hamsters that were fed rations spiked with blueberry peels and other
blueberry-juice-processing leftovers had better cholesterol health than
hamsters whose rations weren’t enhanced with blueberries. That’s according to a
study led by U.S. Department of Agriculture (USDA) chemist Wallace H. Yokoyama.
out that further research is needed to confirm whether the effects observed in
hamsters hold true for humans. He works at the Western Regional Research Center operated in Albany, California,
by the Agricultural Research Service (ARS), the principal scientific research
agency of USDA.
investigation, hamsters were fed high-fat rations. For some animals, those
rations were supplemented with one of three different kinds of juice
byproducts: blueberry skins – that is, peels leftover when berries are pressed
to make juice; fiber extracted from the peels; or natural compounds known as
polyphenols, also extracted from the peels. Blueberry polyphenols give the
fruit its purple, blue, and red coloration.
In an article
published in the Journal of Agricultural and Food Chemistry in 2010, Yokoyama and his coinvestigators reported that all the hamsters that
were fed blueberry-enhanced rations had from 22 to 27 percent lower total
plasma cholesterol than hamsters fed rations that didn’t contain blueberry
Levels of VLDL
(very low density lipoprotein – a form of “bad” cholesterol) were about 44
percent lower in the blueberry-fed hamsters.
Yokoyama and his
coinvestigators used a procedure known as real-time reverse transcription
polymerase chain reaction, or RT-PCR, to learn about the genes responsible for
these effects. This approach allowed the scientists to pinpoint differences in
the level of activity of certain liver genes.
In hamsters – and
in humans – the liver both makes cholesterol and helps get rid of excessive levels
of it. Results suggest that activity of some liver genes that either produce or
use cholesterol resulted in the lower blood cholesterol levels.
The study is
apparently the first published account of cholesterol-lowering effects in
laboratory hamsters fed blueberry peels or fiber or polyphenols extracted from
Of course, some
pieces of the cholesterol puzzle are not yet in place. For example, the
researchers don’t know which berry compound or compounds activated the liver
genes, or which parts of the berry have the highest levels of these compounds.
collaborated in the study with former Albany
postdoctoral research associate Hyunsook Kim and ARS research chemist Agnes M.
Rimando, who is based at Oxford,
More details about
this study are available in the May/June 2011 issue of Agricultural Research