膳食纖維是一種多糖,它既不能被胃腸道消化吸收,也不能產(chǎn)生能量。因此,曾一度被認(rèn)為是一種“無營養(yǎng)物質(zhì)”而長期得不到足夠的重視。近年來,隨著營養(yǎng)學(xué)和相關(guān)科學(xué)的深入發(fā)展,人們逐漸發(fā)現(xiàn)了膳食纖維具有相當(dāng)重要的生理作用。以致于在膳食構(gòu)成越來越精細(xì)的今天,膳食纖維更成為學(xué)術(shù)界和普通百姓關(guān)注的物質(zhì),并被營養(yǎng)學(xué)家列為“第七營養(yǎng)素”,是平衡膳食結(jié)構(gòu)的必需營養(yǎng)素之一。 全球面臨膳食纖維攝入不足問題! |
那么,30g膳食纖維到底是怎樣的呢,如下圖所示。結(jié)合我國居民膳食纖維攝入明顯不足,想要在短時間內(nèi)改變大眾的飲食習(xí)慣,從日常飲食增加膳食纖維攝入量并不容易,所以人們需要通過飲食其他食品或藥品來達到膳食纖維正常量。 膳食纖維分類 膳食纖維按照其溶解性,可分為水溶性膳食纖維和水不溶性膳食纖維。水溶性膳食纖維由于其良好的溶解性、穩(wěn)定性以及平和的口感等特性,應(yīng)用于飲料、乳制品、糖果、啤酒等領(lǐng)域,水不溶性膳食纖維因其良好的溶脹性能,能夠為產(chǎn)品提供必要的體積,常用于面包、飲料、餅干、乳制品等食品中。 水溶性膳食纖維是能夠溶解于水中的纖維類型。具有黏性,能在腸道中大量吸收水分,使糞便保持柔軟狀態(tài)。水溶性纖維能有效促進腸道有益菌繁殖,調(diào)節(jié)腸道微生態(tài)平衡。常見的水溶性膳食纖維包括聚葡萄糖、菊粉、低聚果糖、低聚木糖、低聚異麥芽糖、低聚半乳糖、大豆低聚糖等。 水不溶性膳食纖維主要包括纖維素、半纖維素和木質(zhì)素等。水不溶性膳食纖維能吸收水分,軟化糞便,增加糞便的體積,以刺激腸的蠕動,加速排便,從而減少糞便中有害物質(zhì)與腸道接觸的時間。 膳食纖維能帶來哪些益處? ? 減少疾病風(fēng)險及降低全因死亡率 2019年Lancet上發(fā)表的一項大型研究,涉及1.35億人年的前瞻性隊列研究數(shù)據(jù)和4635名成年人的臨床試驗數(shù)據(jù),發(fā)現(xiàn)對于廣大健康人群,膳食纖維攝入與慢性病發(fā)病和死亡率的降低顯著相關(guān):每增加8g/天的膳食纖維攝入量,可降低約7%全因死亡風(fēng)險、19%冠心病風(fēng)險、15%糖尿病風(fēng)險、8%大腸癌風(fēng)險。 研究發(fā)現(xiàn),膳食纖維還與直腸癌(CRC)死亡率和全因死亡率的下降、肺癌風(fēng)險降低、中年婦女高血壓風(fēng)險的降低等有關(guān)。 ? 改善胃腸道功能 2020年英國《自然》雜志子刊發(fā)表綜述文章,表明每攝入1g小麥纖維,就能將腸道通過時間減少0.78h;幾乎所有種類的膳食纖維,都能促進排便,并維持排便的穩(wěn)定性。 研究表明,膳食纖維還可降低放療患者急性和長期的胃腸道毒性、降低大便失禁風(fēng)險、幫助抵抗腸道病原體的感染等。 近年來,微生物組的研究,進一步揭示了膳食纖維是許多體內(nèi)有益微生物的食物,能夠促進有益微生物的生長,顯示出“益生元”的特性,既能刺激有益腸道菌群生長,如雙歧桿菌和乳酸菌,也有利于產(chǎn)生丁酸等短鏈脂肪酸,促進腸道健康。 ? 改善肥胖、調(diào)節(jié)血糖 2017年American journal of clinical nutrition上綜述了12項持續(xù)時間2-17周的隨機對照試驗,共涉及609名參與者,發(fā)現(xiàn)與對照組相比,可溶性膳食纖維最多可以幫助降低BMI 0.84,減重2.52kg,減脂0.41%,空腹血糖降低0.17mmol/L,空腹胰島素水平降低15.88pmol/L。 經(jīng)研究還發(fā)現(xiàn),每日50g膳食纖維可顯著改善2型糖尿病人糖脂代謝、膳食纖維可富集關(guān)鍵腸道菌快速有效地改善2型糖尿病。 ? 其它益處 多項研究表明,膳食纖維在緩解慢性炎癥、改善IBS和IBD、增強中年人的肌肉量和力量、預(yù)防憩室炎等方面也具有潛在的健康益處。 總而言之,膳食纖維對于人體健康來說十分重要,膳食纖維在改善肥胖、糖尿病、胃腸道、降低疾病發(fā)生/死亡風(fēng)險等方面的益處亦不容忽視,人體長期攝入富含膳食纖維的食物或補充膳食纖維的產(chǎn)品,不僅能為身體提供營養(yǎng)物質(zhì),還有助于促進健康的胃腸道功能,控制體重,減少疾病風(fēng)險及降低全因死亡率,對提升整體健康具有重要作用。 1. 《世界胃腸病學(xué)組織全球指南 飲食與腸道》&《中國居民膳食纖維攝入白皮書》 &《中國居民膳食營養(yǎng)素參考攝入量》 2. 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