Dig those blackberries from last summer. Any excuse to reuse my photos! We all know we should be stuffing our faces with lots of fruits and veggies, but what is the evidence and which ones are the best?
In a recent article (1), Seeram reviewed the evidence that berries prevent cancer. This review was a little frustrating to follow, and I started wondering if it was a rewritten introduction to a grant application. For an article published in the Journal of Ag. and Food Chem., I personally could have done with a better overview. Some of the detail, while may be necessary in a cancer journal, lost me without careful concentration and then I lost myself in the acronyms. You may realize this from the discussion below. To be fair, they did explain quite a bit of the science and the subject knowledge might be all over the place with different researchers studying different berries and cancers.
In the USA, commonly consumed berries include blackberries, black and red raspberries, blueberries, cranberries, and strawberries. The active ingredients in berries includes Vitamins A, C, E and folic acid; calcuim and selenium; phytosterols; and phenolic molecules such as anthocyanins, flavonols and tannins.
So how good are berries at preventing and reversing cancer?
In vitro studies, with cell lines, have shown that berry phenolics in addition to being potent antioxidants, they also:
“[…]exhibit anti-inflammatory properties, are able to induce carcinogen detoxification (phase-II) enzymes, and modulate subcellular signaling pathways of cancer proliferation, apoptosis and tumor angiogenesis […].”
Coo. That sounds good, but as I am not a cancer researcher the details of the reviewed studies were difficult for me to follow. Raspberry, cranberry and lowbush blueberry juices showed the strongest inhibition of cell growth, which is good as we do not want cancer cells to grow. A red raspberry extract treated so it went through conditions that mimicked the digestive system decreased the number of colon cancer cells and protected against DNA damage induced by hydrogen peroxide. Blueberries induced apoptosis (cell death) of cancer cells and may influence prostate cancer cells [I assumed to the good]. Cranberry extracts inhibited the growth of human breast cancer.
Animal studies showed that rats fed berries and fruit juices showed a significant reduction in AOM-induced aberrant crypt foci, which is a leading indicator of colon cancer. AOM is azoxymethane and acts as a carcinogen to trigger colon cancer in rats and mice.
As for human studies:
Increased fruit and vegetable consumption has been associated with the decreased risk of a number of cancers of epithelial origin, including esophageal cancer.
As an aside, I prefer the British spelling for oesophagus, the oe looks more dignified and I do say “oh-sophagus” or “oo-sophagus”
It is hard to know how much bioactives we are consuming. This is partly, as this article reports, because the amount of phytochemicals present in foods is not known and changes dramatically depending on growing conditions. Organic strawberries had a greater effect on human colon and breast tumor cells than conventionally grown strawberries. Organic berries were more effective probably because they contain more secondary metabolites than conventionally grown fruit.In addition:
Studies have shown a high variability in phenolic intake based on variations in individual food preferences. A high daily intake of fruits and vegetables is estimated to provide up to 1 g of phenolics.
Unfortunately, “high daily intake of fruits and vegetables” is not defined in the article.
Even if we know how much of the bioactive compounds we consume, we still do not know how bio-available these phenolics in berries or other fruit.
I find it amusing that articles always end up with a statement which in effect says “more research is needed, I am the best person to do it and I need funding now“. In this article the concluding paragraph goes:
In conclusion, it is strongly recommended that this area of research for berry fruits continue to be explored, as this will lay the foundation for the development of diet-based strategies for the prevention and therapy of self types of human cancers.
Eat lots of berries, now and forever more. Fortunately, I have lots in my freezer. Yum.
(1) Seeram, N.P. (2008). Berry Fruits for Cancer Prevention: Current Status and Future Prospects. Journal of Agricultural and Food Chemistry DOI: 10.1021/jf072504n