Greater flavonoid intake linked with lower cancer risk
In a study reported in the latest issue of Nutrition and Cancer, researchers in Milan uncovered an association between a lower risk of several types of cancer and an increased intake of flavonoids and proanthocyanidins. These polyphenolic compounds are found in fruit, vegetables and plant-sourced beverages, and may be responsible for the protective effects observed for plant foods against a number of chronic diseases.
Carlo La Vecchia of the Universit`a degli Studi di Milano and colleagues evaluated data in a network of case-control studies conducted at multiple Italian centers since the early 1990s. The studies included a total of 9,622 cases of cancer and 16,050 controls. Questionnaire responses reported lifestyle habits and food consumed over the two years preceding cancer diagnosis or (for the control subjects) hospital admission. The participants' diets were analyzed for 6 classes of flavonoids, including isoflavones, anthocyanidins, flavanols, flavanones, flavones and flavonols, and 6 classes of proanthocyanidins.
For subjects whose intake of total flavonoids was among the top one-fifth of participants, there was a 44 percent lower risk of oral cancer and a 40 percent lower risk of laryngeal cancer compared to those whose intake was among the lowest fifth. Participants whose intake of flavanones was among the top one-fifth had a 49 percent lower risk of oral cancer and a 40 percent lower risk of laryngeal cancer, and those whose flavonols were highest experienced a 38 percent and 68 percent lower risk. Among those whose flavanol intake was highest there was a 36 percent decrease in laryngeal cancer compared to the lowest group, and for subjects whose flavanone intake was highest, the risk of esophageal cancer was 62 percent lower.
When colorectal cancer was examined, subjects whose intake of anthocyanidins was highest had a 33 percent less risk of the disease compared to the lowest group, and for those having the highest intake of flavonols, flavones and isoflavones, there was a 36 percent, 22 percent and 24 percent lower risk. Proanthocyanidins also emerged as protective against the disease.
High intake of flavonols and flavones were associated with a lower risk of breast cancer. Furthermore, increased consumption of flavonols and isoflavones were protective against ovarian cancer and greater intake of flavones and flavonols were associated with a lower risk of kidney cancer.
Although flavonoids were not associated with prostate cancer protection in this study, Dr La Vecchia and coauthors note that a recent Japanese investigation revealed a decreased risk of localized prostate cancer among those with a greater intake of isoflavones, sources of which are consumed less frequently in Italy.
The authors remark that flavonoids have demonstrated antioxidant, antimutigenic and antiproliferative properties in laboratory studies. "The findings from this large network of Italian case-control studies have provided support for an apparent protective role of flavanones on upper aerodigestive tract cancers; flavonols, anthocyanidins, and proanthocyanidins on colorectal cancer; flavonols and flavones on breast cancer; isoflavones on ovarian cancer; and flavonols on renal cancer," they conclude.
Natural strategies known to prevent the development and progression of cancer include:
Green and black teas
Catechins and theaflavins, compounds found in green and black teas, have anti-cancer properties (Yang CS et al 2005).
Clinical studies have shown that consuming five or more cups a day of green tea reduces the risk of developing breast cancer, and may help reduce the risk of recurrence in breast cancer survivors (Seely D et al 2005).
Consumption of green tea also significantly improves the survival of ovarian cancer patients (Zhang M et al 2004) and reduces the risk of developing cancers of the lung, breast, and prostate (Bonner MR et al 2005; Doss MX et al 2005).
Such is the strength of data demonstrating green tea’s potential in preventing cancer that Japanese researchers are trying to develop a strategy, based on green tea consumption, for delaying cancer onset in the Japanese population, as well as reducing the risk of recurrence in cancer survivors (Fujiki H 2005).
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St. John’s Wort (hypericin extract) is a weak inhibitor of monoamine oxidase (MAO), which may destroy dopamine in the brain and lead to low spirits. It has also been shown to inhibit re-uptake of several neurotransmitters, including serotonin, dopamine, noradrenaline, GABA, and L-glutamate in the brain, and to reduce expression of interleukin-6. Each of these actions can contribute to alleviating low mood status by slowing the recycling of neurotransmitters needed for maintaining emotional balance. Flavonoids, hypericin, and pseudo-hypericin are the constituents thought to be associated with the benefits of St John’s Wort. In particular, hypericin appears to be the active ingredient.
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