Health & Science

Understanding Digestion and Your Gut

February 4, 2022

Patty James

What Is the Gut?

We know that our body must provide our organs and tissues with nutrients to perform the necessary functions and processes that sustain life. Our digestive system aids in just that—this system, also known as the gastrointestinal or digestive tract, comprises the mouth, esophagus, stomach, gallbladder, liver, pancreas, small intestine, large intestine, and anus.

Our small intestine consists of three parts – in the following order – duodenum, jejunum, and the ileum. The large intestine includes the appendix, cecum, colon, and rectum. Our digestive system works by helping to move food and liquid through our digestive tracts. The digestive system also breaks down food and liquid into smaller parts that enable our bodies to absorb and move nutrients where they are needed in the body.

The digestion process begins in the mouth, where your saliva (excreted from saliva glands) and teeth aid in the initial breakdown of food. Your food then moves down your esophagus (peristalsis) and it enters your stomach through the lower esophageal sphincter. The muscles in your stomach mix the food with the digestive’ “juices.” This mixture of food and digestive juices called chyme is then slowly emptied into the small intestine.

In your small intestine, the chyme is mixed with digestive fluids from the pancreas, liver, and intestine – this mixture is pushed forward for further digestion. The small intestine absorbs water through its walls, and the nutrients from the digested food are distributed to organs and tissues via the bloodstream.

Digestive System

The peristalsis continues, and waste products from the digestion process are moved into the large intestine, where undigested food, fluid, and older cells from your digestive tract are being prepared to be expelled from the body.

Prior to this, the large intestine absorbs water and changes the waste from liquid to solid waste or stool – the stool is then moved into the rectum, where it will be stored until your rectum pushes it out of your anus during a bowel movement.

Your GI tract requires important organisms such as bacteria to assist in the digestion process. These bacteria are commonly referred to as the gut microbiota or microbiome. For better context, the microbiota is defined as “the community of microorganisms themselves,” and the microbiome is “the collective genomes of microorganisms in a particular environment.”

The human GI tract contains a diverse and abundant number of microorganisms. In fact, the GI tract has more than 100,000 billion microorganisms. Although there is no “optimal” gut microbiota composition, a rich and diverse gut microbiome leads to a well-balanced and healthy gut.


The Brain-Gut Microbiome Connection

The Brain-Gut Connection or System is the bidirectional relationship between the brain and the human gut microbiome. It is believed that the gut microbiota has a significant and influential role in the connection between the gut and nervous system.

Gut microbiota also “promotes gastrointestinal (GI) homeostasis.” The brain-gut microbiome also ties in closely with other systems of the body, such as the immune system and the autonomic nervous system, which regulate involuntary physiological processes such as heart rate, bold pressure, respiration, and digestion.

brain-gut microbiome connection

Disruption of the gut microbiota can harm one’s health resulting in GI disorders such as irritable bowel syndrome (IBS). An estimated 60-70 million people are affected by digestive diseases, and direct medical costs are estimated to be 97.8 billion.

It is also thought that the brain-gut connection may be at play in individuals with autism spectrum disorder (ASD) as gastrointestinal dysfunction is one of the most prevalent physiological symptoms of autism spectrum disorders (ASD), and there is substantial evidence to suggest that unhealthy changes in the gut microbiota may regulate brain function and social behavior.

However, little is known about the mechanisms that underlie these relationships and how they may affect the natural history of disease or severity of ASD.

Changes in gut microbiota can also lead to changes in mood – note that 90% of serotonin receptors are located in the gut. It is important that you understand the interplay between gut health and your diet and how they can negatively or positively affect your mood.

Consider an individual who has depression – they have been prescribed a selective reuptake inhibitor (SSRI), an antidepressant. The most common side effects of this antidepressant drug are gut-related, and many individuals experience temporary gastrointestinal issues such as diarrhea, nausea, and other GI problems. This substantiates the two-way connection between to gut and brain.

Stress may also impact the microbiota, specifically short-term stressors. In fact, exposure to a social stressor for only 2 hours can significantly change the gut microbiome.


Types of Dietary Fiber

Dietary fiber is an integral part of one’s diet as it helps to regulate many processes in the body and establishes good gut health. For example, dietary fiber has been shown to lower serum cholesterol, improve glycemic control, lower blood pressure, and improve regularity in stool elimination.

types of dietary fiber

Research has also demonstrated associations between high-fiber intakes and reductions in chronic diseases risk. Defining dietary fiber is a difficult task as there is no agreement on its definition among nutritional scientists. One definition describes dietary fiber as “remnants of plant cells that are resistant to digestion by human enzymes.”

Dietary fibers are either classified as polysaccharides or oligosaccharides. Dietary fiber is further classified based on its water solubility, viscosity, and fermentability. Polysaccharides are further classified into non-starch polysaccharides (NSP) and resistant starch (RS), and oligosaccharides include resistant oligosaccharides (RO). NSP, RS, and RO consist of several different fibers with different solubility, viscosity, and fermentability characteristics.

Different types of dietary fibers:

  • Ligin
  • Cellulose
  • Β-Glucans
  • Hemicelluloses
  • Pectins
  • Gums
  • Inulin and oligofructose
  • Resistant starch

It is worth noting that the other definitions of fiber include functional fiber, which “consists of isolated, nondigestible carbohydrates that have beneficial physiological effects in humans.”

Fibers identified as functional fibers are:

  • Isolated forms of the types of fibers listed above
  • Psyllium
  • Chitin and chitosan
  • Fructooligosaccharides
  • Galactooligosaccharides
  • Polydextrose and polyols
  • Resistant dextrins

It is essential to stress the importance of fiber in our diets as it feeds the bacteria in our gut, leading to healthy digestion. For healthy digestion, it is recommended that you consume that appropriate amount of fiber.

According to the Food and Nutrition Board of the National Institutes of Medicine, National Academy of Sciences, the Adequate Intake (AI) recommendation for total daily fiber intake is 38 g per day for men and 24 g per day for women.

However, many Americans do not meet these recommendations for total dietary intake. In fact, the average American only consumes about 17 g per day of dietary fiber.


Symptoms of Gut Problems

As discussed earlier in this article, the gut microbiome plays a crucial role in proper digestion and immune system function. Disruptions in the gut microbiome or community profile can often negatively impact the health of the GI tract and cause digestive problems.

Symptoms of gut problems include the following:

  • Frequently upset stomach
  • Unintentional weight changes
  • Sleep disturbances or constant fatigue
  • Skin irritation
  • Autoimmune conditions (i.e., irritable bowel disease (IBD))
  • Food intolerance

gut health problems


Gut Health Testing

Appropriate diagnosis of disorders of the gut or digestive tract often involves your healthcare provider first collecting a thorough and accurate medical history. You may need to have more extensive diagnostic procedures performed, including lab tests, imaging tests, and endoscopies. These gut health tests may include the following*:

Lab tests

  • Fecal occult blood test – checks for hidden blood in stool
  • Stool culture – identifies whether there is a presence of abnormal bacterial in the digestive tract that may be causing diarrhea or other digestive problems

Imaging tests

  • Barium beefsteak meal – involves eating a meal containing barium; allows for the radiologist to watch the stomach as it digests the meal
  • Colorectal transit study – test to demonstrate how well food can move through the colon
  • Computed tomography scan (CT or CAT scan) – imaging tests that utilize X-rays and a computer to make images of the body
  • Defecography – X-ray of the anorectal area that evaluates completeness of stool elimination, checks for anorectal abnormalities, etc.
  • Lower GI series (also called barium enema) – test that examines the rectum, the large intestine, and the lower part of the small intestine
  • Magnetic resonance imaging (MRI)

Endoscopic procedures

  • Colonoscopy – allows provider to examine/view entire length of the large intestine (colon)
  • Endoscopic retrograde cholangiopancreatography (ERCP) – allows for diagnosis and treatment of liver, gallbladder,
  • Esophagogastroduodenoscopy (also called EGD or upper endoscopy)
  • Sigmoidoscopy

*Note that this is not meant to be an exhaustive list of tests and procedures that measure gut health.

There are also at-home microbiome tests that seek to identify gut issues. With these tests, you can take them in the comfort of your home, and results are provided digitally within a few weeks. Unfortunately, there are downsides to these tests as they are not approved by the U.S Food and Drug Administration (FDA).

Additionally, the results of many of these tests have often proved unreliable and inaccurate. You can also take food sensitivity tests as they are also linked to gut microbiota imbalances.


How to Improve Gut Health

There are multiple ways that you can improve your gut health. In western society, we often default to pharmacological interventions to improve our health. However, you can improve your gut health naturally by using “food as medicine.”

One way to improve your gut health and encourage bacterial diversity is by eating a nutrient-dense, fiber-rich diet. To promote a healthy gut, you may do the following:

  • Eat whole foods
  • Limit or avoid processed foods
  • Eat fresh fruits and vegetables
  • Eat foods rich in fiber to aid in digestion
  • Introduce probiotic-rich foods
  • Reduce sugar intake
  • Add fermented foods


Exercise may also improve your health. In a review by,  Mailing et al.,  increasing evidence suggests that “regular aerobic exercise confers benefits to the gut microbiota….”

To ensure you are getting enough exercise, refer to the 2018 Physical Activity Guidelines for Americans, 2nd edition. The physical activity guidelines recommend that adults exercise for 30 minutes a day, five times a week at moderate intensity. This may vary depending on your health status and mobility.

At Foogal, we genuinely believe “food as medicine” is the key to preventing and managing diseases. Our app can help you manage and improve your gut health by providing meals rich in nutrients and fiber. We also have a fiber filter that allows user-specific customization to meet your dietary needs.


Discover healthy recipes that can improve your gut health by downloading the Foogal app on Google Play and the App Store.

Learn more about how Foogal can help you improve your health and prevent and manage diseases through healthy eating.