There is good evidence to suggest that plant-based diets lower esophageal cancer risk; however, evidence for specific foods, fruits, or vegetables is more difficult to ascertain. Diets and even specific fruits and vegetables are really complex mixtures whose constituents vary based upon a plethora of factors including growing conditions (soil, water, and specific variety), time of harvest, storage, processing and preparation.
Numerous food frequency questionnaires have been created and validated to differing extents for evaluation of diet as it relates to cancer risk; however, limitations persist particularly for assessing multidimensional exposures in free living populations. However, development of new tools to address previously unmeasured intakes may provide additional insight with regard to specific foods or categories of foods with cancer inhibitory properties.
Recent reports have linked proanthocyanidins or anthocyanidins to risk reduction for colon, stomach, and esophageal cancers. The three studies utilized a proanthocyanidins (PAC) database developed by the US Department of Agriculture in 2004 which quantifies PACs in multiple foods.
This type of tool enables new dietary comparisons to be explored in a more specific way and may better inform our understanding of the relative cancer inhibitory contribution that specific categories of foods impart. The data base does not, however, attempt to separately quantify PACs based on their chemical linkage type, but only according to their oligomeric fraction. Linkage type has proven very important for urinary tract health effects.
Is specifically the A-type linkages of cranberries that inhibit adhesion of p-fimbriated uropathogenic Escherichia coli to uroepithelial cells inhibiting infection. Other types of PACs with mainly B-type linkages such as those found in apple juice were not significantly inhibitory. The importance of the linkage type is not currently known in terms of cancer prevention, but important to consider.
The berry type most extensively studied for cancer inhibitory effects in the esophagus is the black raspberry. In brief, black raspberries and black raspberry extracts have shown inhibitory effects in multiple preclinical models of epithelial cancers, including esophageal SCC. Mechanisms of inhibition include reduced cell proliferation, induction of apoptosis, alteration of inflammatory markers, and effects on angiogenesis.
Various berry types including black and red raspberries, strawberries, blueberries, noni, acai, and wolfberry all significantly inhibited carcinogen induced squamous cell cancer in the rat F344 model and select serum cytokines were altered. It is promising that all the berries investigated significantly inhibited NMBA-induced esophageal SCC given the differences among the berries in terms of composition of bioactive constituents pointing potentially to the involvement of multiple mechanisms.
Daily consumption of BRB significantly reduced urinary excretion of markers linked to oxidative damage, urinary 8-iso prostaglandin F2alpha, and 8-hydroxy-2-deoxyguanosine. About one-third of the patients responded with increased levels of the important detoxification enzyme glutathione S-transferase pi, at the tissue level following the 6 month BRB intervention (unpublished results). Additional studies are warranted with regard to characterizing the various berries, expanding mechanistic studies, and evaluating combinations of berries for improved efficacy in high risk cohorts, such as those with Barrett’s esophagus or esophageal dysplasia.
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1. Clinical evaluation in humans
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