“Quinoa is botanically not a grain, but because it has evolved in a similar biological niche, Quinoa has similar properties to grains, including chemical defense systems that irritate the gut. In the case of Quinoa, it contains soap-like molecules called saponins. Unlike gluten, which attaches to a carrier molecule in the intestines, saponins simply punch holes in the membranes of the microvilli cells. Yes, that’s bad. Saponins are so irritating to the immune system that they are used in vaccine research to help the body mount a powerful immune response. The bottom line is if you think grains or grain-like items like Quinoa are healthy or benign, you are not considering the full picture.”
Robb Wolf, The Paleo Solution: The Original Human Diet (p. 87)