Certain substances present in the foods we eat prevent us from fully benefiting from the nutrients that they should provide. This phenomenon, explained below, is grouped under the term “antinutritional factor”.
Processing foods eliminates antinutritional factors
There are a great many antinutritional factors in the plant kingdom! They include trypsin inhibitors, which prevent proteins from turning into amino acids, antivitamins, antihormones, substances that affect mineral utilization, and, of course, food allergens! Fortunately, for most foods in question, a simple process (cooking, fermentation, germination, etc.) is enough to improve availability of their nutrients. However, this is not true for food allergens, which make it necessary to avoid the vegetable in question. In case of any questions on the subject, ask a medical professional for advice.
A few examples to understand better
Raw egg white, raw milk, and many protein-rich plants (beans, soy, lentils, and grains) contain trypsin inhibitors. But cooking the egg white, processing raw milk with a heat treatment (boiling, UHT), and using heat, fermentation, or even germination for plants causes the trypsin inhibitors to degrade. Raw fish is one food that contains heat-sensitive antivitamins which degrade thiamin (vitamin B1). Corn contains an antivitamin PP, which can be degraded only by certain kinds of traditional fermentation (such as in the making of Mexican tortillas). Certain antihormones (glucosinolates), present in vegetables including rutabagas, turnips, and all cabbages, can cause hormonal issues in people who eat them, and especially in animals that consume large quantities (goiter development because of effects on the thyroid).
Finally, certain plant compounds such as oxalic acid (in beets, spinach, rhubarb, cocoa, etc.) and phytic acid (in the hull, or bran, of cereals) can reduce the availability of certain minerals, including calcium, iron, and zinc. Oxalic acid can cause urinary tract stones to form (urolithiasis). However, certain enzymes (phytases) have the power to cause phytic acid to degrade with help of the intestinal flora, through fermentation with natural yeast, or during germination.