Is the rs4988235 GG genotype associated with lactase non-persistence and lactose malabsorption?

The claim is largely consistent with current evidence, but the genetic result requires careful interpretation. rs4988235 is informative mainly for European-ancestry lactase-persistence biology, and genotype indicates predisposition rather than current digestive or symptom status.

Genetic and clinical interpretation

• rs4988235 is conventionally reported as the MCM6 −13910 C>T variant regulating LCT. In European-ancestry populations, conventional C/C is associated with developmental lactase non-persistence; T-containing genotypes are associated with persistence.
• A reported GG genotype plausibly represents the reverse-strand equivalent of conventional C/C, but this must be confirmed with the testing laboratory before drawing conclusions.
• If confirmed as C/C-equivalent, GG supports a higher likelihood of reduced adult lactase activity and lactose malabsorption—not a diagnosis of either current malabsorption or symptomatic lactose intolerance. In Polish adult data, only 24.5% of C/C participants had an abnormal breath test.

Symptoms, dose, and diet

• Symptoms are strongly dose-dependent and vary between individuals. Most adults with lactose malabsorption or presumed intolerance tolerate 12–15 g lactose—about one cup of milk—with no or minor symptoms; 40–50 g challenge doses can cause symptoms even in people who tolerate ordinary portions.
• Taking lactose with food or spreading intake across meals may improve tolerance. A personal trial of portion size and food context is more clinically useful than universal dairy avoidance.

Mechanistic context

• With reduced lactase activity, unabsorbed lactose reaches the colon, where microbes ferment it to gases and short-chain fatty acids.
• The resulting osmotic fluid effects, gas, and intestinal distension can cause bloating, pain, flatulence, and diarrhea. Transit time and visceral sensitivity help explain why some people with malabsorption have few symptoms while others react at lower doses.

Bottom line

• GG is a plausible marker of lactase non-persistence only after strand and ancestry-context confirmation; symptoms remain individualized and should be guided by dietary response and, when needed, breath testing rather than genotype alone.