Gut Health in Diabetes: It’s What's Inside that Matters

Ryan Bradley, ND, MPH     September 2006


The gastrointestinal tract, frequently referred to less appealingly as the “gut”, is a complex, finely regulated ecosystem that involves the coordination of the nervous system; multiple organs including the stomach, the pancreas, the liver, and the intestines; and the presence of healthy bacteria that aid our digestion and immune system. 

Few health care providers place as much emphasis on digestion and gut as do integrative medicine providers. This emphasis comes from a long held belief that optimal nutrition, digestion, and elimination are cornerstones to good health and long life.

Nutrition refers to the quality of foods that consumed and includes both the macronutrient content of food, e.g. carbohydrates vs. fats vs. proteins, as well as the micronutrient content of foods, e.g. chromium, zinc, vitamin B12, etc.

Digestion refers to our ability to break down food and absorb the nutrients properly.

Elimination includes our internal detoxification pathways, sweating, and our urination and bowel patterns.


The Complex World of Digestion

Digestion is quite complex and involves many separate steps including chewing, the production of saliva which begins breaking down food in the mouth, the production of stomach acid known called hydrochloric acid, the production and secretion of digestive enzymes mostly from the stomach and pancreas, and the transport of digested food through the gastrointestinal (GI) tract, i.e. the intestines and colon.

Absorption of nutrients is also a multi-step process and includes the breakdown of food by the stomach acid and enzymes, modification of food by the normal bacteria in our intestines and colon, and finally passing nutrients through the gut wall and into the blood stream.

Many people have poor digestion due to stress, poor food choices, food sensitivities, increased consumption of alcohol, and the use of some medications (e.g. antibiotics and acid-suppressive medications). People with diabetes are even more likely to have impairments in this vital function because of long-term blood sugar elevations- and here’s why…


Digestive Impairment in Diabetes

When the blood sugar becomes too high in the blood stream it begins to stick to cells and other structures in the body causing harm. Among the most affected tissues are the small blood vessels that carry oxygen and nutrients to the nerve fibers; this damage is called neuropathy and can occur on any nerve fiber in the body.

Nerve fibers control our sensations, our motions, and many processes we are not aware of - including digestion! Nerves from the brain regulate digestion very carefully and control the production of stomach acid, the release of digestive enzymes, and how rapidly food passes through the GI tract. If neuropathy occurs on the nerves that control digestion, reductions in hydrochloric acid and digestive enzymes can occur, impairing normal digestion and thus absorption.

Also, if stomach acid production is reduced, bacteria that cannot normally live in the small intestine begin to grow. This abnormal gut “flora” causes changes in the normal breakdown of food and is known as small bowel bacterial overgrowth (SBBO). Fermentation can result and produce excess gas, impaired absorption, and cramping. These bacteria can actually begin to use the nutrients that you are supposed to be absorbing!

Finally, the changes in gut flora and the results of fermentation in the bowel can lead to the absorption of incompletely digested proteins and carbohydrates. Theories differ on how the next phase actually occurs, but the predominant theory is that this “malabsorption” may stimulate abnormal immune system responses to food leading to the production of antibodies. Antibodies are used by our immune systems to differentiate foreign substances from normal tissues; normally we do not develop antibodies to our food. Sometimes these immune responses are called “food allergies”, however I prefer “food sensitivities” because these reactions are different than a bee sting allergy or a peanut allergy.


Just Theory or Science?

As frequent readers know, I am hopeful and inquisitive but also skeptical and therefore frequently turn to published science to debunk or support popular myths. The impact of diabetes on digestive health has not been thoroughly studied, but there are a few publications that support the theories described above.

Migdalis et al. demonstrated reductions in gastric emptying in diabetic patients with autonomic neuropathy; symptoms such as sensations of fullness and early satiety are signs of neuropathy (Migdalis et al., Clin Auton Res. 2001). Gaur and colleagues discovered that autonomic nerve dysfunction leads to paralysis of the gall bladder in patients with diabetes, leading to gallstone formation. The gall bladder is also a storehouse for bile acids needed to absorb fats and fat-soluble vitamins (Gaur et al. J Assoc Physicians India. 2000). Kostic and Secen measured pancreatic enzyme secretion in diabetic subjects following a high-protein meal and found significantly reduced enzyme secretion in those with symptoms of neuropathy (Kostic and Secen. Med Pregl. 1996).

Virally-Monod and colleagues measured the number of people with diabetes who have SBBO and found 43% were positive for SBBO when tested (Virally-Monod et al. Diabetes Metab.1998). Virally-Monod describes the consequences of SBBO as including chronic diarrhea; impaired function of bile; fat, vitamin, and micronutrient malabsorption; and worsening of gut motility problems.

According to Zietz and colleagues, gastrointestinal symptoms are present in 50-70% of people with diabetes with delayed gastric emptying and decreased mobility being the most common symptoms; they found 34% of people with diabetes tested positive for SBBO (Zietz et al. Diabetes Care. 2000). Flatulence (gas) and chronic diarrhea were the most consistent symptoms in those who tested positive. They also found the presence of autonomic neuropathy more consistently in those with SBBO.


How Do I Know if I Have Autonomic Neuropathy or Small Bowel Bacterial Overgrowth (SBBO)?

Some degree of autonomic neuropathy is quite common in people with diabetes. Low et al. found that 73% of people with diabetes have some degree of autonomic neuropathy (Low et al. Diabetes Care. 2004). Testing should be discussed with your endocrinologist, cardiologist, or diabetes specialist if you have unexplained chronic diarrhea, frequent heart palpitations, dizziness upon standing rapidly from sitting or lying, or unexplained urinary incontinence (inability to control or hold urine).

It is difficult to definitely prove the presence of SBBO in all people, however some testing is available. Testing includes hydrogen breath testing and sophisticated stool cultures. Hydrogen breath testing is not available everywhere but most regions have at least one hospital or medical clinic that performs the testing. Normal stool culturing is unlikely to discover SBBO, but more sophisticated testing called Comprehensive Digestion and Stool Analysis (CDSA) testing is available through some labs. CDSA testing often checks for less common bacteria, tests for abnormal digestion products from foods, and also tests for markers of inflammation in the gut.

Testing aside, your symptoms may give the best insight. If you have peripheral neuropathy, i.e. pain in your feet or legs and/or lack of sensation, it is likely autonomic neuropathy is present also. If you have improved your diet to be more whole foods based, (i.e. fresh fruits and vegetables, whole grains, legumes, and lean meats) and yet frequent diarrhea, bloating, fullness after meals and gas remain, then an assessment and treatment to improve digestion and eliminate SBBO may be indicated.


What Can I do to Prevent and Treat SBBO?

The best prevention for both autonomic neuropathy and SBBO is achieving good blood sugar control! Following your doctors recommendations on medications, checking your blood sugar frequently, and following a healthy lifestyle of daily activity, stress management, and eating a healthy diet rich in fresh, whole foods are critical steps to good blood sugar control.

Identifying food sensitivities may also help the symptoms of SBBO, but will not cure the problem. Food sensitivities can be detected by one of several ways. The best way to definitively identify your food sensitivities is to undergo a structured elimination and challenge diet. This diet includes 2-3 weeks on a restricted diet eliminating the most common foods and chemicals to which people are sensitive. Following the elimination phase, individual foods are challenged. The challenge phase lasts another 1-2 weeks. It is best to have some physician assistance while going through this elimination diet because it can be difficult to follow and having support and reassurance is helpful along the way. Logging your symptoms and any reactions in a food diary can also be helpful during the process. While 4-5 weeks may seem like a long time, it is really quite short compared to the rest of your life!! Most naturopathic physicians and many dieticians will be eager to guide your through this process.

Blood testing that measures antibodies to food is also available, and although controversial and somewhat expensive, my experience is that patients who follow the results of their testing have significant improvements in symptoms! In fact, although not performed in people with diabetes, patients with irritable bowel syndrome who avoided reactive foods discovered on food antibody testing led to improvement in symptoms of pain, bloating, quality of life, and bowel satisfaction suggesting value in this testing and treatment approach (Zar et al. Scand J Gastroenterol. 2005).

If neuropathy is already present, vitamin B12 and alpha-lipoic acid have both demonstrated success in clinical trials for autonomic neuropathy and may be worth discussing with your complementary medicine provider (Taniguchi et al. Clin Ther. 1987; Sun et al. Acta Neuro Taiwan. 2005; Tankova et al. Rom J Int Med.2004; Ziegler et al. Diabetes Care. 1997).

If SBBO is suspected, optimization of stomach acidity and availability of digestive enzymes is critical; this can be accomplished through supplementation. Acid-suppressing medications, including over-the-counter antacids and drugs like Zantac®, should be avoided as suppression of stomach acid is known to contribute to SBBO (Lewis et al. Aliment Pharmacol Ther.1996). If a stomach ulcer and/or reflux is present, the avoidance of trigger foods, weight loss, stress management and other possible treatments should be discussed with your provider prior to stopping any medication.

Supplements which improve SBBO include fructo-oligosaccharides (FOS), probiotics like Lactobaccilus, peppermint and/or oregano oil (available in enteric coated capsules), and herbal digestive bitters. 



Gut health in diabetes is complex and is impacted by the diet, blood sugar, the nervous system, the degree of stomach acidity, the availability of proper digestive enzymes, and having the normal bacterial flora. Symptoms of neuropathy and small bowel bacterial overgrowth (SBBO) are common in people with diabetes and include flatulence (gas) cramping, and chronic diarrhea. Testing and treatment is available for both SBBO and neuropathy. Since assessment and treatment of SBBO is not a routine part of conventional medical assessment in diabetes, a complementary provider may be a better source of information, assessment, and treatment.