The Straight Dope 06/03/2005

The Straight Dope -- By Cecil Adams
http://www.straightdope.com

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THE STRAIGHT DOPE 06/03/2005

Dear Cecil:

Your column about microwave ovens moves me to ask: Is
cancer increasing because we've wrecked the environment?
For years we've heard about the chemicals and emissions
we carelessly spew with dire implications for our health.
Meanwhile, cancer seems to be on the rise: I've heard
breast cancer is up sharply, and melanoma too. But I've
also heard cancer is increasing because we now live long
enough to get it, thanks to modern medicine's success
against illnesses that used to kill people at an earlier
age. What's the story? Is cancer really more common, and
if so, why? --Nick Stalnos, Kankakee, Illinois

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Cecil replies:

If I ever get this figured out, bub, I'll invest the
Nobel money in beer and comic books and spend the rest of
my days on the beach--I'll have earned it. The question
is complicated by countless variables, and establishing
the simplest facts can be maddeningly difficult. For now
here's what we know:

For a while we thought some key cancer rates were
flat or declining, but on further study it turns out
they're going (oops) up. This bombshell dropped in 2002
with the publication of a paper innocuously titled
"Impact of Reporting Delay and Reporting Error on Cancer
Incidence Rates and Trends." The gist: A significant
fraction of cases (3 to 12 percent, depending on cancer
type) don't get reported promptly to the leading U.S.
cancer data registry--in fact, it can take anywhere from
4 to 17 years following initial diagnosis before most
(99-plus percent) cancers are counted. The missing cases
can make early trend reports misleadingly rosy. Melanoma
incidence in white males, for example, was once thought
to be easing; now analysts think it's rising 4 percent
per year.

Notwithstanding such fine points, few dispute that
(a) rates for many common cancers over the past 30 years
are way up; (b) that's partly a function of the fact that . . . 

For more, see:
http://www.straightdope.com/columns/050603.html

STAFF REPORT

Dear Straight Dope:

Some guacamole recipes say to leave the avocado pit in
the bowl with the guacamole to prevent the guacamole from
turning brown. Does this work, and if so, how? -- Nicki

SDSTAFF Una replies:

Does it work? Yes. Does it work for some really cool and
exotic reason? No. 

Most fruits and vegetables change color when their flesh
is exposed to the air due to oxidation--that is, reaction
with oxygen in the air. Some fruits and vegetables, such
as the avocado, are more susceptible than others because
they contain an enzyme called polyphenol oxidase. This
enzyme works on phenolic compounds in the flesh of the
avocado, changing their chemical structure and thus their
color.

So there are two culprits in this browning process--the
enzyme in the avocado, and the oxygen in the air. Logic
suggests that if the avocado pits prevents browning, one
of two things must be happening: Either the avocado pit
chemically changes the guacamole, or it prevents oxygen
from getting to the guacamole in the first place. I
originally proposed to Ed that I do some hard-core
experimentation with multiple guacamole preparations, but
I was talked out of it, and referred instead to the book
The Curious Cook by Harold McGee. 

For more, see: 
http://www.straightdope.com/mailbag/mavocadopit.html

STRAIGHT DOPE CLASSIC - 07/10/1987

Dear Cecil: 

Why is it that when I yawn, everyone around me yawns too?
Am I so boring that I put even myself to sleep? Or is
yawning just the latest STD (socially transmitted
disease)? --Daniel C., Washington, DC  

Cecil replies: 

Not being personally acquainted with you, Dan, I'm not in
a position to say just how tedious the experience of your
company really is.  But I should note that yawning isn't
always a sign of boredom.  Adelie penguins, for
instance, employ yawning as part of their courtship
ritual. The happy couples face off amid the ice floes and
the males engage in what is described as an "ecstatic
display," their beaks open wide and their faces pointed
skyward.   It may be, therefore, that when your entry
upon the scene inspires a round of uncontrollable
yawning, you have merely stumbled onto a gaggle of Adelie
penguins in disguise, who are signaling their powerful
erotic longing for you. A slim hope, admittedly, but any
port in a storm.  

For more, see:
http://www.straightdope.com/classics/a2_304.html

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