Bioflavonoids found in soy beans have weak estrogen-like activity. If a women is deficient in estrogen (early menopause, for example), consuming soy products can replace the missing estrogen and relieve hot flashes. If a person is exposed to an excess of estrogen, the flavonoids in soy act as estrogen blockers and lower the effects of estrogen. The low frequency of breast cancer in east Asia, where soy is a major source of protein, has been attributed to the mild estrogen-blocking effect of soy flavonoids. Preliminary research indicates that soy flavonoids can block the estrogenic effects of dioxin.
A high intake of vegetables increases the consumption of a group of natural chemicals called saponins, which have immune-stimulating and antibiotic effects. Saponins are the latest in a long list of plant chemicals that are not considered nutrients, the way that vitamins are, because no deficiency state has been identified, but which promote health. In plants, saponins seem to function as natural antibiotics, protecting the plant against microbial parasites. In humans, they may thwart cancer and ward off infection. Saponins are most highly concentrated in soybeans, chickpeas, bean sprouts, asparagus, tomatoes, potatoes and oats. They have a creamy texture and a sweet taste that separates them from other plant components. Some biotechnology companies are presently attempting to harvest saponins and use them as drugs.
Carrots, carob, blueberries and raspberries contain complex sugars (oligosaccharides) which interfere with the binding of pathogenic bacteria to the intestinal lining. These have been used in Europe for centuries for the treatment or prevention of diarrhea.
Before they were used as seasoning, culinary herbs and spices were probably used for food preservation. Many varieties have natural antimicrobial activity and can retard spoilage. They are also used to mask the flavor of spoiled food, so I suggest using them at home, where you know the food they flavor is fresh to begin with.
The world's most extensively studied spice is garlic. Its medicinal use predates recorded history. Garlic is mentioned in the earliest Vedic medical documents, written in India over five thousand years ago. During an epidemic of plague in Marseilles, in 1721, four condemned criminals were enlisted to bury the dead. None of them contracted plague. It seems that they sustained themselves by drinking a cocktail of crushed garlic in cheap wine, which came to be called vinaigre des quatre voleurs (vinegar of the four thieves). In 1858, Louis Pasteur demonstrated garlic's antibiotic activity. The herb was used by Albert Schweitzer for the treatment of amoebic dysentery at his clinic in Africa. Antimicrobial activity of garlic has been repeatedly demonstrated against many species of bacteria, fungi, parasites and viruses. In addition, garlic lowers cholesterol and blood pressure and may protect against cancer. The dose of garlic needed to obtain significant benefit is at least ten grams (about three small cloves) per day. Garlic also has a great immune-enchancing effect, stimulating activity of natural killer cells in healthy people and in people with AIDs. AIDS patients taking five to ten grams of aged garlic (equivalent to two to three small cloves) per day developed normal natural killer cell activity after twelve weeks which was associated with clinical improvement.
Onion, garlic's closest edible relative, has also been widely used for medicinal purposes. Although it lacks the potency of garlic, it can be consumed it much larger quantity, so that its antimicrobial benefits may be equal to those of garlic if consumed regularly.