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。
无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,主要为麦胶蛋白和谷蛋白,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、乳糜泻和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、免疫原性和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。
红色——发挥细胞毒性[19]
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]
蓝色——破坏肠道屏障,产生炎症,触发免疫反应[21]
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、精神分裂症和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“好”或“坏”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、骨骼健康与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与行动能力得到改善,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
热门跟贴