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Listen to this siteFriday 21 January 2005
This research project investigates which drug-metabolising enzymes are present in human colon and whether expression is affected by cruciferous vegetable extracts.
Study Duration : April 1998 to September 2001
Contractor : University of Dundee, Ninewells Hospital and Medical School
Cruciferous vegetables, such as brussels sprouts and broccoli, are considered to be beneficial as they contain high levels of glucosinolates, which have been associated with reduced incidence of cancer. Glucosinolates are broken down by the enzyme myrosinase that is released from the plant by the actions of chewing and cutting, to form isothiocyanantes. The isothiocyanates may induce the production of enzymes which have the ability to detoxify harmful chemicals thus speeding up excretion from the body and thereby offering a chemoprotective effect.
A number of in vitro and in vivo studies have shown that cruciferous vegetables have the ability to induce detoxifying enzymes in animal tissue. This study examined the effects cruciferous vegetable consumption on the levels of detoxification enzymes in humans.
The project addressed four main issues:
A glucosinolate-enriched extract of brussels sprouts was prepared and its effects on drug metabolising enzymes in mouse, rat and human colon examined. In humans, the levels of detoxifying enzymes in blood were also examined to see if they could be used to predict levels in the gut.
Glucosinolates are hydrolysed by myrosinase, an enzyme found in the gut of mammals and also released from plants by cutting, chewing and tearing of the tissues. The glucosinolate breakdown products are thought to reduce the risk of cancer via their ability to induce and/or inhibit the induction of phase 1 and phase 2 detoxifying enzymes.
Glucosinolates were extracted from Brussels sprouts and administered to mice, rats and human volunteers, and the levels of detoxifying enzymes in the gut were examined. In humans, the levels of these enzymes were also examined in blood to see if they could be used to predict levels in the gut.
In mice and rats, a number of detoxifying enzymes were induced in the gut, suggesting that the extract had the same chemoprotective effect shown by cruciferous vegetables. These enzymes were also induced by the extract in some human volunteers. However, blood levels of detoxifying enzymes in humans could not be used to predict enzyme levels in the gut.
These studies have provided evidence, that in some individuals, a cruciferous vegetable extract induces the expression of detoxifying enzymes. This could contribute to a protective effect of vegetables against cancer. Further studies are required to establish optimum preparation and cooking conditions for this beneficial effect.
The final report is available from the FSA Library and Information centre.
To obtain a copy, please contact the Enquiry Desk, Dr Elsie Widdowson Library and Information Services, Food Standards Agency ( tel: 020 7276 8181/8182 or email:
library&info@foodstandards.gsi.gov.uk
)
Contact
: For any enquiries concerning this research project, please contact the relevant Programme contact or email
science@foodstandards.gsi.gov.uk
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