Four patients, two women aged 29 and 42 years and two men aged 45 and 34 years, with longstanding complaints of (watery) diarrhoea were referred for a second opinion after extensive and costly analysis, including numerous examinations. An accurate medical history revealed deviant food patterns with abundant intake of coffee and sugar or sugar-containing products like cola or sweeteners in all four patients. Coffee (and caffeine) has a stimulating effect on both intestinal motility and net secretion, possibly leading to diarrhoea. Over-consumption of sugars and sweeteners (sometimes added to medication) can also cause osmotic diarrhoea. In all four patients, dietary advice was sufficient to resolve the diarrhoea, thus emphasizing once more the importance of an accurate and complete medical history.