Caffeine is consumed worldwide in coffee, tea, and soft drinks, and its health benefits have been studied for years. Now, researchers have looked at the genes associated with caffeine metabolism to determine how the level of caffeine in the blood affects body fat and the risk of type 2 diabetes and cardiovascular disease.
The standard cup of coffee – in the US, that’s 8 oz or around 250 ml – contains 70 to 150 mg of caffeine. By comparison, 12 oz (around 350 ml) of caffeinated soft drink usually contains 30 to 40 mg of caffeine, and an 8-oz cup of green or black tea contains 30 to 50 mg.
Small, short-term trials have shown that caffeine intake reduces body mass index (BMI) and fat mass, but its long-term effects are unknown. Other studies have observed that drinking three to five cups of coffee daily reduces the risk of type 2 diabetes and cardiovascular disease. But most studies have not been able to reliably establish a causal link between caffeine intake and disease.
Caffeine is metabolized largely by the liver, but its metabolism can be affected by variations of the genes CYP1A2 and AHR. People with variations of these genes metabolize caffeine more slowly, so while they consume less coffee on average, their blood caffeine levels are higher.