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An apple a day makes the gastroenterologist's day!

An apple a day keeps the gastroenterologist on pay!


Today’s post will cover a question that repeatedly comes up. It’s a question I’m sure many of you also have: “What diet should I be following when dealing with a gut issue?”

Let me first dispense with dietary recommendations that have not been subjected to controlled trials to assess efficacy for controlling annoying or painful gut symptoms. In this category I include low carbohydrate diets like the Specific Carbohydrate Diet and vegan/vegetarian diets.

Absence of evidence is, of course, never evidence of absence. However, for any dietary claim to meet the threshold of scientific evidence I require for my blog readers, I want more than anecdotal evidence, slick marketing, Amazon book reviews or blogger endorsements.

Anecdotal evidence is the weakest form of evidence. It is when someone claims that something or other cured their condition, but with no independent scientific confirmation of said claim.

Such stories don’t mean they’re untrue, but humans can easily fool themselves into believing that a treatment was actually causative of an observed result when it wasn’t. Just as associations derived from nutritional epidemiology can never prove causation, so to anecdotal accounts.

People often forget this when they experience relief during an intervention. Many disease states are self-limiting, so it’s entirely possible that what was credited for making them feel better was nothing more than a sheer coincidence. And then, of course, there is the placebo effect.

Now let me state for the record that my very positive experience with garlic also falls under the purview of anecdotal evidence. Garlic does indeed have antibacterial, antifungal, antiparasitic and antiviral effects as I wrote in this post. Nevertheless, my scientific mind prevents me from having 100% certainty that garlic was indeed the reason for my cure.

The only way to ferret out whether a treatment is truly efficacious, or to be more precise, has an effect exceeding that of a placebo, is to subject it to a blinded clinical trial to control for this and other confounding variables. If this is not done, the belief that the intervention is effective is just that, belief. Convincing yourself of a belief without replicable scientific evidence is the definition of faith.

This being a science-based health blog and not a faith-based one, I’m sure you’ll forgive me for retaining a healthy dose of skepticism for dietary recommendations that have nothing more than anecdotes to back them up.

Why? Because I assume, maybe incorrectly, that someone willing to pay for my personalized advice is seeking scientifically sound information. And if they’re not, then they’re likely to note more than a hint of skepticism in my voice when I’m asked about these alternative strategies during a consult.

Anyone claiming efficacy for a diet that “cures” gut dysbiosis, or at the very least offers symptom relief, has to meet the burden of proving it. It is not up to me to disprove their hypothesis. You can’t prove a negative. That’s logic 101.

On this blog, I’ve repeatedly cautioned against using very low carb diets to treat gut issues. One major reason is because of the well-documented effect of these diets to induce euthyroid sick syndrome (ESS). (1) (2) (3) (4) Common symptoms reported by many on these ketogenic-type diets include lethargy, cold hands and feet, thinning or dry skin, insomnia and constipation.

These are all symptoms of ESS. The last thing in the world a person needs who suffers from gut dysbiosis is depressed metabolism. And as I’ve blogged, low thyroid function via its negative effects on intestinal peristalsis is more than capable of precipitating a case of small intestinal bacterial overgrowth (SIBO).

Another major concern of mine with these diets is their propensity to deplete the glucose-rich mucus layer lining both the respiratory and digestive tracts. I explained those reservations here.

Finally, the Specific Carbohydrate Diet eliminates the very soluble fibers that beneficial gut flora depend on to thrive. As I wrote in this post, there is more than ample scientific evidence documenting the health benefits of including these fibers in a well-rounded omnivorous diet. And as you’ll soon read, elimination of these dietary fibers is a worrying downside for another symptom-reducing diet.

As for vegan and vegetarian diets, inclusion of large amounts of carbohydrates often results in a plethora of gas production from high fiber intake. Moreover, these diets tend to contain shitloads (pun intended) of bulking insoluble fiber and anti-nutrients (phytic acid, lectins, protease inhibitors, lipase inhibitors, amylase inhibitors, oxalic acid, goitrogens and flavonoids).

This can result in colonic distension, gastric and intestinal phytobezoars, mineral and vitamin deficits and diverticulitis. (5) (6) (7) (8) Nor is it unusual for vegans and vegetarians to complain of anal fissures and hemorrhoids from repeatedly straining to pass bulked-up stools through a relatively narrow anal opening.

As many vegetarians and vegans also eat hefty amounts of gluten grains and omega 6 vegetable oils, the pro-inflammatory effects of both will increase preexisting gut inflammation and lead to compensatory cortisol generation.

 All these factors likely explain the results of a German study that found:

“…evidence for elevated prevalence rates in vegetarians for depressive disorders, anxiety disorders, somatoform disorders and syndromes as well as for eating disorders. It is important that such higher rates cannot be explained by different socio-demographic characteristics (e.g., 70% vegetarians were females, and females show higher base rates than men for these disorders). For this reason we designed a non-vegetarian control group that was matched with variables known to be associated with mental disorders (sex, age, educational level, marital status, urban residency). When compared to the non-vegetarian matched comparison sample, the vegetarian group showed even greater differences in the prevalence of mental disorders than when compared to the entire non-vegetarian sample.” (9)

Now, before you jump to the conclusion that eating a vegan or vegetarian diet causes mental disturbances, note that most of these people chose to eat this way to correct a preexisting mood disorder:

“For depressive disorders, anxiety disorders, and somatoform disorders and syndromes we found that on average the adoption of the vegetarian diet follows the onset of mental disorders.”

In other words, there is no clear evidence that eating vegan or vegetarian causes mood disorders, although I know some people who would dispute that. That said, this study pretty much puts the kibosh on the notion that adopting these diets will improve their health:

“Our analysis revealed that individuals suffering from mental disorders consistently showed lower frequencies of meat consumption during the past 12 months. These results again indicate that current vegetarian or low meat consumption diet pattern is associated with elevated prevalence rates of mental disorders.”

If anything, depriving yourself of many health-promoting nutrients found either exclusively or in highest concentrations in animal foods like ready-made fat soluble vitamins A and D, B12, whey protein, conjugated linoleic acid, carnitine, taurine, heme iron and gelatin is equivalent to shooting yourself in the foot.

Ongoing scientific research on the gut-brain axis continues to show how gut bacteria and increased intestinal permeability affect mood via effects on the hormonal, immune, central nervous, and enteric nervous systems. (10) These findings clearly caution against the belief that diets exclusively based on plant foods are somehow the royal road to health, mental or otherwise.

It’s now time to concentrate on a gut friendly diet I originally wrote about in this post. Unlike low-carb or vegetarian/vegan diets, the FODMAP (Fermentable Oligo-, Di- and Mono-saccharides and Polyols) elimination diet has been clinically proven to be effective in relieving symptoms typical of those with gut dysbiosis. (11) To spare time, I’ll leave it to you to read or reread that earlier post to familiarize yourself with this approach.

Generally, this is the diet I recommend to those battling any form of gut dysbiosis. That includes anyone with irritable bowel syndrome (IBS), SIBO, Crohn’s disease and ulcerative colitis. As you all know, it isn’t the only dietary recommendation I make, but it’s a start.

Many who’ve tried this diet report good symptom relief while on it. Nonetheless, most fail to adhere to it. There are various reasons for this.

Some find the diet too difficult to implement. Others are dismayed that their favorite food makes the list and can’t countenance depriving themselves of it. Most, however, conclude that strict adherence fails to completely resolve their gastrointestinal issues.

And you know what? They’re absolutely right!

In my post on this diet, I cautioned that eliminating prebiotic fibers needed by beneficial gut bacteria carries a real risk. As I wrote then:

“…the researchers who devised FODMAP caution:

Restrictions in FODMAP intake might potentially have a down side. It does mean restriction of dietary components with prebiotic effects. This might potentially be detrimental to large bowel health (such as the promotion of colerectal carcinogenesis), although no studies have addressed this issue to date.

Remove the weasel words “might” and “potentially” and you have a more accurate description of what is likely to happen if you cut these foods entirely from you diet.”

In a recently published interview, the originators of FODMAP, Dr. Jane Muir and Dr. Peter Gibson, had this to say:

“…restricting the dietary intake of the oligosaccharides, fructans, and GOS [galacto-oligosaccharides], which are natural prebiotics, can result in changes in the luminal bacterial populations. Although the health consequences are not known, we do not recommend that the low FODMAP diet be strictly followed over the long term. Rather, a reintroduction of FODMAP foods should be instituted after good symptomatic response is achieved to find the level of food restriction that the person requires to adequately control symptoms.” (12)

A study recently published in the British Medical Journal corroborates these concerns. (13) Interestingly enough, this trial was conducted by these very same researchers.

This study followed thirty-eight patients with confirmed IBS and eight healthy subjects. Data are available for only twenty-seven IBS patients and six healthy controls owing to the failure of some participants to fully comply with requirements.

All were randomly assigned to either a diet low in FODMAPs, or one containing them. Diets lasted for 21 days after which they went back to eating their normal diet for an additional 21 days. This latter period served as a washout before beginning the next leg of the study.

At the end of this period, those who had been on the low FODMAP diet were switched over to a diet containing FODMAPs, and those who were on the diet containing FODMAPs were now placed on a low FODMAP diet. This leg of the trial also lasted 21 days. Stool samples were collected for five days from all participants during both legs of the study to assess changes in gut bacteria.


There were no statistically significant differences seen as far as intestinal transit time or levels of short-chain fatty acids between groups. However, when it came to bacterial diversity and abundance, the news for the FODMAP group was not good.

Compared to the FODMAP-containing diet, those on the FODMAP exclusion diet experienced significant reductions in various species of beneficial bifidobacteria as well as the mucus degrading bacteria Akkermansia muciniphila (A. muciniphila). As I’ve written before, low levels of bifidobacteria are highly associated with a whole host of disease states like diabetes, obesity, autoimmune diseases, IBS, Crohn’s disease, anxiety, depression, colon cancer, fibromyalgia, chronic fatigue syndrome, heart disease, Alzheimer’s and ulcerative colitis to name just a few. And as I explained here, healthy colonies of A. muciniphila have been shown to reduce obesity and endotoxemia in humans.

Decreases were also noted in Clostridium cluster XIVa. Not all species of Clostridia are harmful, and this is one of them. These bacteria are butyrate producers. Butyrate is an important food source for cells lining the digestive tract, and is therefore essential for maintaining gut wall integrity and preventing initiation of the Inflammatory-Cortisol Ballet.

So what conclusion can we draw from this study? Well, while this diet is highly effective at reducing annoying and painful intestinal symptoms, long-term adherence will likely lead to a gut microbial makeup that makes resolving any dysbiotic state nearly impossible. As the researchers concluded:

“The functional significance and health implications of such changes might lead to caution about reducing FODMAP intake in the longer term. Liberalising FODMAP restriction to the level of adequate symptom control should be exercised. [Emphasis mine] The low FODMAP diet should not be recommended for asymptomatic populations.”

The best way of “liberalising” [British spelling] the FODMAP diet is by taking prebiotics or resistant starch or both while on it. This can be accomplished either by supplementation or diet, although precisely controlling intake and resultant symptoms will be far easier to achieve via the former. Failing to do so will result in a gut bacterial composition that will leave you further from your goal of permanently taming a rebellious gastrointestinal tract.

Another take home message is that no diet exists that resolves gut dysbiosis on its own. As I’ve said before, and will no doubt say again, healing a gut requires the introduction and nurturing of beneficial gut bacteria. Anything less will leave you at the mercy of shysters more interested in performing biopsies of your wallet and/or pushing a dietary dogma than helping you resolve your health issues.

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