Health Tips From The Professor: How Tall Is Too Tall?

Every once in a while you see a headline that makes you
do a double take – one that makes you say “Did I just
see what I thought I saw?” This headline was like that.
It said “Taller Women May Have a Greater Risk of
Cancer”.

You may not have seen the headline. It didn’t exactly
make the rounds of all of the nightly news broadcasts
and online blogs (more about that latter). But it did
arouse my curiosity, so I decided to investigate it
further.

The study (Kabat et al., Cancer Epidemiology,
Biomarkers & Prevention, 22: 1353-1363, 2013) is
actually a pretty robust study. The authors included
144,701 women aged 50-79 in the study and followed them
for 12 years. During that time period over 20,000 of
the women in the study developed some type of cancer
and the authors correlated the incidence of 19 kinds of
cancers with the women’s heights.

The results were pretty impressive. Overall, there was
a 13% increased risk of cancer for every 4 inch
increase in height. For melanoma, breast, ovarian,
endometrial and colon cancer the increased risk was
13-17% for every 4 inch increase. For kidney, rectal,
thyroid and blood cancers the increased risk was 23-29%
for every 4 inch increase. There were no cancers for
which increased height was associated with decreased
risk. Finally, the association between height and
cancer risk was unaffected when the authors corrected
for every known cancer risk factor.

So the association between a woman’s height and her
cancer risk is very strong – stronger, in fact, than
the association between obesity and cancer risk. So
what can we make from such a study?

It is important to emphasize that this study merely
shows a strong correlation between a woman’s height and
her cancer risk, it does not imply cause and effect.
Neither the authors of the study nor any of the experts
reviewing the study suggested that increased height
causes cancer. That would be absurd! Instead they
suggested that the real cause must be the genetic,
hormonal, environmental or nutritional factors
associated with increased height that cause the
increase in cancer risk.

You might be saying to yourself: “This doesn’t seem
like a very important study. Why did Dr. Chaney even
mention it?” I did have a purpose in featuring this
study (I always have a purpose).

If you think about it, the headlines associated with
this study are like many of the other recent headlines
that you have seen. For example, one example could be
the recent headlines warning that omega-3 fatty acids
may increase the risk of prostate cancer. That too was
simply a study looking at associations. It also did not
prove cause and effect. Yet the response to the two
studies was totally different.

In the case of the omega-3 fatty acid study, it was
featured on all the TV stations, newspapers and health
blogs. It was hyped for weeks. There were even warnings
not to take fish oil supplements (even though there was
no evidence that anyone in the study was actually using
fish oil supplements).

In contrast, interest in this study died down quickly.
And, nobody is suggesting that tall women hunch over or
have height reduction surgery. Why is that? Both
studies are similar in that they simply measure
associations – not cause and effect.

Perhaps it’s because it’s too far-fetched for anyone to
believe that excess height could actually cause cancer.
Or maybe it’s just that nobody has an anti-height bias
– except perhaps for a few very, very, very short
people.

What is the bottom line for you?

Don’t pay much attention to all the scary headlines
about foods or nutrients that might just kill you. Be
equally skeptical about the headlines claiming miracle
cures. Associations don’t prove cause and effect.
Single studies are often wrong. Good science is like a
fine wine. It takes lots of grapes (lots of individual
studies) and a long time before it is fit for
consumption.

To Your Health!
Dr. Stephen G Chaney

Professor of Nutrition & Biochemistry UNC, Chapel Hill

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