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Are you familiar with the term, Functional Gastrointestinal Disorders (FGIDs)? Don’t let this five-letter acronym intimidate you. It simply refers to conditions or symptoms affecting the digestive tract for which no structural problem or biochemical cause is observed by standard testing such as endoscopy, imaging or blood tests.

These are some examples of FGIDs:

  • Irritable bowel syndrome (IBS)
  • Idiopathic or functional diarrhea
  • Idiopathic or functional constipation
  • Functional bloating or distention
  • Functional dyspepsia (indigestion, full feeling in upper abdomen)
  • Functional heartburn and other symptoms of acid reflux and laryngopharangeal reflux (LPR) including globus (feeling a lump or something stuck in your throat)

The “functional” means that everything seems to be working or functioning through routine testing. The term “idiopathic” is also common in describing FGIDs, indicating that the cause is unknown.

There are many more, but you get the idea. These conditions are painful, debilitating and often chronic lasting for years or even decades. FGIDs affect millions of people resulting in almost half of our trips to the doctor’s office [i] and an estimated cost of 25 billion dollars annually.

What are the common treatments for these conditions?

By definition, mainstream medicine is telling us that:

  1. There is nothing wrong with you according to the tests
  2. The cause of these ailments is unknown
  3. Here is some medicine for your symptoms

A cynic might conclude that there is a financial incentive in the status quo. But the problem goes beyond money. These medications are aimed at the symptoms and don’t address the underlying causes for the most part. Also, most of them carry potential serious side effects and health risks.

These are common examples:

IndicationMedicationSide Effects and Health Risks
Abdominal pain and diarrheaAntispasmotics (hyoscyamine, dicyclomine)Dry mouth, confusion, dizziness, headache, forgetfulness, hallucinations, unsteadiness, coma, anxiety, tiredness, insomnia, excitement, mood disorders, blurred vision, constipation, difficulty breathing or swallowing
DiarrheaAnti-diarrheal medications containing loperamideAbdominal pain, bloating, nausea, vomiting and constipation
DiarrheaAlosetron (Lotronex)Removed from market, then reintroduced for women with sever IBSD. Severe constipation
Diarrhea predominant IBSDAntibioticsBacterial resistance, dysbiosis (unbalanced microbiota), C. diff infection, allergic reactions
ConstipationOsmotic, lubricating and stimulant laxativesNausea, bloating, abdominal pain, cramping, flatulence, diarrhea, vitamin malabsorption, dependence
ConstipationTegaserod (Zelnorm)Removed from market, then reintroduced for women under 55. Heart attack and stroke
Constipation predominant IBSCLubiprostone (Amitiza)Nausea, diarrhea, headache, abdominal distension, flatulence, vomiting, difficulty breathing
Constipation predominant IBSCLinaclotide (Linzess)Diarrhea, heartburn, vomiting, gas, bloating, headache
IBSAntidepressants including tricyclic and selective serotonin reuptake inhibitors (The side effects are worse for the tricyclic medications)Constipation, cramps, nausea, vomiting fatigue, headaches, difficulty urinating and more.
Heartburn, acid reflux and LPRPPIs, H2 Blockers, Antacids (the side effects mostly relate to PPIs and H2 blockers but excessive use of antacids can pose similar risks)C diff infection, pneumonia, bone fractures, heart and kidney problems, anemia, malabsorption of: calcium, magnesium, vitamin B12 and other vitamins and minerals
Nausea, vomiting, heartburnMetoclopramide (Reglan)Diarrhea, dizziness, drowsiness, headache, nausea, vomiting, and more.


The whole FGID concept is faulty in my view because people would not be sick if things were working or “functioning” properly. It’s about time to take a fresh look at what we already know about the underlying causes of these conditions. Perhaps, this will lead to a more sensible way to treat them at a fundamental level.

In fact we know a lot more than what we think. It’s a little like an episode of X-Files, “the answers are out there.” But they are lost in medical journals and even medical text books.

It’s all about the gas

Here is one powerful statement I found on page 1192 in “The Textbook of Primary and Acute Care Medicine,” one of the books used to train doctors:

“Dietary alterations to reduce (intestinal) gas require the elimination of most of the foods in Table 1 (which includes lactose, fructose, resistant starch, fiber and sugar alcohols)”

The connection between intestinal gas and basic FGIDs symptoms such as bloating, cramps, distention and abdominal pain is pretty straightforward. You can easily imagine lots of trapped gas causing these symptoms.

Now, if we can fully understand the connection between intestinal gas, FGIDs and these carbohydrate types (lactose, fructose, resistant starch, fiber and sugar alcohols), we should be able to translate this knowledge into an effective dietary treatment.

What are intestinal gasses and how are they produced?

Intestinal gases include hydrogen, carbon dioxide and methane. They come from bacteria fermenting carbohydrates and Archaea organisms in the case of methane. The carbohydrate types listed above have been flagged as the source of intestinal gas because they are the hardest to digest and absorb into our bloodstream. As a result, they persist in the intestine potentially fueling bacteria or Archaea organisms to produce excessive gases in our intestine – makes sense, doesn’t it?

IBS, Diarrhea and Constipation

There’s more. Hydrogen and methane also affect motility, which is how fast food moves through our digestive tract.

Most people are aware of common causes of diarrhea including: food poisoning, bacterial, viral or parasital gastrointestinal infections (gastritis) which tend to come on suddenly and resolve naturally over the course of one to several days. Most often, staying hydrated with electrolyte rich liquids is the only treatment required for these conditions.

But chronic diarrhea (after other causes such as C. diff are ruled out) may be caused by SIBO (Small Intestinal Bacterial Overgrowth) specifically involving bacteria which produce excessive amounts of hydrogen. A number of researchers including Dr. Mark Pimentel’s group at Cedar Sinai in Los Angeles have shown that IBSd patients whose gut microbes produce excessive hydrogen frequently suffer with diarrhea. [ii],[iii]

Constipation, defined as hard or lumpy stools, straining or a feeling of incomplete defecation also has many potential underlying causes including: constipating medications (i.e. especially painkillers and laxative abuse), dehydration, bowel obstruction, colon cancer, hypothyroidism or neurological problems. But newer research indicates that idiopathic constipation experienced by IBSc patients is linked to an excess of methane-producing gut microbes known as Archea. [iv],[v]

Testing via the lactulose breath test including both methane and hydrogen detection can help you determine if your symptoms are due to hydrogen or methane producing microbes.

Heartburn, LPR and Acid Reflux

I personally suffered severely from acid reflux for 20 years taking PPIs, H2 blockers and antacids without adequate relief. One day I went on a low-carb and high fat diet for weight loss, and my acid reflux symptoms vanished within a day. Astonished? Yes! And I got so CURIOUS and had to find out WHY.

As I investigated how each food type (carbohydrates, fats and proteins) was digested, a light bulb went off. Being a microbiologist, I knew that most gut bacteria prefer carbohydrates for fuel and they produce lots of the gases mentioned above. Sound familiar?

My idea was that acid reflux is actually caused by too much gas pressure in the small intestine and stomach due to intestinal bacterial overgrowth of gas-producing strains. Think of it as dropping a Mentos candy into a bottle of coke.

This concept is supported by over 100 scientific journal articles in my books, Fast Tract Digestion Heartburn and Fast Tract Digestion IBS. My theory challenges the antiquated idea that acid reflux is caused by dysfunctional lower esophageal sphincter muscles located at the top of the stomach that is designed to contain stomach contents. But the new idea suggests that gas pressure actually forces this sphincter to open. Again make sense, doesn’t it?

Here is the solution

Consuming too many foods containing the five hard-to-digest carbohydrate types is a big part of the problem. With this information, I created a science-based and drug and antibiotic free diet to help not only people with acid reflux, but also to help people with a variety of other FGIDs and systemic and autoimmune conditions involving SIBO. This diet is called the Fast Tract Diet.

The Fast Tract Diet approach quantitatively limits these hard to digest carbohydrates based on a mathematical equation called Fermentation Potential (FP). Think of FP as “symptom potential” in low, medium and high as well as points based on serving sizes of your food items. FP uses the glycemic index to measure the “symptom potential” in virtually any food item. And the beauty is that the math has already been done on many food items for you.

In addition to the FP calculation and food list, the Fast Tract Diet includes pro-digestion strategies to reduce the impact of hard-to-digest carbohydrates along with a process for identifying and addressing other potential underlying and contributing causes that can promote intestinal bacterial overgrowth.

To complement the Fast Tract Digestion books which fully explains the Fast Tract Diet, the Fast Tract Diet mobile app makes it easy to start the diet and to track meals and symptoms based on FP values for over 800 food items.

3 Step Action Plan for FGIDs

If you suspect that you have a FGID, these are three steps you can take:

1. Reduce the hard to digest carbohydrates in your diet including:

  • Lactose (high lactose dairy)
  • Fructose (sucrose, high fructose corn syrup, agave sweetener, and many fruits)
  • Fiber (legumes, whole grains, and many fruits)
  • Resistant starch (pasta, most breads, most potatoes, most rices)
  • Sugar alcohols (dietetic candy and snack bars, etc.)

The Fast Tract Diet recommends several low FP alternatives for each of these food groups.

2. Incorporate Gut Friendly Practices in your daily life including:

  • Chewing well to allow amylase in your saliva more time to digest starches
  • Taking amylase of lactase supplemental enzymes when appropriate
  • Preparing foods, particularly starches in ways to reduce resistant starch
  • Selecting only fully ripe fruits and vegetables, etc.

These practices will help you digest the five hard-to-digest carbohydrate types better.

3. Identify and address other potential underlying factors that can promote bacterial (or Archea) overgrowth including:

  • Motility issues from GI infections, medications, scarring, surgery, etc.
  • Immune deficiencies from medications, viral infections, etc.
  • Digestive enzyme deficiencies
  • Antibiotics which can disrupt the microbiota
  • Low stomach acid from prolonged H. pylori infection or other causes
  • Ileocecal valve problems
  • Food or water poisoning, gastroenteritis
  • Carbohydrate intolerance

[i] Talley NJ1. Functional gastrointestinal disorders as a public health problem. Neurogastroenterol Motil. 2008 May;20 Suppl 1:121-9.

[ii] Pimentel M1, Kong YPark S. Breath testing to evaluate lactose intolerance in irritable bowel syndrome correlates with lactulose testing and may not reflect true lactose malabsorption. Am J Gastroenterol. 2003 Dec;98(12):2700-4.

[iii] Jahng J1, Jung ISChoi EJConklin JLPark H. The effects of methane and hydrogen gases produced by enteric bacteria on ileal motility and colonic transit time. Neurogastroenterol Motil. 2012 Feb;24(2):185-90, e92.

[iv] Chatterjee S , Park S , Low K et al. The degree of breath methane production in IBS correlates with the severity of constipation . Am J Gastroenterol 2007 ; 102 : 837 – 41.

[v] Jahng J1, Jung ISChoi EJConklin JLPark H. The effects of methane and hydrogen gases produced by enteric bacteria on ileal motility and colonic transit time. Neurogastroenterol Motil. 2012 Feb;24(2):185-90, e92