In much the same way that the Keto diet is a reincarnation of Atkins, Gundry’s lectin-free diet for humans actually draws heavily on the Blood Group Diet and Paleo Diet that came before it. Unfortunately, another similarity is that some are proposing it as a solution to equine health issues, including insulin resistance.
Lectins are present in all forms of life, including grass and the horse itself
What are Lectins?
Lectins are proteins produced by all life forms, from viruses to plants to humans. In the plant world, they are particularly concentrated in some seeds and beans. Each lectin will bind to specific carbohydrate (the”glyco” portion) patterns in glycoproteins or glycolipids found on cell walls. The name lectin comes from the Latin “legere” meaning to select.
Lectins have a variety of functions in animals, plants and microorganisms. They facilitate cells adhering to each other, regulate protein and glycoprotein levels, serve as receptors for the removal of glycoproteins for recycling and also function in the innate immune system, first line of defense against organisms. If none of these things sound sinister it’s because they are not. Lectins are not inherently dangerous or toxic.
Lectins serve similar housekeeping functions in plants. There is also a small number of plant lectins that have undesirable side effects in animals and people. These include the extremely poisonous ricin from castor bean and agglutinins in raw soybeans which can interfere with mineral and protein absorption. Ingestion of raw or incompletely cooked kidney beans can also cause GI distress, primarily through an overgrowth of bacteria which preferentially feed on them.
Lectins and Insulin Resistance
A legion of highly controversial claims have been leveled against lectins as a class in terms of their potential for adverse health effects. I cannot address all of them here but do want to talk about the claim that dietary lectins are causing insulin resistance in horses.
Among the claims is that feeding grains to horses only became common about 50 years ago, but the fact is Ralston Purina was making Horse Chow in the 1890s and grain feeding dates back at least to the ancient Romans. It is further claimed that widespread availability of grain is the major reason insulin resistance is more common today than in the 1800s. It is alleged that lectins are binding to the insulin receptor and causing insulin resistance.
What’s wrong with this theory? As the proponent himself admits, there is zero scientific documentation to back it up. It is full of inaccurate claims and there are well recognized legitimate alternative explanations.
As mentioned, feedings grains has been a mainstay of feeding horses for as long as people have also eaten grains. They have been a staple of the human diet in the US and the world for a lot longer than 50 years. While a diet including high starch grain is inappropriate for a horse with EMS, it does not cause it. The root predisposition is genetic and EMS is aggravated by insufficient exercise – the main difference between today’s horse and those of the 1800s. There are plenty of EMS animals that get into trouble on grass or hay only diets with no exposure to lectins from grain.
As for lectins binding to the insulin receptor, that applies to lectins, galectin-3, produced by macrophages in human fat deposits, not plant lectins. Big difference.
Fringe group theories will always be with us. They’re great for grabbing headlines and recruiting those looking for new theories that are quick fixes. The real problem is the horses which will suffer as a result. If you have a horse with EMS please don’t think that going lectin free will solve the problem and protect the horse from laminitis. It won’t.
Eleanor Kellon, VMD