大肠激躁症饮食难以下咽的证据


  【24drs.com】专家们在美国胃肠科学院2015年会中表示,尽管有多种饮食是为了帮助大肠激躁症患者,但是缺乏支持它们的有力证据。
  
  安娜堡密西根大学的William Chey医师表示,当论及饮食时,是由病患主导,他们主动进来并咨询饮食,或者他们已经在使用某种饮食,或者,他们看到健康照护者建议饮食的某种替代类型。
  
  他指出,这对医师来说有点困难,因为医师没有那么多时间去读到全部的任何信息。
  
  Chey医师将这个状况比喻为1990年代电视风靡一时的经典电视剧-X档案(The X-Files),剧中,FBI专案探员追查来势汹汹的超自然现象。他解释,这个节目会采用一些当下流行的主题,添加足够的假科学让它变得可信。
  
  他认为,有多种饮食确实发生了一些作用,人们捕风捉影之后就渲染说它有「临床证据」,然后,病患就突然认为这些有科学验证。不幸的是,肠道疾病患者目前所用的各种饮食方法的支持证据相当少。
  
  Chey医师表示,这并不意谓著这些饮食无效,问题是我们无法确切知道。我们真正需要的是,应用如同药品的严谨科学方法。
  
  他回顾了关于大肠激躁症饮食处置的已知论述与猜测论述。
  
  他表示,没有标准化饮食,不过,一般会劝告患者避免过多的咖啡因、巧克力、酒、乳糖、山梨糖醇、高脂食物、垃圾食物。鼓励便秘(硬便)患者在饮食中多吃纤维,且要有足够时间安静地用餐。
  
  乳糜泻患者受麸质影响很大;麸质是在小麦籽胚乳中储存的蛋白质。
  
  Chey医师指出,不过,避免吃麸质的人大部份并没有乳糜泻,食品饮料界一窝蜂的推出无麸质啤酒、甚至有无麸质狗食。
  
  麸质敏感性或小麦敏感性的盛行率尚未知,这两个疾病在临床上与乳糜泻不同,但是在乳糜泻测试结果为阴性或不确定。这些病患大部份都报告指出,无麸质饮食有助改善。
  
  在非乳糜泻情况,麸质本身并无问题, 已有人提出,短链碳水化合物,也被简称为FODMAPs(发酵的寡糖、双糖、单糖和多元醇)才是罪魁祸首。
  
  摄取FODMAPs被认为会引发胃肠道疼痛、胀气、腹胀、和改变肠蠕动等症状。一系列复杂的渗透作用导致食物移动加速、细菌发酵,以及产生短链脂肪酸,而这又导致气体产生、改变运动性、内脏感觉、免疫活化和肠渗透性。
  
  果糖含量超过葡萄糖含量的水果,例如苹果、梨子、西瓜也含有FODMAPs,含有果聚醣的蔬菜,如:洋葱、韭菜、芦笋、朝鲜蓟也是,果聚醣是果糖分子的聚合链。
  
  小麦为主的产品,如面条、面包、谷物、蛋糕、饼干、含有山梨糖醇及乳糖的食物,以及含有三糖棉子糖的食物,如豆类、扁豆、小白菜和甘蓝,都可能会引起问题。
  
  Chey医师报告指出,一篇研究显示,吃富含FODMAPs的饮食2天之后,30名肠大激躁症患者呼吸产氢值显著上升(呼吸产氢值是乳糖、葡萄糖、或果糖不耐的一种征兆)且增加胃肠道症状和嗜睡(J Gastroenterol Hepatol. 2010;25:1366-1373)。
  
  一篇交叉研究显示,在30名肠激躁症患者与8名健康志愿者,使用低FODMAP饮食21天可以使整体症状、腹胀、疼痛、胀气都显著降低(Gastroenterology. 2014;146:67-75.e5)。
  
  加拿大安大略汉弥尔顿McMaster大学妇产科主任Paul Moayyedi医师提醒,吃低FODMAP饮食并不代表能简单地将麸质从饮食中除去。
  
  他表示,这是严格的,对病患来说是不容易的,他们不允许食用的食物项目相当多。
  
  举例来说,玉米糖浆是低FODMAP饮食的禁忌,但是枫糖浆是可以的。他指出,如果你住在加拿大或新英格兰,这或许不是问题,但是,在其它地方,这是个昂贵的提议。
  
  他表示,我们真的需要知道这是否有用,我们发现某些新东西且认为它不错,然后其它人进行研究,接著我们意识到这一切如毒药般可怕。最后,我们找到这是否值得的某些证据。
  
  Chey医师反驳指出,我不认为FODMAP饮食就是一切议题的终点,我认为FODMAP饮食对于肠胃道症状患者的饮食是具有相当重要角色的机转。
  
  资料来源:http://www.24drs.com/
  
  Native link:Evidence for IBS Diets Tough to Swallow

Evidence for IBS Diets Tough to Swallow

By Neil Osterweil
Medscape Medical News

HONOLULU — Despite the number of diets that purport to help people with irritable bowel syndrome, rigorous evidence supporting their use is lacking, experts said here at the American College of Gastroenterology 2015 Annual Meeting.

When it comes to diet, "patients are leading the way," said William Chey, MD, from the University of Michigan at Ann Arbor. "They are proactively coming in and asking about diets, or they're already on diets, or they're seeing some type of alternative healthcare provider who has recommended a diet."

"It's difficult for physicians who perhaps don't spend a lot of time reading about this space to sift through all the noise," he pointed out.

Dr Chey likened the current situation to the 1990s television cult classic The X-Files, in which FBI special agents track down menacing paranormal phenomena. The show "would take some popular theme and sprinkle just enough pseudo-science on it to make it believable," he explained.

"I think that's exactly what's happening with a lot of diets; people sort of spread around a little bit of special sauce, a little bit of magic dust, say that it's 'clinically proven,' and then suddenly patients believe it as scientifically validated," he said. "Unfortunately, there are very few data supporting the various diets that are being used by patients with GI illness right now."

Secret Sauce and Magic Dust

"That doesn't mean that diets don't work. The problem is that we don't know one way or the other. What we really need to do is to apply the same scientific rigor that we do to pharmaceuticals," said Dr Chey.

He reviewed what is known and what is conjecture about the role of diet in the management of irritable bowel syndrome.

There is no standardized diet, he said, although patients are frequently counseled to avoid excess caffeine, chocolate, alcohol, lactose, sorbitol, fatty foods, and junk foods. Patients with hard stools are encouraged to bulk up their diets with fiber and to allow sufficient time and quiet for meals.

People with celiac disease are seriously affected by gluten, a storage protein found in the endosperm of wheat kernels.

However, the vast majority of the people who shun gluten do not have celiac disease. And the food and beverage industry is cashing in on the craze, flogging everything from gluten-free beer to gluten-free dog food, Dr Chey pointed out.

The prevalence of gluten sensitivity or wheat sensitivity — which can be clinically indistinguishable from celiac disease but will yield negative or inconclusive results on celiac testing — is not known. Most of these patients report improvement with gluten-free diets.

Gluten itself might not be the problem in nonceliac disorders. It has been suggested that short-chain carbohydrates, also known as FODMAPs — fermentable oligo-, di-, monosaccharides and polyols — are the culprit.

The consumption of FODMAPs is thought to induce symptoms of GI pain, gas, bloating, and altered bowel movements. A complex series of osmotic effects leads to the acceleration of food transit, bacterial fermentation, and the production of short-chain fatty acids, which in turn lead to gas production, changes in motility, visceral sensation, immune activation, and bowel permeability.

More Fructose Than Glucose

Fruits in which the amount of fructose exceeds the level of glucose, such as apples, pears, watermelons, contain FODMAPs, as do vegetables containing fructan, a polymeric chain of fructose molecules, such as onions, leeks, asparagus, and artichokes.

Wheat-based products, such as pasta, bread, cereal, cake, biscuits, foods containing sorbitol and lactose, and foods containing the trisaccharide raffinose, such as legumes, lentils, cabbage, and Brussels sprouts, can all cause problems.

One study showed that after eating a diet high in FODMAPs for 2 days, 30 patients with irritable bowel syndrome experienced significantly higher levels of breath hydrogen production (a sign of lactose, glucose, or fructose intolerance) and increased GI symptoms and lethargy (J Gastroenterol Hepatol. 2010;25:1366-1373), Dr Chey reported.

And a crossover study showed that 21 days of a low-FODMAP diet led to a significant reduction in overall symptoms, bloating, pain, and gas in 30 patients with irritable bowel syndrome and 8 healthy volunteers (Gastroenterology. 2014;146:67-75.e5).

But eating a low-FODMAP diet is not as easy as simply eliminating gluten from the diet, cautioned Paul Moayyedi, MD, director of the division of gastroenterology at McMaster University in Hamilton, Ontario, Canada.

Forbidden Foods

"It's strict, so this is not easy for patients. The number of foods that they aren't allowed to consume is huge," he said.

For example, corn syrup is contraindicated in a low-FODMAP diet, but maple syrup is okay. This is not a problem if you live in Canada or New England, but is a costly proposition elsewhere, he pointed out.

"We really need to know whether this works or not," he said. "We find something new and think it's wonderful, then someone else does a study and we realize it's all poison and awful. Eventually we come to some sort evidence on whether this is worthwhile or not."

"I don't view the FODMAP diet as the end of the story at all," Dr Chey countered. "I view the FODMAP diet as a mechanism that establishes the potentially important role of diet in GI symptoms."

Dr Chey reports financial relationships with Actavis, Arelyx, Asubio, Astra-Zeneca, Forest, Ironwood, Nestle, Prometheus, Salix, Sucampo, Takeda, and Vibrant. Dr Moayyedi reports relationships with AstraZeneca, Forest Laboratories, and Shire Canada.

American College of Gastroenterology (ACG) 2015 Annual Meeting. Presented October 19, 2015.

    
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