Many people can’t start the day without a cup of coffee, but some people feel sick at the mere taste of it. «Each individual can only drink a certain amount of coffee,» internist and dietician Giorgos Panotopoulos told Kathimerini. Coffee acts as a stimulant because it causes blood vessels to twitch and it speeds up the heartbeat. In general, we should not drink more than three to four cups a day, but those who suffer from high blood pressure, cardiac arrhythmia and coronary disease should drink less than that. People who suffer from chronic ulcers, gastritis and colitis may also have less tolerance to coffee. Though tea and cocoa contain substances – theophylin and theobromin, respectively – which give those beverages a similar effect to coffee, caffeine is a stronger stimulant. Though coffee was blamed at one stage for increasing levels of «bad» cholesterol, Panotopoulos says the research referred to Scandinavian countries where people drink large amounts of brewed coffee. As coffee lessens the sense of hunger, it can also cause hypoglycemia and disrupt the secretion of insulin.