A couple of studies caught my eye recently. When I opened our local newspaper this morning, I saw this headline over a short article:
Exercise cuts womb cancer risk
Women who regularly work up a sweat exercising have a 30 percent lower risk of developing endometrial cancer, a new study says.
Researchers at the United States’ National Cancer Institute analyzed 14 previous studies and found physical activity cuts the risk of endometrial cancer by 20 to 40 percent when compared to sedentary women. The study was published online Wednesday in the British Journal of Cancer. It was paid for by the National Cancer Institute.
“We already knew that maintaining a healthy body weight is an important way to reduce the risk of womb cancer, but our study showed that physical activity has a protective effects of its own,” said study author Steven Moore of the National Cancer Institute.
I exercise regularly and believe exercise is good for your overall health, but with all due respect to Dr. Moore, his study does NOT show that physical activity protects against cancer. All it shows is that women who exercise are also less likely to develop endometrial cancer. That’s an important distinction, and one that far too many researchers and health reporters don’t understand.
I looked up the full text of the study and, as I suspected, the previous studies Moore’s team analyzed were all observational studies. The trouble with observational studies is that while the correlations researchers find in them may sometimes point to cause and effect, very often they’re simply the result of comparing different kinds of people.
Perhaps you recall the estrogen fiasco. Examining data from the Harvard Nurses Study, researchers found that post-menopausal nurses who took estrogen had a lower rate of heart disease. Based on that finding, doctors were ready to start prescribing estrogen to every middle-aged women in the country. Just one little problem: when estrogen was tested in a controlled clinical study, the women who took it ended up with a higher rate of heart disease, not lower. Same thing happened in a clinical study with men.
As it turned out, the nurses who took estrogen were simply more health-conscious than most other nurses and were taking estrogen because they believed it was good for them — not because it actually was (at least for heart health). Health-conscious people are different. They exercise more, eat less sugar and other junk food, make sure they get enough sleep, take their vitamins, are less likely to smoke or drink alcohol to excess, and more likely to see a doctor if something doesn’t seem quite right with their health. Estrogen wasn’t making nurses healthy … healthy nurses were taking estrogen.
We could be seeing the same phenomenon here. Exercise may, for all we know, help to prevent endometrial cancer. Or it could simply be that health-conscious women — who engage in host of healthier behaviors that help prevent cancer — are also more likely to exercise. The point is, this study doesn’t tell us diddly about cause and effect.
In the full text, the authors explain that they examined the previous studies to determine rates of sedentary behavior — which, in a rare case of clarity for an academic paper, they describe as “too much sitting.” They found a positive correlation between too much sitting and developing cancer. They also found a negative correlation between moderate-to-vigorous exercise and cancer … in other words, more exercise, less cancer. They speculate that since obese people have a higher cancer rate, exercise may prevent cancer in part by preventing obesity.
I sincerely doubt that. First off, as research has shown over and over, exercise has a minimal effect on controlling weight. Secondly, I think they’ve got the equation backwards. We don’t become fat because of “too much sitting” — we sit around too much because our bodies are accumulating fat, thus storing the fuel that would otherwise be burned, compelling us to move around more.
In a recent interview with Jimmy Moore, Dr. Robert Lustig recounted how kids given certain cancer treatments gained weight and became sedentary afterwards. Lustig suspected the treatments had somehow screwed up their insulin levels. When he gave them an insulin-suppressing drug, they not only lost weight, their parents reported they became much more active — without being encouraged to do so. With their insulin levels down, their bodies were no longer storing fuel and wanted to burn it.
Sugar and fructose tell our bodies to store fat. Going into fat-storage mode makes us feel lethargic and lazy. Sugar and fructose are also cancer’s favorite foods.
So it doesn’t surprise me that people who engage in “too much sitting” are more likely to develop cancer. But I doubt sitting around is the cause, or that exercise is the cure. I think it’s more likely sugar is the cause, sitting around is a related symptom, and cutting sugar is the cure … or at least the best prevention.
This study came to me in an email:
Antagonistic people have increased cardiovascular risk
Antagonistic people, particularly those who are competitive and aggressive, could be increasing their risk of MI or stroke, new research indicates.
Studying more than 5000 people in Sardinia, Italy, US scientists found that those who scored high for antagonistic traits on a standard personality test had greater thickening of the carotid arteries on ultrasound compared with people who were more agreeable. Intima-media thickness of the carotid artery is an independent risk factor for cardiovascular events, say Dr Angelina R. Sutin and colleagues in their paper published online August 16, 2010 in Hypertension.
“We found that although men tended to have thicker arterial walls than women, antagonistic women had arterial walls similar to that of antagonistic men,” Sutin told heartwire. “So the association between antagonism and arterial thickness was much stronger for women.” And although arterial thickening is a sign of aging, young people with antagonistic traits already had such thickening, even after controlling for confounding factors such as smoking, she said.
She cautions, however, that this was a population-based sample and more research needs to be done in clinical settings.
Kudos to Dr. Sutin for exercising caution. Associations don’t prove anything. Their purpose is to suggest hypotheses for clinical research, not to serve as evidence for conclusions.
I have to admit, as a survivor of the Los Angeles freeway battle zones, I kind of like believing that the tail-gaiting, bird-flipping, I’m-more-important-than-you drivers I dealt with were thickening their arteries every time they made another dare-devil lane change. (If you’ve never driven in Los Angeles, a significant portion of the drivers believe if they conduct a dozen death-defying maneuvers every minute or so, they’ll eventually discover the secret fast lane.)
However, I doubt aggressive behavior or even having an antagonistic personality causes heart disease in and of itself. I suspect those people are just wired a little differently. Perhaps they pump out a lot more stress hormones, which causes aggressive behavior and damages their arteries at the same time.
One of the most antagonist people I ever met was a young manager at a comedy club. His favorite motivational technique was yelling at the top of his lungs. As you might imagine, he wasn’t beloved by the staff. I found out later he died of a heart attack at age 26. I didn’t like the guy, but I was sorry to hear about his demise. The punishment seemed to vastly outweigh the crime.
To close on a lighter note, a reader sent me a link to this picture. Apparently the Modest Proposal I posted earlier in the week (let’s consume vegetarians for food and save the planet) is already being put into action.
I never considered storing them in the pantry … although CAN VEGETARIANS could be taken more than one way.
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