維生素B12主要是在回腸末端吸收，并且需要有內因子的輔助。體內維生素B12儲存量大約2000 μg，平均每天只需要量是2 μg。盡管存在大量的儲備，減肥手術(shù)后維生素B12缺乏還是很常見(jiàn)。根據維生素B12在體內的吸收特點(diǎn)，吸收不良性術(shù)式后發(fā)生維生素B12缺乏的可能性更大。Brolin等［11］估計RYGB術(shù)后維生素B12缺乏發(fā)生率是12%~33%，3年后隨訪(fǎng)證實(shí)發(fā)生率為33%。另外一些研究也有類(lèi)似的發(fā)現，RYGB術(shù)后1、2、4年維生素B12缺乏的發(fā)生率分別是33%、36%、33%。BDP手術(shù)后1~2年發(fā)生維生素B12缺乏的患者有12.5%［35］，4年后22%［12］。BDP術(shù)式中行或不行十二指腸轉換對維生素B12水平無(wú)明顯影響。單純的限制性手術(shù)后一般與維生素B12缺乏不相關(guān)。僅有一個(gè)小型的研究發(fā)現術(shù)后1年血葉酸水平下降，但是維生素B12水平正常［16］。
減肥手術(shù)后存在維生素B12缺乏的患者中53%希林實(shí)驗陰性，89%存在內因子缺乏［36］。因此，口服維生素B12不推薦，特別是在內因子缺乏的情況下，影響其在回腸終末端的吸收。目前推薦的補充維生素B12的方案是每月皮下或肌注1000 μg。但是也有研究表示口服維生素B12在減肥手術(shù)也是有效的，不過(guò)需要較大劑量（350μg/d），是飲食參考劑量的175倍［37］。
6.微量元素：鋅在十二指腸及空腸上段吸收，主要通過(guò)糞便排出，少量通過(guò)泌尿系統排出體外。改變腸道結構通常會(huì )影響鋅的吸收。缺鋅在臨床上的表現主要是影響免疫功能，改變味覺(jué)，延遲傷口愈合，導致腸病性肢皮炎。脫發(fā)在減肥手術(shù)后很常見(jiàn)，但是目前對此研究很少，推測這可能與蛋白攝入不足以及鋅缺乏相關(guān)［38］。大約50%的接受BPD或DS-BPD的患者鋅水平下降，11%患者即使在每日補充復合維生素的情況下依然出現鋅缺乏［6］。
對減肥手術(shù)后血鎂變化的臨床研究較少，而且現有研究發(fā)現血鎂缺乏的發(fā)生率也較低。Marceau等［39］報道BPD術(shù)后4~10年無(wú)一例出現鎂缺乏。Dolan等［18］報道BPD術(shù)后2年鎂缺乏發(fā)生率僅5%。但是也有研究報道減肥手術(shù)后血鎂是增加的［40］。所有目前已知的報道中，均無(wú)因鎂缺乏導致明顯臨床癥狀的報道。減肥手術(shù)后硒缺乏發(fā)生率在14.5%~22%，沒(méi)有發(fā)現明顯與之相關(guān)臨床并發(fā)癥［39］。僅有個(gè)別臨床案例報告認為減肥手術(shù)后硒缺乏導致擴張性心肌病，建議減少手術(shù)后對硒進(jìn)行監測［41］。鋅離子吸收很大程度上依賴(lài)脂肪的吸收。因此吸收不良術(shù)式后出現鋅缺乏較常見(jiàn)。據報道BPD術(shù)后50%的患者出現鋅缺乏［42］，但是也有研究報道只有10.8%［18］。鋅缺乏常引起脫發(fā)。但是減肥術(shù)后脫發(fā)也可能是體重下降或是蛋白營(yíng)養不良所導致。對減肥手術(shù)后微量元素含量的變化，不同的研究得出的結論差異較大。這可能與某些礦物質(zhì)或微量元素常與白蛋白結合，當出現低蛋白血癥時(shí)，可能會(huì )出現代謝異常相關(guān)。因此，血漿中微量元素（鋅、硒等），礦物質(zhì)（鈣、鎂等）可能并不能反應組織或器官存儲狀況，依賴(lài)血漿中的濃度不足以評價(jià)這些物質(zhì)的缺乏。目前為止，減肥手術(shù)后導致鋅、硒、鎂缺乏引起的臨床癥狀報道很少，所以對術(shù)后補充這些微量元素，目前缺少明確的證據。
三、結論
減肥手術(shù)能夠有效治療肥胖，緩解糖尿病、高血壓、血脂紊亂等慢性疾病，但是手術(shù)內分泌代謝并發(fā)癥也會(huì )給患者帶來(lái)極大風(fēng)險。如何減少這些風(fēng)險并最大化患者手術(shù)獲益這是我們未來(lái)需要關(guān)注的焦點(diǎn)。現有的研究結果對預測不同類(lèi)型的減肥手術(shù)后會(huì )導致何種營(yíng)養不良，以及如何有效處理這些并發(fā)癥，仍有沒(méi)太多證據形成共識，需要進(jìn)一步研究。蛋白質(zhì)、鐵、鈣、維生素D、以及維生素B12缺乏是減肥手術(shù)后最常見(jiàn)營(yíng)養不良類(lèi)型，但可能減肥手術(shù)后導致?tīng)I養物質(zhì)的改變并不僅限于此。盡可能早期發(fā)現以及給予針對性的干預措施可能是目前最有效臨床治療手段。因此內分泌科醫師早期參與到患者減肥手術(shù)治療過(guò)程中，可能會(huì )更加有效減少術(shù)后營(yíng)養不良的發(fā)生。
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