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Lactose Intolerance

Lactose intolerance is the inability to fully digest the sugar in milk, causing bloating, gas, and diarrhea after dairy; symptoms are managed with diet changes and lactase supplements.

Gastrointestinal
Lactose intolerance is the inability to fully digest lactose, the natural sugar in milk and dairy products, because the small intestine makes too little of the enzyme lactase. Undigested lactose travels to the colon, where bacteria ferment it and produce gas and fluid — the source of the familiar bloating and diarrhea. It is extremely common worldwide and, importantly, it is not a milk allergy: the immune system is not involved, and small amounts of dairy are usually safe. Symptoms can appear for the first time in adulthood, which often surprises people who drank milk comfortably for years. Causes:
  • Primary lactase deficiency: The most common form. Lactase production naturally declines after childhood in a large share of the world's population; how much it declines varies widely by ancestry.
  • Secondary lactase deficiency: Injury to the small intestine temporarily reduces lactase. Causes include stomach viruses, untreated celiac disease, and flares of Crohn's disease. Treating the underlying condition often restores dairy tolerance.
  • Congenital lactase deficiency: A rare inherited condition present from birth.
Symptoms: Symptoms typically begin thirty minutes to two hours after consuming dairy, and their intensity tracks with how much lactose was eaten and how much lactase you still make:
  • Bloating and abdominal cramps: From gas produced by colonic fermentation.
  • Flatulence: Often the most noticeable and persistent symptom.
  • Diarrhea: Unabsorbed lactose pulls water into the bowel.
  • Stomach rumbling and nausea: Occasionally with vomiting.
Because these symptoms overlap with other digestive conditions, such as irritable bowel syndrome, an accurate diagnosis matters — dairy is not always the culprit it appears to be. Lactose intolerance never causes hives, wheezing, or swelling; those symptoms suggest a true milk allergy and need separate evaluation. Diagnosis: Many people can identify the pattern themselves, and a structured trial — removing dairy for two weeks, then reintroducing it — is often revealing. Keeping a simple food and symptom diary during that time frequently makes the connection obvious. When the picture is unclear, a hydrogen breath test provides objective confirmation: after drinking a lactose solution, elevated hydrogen in the breath indicates the sugar was fermented rather than absorbed. Your doctor may also check for celiac disease or other conditions if symptoms do not fit a simple lactose pattern or if there are warning signs such as weight loss or blood in the stool. Management: Lactose intolerance is managed, not cured — and management is usually easy:
  • Learn your threshold: Most people tolerate up to about a cup of milk with a meal; spreading dairy through the day in small portions works better than a large serving at once.
  • Choose lower-lactose dairy: Hard aged cheeses such as cheddar and Swiss contain little lactose, and yogurt with live cultures is often well tolerated because its bacteria digest lactose for you.
  • Lactase enzyme supplements: Over-the-counter tablets or drops taken with the first bite of dairy replace the missing enzyme.
  • Lactose-free products: Lactose-free milk is regular milk with the enzyme already added — same protein, calcium, and vitamins.
  • Protect your bones: If you cut back on dairy, be deliberate about calcium and vitamin D from fortified foods or supplements, since chronically low intake contributes to bone loss and osteoporosis. Most adults need roughly 1,000 to 1,200 milligrams of calcium daily, depending on age and sex.
Lactose intolerance is a nuisance, not a danger, and nearly everyone can find a comfortable balance that keeps favorite foods on the menu. The primary care team at Zimmer Medical Group can confirm the diagnosis, rule out look-alike conditions, and help you build a nutritionally complete plan.

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