Pathways to Promote Optimal Digestion

Fundamentals of Optimal Digestion

Stomach acid, digestive enzymes, bile and gut motility all play a key role at multiple stages of food breakdown. When they are inadequate, the gut becomes particularly vulnerable to dysbiosis and other digestive complications. 

Stomach acid initiates digestion and signals the pyloric sphincter to open for gastric emptying. It also kills pathogens on food and triggers the release of digestive enzymes and bile. When stomach acid is low, natural pathogens in food and the mouth can colonize in the digestive tract, leading to dysbiosis. Signs of low stomach acid include bloating and belching after meals, acid reflux, undigested food in stools, low iron and vitamin B12 levels, nausea, constipation and hypothyroidism [1]. While less common in the general IBS population, patients with gallbladder conditions, steatorrhea, foul smelling, oily stools that float or SIBO-related diarrhea or constipation may also be low in bile [2].

Gas and bloating associated with IBS result from the fermentation of undigested food by gut bacteria. Digestive enzymes promote proper breakdown of food, meaning more food is digested before pathogenic bacteria can ferment it. In turn, this helps prevent inflammation and leaky gut because less undigested food enters the bloodstream. In the short term, a reduction in inflammation also allows the gut to heal and restore its normal protective barrier function. Signs that a patient may have low levels of digestive enzymes include bloating 1-2 hours after meals, sensations of a “rock” in the stomach, undigested food in stools, flatulence, and cramping [3].

External Aids: Are Supplements Warranted?

In specific cases, exogenous stomach acid, enzymes and/or bile may help patients with low levels. An easy at-home way to test for low stomach acid is to have patients drink 1 teaspoon of baking soda on an empty stomach; if they burp in under 2 minutes stomach acid is likely too high; if they burp in 2-3 minutes stomach acid levels are likely normal; and if they burp in over 3 minutes stomach acid is likely too low. Betaine HCL can be used to supplement stomach acid in patients with low levels. Doses can range from 200-1000mg, so individualized titration is important. Of note, for those on antacids (eg. Prilosec) stomach acid is contraindicated and for those with heartburn stomach acid can help or exacerbate symptoms, depending on the patient.

In addition, digestive enzymes may help alleviate symptoms, address dysbiosis and support further diet liberalization, though their efficacy is debated [3]. Available options for digestive enzymes include lactases, lipases, amylases and proteases. The enzyme alpha-galactosidase can also support the digestion of galactosaccharides (GOS), found in beans and legumes and a common FODMAP. In addition, some research suggests that a protease DPP IV blend may provide specific support in gluten and dairy digestion. It is important to note, however, that taking a DPP IV enzyme does not mean patients with gluten sensitivity can now eat gluten liberally as it has not been found to help those with gluten sensitivities avoid symptoms [4]. Instead, taking DPP IV may simply provide extra protection against cross-contamination in products with gluten or dairy-free claims.

The Monash University Low-FODMAP certified FODZYME® offers a blend that targets breakdown of fructans, GOS and lactose, though individual responses will vary. A dose of 9000 FCC lactase units with each portion of dairy or 250 mg alpha-galactosidase to break down GOS is commonly recommended for patients with IBS who know they do not tolerate these FODMAPs. Unfortunately, no enzymes have been developed that can reliably support polyol digestion, though research is ongoing. Note that some enzymes contain gluten and dairy themselves, so ensure patients always review ingredient labels carefully [5]. Mode of application may also influence enzyme activity. Powdered enzyme products claim to have increased effectiveness by promoting enzyme-food interactions at an optimal gastric pH.   

Research does not indicate that enzymes suppress the body’s endogenous enzyme production. Still, for those wary of a supplement, liquid digestive bitters can be effective, though their taste is rather unpalatable. Herbal and root teas such as chamomile, dandelion, licorice, ginger and turmeric are also natural options to support digestion, though clinical evidence of their effectiveness is mixed [6,7,8]. Most digestive enzyme and bile supplements and herbal remedies provide product-specific dosing recommendations and are taken with meals. 

Promoting Motility

The migrating motor complex (MMC), or “cleansing wave” of the small intestine, also helps keep bacteria out of the gut. Impaired motility can result in delayed gastric emptying and a host of other common IBS symptoms. Promotility agents (prokinetics) can be immensely helpful to address the overall symptom profile of patients with IBS. A range of options, each with their own mechanisms of actions are available and should be trialed based on the patient’s symptoms. 

Iberogast (STW 5) is a liquid herbal tincture taken with or following meals that promotes gut motility and gastric emptying and reduces dyspepsia [9,10,11]. It contains a mix of nine extracts, including licorice, peppermint and chamomile, so always review the ingredients with patients to check for any allergies. Magnesium may also promote gastric emptying and motility by exerting a laxative effect on the colon [12]. Magnesium citrate is recommended for IBS-C as it draws water in the colon, while magnesium glycinate is recommended for those not experiencing constipation.

Neurotransmitter precursors, like 5-hydroxytryptophan (5HTP) and acetyl-l-carnitine, may also help modulate gut motility and promote the MMC. 5HTP in particular is also a serotonin precursor and low serotonin levels are associated with decreased gut motility [13]. 

For patients seeking to avoid a complex supplement regimen, single ingredient supplements like ginger or digestive bitters, as well as apple cider vinegar or lemon juice, can also be effective in promoting motility, though most evidence to support their use is anecdotal. 

Lastly, behaviors and lifestyle modifications that stimulate the vagus nerve should also be encouraged. Increased vagal tone increases stomach acidity, motility and digestive enzyme production. Activities to trial include light exercise, deep breathing and meditation, stomach massage, cold showers, and adequate meal spacing (4-5 hours between meals).