Intestinal disaccharidase activity in patients with autism: effect of age, gender, and intestinal inflammation.
Over half of autistic kids lack the milk-digesting enzyme, and young boys are hit hardest—so rule out lactose pain before treating 'autistic' behavior.
01Research in Context
What this study did
Doctors took tiny gut tissue samples from autistic children. They tested how well the lining could break down milk sugar.
They also checked for gut inflammation and sorted results by age and sex.
What they found
About six in ten kids lacked the lactase enzyme. Their guts looked healthy, so inflammation was not the cause.
Boys aged five and under had even lower enzyme levels than girls the same age.
How this fits with other research
Zubarioglu et al. (2025) went further. They used gene tests and found 7% of autistic children with tummy pain actually have a different sugar-breakdown problem called CSID.
Panahi et al. (2023) and Cohrs et al. (2017) also show boys carry more metabolic quirks. They found shorter telomeres and higher serotonin only in young autistic boys, matching the male-skewed lactase loss here.
Together these papers flag a pattern: when an autistic boy complains of belly pain or shows vague distress, think biology first, not just behavior.
Why it matters
A child who cannot digest milk may look gassy, cranky, or spaced-out. Those signs mimic escape or attention-maintained problem behavior.
Before you write a behavior plan, ask the family if the child drinks milk and when the behavior peaks. A simple enzyme or gene test can tell you if the issue is pain, not reinforcement.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Add a diet column to your intake form; note milk intake and any post-meal behavior spike.
02At a glance
03Original abstract
Intestinal disaccharidase activities were measured in 199 individuals with autism to determine the frequency of enzyme deficiency. All patients had duodenal biopsies that were evaluated morphologically and assayed for lactase, sucrase, and maltase activity. Frequency of lactase deficiency was 58% in autistic children ≤ 5 years old and 65% in older patients. As would be expected, patients with autism at age 5 > years demonstrated significant decline in lactase activity (24%, p = .02) in comparison with ≤ 5 years old autistic patients. Boys ≤ 5 years old with autism had 1.7 fold lower lactase activity than girls with autism (p = .02). Only 6% of autistic patients had intestinal inflammation. Lactase deficiency not associated with intestinal inflammation or injury is common in autistic children and may contribute to abdominal discomfort, pain and observed aberrant behavior. Most autistic children with lactose intolerance are not identified by clinical history.
Autism : the international journal of research and practice, 2011 · doi:10.1177/1362361310369142