Lactose intolerance (LI) and acid reflux (AR) are two common digestive complaints. Lactose intolerance stems from the inability to properly digest the sugar found in milk, causing discomfort lower in the digestive tract. Acid reflux involves the backward flow of stomach contents into the esophagus, leading to heartburn. The connection between these two conditions is a frequent concern for individuals experiencing both symptoms.
The Relationship Between Lactose Intolerance and Acid Reflux
Lactose intolerance does not cause acid reflux by increasing stomach acid production. Instead, the link is primarily mechanical, acting as an indirect trigger for reflux episodes. When a person with LI consumes dairy, the resulting digestive process creates physical pressure within the abdomen that can disrupt the body’s anti-reflux barrier. This mechanism explains why many people notice heartburn shortly after consuming dairy products.
Acid reflux occurs when stomach acid flows back into the esophagus, which lacks the protective lining of the stomach. The discomfort from the bloating and gas associated with LI is sometimes mistaken for the burning sensation of reflux. However, the physical symptoms resulting from undigested lactose often exacerbate or trigger acid reflux in people who are already prone to it.
How Undigested Lactose Affects the Digestive Tract
Lactose intolerance begins when the small intestine does not produce sufficient amounts of the enzyme lactase. Lactase breaks down the disaccharide lactose into the simpler sugars glucose and galactose for absorption. When this enzyme is deficient, lactose remains undigested and passes into the large intestine.
In the colon, undigested lactose encounters gut bacteria, which readily ferment the sugar. This fermentation generates large volumes of gases, primarily hydrogen, methane, and carbon dioxide. The accumulation of these gases leads to common lower gastrointestinal symptoms like bloating, flatulence, and abdominal distension. Unabsorbed sugar also draws excess water into the bowel, contributing to diarrhea.
Why Digestive Pressure Can Trigger Reflux
The excessive gas and abdominal distension generated by lactose fermentation significantly increase intra-abdominal pressure (IAP). This pressure pushes upward against the stomach, applying mechanical force to the lower esophageal sphincter (LES). The LES is a ring of muscle that acts as a valve between the esophagus and the stomach, designed to remain tightly closed to prevent acid backflow.
When the IAP increases due to intestinal gas, it can overcome the resistance of the LES. If the sphincter is weakened or prone to relaxation, the upward pressure forces stomach contents, including acid, back into the esophagus. This mechanically triggered reflux is a direct consequence of the physical strain placed on the upper digestive tract by gas accumulation. The mechanism is particularly likely to cause reflux in individuals who have an existing structural vulnerability, such as a hiatal hernia.
Dietary Management Strategies
Managing the combined symptoms requires reducing the intake of lactose that causes the pressure trigger. A primary strategy involves reducing the amount of lactose consumed to a tolerated level without triggering excessive gas production. Many people with LI can tolerate about 12 grams of lactose, roughly the amount in one cup of milk, especially when consumed with other foods.
Strategies for Reducing Lactose Intake
- Over-the-counter lactase enzyme supplements can be taken before consuming dairy to help break down lactose in the small intestine.
- Some dairy products naturally contain less lactose than milk, making them easier to digest.
- Hard cheeses, such as cheddar or Swiss, and yogurts that contain live and active cultures are often better tolerated because the fermentation process has already broken down much of the lactose.
- Opting for lactose-free milk and dairy alternatives, such as almond, soy, or oat milk, can eliminate the trigger entirely.