That is because in 1992[2] a team of Johns Hopkins University scientists isolated a cancer-fighting phytochemical in broccoli called glucoraphanin, which is the glucosinolate precursor ofsulforaphane (SGS).[3][4] When chewed, broccoli releases glucoraphanin and myrosinase, an enzyme found in another part of the plant cell, which work together to produce sulforaphane, which, in turn, activates a transcription factor, Nrf2 in the cell. Once activated, Nrf2 then translocates to the nucleus of the cell, where it aligns itself with the antioxidant response element (ARE) in the promoter region of target genes. The target genes are associated with process which assists in regulating cellular defences. Such cytoprotective genes include that for glutathione. Around 200 genes have been well-characterised, as many as 1700 are thought to be related to this aspect of cellular defense.
The 1992 study was followed by the discovery in 1997[5] that glucoraphanin is in higher concentrations in the three- to four-day-old broccoli sprouts, at least 20 times the concentration of full grown broccoli. This discovery was written about in the New York Times,[6][7] and created a global shortage of broccoli seed that could not meet the sudden high demand.
"Broccoli sprouts are available in grocery and natural foods stores across the US and in other countries. Broccoli seeds are available for home growing. One can sprout broccoli seeds using a jar or a commercial sprouting kit. Broccoli sprout powders and capsules are also available. However, many of these products are produced from myrosinase-inactive sprout or seed extracts. It is difficult, if not impossible, for the consumer to identify which products contain both the essential precursor glucoraphanin as well as the active myrosinase enzyme. With a myrosinase-inactive product, an individual may not convert any of the glucoraphanin to sulforaphane. Because so little is known about the role of human gut microflora at this stage, reliance on the gut microflora with its wide variability could pose a significant limitation on the achievement of a biochemical response."
Source: http://en.wikipedia.org/wiki/Broccoli_sprouts
