Cancer, genes and Broccoli - study of genetic differences in cancer protection

‘super’ broccoli developed by traditional plant breeding methods

People who gain less protection from cancer by eating broccoli may be able to compensate for the difference in their genetic make-up by eating ‘super broccoli’, a variety with higher levels of the active plant chemical sulforaphane, or by eating larger portions.

Lead scientist on the new research, Professor Richard Mithen of the Institute of Food Research (IFR), said: “Eating a few portions of broccoli each week may help to reduce the risk of cancer. Some individuals, who lack a gene called GSTM1, appear to get less cancer protection from broccoli than those who have the gene.

“Our studies suggest that this may be because if you lack the gene you cannot retain any sulforaphane inside your body, it is all excreted within a few hours. However, if you consume larger portions of broccoli, or broccoli with higher levels of sulforaphane, such as the ‘super broccoli’, you may be able to retain as much sulforaphane in your body as those who have the gene. Eating larger portions may have additional benefits since broccoli is also a rich source of other vitamins and minerals”.

two varieties of broccoli shows standard broccoli on the left (“Iron”), and ‘super broccoli’ on the right

Broccoli is the main source of natural compound sulforaphane. It belongs to the crucifer family of plants which includes the brassica vegetables cabbage, cauliflower and Brussels sprouts, and the closely related Chinese cabbage and turnips. Other crucifers include watercress and salad rocket. The most distinctive characteristic of crucifers is that their tissues contain high levels of glucosinolates. When they are eaten, glucosinolates are broken down to release isothiocyanates. There is a well established body of evidence to show that isothiocyanates are among the most potent dietary anticarcinogens known.

Sulforaphane is the main isothiocyanate derived from broccoli. ‘Super broccoli’ contains 3.4 times more sulforaphane than standard varieties. It has been developed by traditional plant breeding methods.

Fifty per cent of the population lack the GSTM1 gene. While these people may gain less cancer protection from consuming broccoli, it is likely that they gain more cancer protection from eating other types of crucifers, such as cabbages and Chinese cabbage. So the best advice is to eat a mixture of crucifers.

This research was funded by IFR’s Core Strategic Grant from the Biotechnology and Biological Sciences Research Council and by the University of Nottingham and Seminis Inc. It is part of ongoing research at IFR to identify the optimal levels of a range of food compounds for human health.

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Notes to Editors

Please contact Zoe Dunford for more information, photos and to arrange interviews: zoe.dunford@ifr.ac.uk, tel. 01603 255111 / 07768 164185
Photos available of ‘super’ broccoli growing.
The mission of the Institute of Food Research (www.ifr.ac.uk) is to undertake international quality scientific research relevant to food and human health and to work in partnership with others to provide underpinning science for consumers, policy makers, the food industry and academia. It is a company limited by guarantee, with charitable status, grant aided by the Biotechnology and Biological Sciences Research Council (www.bbsrc.ac.uk).
The University of Nottingham is one of the UK's leading universities and is consistently ranked in the top ten. With recently opened campuses in both China and Malaysia, it has more than 31,000 students in total, including 6,000 international students from more than 100 nations. The University has 33 top-rated teaching subjects and research awards for 2004-5 topped £100m - a testament to its reputation for world-class research. The Sunday Times University Guide 2005 said: "At the cutting edge both academically and in terms of revenue raising, Nottingham is one of the finest institutions in the country."
Seminis Inc. (www.seminis.com) is the world's leading developer, producer and marketer of vegetable seeds. Its products are designed to increase crop yields, reduce dependence on agricultural chemicals, limit spoilage, offer longer shelf life, and produce vegetables and fruits with better taste and nutritional content. Seminis has established a worldwide presence and global distribution network that spans 150 countries. It is developing commercial varieties of broccoli with enhanced levels of glucosinolates for consumers.
Full reference for the paper:
Glutathione S-transferase M1 polymorphism and metabolism of sulforaphane from standard and high-glucosinolate broccoli.
Am J Clin Nutr; 82: 1283: 2005

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