外的其他特点,如富含膳食纤维、镁及B族维生素及低升糖指数等完全解释[12]。

#No.2 毒药!麸质伸魔爪:

炎症、免疫反应全引发,还能让你精神分裂

再把话筒递给麸质的反对方,在他们口中,麸质摇身一变,成了个彻彻底底的毒药。

开篇曾介绍,麸质是一种脯氨酸和谷氨酰胺含量很高的蛋白混合物,正因如此,它在进入人体后,无法被蛋白酶完全消化成小肽或氨基酸[13]。这些残存的麸质片段可能会在肠道菌的作用下,产生促炎底物[14]。

对于健康人群而言,麸质残片的影响几乎可以忽略不计,然而对于小麦过敏乳糜泻非乳糜泻麸质敏感的人群而言,那真是碰都不能碰

在敏感人群中,摄入麸质带来的细胞毒性免疫原性肠道渗透性改变等负面作用被无限放大[15-17]。

敏感人群在意外摄入麸质后,可能会出现呼吸道过敏(哮喘、鼻炎)、皮肤问题(荨麻疹)、胃肠道反应(腹胀、腹泻、腹痛)等,严重时可能会导致休克[17]。

图注:麸质过敏导致的副作用

借助前沿生物与医学等手段,麸质的蛋白质基序(指保守序列,是构成任一特征序列的基本结构)被描绘出来,我们终于得见其隐藏在序列中的“暗杀密码”[18]。

图注:醇溶蛋白的基序结构

麸质的“黑暗序列”主要可分为四段(见上图不同色区),对麸质敏感的人可能会同时受到多个序列的影响

  1. 红色——发挥细胞毒性[19]

  2. 浅绿色——最具免疫原性,能与T细胞特异性结合,引发自身免疫反应[20]

  3. 蓝色——破坏肠道屏障,产生炎症,触发免疫反应[21]

  4. 深绿色——促进乳糜泻患者的炎症因子IL-8释放[22]

值得一提的是,相当数量的研究发现乳糜泻患者存在与大脑和情绪相关的疾病,其中包括认知障碍自闭症精神分裂症注意力缺陷综合征等[23-25],并在无麸质饮食干预后出现好转[26]。

虽然还未能发现乳糜泻患者这些神经系统疾病的直接诱因,但鉴于当前一众临床结果,学者们依旧把枪口对准了麸质。

人人都应无麸质?

不,麸质也许能让你活得更长

说到这里,若是硬要给麸质贴上个“”或“”的标签,派派客观讲,暂时真还做不到

但现实中,总有些“非医学力量”能走在科学前头,抢先对科学问题开展“解释”。在这种力量的推波助澜下,无麸质饮食走向了舞台中央。

不少公众人物也曾在节目或社交平台上表示自己支持无麸质饮食。

图注:部分采用无麸质饮食的明星

钟摆去往一侧,一边倒的言论让大家选择性忽视麸质的优点,口耳相传都是:麸质是毒蛋白,所有食物都该排除麸质。但事实果真如此吗?

虽然对于敏感人群而言,无麸质饮食的确能起到改善胃肠骨骼健康精神面貌等多方面作用[17]。

但放在机能正常吃下麸质也没什么异常反应的普通人身上,却没有证据说明无麸质饮食的益处[27],且长期摄入麸质也没让结肠炎风险率[28]、重要的代谢指标(如体脂率、胆固醇、甘油三酯、C反应蛋白等)[29]、认知能力[30]等走上下坡路。

不仅如此,麸质的酶解物还可能具有延寿价值

研究将模式动物秀丽线虫暴露在不同浓度的麸质酶解物环境中,发现线虫的肠道健康行动能力得到改善,最终拥有了更长的健康寿命[31]。这些益处可能要归功于麸质酶解物先前被证实的抗氧化[32]、修复肌肉损伤[33]及改善肝脏炎症[34]的功效。

图注:麸质酶解物添加对秀丽线虫寿命的影响

所以,限制麸质摄入不太可能为健康人群提供代谢益处,相反适量摄入或许有可能的延寿功效

那为何我们又用了“可能延寿”这样模糊的说法?这是由于当前麸质与生物体寿命关联的研究非常少,证据的逻辑链条确实有些单薄。

《麸质食用指南》

写到这里,我们可以初步下个结论:麸质并非洪水猛兽,可以吃,但部分人却真的碰不得

那么,我如何知道自己是否能吃麸质?日常生活中哪些食物富含麸质?无麸质饮食需求者又该吃什么?

如果你有上述困惑,那时光派精心总结的这份《麸质食用指南》刚好适合你。

不盲目跟风,选择适合自己的饮食方式,才是积极对待生活的正确方式。

—— TIMEPIE ——

不想错过延寿前沿精彩内容?

那就点进时光派主页关注吧!

参考文献

[1] Gluten and Food Labeling. (2021). Retrieved 23 July 2021, from https://www.fda.gov/food/nutrition-education-resources-materials/gluten-and-food-labeling

[2] Yan, D., & Holt, P. R. (2009). Willem Dicke. Brilliant clinical observer and translational investigator. Discoverer of the toxic cause of celiac disease. Clinical and translational science, 2(6), 446–448. https://doi.org/10.1111/j.1752-8062.2009.00167.x

[3] Wieser H. (2007). Chemistry of gluten proteins. Food microbiology, 24(2), 115–119. https://doi.org/10.1016/j.fm.2006.07.004

[4] Shewry P.R., Tatham A.S. (1999) The Characteristics, Structures and Evolutionary Relationships of Prolamins. In: Shewry P.R., Casey R. (eds) Seed Proteins. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-4431-5_2

[5] Biesiekierski J. R. (2017). What is gluten?. Journal of gastroenterology and hepatology, 32 Suppl 1, 78–81. https://doi.org/10.1111/jgh.13703

[6] Lebwohl, B., Cao, Y., Zong, G., Hu, F. B., Green, P., Neugut, A. I., Rimm, E. B., Sampson, L., Dougherty, L. W., Giovannucci, E., Willett, W. C., Sun, Q., & Chan, A. T. (2017). Long term gluten consumption in adults without celiac disease and risk of coronary heart disease: prospective cohort study. BMJ (Clinical research ed.), 357, j1892. https://doi.org/10.1136/bmj.j1892

[7] Liu, S., Stampfer, M. J., Hu, F. B., Giovannucci, E., Rimm, E., Manson, J. E., Hennekens, C. H., & Willett, W. C. (1999). Whole-grain consumption and risk of coronary heart disease: results from the Nurses' Health Study. The American journal of clinical nutrition, 70(3), 412–419. https://doi.org/10.1093/ajcn/70.3.412

[8] Mellen, P. B., Walsh, T. F., & Herrington, D. M. (2008). Whole grain intake and cardiovascular disease: a meta-analysis. Nutrition, metabolism, and cardiovascular diseases : NMCD, 18(4), 283–290. https://doi.org/10.1016/j.numecd.2006.12.008

[9] de Munter, J. S., Hu, F. B., Spiegelman, D., Franz, M., & van Dam, R. M. (2007). Whole grain, bran, and germ intake and risk of type 2 diabetes: a prospective cohort study and systematic review. PLoS medicine, 4(8), e261. https://doi.org/10.1371/journal.pmed.0040261

[10] Johnsen, N. F., Frederiksen, K., Christensen, J., Skeie, G., Lund, E., Landberg, R., Johansson, I., Nilsson, L. M., Halkjær, J., Olsen, A., Overvad, K., & Tjønneland, A. (2015). Whole-grain products and whole-grain types are associated with lower all-cause and cause-specific mortality in the Scandinavian HELGA cohort. The British journal of nutrition, 114(4), 608–623. https://doi.org/10.1017/S0007114515001701

[11] Koh-Banerjee, P., Franz, M., Sampson, L., Liu, S., Jacobs, D. R., Jr, Spiegelman, D., Willett, W., & Rimm, E. (2004). Changes in whole-grain, bran, and cereal fiber consumption in relation to 8-y weight gain among men. The American journal of clinical nutrition, 80(5), 1237–1245.

[12] Liu, S., Stampfer, M. J., Hu, F. B., Giovannucci, E., Rimm, E., Manson, J. E., Hennekens, C. H., & Willett, W. C. (1999). Whole-grain consumption and risk of coronary heart disease: results from the Nurses' Health Study. The American journal of clinical nutrition, 70(3), 412–419. https://doi.org/10.1093/ajcn/70.3.412

[13] Um, C.Y., Campbell, P.T., Carter, B. et al. Association between grains, gluten and the risk of colorectal cancer in the Cancer Prevention Study-II Nutrition Cohort. Eur J Nutr 59, 1739–1749 (2020). https://doi.org/10.1007/s00394-019-02032-2

[14] Ferretti, G., Bacchetti, T., Masciangelo, S., & Saturni, L. (2012). Celiac Disease, Inflammation and Oxidative Damage: A Nutrigenetic Approach. Nutrients, 4(4), 243–257. doi:10.3390/nu4040243

[15] Sapone, A., Bai, J.C., Ciacci, C. et al. Spectrum of gluten-related disorders: consensus on new nomenclature and classification. BMC Med 10, 13 (2012). https://doi.org/10.1186/1741-7015-10-13

[16] Caminero, A., Nistal, E., Herrán, A. R., Pérez-Andrés, J., Vaquero, L., Vivas, S., . . . Casqueiro, J. (2014). Gluten Metabolism in Humans. Involvement of the Gut Microbiota. Wheat and Rice in Disease Prevention and Health, 157-170. doi:10.1016/B978-0-12-401716-0.00013-1

[17] Balakireva, A., & Zamyatnin, A. (2016). Properties of Gluten Intolerance: Gluten Structure, Evolution, Pathogenicity and Detoxification Capabilities. Nutrients, 8(10), 644. doi:10.3390/nu8100644

[18] Fasano A. (2011). Zonulin and its regulation of intestinal barrier function: the biological door to inflammation, autoimmunity, and cancer. Physiological reviews, 91(1), 151–175. https://doi.org/10.1152/physrev.00003.2008

[19] Maiuri, L., Troncone, R., Mayer, M., Coletta, S., Picarelli, A., De Vincenzi, M., Pavone, V., & Auricchio, S. (1996). In vitro activities of A-gliadin-related synthetic peptides: damaging effect on the atrophic coeliac mucosa and activation of mucosal immune response in the treated coeliac mucosa. Scandinavian journal of gastroenterology, 31(3), 247–253. https://doi.org/10.3109/00365529609004874

[20] Shan, L., Molberg, Ø., Parrot, I., Hausch, F., Filiz, F., Gray, G. M., Sollid, L. M., & Khosla, C. (2002). Structural basis for gluten intolerance in celiac sprue. Science (New York, N.Y.), 297(5590), 2275–2279. https://doi.org/10.1126/science.1074129

[21] Lammers, K. M., Lu, R., Brownley, J., Lu, B., Gerard, C., Thomas, K., Rallabhandi, P., Shea-Donohue, T., Tamiz, A., Alkan, S., Netzel-Arnett, S., Antalis, T., Vogel, S. N., & Fasano, A. (2008). Gliadin induces an increase in intestinal permeability and zonulin release by binding to the chemokine receptor CXCR3. Gastroenterology, 135(1), 194–204.e3. https://doi.org/10.1053/j.gastro.2008.03.023

[22] Lammers, K. M., Khandelwal, S., Chaudhry, F., Kryszak, D., Puppa, E. L., Casolaro, V., & Fasano, A. (2011). Identification of a novel immunomodulatory gliadin peptide that causes interleukin-8 release in a chemokine receptor CXCR3-dependent manner only in patients with coeliac disease. Immunology, 132(3), 432–440. https://doi.org/10.1111/j.1365-2567.2010.03378.x

[23] Bürk, K., Bösch, S., Müller, C. A., Melms, A., Zühlke, C., Stern, M., Besenthal, I., Skalej, M., Ruck, P., Ferber, S., Klockgether, T., & Dichgans, J. (2001). Sporadic cerebellar ataxia associated with gluten sensitivity. Brain : a journal of neurology, 124(Pt 5), 1013–1019. https://doi.org/10.1093/brain/124.5.1013

[24] Hu, W. T., Murray, J. A., Greenaway, M. C., Parisi, J. E., & Josephs, K. A. (2006). Cognitive impairment and celiac disease. Archives of neurology, 63(10), 1440–1446. https://doi.org/10.1001/archneur.63.10.1440

[25] Casella, S., Zanini, B., Lanzarotto, F., Ricci, C., Marengoni, A., Romanelli, G., & Lanzini, A. (2012). Cognitive performance is impaired in coeliac patients on gluten free diet: a case-control study in patients older than 65 years of age. Digestive and liver disease : official journal of the Italian Society of Gastroenterology and the Italian Association for the Study of the Liver, 44(9), 729–735. https://doi.org/10.1016/j.dld.2012.03.008

[26] Ergün, C., Urhan, M., & Ayer, A. (2018). A review on the relationship between gluten and schizophrenia: Is gluten the cause? Nutritional Neuroscience, 21(7), 455-466. Retrieved from https://doi.org/10.1080/1028415X.2017.1313569. doi:10.1080/1028415X.2017.1313569

[27] Niland, B., & Cash, B. D. (2018). Health Benefits and Adverse Effects of a Gluten-Free Diet in Non-Celiac Disease Patients. Gastroenterology & hepatology, 14(2), 82–91.

[28] Liu, P. H., Lebwohl, B., Burke, K. E., Ivey, K. L., Ananthakrishnan, A. N., Lochhead, P., Olen, O., Ludvigsson, J. F., Richter, J. M., Chan, A. T., & Khalili, H. (2019). Dietary Gluten Intake and Risk of Microscopic Colitis Among US Women without Celiac Disease: A Prospective Cohort Study. The American journal of gastroenterology, 114(1), 127–134. https://doi.org/10.1038/s41395-018-0267-5

[29] Behrendt, I., Fasshauer, M. & Eichner, G. Gluten intake and metabolic health: conflicting findings from the UK Biobank. Eur J Nutr 60, 1547–1559 (2021). https://doi.org/10.1007/s00394-020-02351-9

[30] Wang, Y., Lebwohl, B., Mehta, R., Cao, Y., Green, P., Grodstein, F., Jovani, M., Lochhead, P., Okereke, O. I., Sampson, L., Willett, W. C., Sun, Q., & Chan, A. T. (2021). Long-term Intake of Gluten and Cognitive Function Among US Women. JAMA network open, 4(5), e2113020. https://doi.org/10.1001/jamanetworkopen.2021.13020

[31] Zhang, W., Lv, T., Li, M., Wu, Q., Yang, L., Liu, H., Sun, D., Sun, L., Zhuang, Z., & Wang, D. (2013). Beneficial effects of wheat gluten hydrolysate to extend lifespan and induce stress resistance in nematode Caenorhabditis elegans. PloS one, 8(9), e74553. https://doi.org/10.1371/journal.pone.0074553

[32] Park, E. Y., Imazu, H., Matsumura, Y., Nakamura, Y., & Sato, K. (2012). Effects of peptide fractions with different isoelectric points from wheat gluten hydrolysates on lipid oxidation in pork meat patties. Journal of agricultural and food chemistry, 60(30), 7483–7488. https://doi.org/10.1021/jf301532e

[33] Aoki, K., Kohmura, Y., Suzuki, Y., Koikawa, N., Yoshimura, M., Aoba, Y., Fukushi, N., Sakuraba, K., Nagaoka, I., & Sawaki, K. (2012). Post-training consumption of wheat gluten hydrolysate suppresses the delayed onset of muscle injury in soccer players. Experimental and therapeutic medicine, 3(6), 969–972. https://doi.org/10.3892/etm.2012.539

[34] Sato, K., Egashira, Y., Ono, S., Mochizuki, S., Shimmura, Y., Suzuki, Y., Nagata, M., Hashimoto, K., Kiyono, T., Park, E. Y., Nakamura, Y., Itabashi, M., Sakata, Y., Furuta, S., & Sanada, H. (2013). Identification of a hepatoprotective peptide in wheat gluten hydrolysate against D-galactosamine-induced acute hepatitis in rats. Journal of agricultural and food chemistry, 61(26), 6304–6310. https://doi.org/10.1021/jf400914e