Friday, January 20, 2012

Hooray for Fiber!

A recent study published January 10, 2012 in the Annals of Oncology concludes that there is an inverse relationship between intake of dietary fiber and breast cancer risk.  How cool is that?  The researchers basically conducted a systematic review and meta-analysis from prospective studies.  All a prospective study means is that we look forward and watch for outcomes such as development of breast cancer relating this to either factors conferring risk or protection such as fiber intake (this is different from a retrospective study where we look backwards analyzing exposure to factors thought to confer risk or protective value to an outcome).  And all a meta-analysis means is that the results of multiple studies are combined, each of which focuses on a related group of hypotheses- in this case sixteen prospective studies from PubMed were included (until August 31, 2011) that addressed the association between fiber intake and breast cancer risk.   
The results of the study showed an inverse association between intake of dietary fiber and breast cancer risk.  This relationship was found to be most pronounced at high levels (greater than or equal to 25 g/day) or large ranges (greater than or equal to 13 g/day) of fiber intake.  Furthermore, it is the soluble fiber intake (not insoluble, fruit, veggie or cereal fiber) that was shown to be responsible for this inverse association.  
How do we explain this inverse association?  First off, epidemiological studies have shown that dietary fiber can lower levels of circulating estrogen, a hormone which has been implicated in breast cancer.  Secondly, high dietary fiber intake may reduce the risk of obesity, a risk factor for post-menopausal breast cancer.  And finally, experimental studies have shown that a soluble fiber--modified citrus pectin—reduced breast tumor growth, angiogenesis (growth of new blood vessels) and metastasis in mice.  Mammary tumor incidence was also found to be reduced with high fiber intake in rat models.      
So what can we practically draw from this study?  That fiber intake is AMAZING!  We already know fiber normalizes bowel function, lowers cholesterol levels, assists in weight reduction and prevents colon cancer.  Now, we can add breast cancer risk reduction to this list!  
My advice: get to the store and fill your cart with items high in soluble fiber.  Just to name a few (well more than a few): bran, oatmeal, barley, lentils, lima beans, black-eyed peas, cabbage, cauliflower, brussel sprouts, broccoli, unpeeled pears and apples, citrus fruits, psyllium seeds and almonds…all excellent sources of soluble fiber.  Not only will you get to partake in the deliciousness of these ingredients, but more importantly, you’ll be fighting off a host of preventable diseases!  

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