Soy, PIT, and Cystic Fibrosis

Soy and soybean foods are very popular. However, it may be wise to use caution if you are a cystic fibrosis patient. As with almost all food plants, soybeans have been bred to accentuate certain characteristics that are viewed as valuable. Over the last 50 years, the major strains of soybean have been bred to increase the plant's level of a naturally occurring fungicide - phenyl isothiocyanate, or PIT for short. Whereas heirloom varieties of soy may contain only 1-2 parts per million of PIT, modern varieties may contain 2000-2500 parts per million of PIT.

This is important for those who have cystic fibrosis. As you may know, the glutathione system of CF persons is dysfunctional. (See the "glutathione" heading under this website's "Research" section for more information on this topic.) Selenium plays an important role in that system, specifically in the formation of glutathione peroxidase, the enzyme that facilitates the reduction of GSH to GSSG in the presence of water-soluble oxidants. Without adequate amounts of selenium, there will not be adequate amounts of glutathione peroxidase. Without adequate amounts of glutathione peroxidase, glutathione cannot function well in its antioxidant capacity.

PIT displaces selenium, in essence, sucking selenium from the body. This was first discovered in the dairy industry, where calves are separated from their mothers before the natural weaning age and thus are put on a substitute feed. When fed with soy replacer formulas, about 1/3 of the calves would die of the scours, which is the dairy term for dysentery. It turned out that PIT was the culprit. By displacing selenium, the calves' intestines lost their membrane integrity. PIT also interfered with digestive enzymes, particularly proteases. (Cows have the same digestive enzymes as humans.)

Because CF persons have both glutathione system dysfunction, as well as an impaired digestive enzyme system and inflamed gut, it might be wise to use caution when using modern soybean products. The PIT in the soy products could aggravate these conditions.