Theobromine is an alkaloid substance found in chocolate. It is in a class of substances known as methylxanthines, making it chemically related to caffeine, among other stimulants. The effects of theobromine are much more mild than those of caffeine, although the substance can cause medical problems if it is consumed in high volume. Fortunately for most humans, the threshold at which theobromine becomes dangerous is very high.

The name of the substance was taken from the genus name for the cacao plant, Theobroma, which means “food of the gods” in Greek. Theobroma cacao was cultivated and used in the New World for centuries before European explorers were introduced to it, and the food quickly became a hit, especially when it was combined with cane sugar from the Caribbean colonies. The plant contains a complex assortment of chemical compounds, all of which contribute to the unique flavor and physiological effects of chocolate.

In 1878, theobromine was isolated from cacao beans, and it was successfully synthesized from xanthine shortly thereafter. The substance is sometimes called xantheose, and its chemical formula is C7H8N4O2. When isolated from cacao beans, the substance is colorless to white, and quite bitter. All chocolate products contain theobromine, although dark chocolate has much higher concentrations, since it is not diluted with ingredients like milk and cream. Some chocolate can contain as much as three percent theobromine, or it can be diluted to less than half a percent.

Like caffeine, theobromine is a diuretic, and it also acts as a stimulant. In addition to causing the heart to beat more rapidly, theobromine also widens the blood vessels, reducing blood pressure. Unlike caffeine, theobromine does not act as extensively on the central nervous system, so it is unlikely to cause the shakes and tremors associated with excessive caffeine consumption. The compound is also a bronchiodilator, and it has been used in the treatment of asthma with some success.

Theobromine is only one among many substances which interact in a chocolate bar. Many of these substances must actually be consumed in very high concentrations to offer health benefits, making chocolate a less than ideal source of health food, despite articles in the news to the contrary. For many animals, especially dogs, chocolate is actually extremely dangerous, since they metabolize theobromine very slowly. Pets should not be offered products with chocolate in them, as it only takes a small amount of chocolate to be deadly.