R(+)-Lipoic acid is the natural form of this vital antioxidant. It is the sole form produced in the body for use in the mitochondria. Conventional "lipoic acid" or "alpha lipoic acid" supplements are only 50% R(+)-lipoic acid; the other half of such supplements is the artificial S(-)-enantiomer. Research demonstrates that R(+)-lipoic acid is more potent that the S(-)-form, and that in some cases the S(-)-form interferes with R(+)-lipoic acid's actions in the body. If you're taking a conventional lipoic acid pill, then you need to know that the health-promoting, anti-aging benefits associated with this nutrient are only being delivered by half of your supplement. The other half is worse than useless: it actually antagonizes the effects of the good half of the supplement. To put it bluntly: the lipoic acid you're taking harbors both a hero ... and an "evil twin." Many molecules used by the body have a specific "handedness" (chirality). For example, alpha-tocopherol, or essential fatty acids. In some cases, synthetic versions of these molecules have a different "handedness" than the natural molecule. You're probably familiar with some examples of this phenomenon, such as natural d- vs. synthetic dl-alpha-tocopherolor natural cis- vs. unnatural trans-fatty acids. Some of these artificial molecules are merely less potent than the natural forms, such as in the case of dl-alpha-tocopherol. But others are actually harmful - for example, trans-fatty acids. Unless they specify otherwise, "lipoic acid" supplements are a 50/50 mixture of the natural R (+) lipoic acid, and the synthetic S (-) lipoic acid. These mixtures are called "racemates." In some cases, S (-) lipoic acid - or the racemate - is simply less effective than R (+) lipoic acid. But in other cases, the S (-) form actually acts in opposition to the activity of R (+) lipoic acid.