Lactose Intolerance
Pathology: Lactose is digested by the lactase enzyme on the microvilli (small intestine). Lactose digestion may be compromised if lactase activity is reduced or the intestinal transit time increases. Undigested lactose is fermented by bacteria in the large intestine, producing gas, bloating, pain and diarrhea.
Food-Symptom Interval: It takes approximately 4 – 6 hours for lactose to travel to the large intestine and be fermented.
Diagnosis: Hydrogen breath tests provide some information, but the results do not always correlate with symptoms. The best diagnosis is elimination and reintroduction.
Treatment: Most patients can consume small quantities and may be able to increase their lactose intake over time (i.e., lactase enzyme activity may gradually increase with lactose consumption). The lactase enzyme can be purchased in drops or tablets.
Lactose (milk sugar) is a disaccharide (i.e., glucose bonded to galactose). Lactose is broken into these monosaccharides by the lactase enzyme on the small intestinal microvilli. The monosaccharides are absorbed into the body. If lactase activity is compromised, unabsorbed lactose enters the large intestine, where bacteria ferment it.
The physiological effects depend on many factors, including:
- Gastrointestinal flora – Everyone has a unique microbiome, producing different fermentation patterns. Additionally, small intestinal bacteria overgrowth (SIBO) may lead to fermentation in the small intestine before the lactose is digested and absorbed.
- Digestive transit time – When contents move too quickly through the small intestine, there may not be enough time for proper digestion and absorption.
- Gastrointestinal function – the overall health and function of the gastrointestinal tract will impact carbohydrate digestion and absorption.
Primary lactose intolerance is a genetic reduction in lactase enzyme after infancy and is common in specific ethnic backgrounds. Secondary (acquired) lactose intolerance results from atrophy of the microvilli. For example, lactose intolerance is common with untreated celiac disease but improves as the microvilli heal.
Lactose fermentation produces gasses and increased osmotic pressure (which draws water from surrounding tissue into the lumen). Bloating, flatulence, pain and diarrhea start around four to six hours after lactose consumption. However, many clients have reported more immediate symptoms with lactose consumption.
The video summarizes the pathology and symptoms.
Breath hydrogen tests are sometimes used to diagnose lactose intolerance. The patient drinks lactose, and the lab monitors the amount of hydrogen in the patient’s breath. Hydrogen is one of the gasses produced during fermentation, so elevated levels indicate lactose intolerance. However, the results are not definitive. Other factors, such as rapid transit through the small intestine, can result in a positive test (because lactase does not have enough time to do its job).
Lactose elimination and challenge is the most practical diagnostic tool. The symptoms are functional and resolve quickly after restriction (i.e., compared to a condition like EGID, where inflammation needs to subside).
A lactose-reduced diet is relatively easy and not overly restrictive (depending on the severity). Several lactose-reduced dairy products are available, and fermented dairy (e.g., yogurt) is usually better tolerated. Lactase enzyme drops (added to regular milk to break lactose apart) or tablets (taken orally before lactose-containing food) are available.
Secondary lactose intolerance will improve as the intestine heals, and the client should be encouraged to rechallenge lactose periodically. Additionally, gradually increasing lactose intake may increase the body’s lactase production.