By Dr. Mercola While whole foods are healthy, there are certain caveats to consider even here. Lectins (not to be confused with the phospholipid lecithin) are carbohydrate-binding proteins that are widespread in the plant kingdom. An estimated 30 percent of fresh foods contain lectins.1 Even dairy contains lectins. Grass fed butter is an exception. Grass fed milk is also lower in lectins than grain-fed milk, thanks to higher amounts of SlgA, an immunoglobulin that binds to lectins.2 Lectins get their name from the Latin word legere, from which the word “select” derives — and that is exactly what they do: They select (attach to) specific biological structures that allow them to do harm, as part of the plant’s self-defense mechanism. It’s nature’s ingenious way of keeping natural enemies like fungi and insects at bay. Unfortunately, some of these glycoproteins may also cause trouble in humans. Lectins were first discovered in castor bean casings, which contain the lectin ricin.