The other day I was at a deli and picked up a bottle of Endurance Vitaminwater. I was excited when I saw that it contained ribose, thinking it must be a form of riboflavin (I wasn't thinking clearly since it was 1:30 and I was starving for lunch). After taking a few bites of my sandwich and reading the bottle, I discovered that it's not actually a B vitamin, or any vitamin for that matter.
Ribose is a simple sugar derived from glucose and produced by the human body. It is an essential component of ATP (adenosine triphosphate), the compound that stores and delivers energy in all cells and powers all the body's processes. When you work out intensely, ATP is used up quickly by your muscles, so that's why ribose is being added to energy drinks. It's supposed to give you sustained energy and help speed up the recovery of your muscle tissues.
To find out if ribose is safe, read more.
There aren't a ton of extensive studies on ribose, but it has been shown to help people with conjunctive heart failure and fibromyalgia. The maximum recommended dose is 5g, three times a day, and it should be taken with food. Ribose is being added to other energy drinks besides Vitaminwater, and you may be getting more ribose than you think, since one bottle can contain more than one serving. Since there isn't a whole lot known about what could happen if your body overdoses on ribose consistently, this is just one more thing to keep in mind when label reading.