Cruciferous Phytochemicals at Work

From the July 2007 edition of Dr. Fuhrman's Healthy Times:

Cruciferous vegetables contain phytochemicals that have unique abilities to modify human hormones, detoxify compounds, and prevent toxic compounds from binding to human DNA, preventing toxins from causing DNA damage that could lead to cancer.

Cruciferous vegetables are unique in that they are rich sources of sulfur-containing compounds known as glucosinolates. It is the presence of glucosinolates that makes a vegetable earn the designation of cruciferous. There have been over 120 glucosinolates identified. These compounds help produce other healthful compounds, which is important since humans do not absorb glucosinolates well.

Myrosinase is an enzyme that is compartmentalized (separated) in the cell walls of cruciferous vegetables. It is released only when the cell walls are damaged (for example, via chewing, chopping, blending, or juicing), at which point it catalyzes the conversion of glucosinolates into isothiocyanates (ITCs) such as indole 3-carbonole. These ITCs are well absorbed and have potent and diverse beneficial effects in humans and other animals.

Myrosinase is deactivated by cooking. The more the food is heated, the more is lost. As a result, fewer isothiocyanates are produced when we cook and overcook these vegetables. Maximum levels of these highly potent anticancer compounds are available from raw vegetables that are somewhat bitter, such as broccoli sprouts, watercress, and arugula.The very high levels of isothiocyanates (ITCs) produced by these foods give that “bitter” taste. However, myrosinase also is produced by the gut flora, so absorption of compounds derived from cruciferous vegetables is still possible from cooked greens.

Sulforaphane, broccoli’s much studied compound, is an isothiocyanate that has a unique mechanism of action. This compound blocks chemical-initiated tumor formation and induces cell cycle arrest in abnormal cells, meaning that it inhibits growth and induces cell death in cells with early cancerous changes in a dose-dependent manner (i.e., the more you eat, the better). Recent studies show that the amount of sulforaphane derived from eating a reasonable amount of broccoli can have dramatic effects to protect against colon cancer.
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