Flavonoid-rich Diet Helps Women Decrease Risk Of Ovarian Cancer

Daily Science Journal (Nov. 20, 2007) — New research out of the Channing Laboratory at Brigham and Women’s Hospital (BWH) reports that frequent consumption of foods containing the flavonoid kaempferol, including nonherbal tea and broccoli, was associated with a reduced risk of ovarian cancer. The researchers also found a decreased risk in women who consumed large amounts of the flavonoid luteolin, which is found in foods such as carrots, peppers, and cabbage.

Broccoli and carrots are among the foods that are high in flavinoids. (Credit: iStockphoto/Albert Lozano)

“This is good news because there are few lifestyle factors known to reduce a woman’s risk of ovarian cancer,” said first author Margaret Gates, a research fellow at BWH. “Although additional research is needed, these findings suggest that consuming a diet rich in flavonoids may be protective.”

The causes of ovarian cancer are not well understood. What is known is that the earlier the disease is found and treated, the better the chance for recovery; however, the majority of cases are diagnosed at an advanced (metastasized) stage after the cancer has spread beyond the ovaries. According to the National Cancer Institute, the five-year relative survival rate for women diagnosed with localized ovarian cancer is 92.4 percent. Unfortunately, this number drops to 29.8 percent if the cancer has already metastasized.

In this first prospective study to look at the association between these flavonoids and ovarian cancer risk, Gates and colleagues calculated intake of the flavonoids myricetin, kaempferol, quercetin, luteolin, and apigenin among 66,940 women enrolled in the Nurses’ Health Study. In this population, 347 cases of epithelial ovarian cancer were diagnosed between 1984 and 2002.

Although total intake of these five common dietary flavonoids was not clearly beneficial, the researchers found a 40 percent reduction in ovarian cancer risk among the women with the highest kaempferol intake, compared with women with the lowest intake. They also found a 34 percent reduction in the risk of ovarian cancer among women with the highest intake of luteolin, compared with women with the lowest intake.

“In this population of women, consumption of nonherbal tea and broccoli provided the best defense against ovarian cancer,” concluded Gates, who is also a research fellow at the Harvard School of Public Health. “Other flavonoid-rich foods, such as onions, beans, and kale, may also decrease ovarian cancer risk, but the number of women who frequently consumed these foods was not large enough to clearly evaluate these associations. More research is needed.”

These findings appear in the Nov. 15, 2007, issue of the International Journal of Cancer.

Adapted from materials provided by Harvard University.

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Consumption Of Green Tea Associated With Reduced Mortality In Japanese Adults, Drinking Tea Associated With Lower Risk Of Ovarian Cancer

Daily Science Journal (Sep. 13, 2007) — Adults in Japan who consumed higher amounts of green tea had a lower risk of death due to all causes and due to cardiovascular disease, according to a study in the September 13 issue of JAMA. But there was no link between green tea consumption and a reduced risk of death due to cancer.

Tea is the most consumed beverage in the world aside from water. Three billion kilograms of tea are produced each year worldwide, according to background information in the article. Because of the high rates of tea consumption in the global population, even small effects in humans could have large implications for public health. Among teas, green tea polyphenols have been extensively studied as cardiovascular disease (CVD) and cancer chemopreventive agents. Although substantial evidence from in vitro and animal studies indicates that green tea preparations may impede CVD and carcinogenic processes, the possible protective role of green tea consumption against these diseases in humans remains unclear.

Shinichi Kuriyama, M.D., Ph.D., of the Tohoku University School of Public Policy, Sendai, Japan, and colleagues examined the association between green tea consumption and mortality (death rate) due to all causes, CVD, and cancer within a large population. The study, initiated in 1994, included 40,530 adults (age 40 to 79 years) in northeastern Japan, where green tea is widely consumed. Within this region, 80 percent of the population drinks green tea and more than half of them consume 3 or more cups and day. The participants, who had no history of stroke, coronary heart disease, or cancer at baseline, were followed for up to 11 years (1995-2005) for all-cause death and for up to 7 years (1995-2001) for cause-specific death.

Over 11 years of follow-up, 4,209 participants died, and over 7 years of follow-up, 892 participants died of cardiovascular disease and 1,134 participants died of cancer. The researchers found that green tea consumption was inversely associated with death due to all causes and due to cardiovascular disease. Compared with participants who consumed less than 1 cup/d of green tea, those who consumed 5 or more cups/d had a risk of all-cause mortality and CVD mortality that was 16 percent lower (during 11 years of follow-up) and 26 percent lower (during 7 years of follow-up), respectively.

These inverse associations of all-cause and CVD mortality were stronger among women, although the inverse association for green tea consumption was observed in both sexes. In women, compared with those who consumed less than 1 cup/d of green tea, those who consumed 5 or more cups/d had a 31 percent lower risk of CVD death.

The researchers found there no significant association between green tea consumption and death from cancer. There were weak or neutral relationships between black tea or oolong tea and mortality.

"Clinical trials are ultimately necessary to confirm the protective effect of green tea on mortality," the authors write.

This study was supported by a Health Sciences Research Grant for Health Services, Ministry of Health, Labour, and Welfare, Japan.

Adapted from materials provided by JAMA and Archives Journals, via EurekAlert!, a service of AAAS.

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Drinking Tea Associated With Lower Risk Of Ovarian Cancer

Women who drank at least two cups of tea a day had a lower risk of ovarian cancer than those who did not drink tea, according to a study in the December 12/26 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.

Evidence from laboratory studies indicates that green and black tea preparations may protect against various cancers. But few epidemiological studies have examined the relationship specifically between tea consumption and the risk of ovarian cancer, according to background information in the article.

Susanna C. Larsson, M.Sc., and Alicja Wolk, D.M.Sc., of the National Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden, prospectively examined the association between tea consumption and the risk of ovarian cancer in 61,057 women, aged 40 to 76, who were participants in the population-based Swedish Mammography Cohort. Participants completed a validated 67-item food frequency questionnaire at enrollment between 1987 and 1990, and were followed for cancer incidence through December 2004. At baseline, 68 percent of the participants reported drinking tea (mainly black tea) at least once per month. During an average follow-up of 15.1 years, 301 women were diagnosed as having invasive epithelial ovarian cancer.

"We observed a 46 percent lower risk of ovarian cancer in women who drank two or more cups of tea per day compared with non-drinkers," the authors report. "Each additional cup of tea per day was associated with an 18 percent lower risk of ovarian cancer."

Women who drank less than one cup of tea per day had an 18 percent lower risk of ovarian cancer than non-drinkers. The risk was 24 percent lower for women who drank one cup of tea per day.

"This association does not depend on lower coffee consumption among women with high tea consumption; coffee is not associated with ovarian cancer risk in this cohort," the authors write.

"In summary, our results from a large population-based cohort of Swedish women suggest that tea consumption may lower the risk of ovarian cancer," the authors conclude. "Because prospective data on this relationship are scarce, our findings need confirmation by future studies."

(Arch Intern Med. 2005;165:2683-2686. Available pre-embargo to the media at www.jamamedia.org.)

Editor's Note: This work was supported by research grants from the Swedish Cancer Foundation and the Swedish Research Council/Longitudinal Studies, Stockholm, Sweden.


Adapted from materials provided by JAMA and Archives Journals, via EurekAlert!, a service of AAAS.

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Vitamin D And Flavonoids Examined For Impact On Breast And Ovarian Cancers

Daily Science Journal (Jul. 7, 2007) — While risk factors for breast and ovarian cancers include menopause, obesity, family history and specific genetic mutations, researchers also are looking at the role of diet in the development, as well as the treatment and prevention of these tumors. At the 97th Annual Meeting of the American Association for Cancer Research, two groups of scientists using sophisticated statistical techniques report their findings of possible preventive properties of Vitamin D against breast cancer. Two other groups of scientists present their work analyzing the possibility that natural antioxidants found in plants, substances called flavonoids, could play a powerful role in preventing both breast and ovarian cancer.

Potential Reduction in Breast Cancer Risk Associated with Vitamin D: Abstract No. 4009

Though scientists have suspected that Vitamin D helps to prevent and possibly even treat breast cancer, population-based studies on the possible link have been few and of limited scope.

Now, new studies by researchers at the Samuel Lunenfeld Research Institute at Mount Sinai Hospital in Toronto suggest the "sunshine" vitamin may play a significant role in reducing breast cancer risk. The results, based on population data, found the reduction was most apparent among subjects exposed to the highest levels of vitamin D when they were young.

By interviewing about 576 patients who had been diagnosed with breast cancer and 1,135 people who had no cancer, the scientists discovered that significant reductions in breast cancer were found in those who had either worked in an outdoor job, had taken part in outdoor activities when young, or consumed cod liver oil or milk.

Working an outdoor job between ages 10 to19 resulted in an estimated 40 percent reduced risk of breast cancer, while frequent outdoor activities between ages 10 to 29 lowered breast cancer risk by an estimated 35 percent.

"These outdoor activities included those that didn't involve physical activity," said Julie Knight, who headed the Mount Sinai research team. "And so we believe that this is evidence of a reduction of breast cancer risk, associated with earlier exposure to the sun."

For dietary influences on cancer development, taking cod liver oil between ages 10 to 19 reduced breast cancer risk by about 25 percent, and consuming at least nine glasses of milk every week between the ages of 10 to 29 reduced the risk by 35 percent. The dietary and lifestyle reductions were significant, even when adjusted for other risk factors for breast cancer such as age, ethnicity, close relatives with breast cancer, age at menarche and age at a woman's first birth.

"What you are exposed to during breast development may be particularly important in determining future breast cancer risk," Knight said. "Current thinking is that exposures during adolescence or before a full-term pregnancy may have a greater effect, as that is when breast tissue is going through the most rapid development."

Knight emphasizes that these findings are preliminary estimates of the risk reduction of breast cancer brought about by Vitamin D. The researchers are now looking to solidify these findings, and determine whether physical exercise while outdoors is in any way associated with breast cancer.

Evidence of Need for Increased Vitamin D Fortification of Food Based on Pooled Analysis of Studies of Serum 25-hydroxyvitamin D and Breast cancer: Abstract No. 4008

Increasing doses of dietary Vitamin D may help prevent breast cancer, with the optimal level of intake of Vitamin D more that three times the current average for Americans, according to a study conducted at the University of California, San Diego.

Previous studies have suggested a link between Vitamin D deficiency and higher incidence of breast cancer. Cedric Garland, Dr. P.H., and Edward Gorham, Ph.D., of UCSD, and their colleagues examined existing cancer studies to determine if higher Vitamin D levels in the blood could reduce the risk of cancer.

"There is a strong inverse dose-response relationship between the serum concentration of 25-hydroxyvitamin D and the risk of breast cancer," Garland said. "It's a close fit to a linear model," meaning that higher amounts of 25-hydroxyvitamin D in the serum resulted in decreased risk of breast cancer. The evidence further pointed to a level of Vitamin D measured in blood that correlated with a 50 percent reduction in the incidence of breast cancer.

Garland, Gorham and their colleagues studied a serum Vitamin D metabolite known as 25 hydroxyvitamin D and its association with breast cancer occurrence in a pooled study that included 1,760 women. The studies that provided the data for the pooled analysis were conducted by Elizabeth R. Bertone-Johnson and colleagues at Harvard, and L.C. Lowe and associates at Saint George's Hospital Medical School in London.

According to the pooled analysis, Vitamin D in blood serum equal to 52 nanograms per milliliter was associated with a 50 percent reduced risk of breast cancer. To move closer to a serum concentration of 52 nanograms/milliliter, a typical individual would have to consume no less than 1,000 International Units (IU) of Vitamin D every day, through supplements or vitamin D-fortified foods. Currently, a typical American consumes only 320 International Units of Vitamin D a day. The upper limit for vitamin D intake established by the National Academy of Sciences is 2,400 IU/day, but no toxic effects of vitamin D intake have been reported for intakes below 3,800 IU per day.

"There is no substantial downside to a serum level of 52 nanograms per milliliter of Vitamin D," said Gorham. "Such levels are common in sunny climates. There is no known adverse effect of serum levels below 160 nanograms per milliliter."

However, since many people use sunscreens and are involved in indoor occupations or shift work, dietary supplements and vitamin D fortified foods are necessary to maintain optimal levels of Vitamin D, the scientists noted.

High intakes of calcium, which could occur with intake of Vitamin D supplements containing calcium, could increase the risk of kidney stones, they warn. However, the dosage level of vitamin D associated with kidney stones in patients far exceeded 3,800 IU/day. Until more studies are completed, the scientists recommended that everyone consume at least 1,000 IU/day of vitamin D3.

Dietary Flavonoid Intake and Breast Cancer Risk among Women in the Long Island Breast Cancer Study Project: Abstract No. 4014

Flavonoids, a class of antioxidants found in plants, is associated with a reduced risk of breast cancer among post-menopausal women, according to results of the Long Island breast cancer study project. The results are one of the first epidemiologic studies to suggest that these compounds could have a chemoprotective effect among women.

Brian Fink, Susan Steck and Marilie Gammon of the University of North Carolina, Chapel Hill, and other colleagues studied data from a large study of breast cancer incidence and risk factors conducted among women living during the mid-1990s on Long Island, N.Y.

Breast cancer risk was reduced for the highest percentages of total flavonoid intake, compared to the lowest intake of the plant antioxidants. The decreased risk was about 45 percent among post-menopausal women. Risk decreases were not seen in pre-menopausal women. Specific flavonoids -- including flavones, flavan-3-ols and lignans -- were associated with reduced cancer risks ranging from 26 to 39 percent; other flavonoids, such as flavanones, isoflavones and anthocyanidins, showed no relationship with reduced cancer risk.

"These results are consistent with other studies conducted among Mediterranean women," said Fink. "Few epidemiologic studies have examined whether there is a relationship between breast cancer and dietary flavonoids. Our study proposes that dietary flavonoids can help American post-menopausal women reduce their risk of breast cancer."

The researchers examined data from the Long Island study, which was conducted by Dr. Gammon and colleagues between August 1996 and July 1997. The team compared data from 1,434 women with breast cancer to data from 1,440 women who were not diagnosed with the disease.

Flavonols, flavones, lignans and anthocyanidins are all flavonoids, molecules that give plants protection from oxidative damage due to disease and environmental stresses. Flavonoids are classified according to chemical structure, and have been studied for their varying degrees of effectiveness against human diseases, both in treatment and prevention. They are found in green tea, red wine, soybeans, fruit and vegetables.

"There are no recommended dietary standards for ingestion of flavonoids, and we do not know exactly how these chemicals may work on a cellular level," said Fink, whose work was supported with funding from the National Institutes of Health and the Lance Armstrong Foundation. "Minute differences in chemical structure could determine how a certain natural antioxidant may work to prevent disease, including cancer. More study is needed to determine why certain flavonoids appear to be effective at reducing cancer risk, and others do not appear to have these properties."

A Prospective Analysis of Dietary Flavonoid Intake and Epithelial Ovarian Cancer Incidence: Abstract No. 4013

The incidence of ovarian cancer may be reduced with increased consumption of dietary flavonoids, plant chemicals that are found in tea, red wine, fruits and vegetables, according to researchers from Brigham and Women's Hospital and the Harvard School of Public Health.

The study, conducted by Margaret Gates, a doctoral candidate at the Harvard School of Public Health, looked at food intake surveys and ovarian cancer data from 66,384 participants in the Harvard Nurses' Health Study, which collected health data from 121,700 women over a period of 30 years. "This is the first prospective analysis of flavonoid intake and ovarian cancer incidence," Gates said.

Gates studied the association between flavonoid intake from food frequency questionnaires completed by the women in 1984, 1990, 1994 and 1998; and 344 confirmed cases of ovarian cancer diagnosed between 1984 and 2002. While there was a significant trend toward decreasing incidence of ovarian cancer with increasing total flavonoid intake, Gates warned that "because this is one of the first studies of the topic, this association needs to be evaluated in another prospective study population before conclusions can be made."

Gates also analyzed individual flavonoids to evaluate their impact on ovarian cancer incidence. The flavonoid kaempferol, which the nurses consumed primarily from caffeinated tea, broccoli and kale, was associated with decreased ovarian cancer risk. Women with the highest levels of kaempferol intake had a significant 38 percent decrease in ovarian cancer incidence, compared to women with the lowest levels of intake. Two other flavonoids, myricetin and quercetin, showed a possible inverse association with ovarian cancer risk, although the results were largely non-significant.

"The associations were stronger when exposure was defined as cumulative average flavonoid intake over a period of 14 years, which suggests that long-term intake of flavonoids may be important," Gates said.

But she cautioned that "these findings need to be confirmed by others before any public health recommendations can be made. However, if confirmed, consumption of flavonoids would provide another means for women to decrease their risk of ovarian cancer."

Adapted from materials provided by American Association for Cancer Research.

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