An Intro to Small Intestinal Bacterial Overgrowth

When bacteria proliferate in the wrong place, instead of aiding digestion, they can disrupt it
June 9, 2021 Updated: June 9, 2021

The human digestive system is a mighty and miraculous yet delicately balanced realm. It doesn’t take much to disrupt the gut microbiome and create a tangle of uncomfortable and disruptive symptoms.

Bacteria are a critical component to a healthy gut and small intestine, but when bacteria overgrow in the small intestine, it can lead to a leaky gut and a host of other gastrointestinal symptoms.

Many Americans experience intense or unspecified abdominal pain along with bloating and irregular bowel habits. Quite frequently, the cause of these symptoms is a common but often misunderstood condition that can wreak havoc on your body: SIBO—small intestinal bacterial overgrowth.

The Small Intestine

Before we delve into SIBO, it’s important to understand the job of the small intestine. The small intestine has a significant role in helping us digest and absorb nutrients. It’s also an important part of the immune system as it houses a complex organization of immune cells called lymphoid cells. Also known as the gut-associated lymphoid tissue (GALT), this component of the immune system helps fight infection and regulate the immune system.

Because the small intestine has an essential role in overall health and well-being, it’s crucial to understand what can go wrong in this part of the digestive tract.

What Is SIBO?

As the name suggests, small intestinal bacterial overgrowth, or SIBO, occurs when there is an increase in the amount or the types of bacteria found in the small intestine. In SIBO, bacteria normally found in the large intestine, most of which is made up of the colon, finds its way to the relatively sterile small intestine, where few bacteria normally reside. Usually, SIBO isn’t caused by just one type of bacteria, but an assortment of bacterial strains that would usually be found in the colon. The cause of SIBO is often a complex combination of issues such as decreased intestinal motility, low stomach acid, poor immune function, and dysfunction in the ileocecal valve.

Once the food you consume is broken down, nutrients and minerals are absorbed in the small intestine and waste products are formed and eliminated through the large intestine and colon. In a healthy digestive system, there is a high concentration of many bacterial strains in the large intestine.

Sometimes, that bacteria migrates backward because of a malfunction in the ileocecal valve, a sphincter muscle that separates the small intestine from the large and controls the flow of digestion between the two. This malfunction can start a microbial imbalance. When bacterial species shift or proliferate in the small intestine, it can affect macro and micronutrient absorption as well as spark SIBO symptoms.

When what you eat lingers for too long in the small intestine, trouble brews. This slow movement—often caused by reduced gastric motility or low gastric acid secretion—spawns the overgrowth of bacteria. This creates a microbial imbalance in the small intestine and discomfort ensues.

In any of these scenarios, bacteria species (whether too much or the wrong types) in the small intestine can contribute to nutritional deficiencies because they hinder digestion and assimilation. In fact, these bacteria inhibit the absorption of nutrients such as vitamin B12, vitamin A, vitamin D, vitamin K, iron, and some amino acids.

Who Is at Risk?

People with weakened immune systems are especially susceptible to SIBO. Chronic conditions such as diabetes (Type 1 and Type 2), IBS, celiac disease, Crohn’s disease, and lupus can also put you at risk for the condition. Low stomach acid can put someone at risk for SIBO as can abdominal scar tissue or a blockage in your gastrointestinal tract.

Medications such as antibiotics, proton pump inhibitors, antacids, and narcotics can also increase your chances of developing SIBO. Heavy alcohol consumption has been associated with SIBO in certain studies. Even a bout of food poisoning can disrupt your system enough to trigger an overgrowth of small intestinal bacteria—which is exactly what happened to a few members of my own family in the past.

What Are the Signs and Symptoms?

Symptoms of SIBO can be mild or easily (mistakenly) attributed to another condition, while others can be severe and impossible to ignore. This is why SIBO has been so difficult to diagnose. Any of the following may indicate SIBO:

  • Abdominal pain and discomfort
  • Bloating and abdominal distention
  • Gas and belching
  • Heartburn
  • Fatigue
  • Queasiness
  • Diarrhea or constipation
  • Irritable bowel syndrome (IBS)
  • Inflammatory bowel disease (IBD)
  • Weight loss
  • Anemia and other nutrient deficiencies
  • Brain fog and mood symptoms

Some experience systemic symptoms including headaches, fatigue, joint and muscle pain, and some skin conditions.

What Happens Next?

The good news is that even though research on SIBO is ongoing and there’s still much to learn, there are ways to correctly diagnose and treat the condition. Next week, we’ll look at how and where SIBO and IBS symptoms overlap, and the various tests available to determine whether you have SIBO.

If you think you might have SIBO and want relief from your symptoms, please reach out to a skilled clinician to walk you through the process.

Dr. Ashley Turner is a traditionally-trained naturopath and board-certified doctor of holistic health for Restorative Wellness Center. An expert in functional medicine, Turner is the author of the gut-healing guide “Restorative Kitchen and Restorative Traditions,” a cookbook comprised of non-inflammatory holiday recipes.