One negative aspect is that commercial ALA contains 50% by weight of the S-isomer, which is a stereoisomer which is not found in nature, nor in the human body. ALA is a racemic mixture. Studies have shown that one would is better off using R-lipoic acid, versus the racemic mixture.
At this stage, one can only ponder the potential long-term effect that ingestion of the un-natural S-isomer may have on organs such as the kidney and liver.