Myths vs facts: LCT and blood sugar

The link between LCT (lactase persistence) and blood sugar is often misunderstood. Fact: Lactose is broken down by lactase into glucose and galactose, which can raise blood sugar – similar to other sugars. Myth: Lactose intolerance causes blood sugar spikes. In reality, undigested lactose in non-persistent individuals leads to diarrhea and bloating, which may even reduce absorption. Some studies show a lower glycemic response after lactose ingestion in lactose-intolerant individuals, likely due to accelerated transit. However, the effect is small and variable. LCT genotyping (e.g., rs4988235) only predicts lactose digestion ability, not directly blood sugar levels. For people with diabetes or prediabetes, the influence of LCT genotype on fasting glucose or HbA1c is not well established. Evidence is based on observational studies (human-moderate). Caveat: Blood sugar regulation is far more influenced by total carbohydrate intake, fiber, exercise, and insulin resistance. A DNA test for LCT is no substitute for a balanced diet or medical advice. Safety note: If lactose intolerance is suspected, a hydrogen breath test or elimination diet under medical supervision is recommended.