What is the difference between: Alpha Lipoic Acid (R-ALA) and Alpha Lipoic Acid (RS-ALA)?

R = Rectus (Latin for Right)
S = Sinister (Latin for Left)
R and S are the stereoisomers for this molecule, alpha lipoic acid.

Click below:
http://en.wikipedia.org/wiki/Stereoisomerism

When you see both RS before a given molecule name it means that it is a racemic mixture of both the Rectus and Sinister stereo isomers and in this case both are also enantiomers.
http://en.wikipedia.org/wiki/Enantiomers

A racemic mixture is typically 50% of each of two stereo isomers below
http://en.wikipedia.org/wiki/Racemic

The biggest difference between the R and the RS enantiomers of Alpha Lipoic acid is the cost. The R is about 10 times more expensive than the RS. Another consideration you might relate to is the fact that there is about 100 times more RS than R manufactured and consumed nutritionally.

Why would only 1% of alpha Lipoic Acid manufactured be the R? Because its cheaper than the RS.

Is there a difference between the R and the RS such that one would be better nutritionally than the other? Yes. The R is about twice as effective than the RS because the S is basically useless.

Is there a problem with the S such that having it with the R would justify paying 10 times more for the R versus the RS? Maybe. It depends upon what research you read and what you think of the research. Given that almost all the research supporting one camp or the other is theoretical there doesn't seem to be a whole lot of facts supporting either opinion.

My belief is that deciding which to take would depend upon your choice in the matter, and how much money you have to spend. The more money you have to spend on Alpha Lipoic acid the more you would probably want to purchase the R versus the RS. The less money you have to burn on Alpha Lipoic acid the more likely you would choose the RS. Unquestionably, the greatest bang for your buck is with the RS as 99% of Alpha Lipoic acid consuming public would likely concur.