Re: Science is cruel

TC wrote:
http://www.guardian.co.uk/commentisfree/story/0,,1864989,00.html

The truth about juice

Science is cruel. Reports about the benefits of healthy foods should be
treated with great caution

Not with great caution, but rather a basic understanding that it's
extremely difficult to prove the degree of benefits a single food
provides.

Richard Smith
Tuesday September 5, 2006
The Guardian

Who knows how many people have started guzzling fruit juice thanks to
the blizzard of publicity surrounding an article in the American
Journal of Medicine last week that suggested drinking the stuff might
help fend off Alzheimer's disease. A survey of 1,836 Japanese
Americans, the journal reported, found that those who drank fruit juice
at least three times a week were not as likely as those who consumed it
less than once a week to develop "probable Alzheimer's disease". It may
be that fruit juice does protect against dementia, but my bet is that
it doesn't. We've been here before.

Oh, be careful about trying to connect dots.

A study like this has many potential scientific problems, but the
biggest is that those who drink lots of fruit juice will be different
in many ways from those who drink little. The people who drink more
juice are likely to be better educated, richer, more concerned with
their health, less likely to smoke, more likely to exercise, and
generally healthier. It's not surprising that they are less likely to
develop dementia. The authors "risk adjusted" the data, but there may
be other factors that the scientists don't know about and cannot adjust
for.

Agreed, there are lots of variables.

Another scientific and logical problem is that just because people who
take a lot of x don't get disease y, it doesn't follow that giving
people x will prevent y.

In the 80s, several studies showed that people who had high intakes of
the antioxidant vitamin betacarotene from eating fruit and vegetables
were less likely to develop cancer. The evidence was "convincing".
Scientists then conducted a randomised controlled trial in which some
people were given betacarotene and their chance of developing cancer
was compared with those who weren't given the treatment. Such trials
are the best scientific way of testing whether a treatment works.
Sadly, those given betacarotene proved more likely to develop cancer.

Besides the variables, singling out and taking just betacarotene isn't
likely to have any effect. However, betacarotene along with the other
hundereds of yet unknown chemicals in say a carrot, or more better yet
a diet full of whole foods that contain betacarotene can have a
positive effect on health.

A similar thing happened with the suggestion that people who had high
intakes of vitamin E were less likely to develop heart disease. In a
randomised trial, it was found that those given vitamin E were actually
more likely to do so.

Same story as above.

We've experienced the same scientific problem with hormone replacement
therapy for menopausal women - only this time the idea that the therapy
would reduce heart disease was pushed very strongly by the drug
industry. In the 80s and 90s thousands of women were reported to be
taking hormone replacement therapy. What happened to them was compared
with what happened to women who didn't take it. Those taking the
therapy were found to have fewer deaths from heart disease, and women
were strongly advised to take it. But when the first results were
announced at the end of 2002 from a large randomised trial, it emerged
that hormone replacement therapy made women more likely to suffer heart
disease.

Medicines are a whole 'nother story.

It was also claimed from non-randomised comparisons that taking hormone
replacement therapy decreased a woman's chance of developing dementia.
But yet again a randomised study (when there is no difference among the
women except that some take the treatment and some don't) showed that
the treatment actually made dementia more likely.

Science is cruel and hard. Many things that seem bound to do you good
when properly tested prove to be harmful. Most Guardian readers
probably drink three glasses of fruit juice a week anyway, and I
wouldn't stop. I drink as much myself. But nor should you bet your
brain that it will prevent dementia. It may even make it more likely.

If the ingredients of the juice are quality, I say drink up.

Patrick

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