IBS: Bran is bad... when will doctors catch up?


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Welcome to the site! This content is old and may not reflect my current opinions. I keep it up mainly for reference and because I hope at least some of it is still good, but I encourage you to check out more recent posts as well as my Start Here page

 In the next few months I hope to write a couple of posts on irritable bowel syndrome. It's interesting because so many (including myself) get relief from IBS by following a low-carb low-fiber grain-free fructose-free diet with probiotic supplementation. There are many reasons this works, but in the long term people following it might want to wean away from probiotic dependence, since probiotics in pills cannot become part of the permanant microbiome of most adult guts. In addition, there are real benefits from short chain fatty acids produced in the colon by fermentation. It's unfortunate so much fiber research has been done on grains, but more and more is being done on the type of fiber that horticulturalists and foragers consume. Here we are getting into self-experimentation since the research is so thin right now. My own goal has been to establish a gut bacterial population that is an asset (har har) rather than a nuisance. I've been trying to do this by feeding my bacterial population appropriately in a way that encourages good bacteria, but does not allow overgrowth. 

On Paleohacks someone said something like "the kind of food you eat cannot affect constipation, just the mechanics of the food, IE, how much fiber and fat." That is the OLD view. The reality is that different gut bacteria react differently to different foods. I've been reading a lot of articles by Dr. Kok-Ann Gwee, who studies IBS in Singapore. His article Fiber, FODMAPs, flora, flatulence, and the functional bowel disorders is a really good one and should be essential reading for all doctors. I'd estimate the majority of primary care physicians are still recommending things like bran to treat IBS when there are mountains of scientific evidence against it. 

The issue was in the 70s some papers came out that said, "huh, looks like this African farmers don't have stomach problems. Must be all the fiber in their diet!" Nevermind their methods for measuring fiber were bad and that certainly wasn't the only difference in their diets. Then some poorly-designed studies were done on bran, which the cereals industry picked up in order to promote BRAN FOR EVERYONE1111!!!!! Dr. Kok-Ann says:

In fact, a number of contrarian studies, which had been largely ignored, had suggested that favorite sources of dietary fiber such as bran and other cereals, and vegetables and fruits, might actually aggravate symptoms in IBS. The symptoms that appeared to be aggravated were flatulence, bloating and abdominal pain.

Yikes, that certainly was my experience. The more I ate the high-fiber stuff my doctor told me to eat, the worst I felt. 

I didn't have Celiac, so that meant wheat was AOK right? Nope, gluten is not the only bad thing in wheat, the fiber in wheat can be quite bad for people with IBS as well. 

Based on the use of an exclusion diet, Nanda et al. from Oxford reported that dairy, grains, in particular wheat and rye, and onions were the major foods implicated by IBS patients, and that patients responding to dietary manipulation were likely to have presented with flatulence as an initial symptom.3 They had also observed that intolerance to either wheat or rye was specifically associated with abdominal distension. Whorwell and Prior from Manchester recorded that 55% of their patients felt worse and only 10% felt better on bran.4 John Hunter's group from Cambridge used a whole-body calorimeter to measure the 24-h excretion of hydrogen and methane in both the flatus and the breath.5,6 They compared the gas production of IBS patients and healthy controls on a standard diet with regular fiber intake, an exclusion diet, and a fiber-free diet. They found that IBS patients had a significantly faster rate of gas production on a fiber-rich diet, which reduced significantly on the exclusion and the fiber-free diet, and this appeared to be associated with an improvement in symptoms. Others have also suggested that malabsorption of fructose and sorbitol, of which fruits are rich sources, may give rise to symptoms in IBS patients.7

So fiber not only doesn't help, it makes you gassy and bloated. This paragraph highlights the foods I found triggered my symptoms through trial and error: onions, grains (esp wheat), and a lot of dairy. These are foods I now know are rich in FODMAPS (Fermentable Oligo-, Di- and Mono-saccharides, and Polyols). Interestingly I've found not all FODMAPs trigger my symptoms. 

In [the Cambridge study], total gas, as well as breath hydrogen production, was similarly reduced with metronidazole (an antibiotic with activity against intestinal anaerobic organisms) treatment despite a fiber-rich diet. This observation brings us back to our recent appreciation that the flora of intestinal microbes is a key player in the development of IBS.10 Even Segal and Walker, two of the early proponents for the high-fiber diet, have recently acknowledged that reduced dietary fiber intake has not resulted in increased colonic diseases in Africans.11 In fact they have now recognized the importance of the “quality of the intestinal bacteria”, and the impact that this has on the fermentation of malabsorbed carbohydrates.12 In their recent paper they have assembled measurements for various classes of immunoglobulins, and other markers of immune activation, that support a high level of exposure to gastrointestinal infections in childhood.11 Their new hypothesis is that it is this early priming that gives the African a more robust gut microflora, better able to withstand the insults in adult life. The corollary is also that if we expect fiber and oligosaccharides that are promoted as prebiotics to enhance the proliferation of ‘good bacteria’, we have to start feeding these substrates to our gut in the early years of life. In the meantime, it appears that eating a ‘healthy Western breakfast’ of milk with high-fiber cereals, whole grain bread with honey, washed down with apple juice, is perhaps the worst way to start off the day for an adult IBS patient!

What about those of us who didn't get that advantage? Is there hope to normalize? In his other article he points to several factors anyone with IBS should think about: 

  • The role of gut flora in their end products, immune mediators, and neuroendocrine factors
  • Beneficial and pathogenic parasites

Then there are some more factors to think about from Irritable bowel syndrome: towards biomarker identification:

  • The gut-brain axis
  • Hypothalamic-pituitary-adrenal (HPA) axis dyfunction
  • Inflammation
  • Stress

More soon!