Posted on Sat, 13 Feb 10
What we eat is a major determinant of cancer development. It has been estimated that 30-35% of cancer cases are due to dietary factors, a figure that may be higher for specific cancers such as bowel cancer where diet has been linked to 70% of cases (1). Fruits and vegetables contain literally thousands of chemicals that have potential to reduce cancer risk and some vegetables have unusually high concentrations of anti-cancer compounds.
Meet the family
Regular consumption of various members of the cruciferous vegetable family has been associated with a greater reduction in cancer risk - particularly lung, stomach, colon, and rectal cancer - than that of other vegetables (2). Cruciferous vegetables are a family of vegetables that includes broccoli, Brussels sprouts, cabbage, cauliflower, collard greens, kale, kohlrabi, mustard, rutabaga, turnips, bok choy and Chinese cabbage.
Nutritional treasure trove
Like all vegetables the cruciferous vegetables are a source of nutrients (e.g. fibre, folate) and phytochemicals (e.g. carotenoids, chlorophyll) with anti-cancer properties. The cruciferous vegetables however are a unique and rich source of glucosinolates, a class of sulphur-containing phytochemicals responsible for their pungent aroma and spicy (or bitter) taste. When eaten the glucosinolates are metabolised to produce several anti-cancer compounds that may collectively reduce cancer risk (3).
Cooking can dramatically destroy glucosintaes and the best cooking methods are very light cooking such as steaming (4). Conversely, stir-frying and boiling result in the greatest nutrient losses (5). However by cooking your cruciferous vegetables you lower your glucosinolate intake 60% to 90% that if you had simply eaten them raw. Eaten in their raw state these vegetables may be particularly powerful, in fact as little as three serving a month of raw cabbage, broccoli and cauliflower has been shown to reduce bladder cancer risk in smokers (6). Regularly eating cruciferous vegetables, especially broccoli, especially raw, is a great way to maximise the health giving potential of your diet. Epidemiological studies suggest adults should aim for at least five servings a week.
1. Anand P, et al. Cancer is a preventable disease that requires major lifestyle changes. Pharm Res. 2008 Sep;25(9):2097-116.
2. Verhoeven DT, Goldbohm RA, van Poppel G, et al. Epidemiological studies on brassica vegetables and cancer risk. Cancer Epidemiol Biomarkers Prev. 1996 Sep;5(9):733-48
3. Higdon JV, Delage B, Williams DE, Dashwood RH. Cruciferous vegetables and human cancer risk: epidemiologic evidence and mechanistic basis. Pharmacol Res. 2007 Mar;55(3):224-36
4. Rungapamestry V, Duncan AJ, Fuller Z, Ratcliffe B. Effect of meal composition and cooking duration on the fate of sulforaphane following consumption of broccoli by healthy human subjects. Br J Nutr. 2007 Apr;97(4):644-52.
5. Yuan GF, Sun B, Yuan J, Wang QM. Effects of different cooking methods on health-promoting compounds of broccoli. J Zhejiang Univ Sci B. 2009 Aug;10(8):580-8.
6. Tang L, Zirpoli GR, Guru K, et al. Consumption of raw cruciferous vegetables is inversely associated with bladder cancer risk. Cancer Epidemiol Biomarkers Prev. 2008 Apr;17(4):938-44.