Epidemiological studies have shown the protective effect of vegetables, particularly cruciferous vegetables, such as broccoli, are protective against colon cancer. In Asia the lower incidence of degenerative diseases, such as cancer and heart disease, are believed to be due to the high consumption of fruits and vegetables. Green vegetables are widely consumed in Asia and are a major source of antioxidant and antioxidant like compounds. In addition, these green vegetables contain compounds that aid in the body’s natural detoxification pathways to remove potential carcinogens.
A study in the World Journal of Gastroenterology, examines the antioxidant and the detoxification inducing ability of green leaf vegetables consumed in Asia.
Free radicals are generated in the body by many mechanisms including response to inflammation, normal metabolism, and exposure to radiation. At places in the body where there is inflammation the immune system dispatches white blood cells, called neutrophils, to fight infections. These neutrophils use hydrogen peroxide (H2O2) and hypochlorous acid (HOCl) to kill foreign invaders such as bacteria and fungus.
Although neutrophils use these chemical mechanisms quite effectively to protect the body the resultant chemicals also can cause damage to the body through oxidative stress. “HOCl and species derived from it can oxidize lipids, proteins, DNA, and carbohydrates.” In fact, the generation of these chemicals in the body is “implicated in a wide range of human diseases ranging from cancer and cardiovascular disease to chronic inflammation.”
Antioxidants help neutralize free radical damage to the body. However, as they neutralize these free radicals the antioxidant levels in the body are depleted. The depletion of antioxidants allows for other free radicals to cause more damage that can lead to disease because they “participate in the carcinogenesis by inducing genetic mutations.” Antioxidants have been shown to “reduce oxidant induced damage.”
In this study the authors examined the ability of a variety of vegetables frequently consumed in Asia, such as broccoli, Rorripa, Sio Pek, Pa Po, Pheuy leng, and Choi Sum to help protect the body from damage caused by free radicals. The authors also wanted to examine detoxification mechanisms of these vegetables that help protect the body in other ways.
The authors found that these cruciferous vegetables do in fact reduce genetic damage from free radicals by being a “potent source of antioxidants that may offer protection against oxidant induced damage in human beings.”
The authors also found that in addition to neutralizing free radicals that there is a secondary mechanism of protection against oxidative damage by stimulating the body’s own detoxification mechanisms. “The induction of phase 2 detoxification enzymes provides protection against electrophilic [electron-deficient molecules] and oxidant induced damage.”
Cruciferous vegetables contain phytochemicals known as glucosinolates that are converted in the body to bioactive substances called isothiocyanates or ITCs. “ITCs are potent inducers of phase II detoxification enzymes in mammals.”
ITCs act to prevent cancer at three different stages. First, ITCs prevent carcinogenic activation by stopping certain cancer promoting enzymes. Second, they help with phase II enzymes that result in the elimination of potential carcinogens from the body. Third, ITCs can induce apoptosis, or cell death of damaged cells. These ITC mechanisms are consistent with the results of many studies “which have suggested a reduced risk of cancer, particularly of the gastrointestinal tract, through the consumption of cruciferous vegetables.”
Examining the vegetables they authors found that the different vegetables had different effects on their ability to detoxify. Both broccoli and Rorripa were found to be the strongest in helping to form enzymes that help rid the body of carcinogenic chemicals.
The authors conclude, “Green leaf vegetables are potential sources of antioxidants and phase II detoxification enzyme inducers in the Asian diet. It is likely that consumption of such vegetables is a major source of beneficial phytochemical constituents that may protect against colonic damage.”
Source: World Journal of Gastroenterology, December 2005
Author: Roman Bystrianyk