Which group is least likely to be concerned about potential long-term side
effects of genetically modified (gm) food?

The starving child is least likely to be concerned about potential long-term side  effects of genetically modified (GM) food

Explanation:

The GM food are prepared by isolating the strands of DNA using various methods  genetic engineering. A smaller defect in the strand can even become risk to life. Which first affects the starving children, various cases has been noted in the same reason. Proper testing should be done before the introduction. Testing should be done with respect to the toxicity, allergenicity, and possible transfer of the gene in the human or can also be said as the genetic out-crossing to other organism.  

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.