I just started reading Dr. Gundry's book. I don't know if this is the correct place to put this criticism/correction or not and I suppose in the grand scheme of issues with lectins in humans it's a small one, but it really makes me not want to read the rest of his book. In the first chapter, Dr. Gundry talks about feeding corn and soy to cattle. He makes the claim that the lectin in these foodstuffs give cattle heartburn and so they feed limestone to the cattle to prevent the heartburn. I have a masters degree in ruminant nutrition (I know, random) and this is completely incorrect. I will give Dr. Gundry a bit of a pass in that I believe he was trying to simplify the issues of feeding corn and soy to cattle, but it's just wrong.
Cattle do not have stomachs that are anything like we have. You've probably heard that they have four stomachs - yes they do, or you could think of it as one stomach with four chambers. Regardless, the first stomach, the Rumen is an incredibly large fermentation vat. (why they are called ruminants). In fully grown cattle, it can hold 40/50 gallons....pause for a minute and think about the size of a 40 gallon trash bag that you use to clean your yard - it's impressive. In that Rumen is a vast array of fermenting bacteria, fungi, and protozoans, water, and foodstuffs. Those microflora have one job and that is to digest the plants for the cow. The cow eats grass/hay/etc. the fiber goes into the rumen, the fiber is fermented. That fermentation produces volatile fatty acids, gases, more bacteria as they reproduce, etc. The VFAs are absorbed by the cow for energy. Cows will regurgitate the fiber to chew some more = increased surface area = more fermentation = "chewing the cud."
After the rumen, the water/small particles of foodstuffs/microflora then pass through the reticulum (tripe), omasum, and abomasum (considered the true stomach = stomach acid), and then into the intestines. This chewing and fermentation is why cow pies don't have fibers in them like horse manure and elephant manure (if you've ever stopped to look). Farm girl here...
Anyway, it is extremely important for the cow to maintain a fairly neutral pH in the rumen because that supports optimal production of VFAs for energy and optimal production of bacteria which the cow digests and serves as an important source of protein. When a cow eats grass/hay etc, they eat a mixture of structural carbohydrates (cellulose), non-structural carbohydrates (starch), and indigestible fiber (lignin, etc). A proper ratio of structural to non-structural carbohydrates, along with the buffering of saliva keep the pH where it needs to be (a little starch: a lot of cellulose). When a cow is fed too much non-structural carbohydrate, it favors a different group of bacteria which produce different VFAs and the pH in the rumen goes down. This change in microflora can start a downward spiral of pH which eventually can kill off/reduce the microbes that digest the non-structural carbohydrates. This can then cause acidosis which leads to a whole host of problems that would take all kinds of space to write about - I'll leave it with -it's bad. THIS is why you might feed a buffering agent such as limestone to a cow eating non-structural carbohydrates (soy/corn). NOT because of lectins.
Should cattle eat corn and soy? Probably not. Does feeding them things they aren't really supposed to eat mess up their digestive system? Generally yes. Does feeding them non-structural carbohydrates like corn and soy provide a cheap source of calories (think government subsidies) that fattens them up quickly for slaughter and thereby turns a greater profit? Yes. Is that the right thing to do? Well, that's a whole different subject.
POINT BEING. I read that short paragraph about cattle getting heartburn because of lectins and obviously had a cow. (see above) I will try not to throw out the baby with the bathwater and will keep reading.