Citrus Fruit May Reduce Breast Cancer Risk by 32%
A high intake of citrus fruits lowers breast cancer risk in women by 10 percent, according to a new systematic review of past studies. But importantly, “high” intake was only 17 to 33 grams daily in one of the studies analyzed, and this provided a 32 percent risk reduction of breast cancer.
The anti-cancer effects of citrus fruits
Citrus fruits are excellent sources of numerous phytochemicals such as beta-cryptoxanthin, limonoids and quercetin, each of which has shown potent activity against cancer in laboratory studies. In particular, one recent study showed that a limonoid-rich lemon extract potently suppressed breast cancer cells. In human studies, citrus fruit consumption has been shown to offer protection from pancreatic, stomach, throat, colorectal and breast cancers. However, in some studies there is only borderline significance or even conflicting results. This is often due to the low level of citrus fruit eaten (even by the highest consumers) and the difficulty in separating the protective effects of citrus from other fruit or vegetables.
Citrus reduces breast cancer risk by at least 10 percent
For the above reasons, researchers in Korea produced a new systematic review which combines previous studies from China, the USA and Australia, in an attempt to clarify the role of citrus fruit in breast cancer prevention. It includes a total of 8,393 participants with ages ranging from 20 to 98. When all the data was combined together, an overall risk reduction of 10 percent was observed for the highest consumers of citrus fruit compared to the lowest. However, if one single study from 20 years ago is left out of the analysis, the results look far better with an average overall risk reduction of about 20 percent.
Interestingly, the largest study of all those in the analysis (with 3,015 participants), and the only one to reach statistical significance on its own (p=0.002), also happened to show the highest protective effect of citrus consumption, yielding 32 percent risk reduction. This study, out of China, also showed citrus to be the most protective of all the fruits observed in the diet (including grapes, peaches, pears, bananas, apples) and on par with the protective effects of vegetables. Most notable is that such a level of protection was achieved with a citrus intake of just 17 to 33 grams daily, which equals about one eighth of a cup of orange juice.
The China advantage: citrus synergies with green tea?
It appears that Chinese women may require considerably less citrus for protection from breast cancer than Americans. For example, a previous study showed that American women consuming a half-cup serving (125 grams) daily had risk reductions of only 20 percent for postmenopausal, and 17 percent for premenopausal breast cancer. Why might Chinese women be protected by less citrus fruit?
The answer might come from the green tea they drink. A recent and very surprising study from Japan showed that when green tea drinkers consumed citrus fruit daily, they (women) saw a statistically significant 18 percent reduction in overall cancer risk, including a non-statistically significant 26 percent reduction in breast cancer. Importantly, these risk reductions were over and above the protective effects of green tea. Since green tea consumption was not factored into to the Chinese study in this way, it is possible we are seeing a similar synergistic effect in that population.
The new systematic review confirms that citrus fruit clearly has a role to play in breast cancer prevention. While it appears that even small amounts of citrus may offer meaningful protection, women looking to maximize their risk reduction should consider eating at least half a cup of citrus fruit daily, and including green tea for its synergizing effects.
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