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WORLD / Health
Stinky? It's not his sweat, it's your nose
(Agencies)
Updated: 2007-09-24 14:54
Chicago - When it comes to a man's body odour, the fragrance -- or stench
-- is in the nose of the beholder, according to US researchers who
suggest a single gene may determine how people perceive body odour.
The study, published online on Sunday in the journal Nature, helps
explain why the same sweaty man can smell like vanilla to some, like
urine to others and for about a third of adults, have no smell at all.
"This is the first time that any human odorant receptor is associated
with how we experience odours," Hiroaki Matsunami of Duke University in
North Carolina said in a telephone interview.
Matsunami and colleagues at Duke and Rockefeller University in New York
focused on the chemical androstenone, which is created when the body
breaks down the male sex hormone testosterone.
Androstenone is in the sweat of men and women, but it is more highly
concentrated in men. How one perceives its smell appears to have a lot to
do with variations in one odour receptor gene called OR7D4.
"It is well known that people have different perceptions to androstenone.
But people didn't know what was the basis of it," Matsunami said.
To find out, researchers in Matsunami's lab tested sweat chemicals on
most of the 400 known odour receptors used by the nose to sniff out
smells and chemicals.
They found the OR7D4 gene reacted strongly with the sex steroid
androstenone. Next, they tested whether variations in this gene had an
impact on how people perceived the smell of androstenone in male sweat.
They took blood samples and sequenced the DNA of 400 people who
participated in a smell perception test done in Leslie Vosshall's lab at
Rockefeller.
What they found is slight genetic variations determine whether
androstenone has a pungent smell, a sweet, vanilla-like smell or no smell
at all.
The role of androstenone is not well understood in humans, but in pigs it
sends a powerful sex signal that puts sows in the mood for love.
"It facilitates the courtship behaviour in females," Matsunami said.
"There is some evidence published showing this chemical can modify the
mood or hormone levels in humans," he said. "What we don't know is
whether the receptor we found was in any way involved in this process."
He and colleagues will further study this aspect to understand how
smelling these chemicals might affect human social and sexual behaviour.
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