It’s common to hear about babies or young children with lactose intolerance. But what about adults who suddenly find themselves reacting badly to dairy?
Many people develop this condition later in life, often to their surprise. This shift isn’t random; it’s usually due to a specific type of intolerance.
Let’s explore why some individuals develop lactose intolerance in adulthood.
The Most Common Reason: Primary Lactase Deficiency
This is the leading cause of adult-onset lactose intolerance. It’s also known as “adult-type hypolactasia.”
It’s a genetically programmed decrease in lactase production. Our bodies are designed to produce a lot of lactase in infancy for digesting breast milk.
However, for a large portion of the global population, lactase production naturally declines after childhood. It’s a normal genetic “switch-off.”
Genetic Predisposition and Ancestry
This genetic decline isn’t universal. It’s more prevalent in certain ethnic groups.
Populations with ancestry from East Asia, Africa, Hispanic regions, and Native American groups are more likely to develop it. Their ancestors traditionally didn’t rely on dairy beyond weaning.
In contrast, populations with a long history of dairy farming (like those of Northern European descent) tend to maintain lactase production into adulthood. This is called “lactase persistence.”
The Gradual Decline of Lactase
The decrease in lactase activity isn’t usually sudden. It’s often a gradual process that can begin in late childhood or adolescence.
Symptoms might only become noticeable in adulthood. This happens when lactase levels drop below what’s needed to digest typical amounts of lactose.
Your body might be able to handle small amounts of dairy for years. Then, one day, the symptoms become impossible to ignore.
Secondary Lactase Deficiency: A Different Cause
Sometimes, lactose intolerance develops due to damage to the small intestine. This is called “secondary lactase deficiency.”
Conditions that can injure the lining of the small intestine, where lactase is produced, include:
Gastroenteritis: A severe stomach bug can temporarily reduce lactase. Celiac Disease: An autoimmune reaction to gluten that damages the small intestine. Crohn’s Disease: An inflammatory bowel disease that can affect any part of the digestive tract. Small Intestinal Bacterial Overgrowth (SIBO): An excess of bacteria in the small intestine can interfere with lactase function. Certain Medications or Surgeries: Some antibiotics or intestinal surgeries can also lead to temporary lactase deficiency.
The good news is that if the underlying condition is treated, lactase production can often recover. This means the lactose intolerance can be temporary.
What About Congenital or Developmental Types?
Congenital lactase deficiency is extremely rare. Babies are born with almost no lactase and show severe symptoms from birth. This isn’t an adult-onset condition.
Developmental lactase deficiency affects premature babies. Their intestines aren’t fully mature. This usually resolves as they grow.
So, when adults develop intolerance, it’s almost always the primary (genetic decline) or secondary (gut damage) type.
Recognizing the Shift
If you’ve always enjoyed dairy but now experience gas, bloating, cramps, or diarrhea after consuming it, it’s worth investigating.
These symptoms often appear consistently after dairy intake. They can range from mild discomfort to more significant distress.
Consult a healthcare professional for an accurate diagnosis. They can perform tests to confirm lactose intolerance and determine its type.
Understanding why your body changed can help you manage your diet effectively and live comfortably.