How do energy drinks give you energy?

(Inside Scinece TV) -- Energy drinks are a $50 billion global industry, overflowing with different brands and exotic ingredients. But how do energy drinks actually give you energy?

The answer is familiar: caffeine and sugar. Caffeine makes you feel more energized by affecting your brain, while sugar refuels your body's cells and helps keep you physically active longer. As for any other ingredients, well... we'll get to them later. First, how do caffeine and sugar actually work?

When caffeine reaches your brain, it crosses the blood-brain barrier and stimulates your brain cells - neurons - indirectly. It stops them from detecting the sleep-inducing chemical adenosine. This chemical builds up in your brain throughout the day and slows down the activity of your nerve cells. Block the effects of adenosine with caffeine and you feel less sleepy. Your neurons are more active and you feel more energized. But it's only made you feel more energized; it hasn't actually given you any new energy to burn.

That's where sugar comes in. You absorb sugar through your intestines into your blood where it can travel to all the cells of your body. Simple sugars, like glucose, are the fuel for all cells. The cells absorb sugar, and feed it into their powerhouses, known as mitochondria. The mitochondria create a merry-go-round of chemical reactions. This chemical cascade produces all-purpose energy chemicals that can then be spread throughout the rest of the cell and used like an energy currency. Absorbing sugar doesn't actually make you feel any more energized - and no evidence has been found for 'sugar highs' - but sugar does provide cells, like in your muscles and brain, with energy to keep them going.

Which brings us to all the other ingredients in energy drinks. There is no good evidence that any of these have any effect at all on either your mental or physical energy levels. That includes overhyped ingredients like Taurine, which your body makes loads of anyway - and is one of your body's fundamental building blocks necessary for normal heart, brain and muscle function; glucuronolactone, which is immediately broken down and then peed away in your urine, and the various B vitamins which are also peed out as waste, because you probably get enough of them already in your normal diet.

Like many things, energy drinks give you energy through good old-fashioned caffeine and sugar. The only difference is the flavor. Cheers!

Reprinted with permission from Inside Science, an editorially independent news product of the American Insititute of Physics, a nonprofit organization dedicated to advancing, promoting and serving the physical sciences.