Blueberries, nature's only 'blue' food, are a rich source of polyphenols, potent antioxidants that include phenolics acids, tannins, flavonols and anthocyanins. Researchers have also revealed that a compound found in blueberries called pterostilbene, similar to resveratrol, could be as effective as a widely used synthetic drug in reducing cholestero
Sales of the fruit have boomed from £10.3m (€14.9m) in 2003 to almost £40m (€58m) in 2005, according to UK supplier BerryWorld, driven by dieticians and scientists hailing the fruit as one of nature's superfoods.
"Our study found that phenolics compounds in blueberries could inhibit HepG2 liver cancer cell population growth and induce apoptosis. Dietary intakes of these fruits may have potential to reduce liver cancer," wrote lead researcher Weiguang Yi from the University of Georgia.
The new study, published recently in the journal Food Research International (Vol. 39, pp. 628-638), analysed the polyphenol content of three different blueberry cultivars from the state of Georgia; Briteblue, Tifblue, and Powderblue, and found that the total anthocyanidin content ranged from 89 to 98 per cent of the anthocyanin fraction.
The main anthocyanidins present were delphinidin, cyaniding, petunidin, peonidin and malvidin.
In order to test the inhibition of the blueberry extracts on liver cancer cell growth, the scientists performed in vitro experiments using HepG2 cell cultures. Separate cultures of HepG2 cells were exposed to difference concentrations of the extracts for 48 hours.
The extract concentration under which 50 per cent of the cell population growth was inhibited, IC50, was used as a comparative measure for the three blueberry cultivars. The IC50 value for the Briteblue cultivar was 140 micrograms of anthocyanins per millilitre of solution, and 165 micrograms per millilitre for the Powderblue cultivar. The Tifblue cultivar was less active, with an IC50 value of over 200 micrograms per millilitre.
DNA fragmentation, an early event in programmed cell death (apoptosis), was measured by using a commercially available Cell Death detection ELISA kit. Apoptosis is an event that allows organisms to control the number of cells and therefore tissue size. In cancer cells this process does not function normally leading to rapid growth of the tumour.
Again, the Briteblue cultivar extract produced the most promising results, with DNA fragmentation quadrupled at a concentration of around 100 micrograms per millilitre, compared to control.
While the researchers quoted other research that appeared to support the anti-cancer effects of anthocyanins, no mechanism for the benefits was proposed. "Further studies are required," wrote Yi, "to evaluate the bioavailability, metabolism and beneficial mechanism of phenolics compounds in blueberries before their potential health benefit can be fully determined."
The next step after in vitro studies would to be in vivo animal experiments, and Yi confirmed that such studies were already underway in their laboratory.
For the meanwhile, the researchers propose that incorporating blueberries into the diet could potentially reduce live cancer risk.
Liver cancer is the sixth most commonly diagnosed cancer in the world, and third most common cause of death from cancer, according to Cancer Research UK. Despite these figures, the cancer remains relatively rare, with 18,500 new cases in the US every year, and about 3,000 in the UK.
The highest incidences of the disease are in east and Southeast Asia, and middle and eastern Africa. South Central Asia and Northern Europe have the lowest incidence of the disease.