ＩＢＳとリンクしているのは、腸内の異常発酵である

 

 

日本低フォドマップ食推進会：宇野良治

 

 

私は、これまで、以下のように記してきた。

 

・ＩＢＳでは過剰のガスが症状に影響している。

・ＩＢＳの過剰のガスの原因は、高ＦＯＤＭＡＰ食である。

・過剰のガスは腸内の発酵による。

・腸内の発酵を抑えるとＩＢＳの症状が軽快する。

・ＩＢＳの腸内ｐＨは健常者より低い。

・ＩＢＳでは低フォドマップ食が症状を軽減しうる。 

 

しかし、

発酵を抑えることによって、発酵によって増加するとされる「短鎖脂肪酸：ＳＣＦＡ」の絶対量が増加しない。

ＳＣＦＡは、日本では、「腸の調子を整える」とされ、その理由から、

ＳＣＦＡを増加させる食品が、「特定保健用食品（トクホ）」や「栄養機能食品」に指定されている。

また、ヨーグルト推進者は、

「便のｐＨが上がると悪玉菌が増え、ｐＨが低いと善玉菌が増える」

「便のｐＨを乳児並に低くすることで腸が健康になる」

と、述べている。

そして、実際に、毎日のようにテレビでは、

「便通改善には、発酵性食品を食べて、ＳＣＦＡを増やしましょう」

と、放送されている。

 

 

問題を整理すると、以下になる。

便通異常者において、

・腸内のｐＨを上げるべきか、下げるべきか？

・ＳＣＦＡの量を上げるべきか、下げるべきか？

 

これは、私だけが騒いでいるのではなく、世界中の研究者が疑問を抱いていることである。

 

それについて、

2015年8月25日、Am J Gastroenterologyで、

 

「ＩＢＳは健常者に比して、腸内のｐＨが低い。
しかし、ＳＣＦＡの量に差がない。
大腸内の発酵が異常に多いことがＩＢＳと関連している。
ＳＣＦＡの量は腸内発酵の程度を反映していない。」

 

という、研究報告が発表された。


そして、このことは、世界最大の医学サイトであるMedscapeでも、取り上げられた。 

 

 

http://www.medscape.com/viewarticle/850424?src=wnl_edit_tpal&uac=231753EV

 

Higher Colonic Bacterial Fermentation Linked to Irritable Bowel Symptoms

By Will Boggs MD

September 04, 2015

EW YORK (Reuters Health) - Altered colonic bacterial fermentation is associated with symptoms and colon transit time in individuals with irritable bowel syndrome (IBS), researchers report.

"The interesting finding is that colonic fermentation (as measured by pH and to a certain extent by level of short-chain fatty acid (SCFA)) is higher in patients with IBS than in healthy controls," Dr. Yehuda Ringel from University of North Carolina, Chapel Hill, told Reuters Health by email. "This finding supports the idea that the intestinal microbiota has an important role in the pathogenesis of the disorder."

Altered intestinal fermentation may be associated with intraluminal excessive gas production and altered motility, features commonly observed in IBS, but its role in the pathogenesis of IBS remains uncertain.

Dr. Ringel's team investigated the location and magnitude of altered intestinal bacterial fermentation in IBS and its clinical subtypes and examined their relation to bowel characteristics and gastrointestinal symptoms in a study of 147 individuals, including 114 with IBS and 33 healthy controls.

Their results appear in The American Journal of Gastroenterology, online August 25.

"It is the first study where assessment of intra-luminal intestinal fermentation was done in vivo in humans, and we were able to measure the fermentation process in real time throughout the GI tract and assess and compare this process in different segments," Dr. Ringel said.

Mean total colonic pH levels were significantly lower in the IBS group than in the healthy controls (6.8 vs. 7.3, p=0.042). Lower pH is thought to reflect higher intraluminal bacterial fermentation.

Small bowel pH did not differ significantly between IBS patients and healthy controls, the researchers found.

Fecal short-chain fatty acids (SCFAs) are also thought to reflect intestinal bacterial fermentation, but levels of four SCFAs (acetate, propionate, butyrate, and lactate) did not differ significantly between IBS patients and healthy controls.

"Unlike what we expected, the colonic pH levels positively correlated with IBS symptom scores," the researchers note. "This finding suggests that other factors such as abnormal intestinal motility and psychological disturbances may be more important than bacterial fermentation in determining symptoms severity."

In contrast, fecal SCFA levels had no correlation with either symptom scores or quality-of-life scores.

"The most surprising finding is the lack of fermentation differences between patients with IBS and healthy controls in the small bowel," Dr. Ringel said. "This finding does not support SIBO (small intestinal bacterial overgrowth) as a pathological mechanism for IBS as has often been suggested."

"This study provides possible explanation for physicians to why many patients relate their symptoms to certain types of food, particularly carbohydrates, which serve as substrate for colonic bacterial fermentation," Dr. Ringel concluded. "Our study highlights the need for further investigation of the role of the human microbiota and its function in generating commonly reported functional GI symptoms."

SOURCE: http://bit.ly/1EBhevf

Am J Gastroenterol 2015.

・・・・・・・・・・・・・・・・

この論文の抄録は以下である。
 

http://www.ncbi.nlm.nih.gov/pubmed/26303129

 

 

Am J Gastroenterol. 2015 Aug 25. doi: 10.1038/ajg.2015.220. [Epub ahead of print]

Altered Colonic Bacterial Fermentation as a Potential Pathophysiological Factor in Irritable Bowel Syndrome.

Ringel-Kulka T1, Choi CH2,3, Temas D2, Kim A1,4, Maier DM2, Scott K5, Galanko JA2, Ringel Y2.

 

Abstract

OBJECTIVES:

Dysbiosis leading to abnormal intestinal fermentation has been suggested as a possible etiological mechanism in irritable bowel syndrome (IBS). We aimed to investigate the location and magnitude of altered intestinal bacterial fermentation in IBS and its clinical subtypes.

METHODS:

IBS patients who satisfied the Rome III criteria (114) and 33 healthy controls (HC) were investigated. Intestinal fermentation was assessed using two surrogate measures: intestinal intraluminal pH and fecal short-chain fatty acids (SCFAs). Intraluminal pH and intestinal transit times were measured in the small and large bowel using a wireless motility capsule (SmartPill) in 47 IBS and 10 HC. Fecal SCFAs including acetate, propionate, butyrate, and lactate were analyzed by capillary gas chromatography in all enrolled subjects. Correlations between intestinal pH, fecal SCFAs, intestinal transit time, and IBS symptom scores were analyzed.

RESULTS:

Colonic intraluminal pH levels were significantly lower in IBS patients compared with HC (total colonic pH, 6.8 for IBS vs. 7.3 for HC, P=0.042). There were no differences in total and segmental pH levels in the small bowel betweenIBS patients and HC (6.8 vs. 6.8, P=not significant). The intraluminal colonic pH differences were consistent in all IBSsubtypes. Total SCFA level was significantly lower in C-IBS patients than in D-IBS and M-IBS patients and HC. The totalSCFA level in all IBS subjects was similar with that of HC. Colonic pH levels correlated positively with colon transit time (CTT) and IBS symptoms severity. Total fecal SCFAs levels correlated negatively with CTT and positively with stool frequency.

CONCLUSIONS:

Colonic intraluminal pH is decreased, suggesting higher colonic fermentation, in IBS patients compared with HC. Fecal SCFAs are not a sensitive marker to estimate intraluminal bacterial fermentation.Am J Gastroenterol advance online publication, 25 August 2015; doi:10.1038/ajg.2015.220.

・・・・・・・・・・・・

 
以上から、便通異常に対しては、ＳＣＦＡよりは、発酵を抑制することが基本といえる。
 

しかし、この研究でも、ＩＢＳの便秘型だけは、ＳＣＦＡが低下していたという事実がある。

ＩＢＳの便秘型は、毎日下剤を必要とする慢性機能性便秘、難治性便秘に比べれば、非常に軽度な便秘である。便秘と下痢を繰り返す「混合型ＩＢＳ」よりも、ある意味、軽症便秘である。

 

つまり、軽度の便秘においてのみ、ＳＣＦＡが関係する可能性がある。
 

もし、「ＳＣＦＡが腸内環境を改善する」というのであれば、

テレビで「発酵食品で腸内環境が改善する」という内容は、

全くの嘘ではなく、

「発酵食品は、軽度の便秘でのみ腸内環境が改善する可能性がある」

といえる。