Selenium and glucosinolates in cruciferous vegetables: metabolic interactions and implications for cancer chemoprevention in humans
2007
Finley, J.W.
Cancer is a leading cause of death in North America, and poor diet is suspected as a causative factor in 1/3 of all cancer deaths. Epidemiologic studies have shown that a diet rich in cruciferous vegetables such as broccoli is protective against many cancers. Broccoli contains sulforaphane (Sf), a substance that activates promoter elements in certain phase II detoxification enzymes of animals, and upregulation of these genes may increase the rate of clearance of potential carcinogens. Broccoli also accumulates the mineral selenium (Se) and clinical trials have demonstrated that Se may decrease the incidence of prostate and lung cancer. A series of studies have examined the interaction of Se and Sf in broccoli, and the benefit to the health of the animal that consumes broccoli. Selenium-enhanced broccoli reduces the incidence of colon cancer in rats, but increasing the Se content of broccoli results in a corresponding decrease in the Sf content. Sf and Se also interact in the animal that consumes broccoli to upregulate the antioxidant enzyme thioredoxin reductase (TR). TR activity has been shown to be related to oxidative stress in the cell. These studies demonstrate potential problems that may be encountered if a single substance in a plant is targeted for enhancement. They further show that modified plant foods may cause unintended metabolic interactions in the animal that consumes them.
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