First keep in mind neither are very much of an anti-oxidant in their original form. They don't become powerful until the convert to dihydrolipoic acid which is VERY powerful. So the more you have the better. This is clearly why r-ALA is better for this purpose.
When you swallow a racemic lipoic acid tablet - the kind you get in nearly all "lipoic acid" supplements - both the S(-)- and the R(+)-Lipoic Acid are taken up into your blood and then transported to your cells. Already at this point, another advantage of R(+)-Lipoic Acid becomes clear: the R(+)-Lipoic Acid is dramatically more bioavailable than the S(-)-form.The peak concentration of plasma lipoic acid obtained from R(+)-Lipoic Acid is twice as great as from an equal amount of the S(-)-form 26 and the total R(+)-Lipoic Acid delivered into the plasma over the course of time is 60 to 85% greater than the total amount of the S(-)-form which ultimately reaches the plasma as well.
More importantly, studies show that R(+)-Lipoic Acid is taken up into the tissues to a greater degree than the S(-)-form. In one study scientists gave lab animals the R(+)-, the S(-)-, or the racemate form of lipoic acid - providing it by injection, so as to bypass the differences in absorption in the digestive system, and thus start the animals off on a level playing field. As expected, lipoic acid levels were the same in all three groups within the first hour as the injected lipoic acid made its way through the circulation. But three hours later, the animals which had received R(+)-Lipoic Acid had two to seven times more lipoic acid in the lenses of their eyes than animals given the same amount of the S(-)-form, and three times as much as the animals given the racemate form.
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