Postural Orthostatic Tachycardia Syndrome (POTS) is a disorder of the autonomic nervous system (ANS). The ANS controls involuntary bodily functions, including heart rate, blood pressure, breathing, and digestion. Because the ANS is dysregulated in POTS, the condition impacts far more than just the cardiovascular system. Gastrointestinal (GI) issues, including severe nausea and vomiting, are common, though they are often overlooked as symptoms related to the underlying disorder. Many people with POTS report chronic digestive problems that severely impact their quality of life.
Defining Postural Orthostatic Tachycardia Syndrome (POTS)
POTS is a form of orthostatic intolerance, meaning symptoms worsen when a person is upright and improve when they recline. The defining physiological feature is an excessive increase in heart rate upon standing. For adults, this means a sustained heart rate increase of at least 30 beats per minute within 10 minutes of moving from a lying to a standing position, with no significant drop in blood pressure.
This heart rate response, or tachycardia, is the body’s attempt to compensate for poor blood flow regulation when upright. Common non-GI symptoms include dizziness, lightheadedness, and fatigue. Patients also frequently experience cognitive difficulties, often described as “brain fog,” along with headaches and weakness.
Autonomic Dysfunction and the Gastrointestinal System
The autonomic nervous system regulates the digestive tract, controlling motility and blood flow to the organs. When the ANS is dysregulated in POTS, it directly disrupts these processes, leading to digestive symptoms.
When a person stands up, gravity pulls blood downward. The ANS normally triggers compensatory constriction of blood vessels, but in POTS, this response is faulty, leading to blood pooling primarily in the lower body. This pooling reduces blood volume returning to the heart and decreases blood flow to the abdomen’s splanchnic region, including the stomach and intestines.
The digestive process demands increased blood flow to the gut after a meal to facilitate absorption. For a person with POTS, this necessary diversion of blood exacerbates the systemic blood flow deficit, often worsening orthostatic symptoms immediately after eating. This compromised circulation impairs normal gut function, contributing to nausea and abdominal distress.
The ANS also controls the muscle contractions responsible for moving food through the digestive tract, a process known as motility. Misfiring of the autonomic nerves can cause gut muscles to contract too weakly, too strongly, or in an uncoordinated manner. This dysmotility causes food to move through the stomach and intestines at an abnormal pace, which is the physiological basis for many chronic GI complaints.
Specific Manifestations of GI Distress in POTS
GI symptoms are reported by a large majority of POTS patients. Nausea is one of the most common complaints, often accompanied by vomiting that can limit the ability to maintain adequate nutrition and hydration.
A specific manifestation is gastroparesis, or delayed gastric emptying, where food remains in the stomach too long. This condition is associated with persistent nausea, vomiting, and feeling full after only a few bites of food (early satiety). Some individuals experience the opposite problem, rapid gastric emptying, which leads to symptoms like abdominal pain and bloating.
POTS frequently affects the lower bowel, resulting in alterations in habit. Patients often experience functional bowel symptoms, including chronic constipation or bouts of diarrhea.
Strategies for Symptom Management
Managing GI symptoms often begins with non-pharmacological approaches focused on improving blood volume and mitigating stress on the digestive system.
Volume and Circulation
Increasing fluid intake to two to three liters daily and consuming a high amount of salt are foundational strategies to expand blood plasma volume. This increased volume helps counteract blood pooling and improves systemic circulation, which can indirectly relieve GI symptoms.
Dietary Adjustments
Dietary modifications are beneficial, particularly shifting from three large meals to four to six smaller, more frequent meals throughout the day. Smaller portions require less blood flow to the gut at one time, reducing the post-meal drop in systemic blood pressure and minimizing symptoms like nausea. Some patients find relief by avoiding specific trigger foods, such as those high in gluten, dairy, or eggs.
Positional and Medical Interventions
Positional strategies can help, such as remaining reclined or semi-reclined while eating to lessen the gravitational challenge on the circulatory system. Simple actions like drinking water before getting out of bed can also improve morning orthostatic tolerance and reduce symptom severity. For severe cases, specialists may recommend pro-motility medications or anti-nausea agents to target specific issues like gastroparesis or persistent vomiting.