24Drs好健康報:茶可以對抗卵巢癌與乳
茶可以對抗卵巢癌與乳癌 Tea May Fight Ovarian, Breast Cancers
好健康小單字─ 類黃酮 (Flavonoids)
茶可以對抗卵巢癌與乳癌
綠花椰菜、羽衣甘藍也是對抗癌症的類黃酮有效來源。
最新研究顯示，茶中有效的化學物質有助於避開卵巢癌與乳癌。
哈佛公衛系的博士候選人Margaret Gates表示，綠花椰菜與羽衣甘藍也是富含對抗癌症類黃酮的來源，她有在研究這些食物與卵巢癌的關係；一般相信類黃酮具有抗氧化與抗發炎的活性，她的研究指出，女性增加攝取山奈酚這種類黃酮的量可以降低40%的卵巢癌風險。
第二篇研究顯示，女性攝取富含其他種類黃酮的飲食，尤其是黃酮、兒茶素與木質素，可以將罹患乳癌的風險降低26%到39%。
研究人員向WebMD表示，如果你無法記住這麼多專有名詞，別擔心，它基本上存在於相同的東西中；Gates表示，茶對於降低卵巢癌的風險特別重要；北卡羅來納大學教堂山分校的博士候選人Brian Fink表示，茶也是能夠預防乳癌的重要物質。
這兩篇最新的研究都在美國癌症研究學會的年會中發表。
【山奈酚對抗卵巢癌】
Gates分析66,384位參與護士健康研究的女性，在研究開始時沒有人罹患卵巢癌，從1984年開始，每幾年就會要這些女性填寫詳細的問卷，詢問她們有關攝取120種以上食物的情形。
研究人員用這些資料計算每位參與者攝食的五種類黃酮含量，分別是楊梅素、山奈酚、檞黃素、木犀草素、與芹菜素，另外也有計算總類黃酮含量；從1984年到2002年間，有344位女性罹患卵巢癌。
Gates表示，總類黃酮的攝取量與卵巢癌之間沒有關係，楊梅素、檞黃素、木犀草素、與芹菜素也沒有明顯的影響；攝取越多的山奈酚（大部分是從茶、綠花椰菜、以及羽衣甘藍而得），罹患卵巢癌的機率就越低。
那麼，要攝取多少山奈酚才夠呢？Gates表示，每天10毫克至12毫克就有預防效果了，這個量等於每天4杯茶或是2杯綠花椰菜，綠茶與紅茶都有用。
Gates表示，她希望能在這部分有更多的研究，如果經證實，攝取類黃酮就能有效的預防卵巢癌。
為了解類黃酮與卵巢癌之間的關係，Fink探究於1990年中期針對紐約長島的女性所做的乳癌機率與風險因子的大型研究數據，在1996年與1997年，有近3千位參與者接受家庭訪問，詢問她們的生活習慣，並請她們做有關吃的東西以及攝取量的問卷。
研究結果顯示，停經後的女性如果攝取最多類黃酮，就能比吃最少的女性減少46%罹患乳癌的機率，但是有效的化學物質對於停經後女性的風險沒有作用。
當研究人員探討停經後女性所攝取的類黃酮時，他們發現黃酮能降低39%、兒茶素能降低26%、木質素能降低31%的乳癌風險；Fink表示，除了茶以外，綠色沙拉、蕃茄、蘋果都是富含類黃酮的良好來源，其他像是黃烷酮、異黃酮素、與花青素等類黃酮則跟癌症風險無關。
他表示，化學結構的微小差異能決定這種類黃酮是否有預防效果，也需要有更多的研究。
【研究中有希望的部分】
加州大學聖地牙哥分校的預防醫學專家Cedric Garland表示，類黃酮是預防癌症的希望，他強調，類黃酮也可以用補品的方式取得；問題是，研究剛開始做，所以他們還不知道建議量是多少，最好就是用一杯茶吞下一盤綠花椰菜。
Tea May Fight Ovarian, Breast Cancers
Potent chemicals found in tea can help ward off ovarian and breast cancers, new research suggests.
Broccoli and kale are also rich sources of cancer-fighting flavonoids, says Margaret Gates, a doctoral candidate at the Harvard School of Public Health who has been studying their link to ovarian cancer. Flavonoids are believed to have antioxidant and anti-inflammatory activity. Her research suggests that women who increase their consumption of kaempferol, a type of flavonoid, can lower their risk of ovarian cancer by nearly 40%.
A second study shows that women who consume a diet rich in other types of flavonoids - specifically, flavones, flavan-3-ols, and lignans -- can reduce their chance of developing breast cancer by 26% to 39%.
If you can't keep all those scientific names straight, no worries: It basically comes down to the same thing, the researchers tell WebMD.
For lowering ovarian cancer risk, "tea in particular may be important," Gates says.
For breast cancer protection, "tea again is the predominant contributor," Brian Fink, MPH, a doctoral candidate at the University of North Carolina at Chapel Hill.
Both new studies were presented at the annual meeting of the American Association for Cancer Research.
Kaempferol Fights Ovarian Cancer
Gates analyzed data on 66,384 participants of the Nurses' Health Study, none of whom had ovarian cancer at the start of the study. Every few years, beginning in 1984, the women filled out detailed questionnaires that asked about their consumption of more than 120 foods.
Using the data, the researchers calculated each participant's intake of five different flavonoids -- myricetin, kaempferol, quercetin, luteolin, apigenin -- and of total flavonoids. Between 1984 and 2002, 344 of the women were diagnosed with ovarian cancer.
Gates says there was no link between total flavonoid consumption and ovarian cancer. Nor did myricetin, quercetin, luteolin, or apigenin significantly affect risk.
But the greater the consumption of kaempferol -- which the nurses got mostly from tea, broccoli, and kale -- the lower their chance of developing ovarian cancer.
So just how much kaempferol is enough? Gates says 10 milligrams to 12 milligrams a day, the amount found in four cups of tea or two cups of broccoli daily, appears to be protective. Both green tea and black tea will do the trick, she adds.
Gates says she'd like to see further research in this area. "If confirmed, flavonoid consumption would provide an important target for ovarian cancer protection," she says.
To look at the flavonoid-breast cancer link, Fink studied data from a large study of breast cancer rates and risk factors conducted among women living on Long Island, N.Y., in the mid-1990s. In 1996 and 1997, nearly 3,000 participants were interviewed at home about their lifestyle habits and given questionnaires that asked what they ate and how much they ate.
The study showed that postmenopausal women who consumed the most flavonoids were 46% less likely to develop breast cancer, compared with those who consumed the least. But the potent chemicals had no effect on risk in premenopausal women.
When the researchers looked at specific flavonoids in the postmenopausal women, they found that flavones reduce breast cancer risk by 39%, flavan-3-ols by 26%, and lignans by 31%.
In addition to tea, green salad, tomatoes, and apples are good sources of the breast cancer-fighting flavonoids, Fink says.
Other flavonoids, such as flavanones, isoflavones, and anthocyanidins, showed no relationship to cancer risk.
"Tiny differences in chemical structure could determine why one flavonoid is protective and one is not," he says. "More study is needed."
Promising Area of Research
Cedric Garland, DrPH, a preventive medicine specialist at the University of California, San Diego, says flavonoids are a promising area of research for cancer prevention. He notes that flavonoids are available in supplement form.
The problem: "The research is only beginning to be done so we don't yet know how much to recommend," he tells WebMD.
In the meantime, your best bet may be a plate of broccoli washed down with a cup of tea.
SOURCES: American Association of Cancer Research annual meeting, Washington, April 1-6, 2006. Margaret Gates, Harvard School of Public Health. Brian Fink, MPH, University of North Carolina at Chapel Hill. Cedric Garland, DrPH, University of California, San Diego.
WebMD Medical News
by Charlene Laino
好健康小單字─ 類黃酮 (Flavonoids)
類黃酮存在於植物體內，包括黃酮、黃酮醇、二氫黃酮、甲基黃酮等，是一群頗具發展潛力的天然抗氧化劑，可抑制食物氧化及提供動物有益的代謝作物；而除了具有抗氧化能力以外，生物類黃酮在體內還有其他益處；有研究顯示，生物類黃酮具有抗病毒、抗發炎、抗過敏，甚至於對抗致癌物的能力。
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