[tt] Quercetin and immune stimulus

[Hughes, James J.]

http://www.newscientist.com/article/mg19526214.400;jsessionid=CFMGMDCNCC
PE

A hundred apples a day keep the doctor away

    * 19 September 2007
    * NewScientist.com news service
    * Linda Geddes

It's a common complaint of marathon runners and soldiers alike. Overdo
the exercise and you fall victim to illness, particularly chest
infections. Now it seems that quercetin - a flavonoid found in fruits,
berries and tea - may protect them.

For the past few years, DARPA - the Pentagon's research arm - has been
sponsoring studies of quercetin in the hope that it could protect US
troops. "During missions, soldiers are running around for two or three
days with heavy packs on. They don't eat or sleep, and infections are as
much of a problem if not a more serious issue than injuries," says David
Nieman at Appalachian State University in Boone, North Carolina, who led
the research.

He gave 40 male cyclists either 1 gram of quercetin a day - equivalent
to eating 100 apples - or a placebo, for three weeks. During this time,
the cyclists spent a three-day period training at maximum intensity for
3 hours each day. "By the time they were done they were just wasted,"
Nieman says.

Two weeks later, nine of the cyclists in the placebo group had suffered
chest infections, compared with just one in the quercetin group
(Medicine and Science in Sports and Exercise, DOI:
10.1249/mss.0b013e318076b566).

Tests showed that the cyclists taking the supplement had high levels of
quercetin in their blood. Lab studies have previously shown that
quercetin can bind to viruses and bacteria and stop them replicating;
this is what Nieman believes was happening in the cyclists to stop them
getting sick.

Nieman also found the cyclists had reduced levels of IL-8, a chemical
that helps mediate the immune response to antigens, suggesting that
quercetin may also be influencing the immune system in some way (Journal
of Applied Physiology, DOI: 10.1152/japplphysiol.00707.2007).

He is now looking at whether quercetin could benefit people suffering
from high mental stress, who are also at greater risk of infection. He
also hopes to establish the minimum amount of quercetin needed to
achieve a protective effect. The average American typically eats around
107 milligrams of flavonoids - which are polyphenols - per day. There
are no apparent side effects of boosting the intake, says Nieman.

Nieman's studies "provide important new evidence regarding the health
benefits of polyphenols in general and quercetin in particular", says
Holden MacRae at Pepperdine University in Malibu, California. Last year
he showed that quercetin improved cycling time-trial performance by
around 3 per cent, when given in combination with antioxidants, in a
small study of elite male athletes (International Journal of Sport
Nutrition and Exercise Metabolism, vol 16, p 405).
Sprint or Endurance?

How come some people can run for hours without exhaustion, while others
burn out? The answer may be a gene variant which makes muscle cells work
more efficiently. Mice engineered to lack a protein called a-actinin 3,
which is usually found in fast muscle fibres responsible for explosive
bursts of power, were able to run for 33 per cent longer on average than
mice with a-actinin 3.

a-actinin 3 is usually made by the ACTN3 gene. However, around 20 per
cent of people carry a variant which cannot produce the protein.
Previous studies had suggested that sprint athletes rarely carried this
ACTN3 variant, while it was more common among endurance athletes.

To investigate how a-actinin 3 could influence muscle function, Kathryn
North at the University of Sydney, Australia, and her colleagues
engineered mice to lack a-actinin 3. As well as being able to run for
longer, the muscle fibres of the mice had more mitochondria - the "power
houses" of cells (Nature Genetics, DOI: 10.1038/ng2122). "These findings
suggest that a-actinin 3 is associated with baseline changes in muscle
metabolism," says North.

Moreover, when North's team analysed the DNA surrounding ACTN3 in humans
with the variant gene, they found that it was highly conserved -
suggesting that it had been positively selected for during evolution.
Since the ACTN3 variant is more common in Asians and Europeans, North
suggests that it may have helped people adapt to harsher conditions when
they were migrating out of Africa. "Being more metabolically efficient
may have provided an advantage during times of famine," she says.
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Weblinks

    * Quercetin, Wikipedia
    * http://en.wikipedia.org/wiki/Quercetin
    * Kathryn North, homepage
    *
http://www.medfac.usyd.edu.au/people/academics/profiles/kathryn.php
    * DARPA Peak Soldier Performance programme
    * http://www.darpa.mil/DSO/thrusts/bio/mainhuman/psp/index.htm