A few months ago, a Redditer with access to a protein measurement device offered to measure the protein content of protein powders that readers sent him. He got about twenty samples, presumably from all over the United States. Most of them turned out to have reasonable amounts of protein but four had much less than expected.
The tester interpreted the results here. One of the tested brands, American Pure Whey, clearly has problems. Call it a positive control. By confirming those problems, the rest of the measurements gain credence. One company whose protein powder scored low is Gaspari. Unfortunately I cannot read their reply, which appears on my browser without text.
I look forward to more truth-in-advertising tests. It is really helpful that the data is public — in this case, via Google Docs. Jimmy Moore (of Livin’ La Vida Low Carb) has measured the effect of several supposedly low-carb-friendly products on his blood sugar. His results are here.
Thanks to Eric Meltzer.