Broccoli, Cabbage, Cauliflower: The Vegetables That May Prevent Cancer

· Foods contain chemicals that help repair DNA
· Study backs link between diet and disease

Natural chemicals found in soya beans and vegetables such as broccoli, cabbage and cauliflower boost the body's ability to repair damaged DNA and may prevent cells turning cancerous, scientists said yesterday. Studies have suggested that eating vegetables appears to provide some protection against certain cancers, but until now the reason why has been a mystery.

Researchers at Georgetown University in Washington DC believe the answer lies with two naturally occurring compounds. The first, indole-3-carbinol or I3C is abundant in vegetables including broccoli and cabbage, while the second, genistein, occurs naturally in soya beans.

The researchers found that when the chemicals were added to cells they boosted the activity of two genes, known as BRCA1 and BRCA2, both of which play a crucial role in detecting damaged DNA and marshalling a cell's response to fix it. Mutations in either of these genes often lead to breast, ovarian and prostate cancer because they are unable to prevent damaged DNA being passed on to the next generation of cells.

Writing in the British Journal of Cancer, the researchers said that since very low levels of BRCA proteins are seen in cancerous cells, higher levels might prevent cancer developing.

"We know that one of the functions of the BRCA1 and BRCA2 genes is to maintain genomic integrity, and to do that, they first have to be able to detect DNA damage and signal to the cell that it is there, and then become involved in repairing it," said Eliot Rosen, the lead author of the study.

"I am sure next years study to expose that they are in fact toxic."

Low-fat diet may not reduce cancer and heart risks

17:22 08 February 2006
NewScientist.com news service
Shaoni Bhattacharya

Eating a low-fat diet with plenty of fibre does not reduce the risk of certain cancers and heart disease in postmenopausal women, suggest three major new studies.

But many experts are unconvinced by the research, asserting there are weaknesses in its design, and stressing the many studies which back the importance of a low-fat, healthy diet in preventing cancer and cardiovascular disease.

The three related studies followed 50,000 women from the Women’s Health Initiative trial over 8 years. No statistically significant difference was seen in the rates of breast cancer, colorectal cancer or cardiovascular disease between women on a reduced fat diet – eating five portions of fruit and vegetables and six portions of grains each day – compared with those who made no dietary changes.

“Evidence from this study, along with that from polyp prevention trials, strongly suggests that lowering dietary fat intake and increasing fruit, vegetable and fibre intake in mid-to-late life cannot be expected to reduce the risk of colorectal cancer in this length of time,” writes one research team led by Shirley Beresford at the University of Washington, Seattle, US.

Too short

The breast cancer study did find a reduced risk with a low-fat, high fibre diet, but this finding was not statistically significant. Its authors say this suggests that if the diet was eaten for longer than eight years the reduction in risk could become significant.

The length of the study was one of the study features criticised by others. "Eight years of follow-up is too short a time to show an effect," Michael Fine, from Rhode Island Hospital, told ABC News. "Let's wait for 15 to 30 years of follow-up before we judge significance."

Other experts say that the amount of fat cut in the diet was not enough. "It is easy to identify a number of important reasons why this study did not agree with previous research,” Judy O'Sullivan at the British Heart Foundation told the BBC. The diet "didn't reflect current advice for good heart health, such as salt reduction, increasing intake of good fats such as those in oily fish, and increasing exercise".

O'Sullivan added: "Most of the women in the study were overweight or obese, which increases your risk of developing diabetes – another risk factor for heart disease."

Journal reference: Journal of the American Medical Association (vol 295, p 629, p 643, p 655)

The first, indole-3-carbinol or I3C is abundant in vegetables including broccoli and cabbage

Phytochemical: Indole-3-Carbinol

Synonyms: I3C, 3-hydroxymethyl indole, 3-indole methanol

Description: Pure indole-3-Carbinol is an off-white solid belonging to the group of indoles. Indole-3-carbinol is only formed in these vegetable after crushing or during cooking.

Distribution: The phytochemical indole-3-carbinol is found in cruciferous vegetables such as cabbage, cauliflower, broccoli, kale and brussels sprouts. Indole-3-carbinol is made from indole-3-glucosinolate by the enzyme myrosinase. This enzyme is only activated after maceration of the vegetables. Action of Indole-3-Carbinol: Indole-3-carbinol is a strong antioxidants and stimulators of detoxifying enzymes. Indole-3-Carbinol seems to protect the structure of DNA. Indole-3-carbinol blocks estrogen receptor sites on the membranes of breast and other cells, thereby reducing the risk of breast and cervical cancer.

Indole-3-carbinol increases the ratio of 2-hydroxyestrone to 16 alpha-hydroxyestrone and inhibits the 4-hydroxylation of estradiol. This is a favourable action of indole-3-carbinol because 16 alpha-hydroxyestrone and 4-hydroxyestrone have carcinogenic action. The estrogen metabolite 2-hydroxyestrone has protective against several types of cancer. Studies with animals have demonstrated that indole-3-carbinol reduced the carcinogenic affects of aflatoxins.

The influence of indole-3-carbinol on the development of prostate cancer is less clear. Most studies report protective effects but a few studies indicate that indole-3-carbinol may promote prostate cancer formation. Indol-3-carbinol protects against carcinogenic effect of pesticides and other toxins.

Publications: Preventive Effects of Indole-3-Carbinol on Endometrial Carcinogenesis in Mice

Synergy among Phytochemicals within Crucifers: Does It Translate into Chemoprotection?

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