To understand the virtue of lacto-fermented foods, it's important to understand the digestive process itself. Two things happen when we eat. First, ingested foods are broken down. Second, nutrients are built up. If the breaking-down process is incomplete, the building up will not happen correctly.
In her book Making Sauerkraut and Pickled Vegetables at Home, Annelies Schoneck explains the role of lacto-fermented foods:
What is astonishing is that lactic acid contributes to both processes—that of decomposition and that of reconstruction. On the one hand it supplies digestive juices in the form of organic acids that help break down the foods we eat, and on the other hand it activates the metabolic processes whereby these foods are transformed into new living substances.
Lacto-fermented foods normalize the acidity of the stomach. If stomach acidity is insufficient, it stimulates the acid-producing glands of the stomach, and in cases where acidity is too high it has the inverse effect. Lactic acid helps break down proteins and thus aids in their assimilation of iron. The decomposition in the stomach of the organic forms of iron depends on the quantity of hydrochloric acid present as well as the amount of vitamin C, which is why sauerkraut and other lacto-fermented vegetables rich in this vitamin have such a favorable influence. . . .
Lactic acid activates the secretions of the pancreas, which is particularly important for diabetics. . . Sauerkraut contains large quantities of choline, a substance that lowers blood pressure and regulates the passage of nutrients into the blood. . . Choline has another interesting property in that it aids the body in the metabolism of fats. If choline is lacking, fats accumulate in the liver. . . Sauerkraut also contains acetylcholine, which has a powerful effect on the parasympathetic nervous system. It helps reduce blood pressure, slows down the rate of heartbeat, and promotes calmness and sleep. As acetylcholine is destroyed by cooking, raw sauerkraut and its juice is preferable to cooked.
Sauerkraut is easy to make. It requires a head of cabbage, sea salt, and a mason jar or other container. For those who would rather purchase it, I recommend the Bubbies brand available at stores like Whole Foods.
Sally Fallon points out in her book Nourishing Traditions:
Scientists are mystified by the proliferation of new viruses—not only the deadly AIDS virus but the whole gamut of human viruses that seem to be associated with everything from chronic fatigue to cancer and arthritis. They are equally mystified by recent increases in the incidence of intestinal parasites and pathogenic yeasts, even among those whose sanitary practices are faultless. Could it be that in abandoning the ancient practice of lacto-fermentation and in our insistence on a diet in which everything has been pasteurized, we have compromised the health of our intestinal flora and made ourselves vulnerable to legions of pathogenic microorganisms? If so, the cure for these diseases will be found not in vaccinations, drugs, or antibiotics, but in a restored partnership with the many varieties of lactobacilli, our symbionts of the microscopic world.
In the 1800s sailors made the connection between sauerkraut and the prevention of scurvy. Perhaps in our day we'll make the connection between gut health, toxicity, and lacto-fermented foods.