Harmful Chemicals in Legumes and Soy - Lectins, Phytates, and Enzyme Inhibitors
Lectins are essentially carb-binding proteins universally present in plants (and animals). Just as they protect plant species from Grok-sized predators, lectins also support other immunological functions within plants and animals (against pathogense, parasites, etc.) They also assist in other functions like protein synthesis and delivery in animals. They’re relatively sticky molecules, which makes them effective in binding with their sought after sugars but undesirable for our digestion, in which their binding powers can lead them to attach to the intestinal lining and wreak havoc.1
Legumes’ protein content is dwarfed by the 50+ grams you’d get from six ounces of several meats. And this relatively small amount of protein comes with a hefty carb content: as high as 28 grams for that same ½ cup serving!
Because legumes generally contain so much soluble fiber, they won’t result in sudden blood sugar spikes. However, at the end of the day carbs are carbs.
Yet, the Primal Blueprint philosophy allows for some carbohydrate content. I’ve suggested in the past 150 grams as a daily ceiling. There’s certainly reason to shoot for less (100 is even better), but 150 grams can be a reasonable goal for many of us. The key is to make as much of that carb “allowance” vegetable-based as possible. Legumes offer nutritional benefits, but what they offer can be found in equal to greater amounts within other foods that have lower carb content.2
Soybeans contain large quantities of a number of harmful substances. First among them are potent enzyme inhibitors which block the action of trypsin and other enzymes needed for protein digestion.
These "antinutrients" are not completely deactivated during ordinary cooking and can produce serious gastric distress, reduced protein digestion and chronic deficiencies in amino acid uptake. In test animals, diets high in trypsin inhibitors cause enlargement and pathological conditions of the pancreas, including cancer. The soybean also contains hemagglutinin, a clot promoting substance that causes red blood cells to clump together. Trypsin inhibitors and hemagglutinin have been rightly labeled growth depressant substances. Fortunately they are deactivated during the process of fermentation. However, in precipitated products, enzyme inhibitors concentrate in the soaking liquid rather than in the curd. Thus in tofu and bean curd, these enzyme inhibitors are reduced in quantity, but not completely eliminated.
Soybeans are also high in phytic acid or phytates. This is an organic acid, present in the bran or hulls of all seeds, which blocks the uptake of essential minerals-calcium, magnesium, iron and especially zinc-in the intestinal tract. Although not a household word, phytates have been extensively studied. Scientists are in general agreement that grain and legume based diets high in phytates contribute to widespread mineral deficiencies in third world countries.3
It’s not the ingredients in the peanut butter we don’t like, it’s the peanuts themselves. When peanuts grow, they can harbor carcinogenic mold called an “aflatoxin“. This goes for conventional and organic peanuts. They longer they sit (during shipping, for example), especially in warm temperatures and high humidity, the more mold grows. And as it’s nearly impossible to buy peanuts “local”, as they are only grown in a few Southern locations, more likely than not that even your organic peanuts are suspect.
The far bigger concern, however, is that peanuts contain lectins which are believed to have inflammatory and atherogenic potential. Most plants contain lectins, some of which are toxic, inflammatory, or both. Many of these lectins are resistant to cooking and to digestive enzymes, and some have been scientifically shown to have significant GI toxicity in humans. Lectins from grains (especially wheat) and legumes (including peanuts and soybeans) are most commonly associated with aggravation of inflammatory and digestive diseases in the body.5
3)Fallon, S., Enig, M., PHD, Health Freedom News, September 1995