In a crowded arena of superfruit contenders, with antioxidant claims and new ‘super diets’ backed by star celebrities, it is no wonder consumers are confused which fruits can deliver real health benefits. One berry, however, backed by decades of research, has the potential to change that. The North American cranberry, of the genus Vaccinium macrocarpon, has a long and rich heritage. Grown throughout the Eastern and Northeastern U.S., the Pacific Northwest, upper Midwest, and much of Canada, the cranberry is one of only three fruits native to this region that is commercially cultivated. Its health benefits have long been recognized, first by Native Americans who used cranberry to treat different ailments such as urinary disorders, stomach ailments, wounds and fever, as well as preserving food. Here, we take a look at the science behind these ‘whole body’ benefits.
Antioxidant activity and cranberry polyphenols
As befitting a fruit that is one of the original superfruit, the cranberry is rich in important nutrients such as vitamin C, β-carotene and fiber. However, it is also rich with a complex repertoire of flavonoids-compounds found in many fruits, vegetables, grains and nuts that are linked to helping reduce the risk of chronic diseases (1). These complex and active polyphenols give the cranberry one of the highest antioxidant activities-one of the highest among commonly consumed berries such as strawberry, blueberry, blackberry and raspberry as published in the 2004 USDA database (2). In a study comparing the antioxidant value of fruit extracts from different berries and commonly consumed fruits such as apples and oranges, Kalt et al (3) found that the ORAC value, a measure of the antioxidant value of a food or beverage, was linked to the total polyphenol content of the fruit extracts. Many cell and in vivo studies have linked certain polyphenols, for example, quercetin, with activity that may help mitigate deleterious processes involved in aging, immune defense, cardiovascular disease, cognitive function, obesity and Type 1 diabetes (1). Quercetin, an important polyphenol in plant and vegetables, makes up a large proportion of the dietary intake of flavonoids in many countries, some food sources being onions and broccoli. The good news is that quercetin, as reported in the USDA flavonoid database, is abundant in the cranberry as well, suggesting yet another mode of action for the versatile berry (4). Studies examining the role of cranberry compounds in maintaining heart health are starting to emerge in the last decade (1).
Polyphenols and anti-adhesion activity
In the same study by Kalt et al (3), it was found that the total polyphenol content does not influence one particular activity demonstrated by the cranberry-anti-adhesion- the mechanism by which cranberry compounds bind certain harmful bacteria. This suggested that there were other compounds in the cranberry. This unique group of compounds, called proanthocyanidins or PACs, is responsible for the anti-adhesion activity (5).However, not all proanthocyanidins are created equal, and only one kind of PAC-Type A PACs-demonstrate anti-adhesion activity. Type A PACs are found in cranberries but not in some other PAC containing foods such as grapes, tea, or cocoa. So not only does the cranberry contain one of the highest content of PACs per gram as shown in the USDA database of PAC content (6), it also contains a unique form found only in a very limited number of foods/berries.
The ability of Type A PACS to prevent the harmful bacteria from sticking to the wall is likely responsible for the protective effects of the cranberry on urinary tract health as shown by over sixty years of mechanistic and clinical research (5,7). Several studies that emerged recently suggest that this same anti-stick action may help to prevent other pathogens such as H.pylori from proliferating in the stomach or S.mutans from growing on oral surfaces, helping to support gastrointestinal and oral health as well (8,9). The ability to suppress attachment and proliferation of pathogenic bacteria on surfaces may help support a healthy balance of microflora in the body.
The cranberry research world is now only scratching the surface of another potential health benefit of this superfruit. In the last few years, some exciting cell culture research examined the role of cranberry compounds on the infectivity of the rotavirus -a pathogen implicated in gastroenteritis (10). It is interesting to think that these compounds that can bind bacterial “appendages” can also affect the binding and infectivity of viruses. We look forward to further developments in this emerging area of research, a role that may be complementary to supporting our immune health. Another group of compounds, phenolic acids, are implicated in the anti-microbial effects against food borne pathogens such as Salmonella and E. coli (11). However, human clinical studies need to be conducted to determine the implications or applicability of these in vitro results, but some food safety applications of cranberry compounds have been suggested.
Summary: Evidence based validation
The cornerstone of evidence based diet-health relationship is the link between mechanistic, clinical and finally epidemiological research. In the last 60-70 years, the little cranberry with the super credentials has built up an impressive resume with mechanistic, epidemiological and clinical studies linking urinary tract health to consumption of cranberry and cranberry products . The link between dietary intake of cranberry and clinical efficacy continues to be studied including several trials on urinary tract health being funded by NIH/NCCAM. One NIH/NCCAM study recently published demonstrated a trend towards a 57% decrease in asymptomatic bacteruria –a condition where there is increased bacteria in the urine without urinary infection symptoms- and a 41% decrease in UTI in the study group of healthy, pregnant women (12). The current decade brings more supportive documentation for cranberry and urinary tract health but the focus on other health areas is growing. It will be interesting to see what the next decade brings for cranberry research. The antioxidant quality from the complex mixtures of polyphenols and the unique Type A PACs provide the cranberry the incredible potential to support ‘whole body’ well-being by maintaining the health of the gastrointestinal, oral, urinary tract, cardiovascular, immune, oral and cell systems.
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