Caffeine

There's evidence that caffeine's effects on adenosine and dopamine receptors can have long-term benefits, too, reducing the risk of diseases like Parkinson's, Alzheimer's, and some types of cancer. Caffeine can also ramp up the body's ability to burn fat. In fact, some sports organisations think that caffeine gives athletes an unfair advantage and have placed limits on its consumption. From 1972 until 2004, Olympic athletes had to stay below a certain blood-caffeine concentration to compete. Of course, not all of caffeine's effects are so helpful. It might make you feel better and more alert, but it can also raise your heart rate and blood pressure, cause increased urination or diarrhoea, and contribute to insomnia and anxiety. Plus, the foods and beverages caffeine is found in have their own impacts on your body that have to be taken into account. Your brain can adapt to regular consumption of caffeine. If your adenosine receptors are perpetually clogged, your body will manufacture extra ones. That way, even with caffeine around, adenosine can still do its job of signalling the brain to power down. That's why you may find you need to consume more and more caffeine to feel as alert. There are more and more adenosine receptors to block.