Ribose is a pentose, or 5-carbon sugar, that plays an important role in the synthesis of several important substances in the body. It’s an essential ingredient in the structures of ribonucleic acid (RNA); riboflavin (vitamin B2); nucleotides, the building blocks of RNA and DNA; and adenosine triphosphate (ATP), the most elemental energy source in the body. From a metabolic point of view, ribose can take several different pathways. It can convert into pyruvate and become an element of cellular energy, or it can convert into lactate, which is a usable fuel. Alternatively, ribose may be converted in the liver directly into glucose by simply adding one carbon to its structure.
The body uses ribose to synthesize ATP in the pentose-phosphate pathway. ATP degradation from loss of phosphate groups produces energy, and the ATP is resynthesized in a special salvage pathway using breakdown ATP products called total adenosine nucleotides. It can take up to 72 hours after intense exercise to completely replenish depleted ATP stores through that pathway. Some studies suggest that supplemental ribose speeds up ATP replenishment by providing the primary raw material.
The initial proof of the efficacy of ribose for cellular energetics came from studies of cardiac patients, whose restricted heart-blood circulation keeps them from synthesizing ATP rapidly enough for the high energy requirements of heart function. Giving them ribose greatly increased their ability to exercise, which is why the substance was suggested as a possible ergogenic aid to those engaged in regular intense exercise.
Companies that market ribose claim that it normally takes seven to 10 days to fully replenish depleted ATP stores following intense training. Ribose supplements fully restore ATP after only 12 to 36 hours. In the studies with cardiac patients, the average dose of ribose was 60 grams. By contrast, the suggested supplement dose varies from 2.2 to 12 grams daily. Some studies, which used animals, provided ribose in a perfusion, meaning it passed directly into the body through tubes.
Unfortunately, you can’t get the level of ribose concentration available through perfusion from an oral supplement because ribose rapidly clears from the blood. On the other hand, doses of as much as 100 grams have not caused any side effects. A recent study did examine the effects of oral ribose in a group of bodybuilders.1 It featured a placebo-controlled, double-blind protocol, so neither the subjects nor the researchers initially knew which group was taking the placebo. Nineteen male recreational bodybuilders, aged 18 to 35, began the four-week study, and 12 completed it. All subjects underwent tests to measure baseline work output.
One group took 10 grams of ribose a day, the other a dextrose placebo. Both groups got one five-gram dose 30 to 60 minutes before training and another dose 30 to 60 minutes after training. They trained using a three-days-on/one-day-off split.
The men on the ribose showed a significant increase in strength as measured by one-rep-maximum bench press and total work performed. Neither group experienced changes in body composition, which the authors attribute to the short (four-week) length of the study. The authors speculate that a longer-term study would produce significant positive gains in body composition, based on the fact that the men in the ribose group all showed improvements in muscle strength and endurance. However, baseline tests at the beginning of the study showed that the men in the ribose group were initially weaker than those in the placebo group, which may have influenced the results. Besides, since both groups were taking less than the amount of protein suggested for those engaged in intense exercise, insufficient protein may have played a role in the lack of muscle gains.
Two additional items of note about this study: First, it was paid for by a major distributor of ribose supplements. Second, the dose used in the study, 10 grams, is considerably higher than the two-to-five-gram daily dose suggested for supplemental purposes. When I used ribose, I felt absolutely nothing on five grams, but when I upped the dose to 10 to 12 grams daily, I noticed a significant increase in my ability to train intensely. I would therefore suggest experimenting with the dose to figure out what’s best for you.
1 Gammeren, D.V., et al. (2002). The effects of four weeks of ribose supplementation on body composition and exercise performance in healthy, young, recreational bodybuilders: a double-blind, placebo-controlled study. Curr Ther Res Clin Exp. 63:486-495.