What should you know about fructose and lactose intolerance?

Fructose and lactose intolerance involve different sugars, yet both can cause bloating, abdominal pain, and diarrhoea. Fructose is found in fruits, honey, and some sweetened foods; lactose is the sugar in milk and many dairy products. Symptoms depend on the amount consumed and how well the gut absorbs or digests that sugar.

Lactose intolerance usually relates to reduced lactase, the enzyme that digests lactose. Fructose symptoms may occur when the intestine does not absorb the amount consumed efficiently. A person can have one, both, or neither; similar symptoms can arise from irritable bowel conditions, infection, or other food intolerances. Food timing, portion size, and associated ingredients often provide more useful clues than a single suspected food.

Keep a diary recording the food, portion, time, symptoms, and whether the meal contained several possible triggers. Do not remove all fruit or dairy without a replacement plan. A clinician may discuss food intolerance testing, a supervised elimination and reintroduction process, or nutrition counselling. If dairy is reduced, ask how to maintain calcium and protein; if fruit is reduced, preserve fibre and variety where tolerated.

Seek medical review for persistent diarrhoea, recurrent abdominal pain, weight loss, blood in stool, fever, vomiting, or symptoms that wake you at night. Get emergency help for swelling of the lips or throat, wheezing, difficulty breathing, or collapse after eating, as these can signal allergy rather than intolerance.

Ask which sugar your symptoms most strongly suggest, whether testing is appropriate, and how to trial foods without creating nutritional gaps. Discuss lactose-free alternatives, fruit portions, hidden ingredients, and the point at which symptoms need further investigation.