Protein is in soda now. Dominick Reuter/Business Insider Protein-packed foods and drinks are a huge hit at Costco, the company said last week. The popularity of GLP-1 drugs is fueling a broad demand for added protein in just about everything. At the same time, a looming shortage of whey concentrate is driving ingredient prices higher. Supplies are tight, prices are climbing, and US shoppers are flocking to Costco to get a good deal. No, we're not talking about gas — this time. The wholesale cl