膳食纤维和肠内营养

Dietary fibre and entera nutrition

传统的肠内营养液不含或几乎不含膳食纤维，是一种低渣饮食。因为粘稠度低和不含颗粒物质，很容易管饲。排便量和次数少，结肠处于休息状态被认为是肠内营养的优点。随着膳食纤维假设的提出，人们认为许多非感染性疾病是膳食纤维缺乏性疾病。很多人研究了在肠内营养和临床病人中补充膳食纤维可能的作用。起初的研究集中在结肠的功能，主要是便秘和腹泻，但结果都不确定。研究结果互相矛盾的可能原因有：观察时间短，抗菌素治疗的干扰，膳食纤维的种类不同等。最近快速积累的实验研究资料提示，膳食纤维的细菌分解产物短链脂肪酸（SCFA），可能比膳食纤维有更重要的作用。短链脂肪酸可促进结肠上皮细胞的增殖，防止肠外营养和低渣肠内营养引起的肠道粘膜萎缩，支持肠粘膜屏障功能，防止肠道细菌粘附、过度增殖和易位引起的损害。象所有膳食纤维有关的生理作用一样，短链脂肪酸的产生（速度和方式）也有很大的不同，这是因为膳食纤维的来源以及植物学的、物理学的和化学的结构不同。因此，一种膳食纤维不可能具有膳食纤维的所有作用，同时也不能将应用一种膳食纤维获得的研究结果推广到其它种类的膳食纤维。因此，确定一种标准的研究方法很重要，它应该规定用于研究的膳食纤维的特性（如剂量、颗粒大小、?

The traditional liquid enteral diets were designed as low residue preducts with little or no dietary fibre. Low viscosity and absence of particulate matters ensured ease of administration through feeding tubes. Low sbol weights and ftequencies and the large bowel being 'at rest' were seen as advantage in artificial enteral nutrition.With the advent of the dietary fibre hypothesis considering many non-infectious diseases as fibre deficiency diseases it appeared attractive to study the presumed virtues of fibre supplementation also in enteral diets and in the clinical context. Initially, studies forused on lame bowel functbo, mainly on constipation and diarrhea. In genera1, results were somewhat inconclusive,short study periods (constiPation),interference by antibiotic therapy (diarrhea) and variable fibre sources being like1y explanations for inconsistent findings. More recent but rapidly accumulating experimental evidence indicates that bacterial breakdown preducts of dietary fibre, the short-chain fatty acids (SCFA), may play a more important role than fibre per se. SCFA can enhance colon epithelial cell proliferation,may prevent gut atrophy associated with parenteral and low residue enteral feedings,and may also support the gut barrier function against the deleterbos sequence of bacterial adhesion, colonization and translocation. The SCFA production (rat and pattern), as all other fibre-mediated physiological effects, varies in wide limits depending on the fi bre source and its botanical, physical and chemical structure. It can therefore not be expected that a single fibre amrce will exhibit all ghtive attributes commonly attributed to dietary fibre,or that the results obtained with a particular fibre source can be extrapolated to other preparations. It is therefore important to develop and validate standard metheds, both for the characterization of dietary fibre (quantification, particle size, water binding, fermentability, solubility) and for the eva1uation of its clinical efficacy.