Dietary Supplement Industry Hops on Low-Carb Diet Trend By ALICIA CHANG    (AP) -- Stroll down any pharmacy aisle these days and you'll find that the low-carb craze has invaded the \$20 billion dietary supplement industry.    From multivitamins to starch blocker pills, loosely regulated supplements are popping up in the burgeoning low-carb market dominated by food companies...