Friday, September 4, 2009

Inflammation and Heart Disease

We all know that chronic inflammation is a bad thing, and many of us try to eat antinflammatory foods or we take supplements that are supposed to reduce inflammation.

But like everything in human biology, inflammation may not be as simple as some people think.

In the short term, inflammation is usually a good thing. It's what protects us from infection. When you cut your skin, it usually hurts and becomes hot and red. Sometimes it swells. This is a sign of inflammation. (Doctors sometimes refer to rubor, calor, dolor, and tumor, referring to red, heat, pain, and swelling.)

What happens is that the wound releases signals that tell the body to send white blood cells to the area to repair the damage, removing dead tissue and replacing it with new tissue. Local blood vessels dilate and become leaky, allowing fluids and white blood cells to exit and get to the wound. This results in swelling, heat, and redness.

Again, short-term inflammation is a good thing. It's chronic inflammation that is supposed to contribute to chronic diseases such as diabetes and heart disease.

But a paper published last month showed that among an obscure tribe in the Amazon, chronic inflammation is the norm, but heart disease is rare.

According to the scientists, the Tsimane tribe still live a traditional lifestyle, fishing, hunting and gathering, growing crops, and also growing and using tobacco, although they smoke much less than Americans who smoke. Most of them die from infections or parasitic diseases. About three-quarters harbor intestinal worms or protozoa. Their life expectancy at birth is only 43 years.

Chronic inflammation is prevalent, and they have high levels of C-reactive protein (CRP), which is often used as a marker of inflammation in the Western world.
The Tsimane also have low HDL levels, which is supposed to mean high risk of heart disease.

But the Tsimane had almost none.
Not a single adult, even the elderly ones, showed signs of peripheral artery disease, a sign of atherosclerosis. Peripheral artery disease increases with age in every other population studied.

The scientists reported that no one died of a heart attack during the 7 years that they were studying the population, which consisted of about 9000 people.

What this suggests is that chronic inflammation alone is not enough to trigger heart disease in a population living a traditional lifestyle. That means they're pretty lean and get plenty of exercise every day just obtaining their food. Their food is fresh.

Of course, many of them died from infectious diseases before they were old enough to be at higher risk of heart attacks and type 2 diabetes.

And one of the flaws of this study is that the authors do not indicate how many people were in each age group for which they reported data. There were only several hundred people in the whole samples
(they did more of the simple tests like blood pressure than the more complicated ones), sometimes even less, and they report the results as percentages, so you have no idea how many people were in each age group.

Nevertheless, I think it illustrates one of the flaws to the American approach to health. Too many people focus on one or two factors, try to control those with drugs, and then expect chronic diseases to go away.

It doesn't happen like this.

Our entire lifestyle makes a difference. We can't pop antioxidant and anti-inflammatory pills and think the risk of cardiovascular disease will evaporate. We need to try to live more like the Tsimane, getting exercise as we go about our daily lives and eating real foods that are as fresh as possible.

One would hope that it's not the parasites that are protecting the Tsimane from heart disease. But that's also possible. Some people theorize that allergies in the developed world have risen because our parasite loads are so low. Maybe parasites also help our arteries. One never knows. As I said, human biology is never simple.

Another possibility discussed by the authors is that the Tsimane are somehow protected by genetic differences. In my opinion, that's always a way to explain the results when they don't come out as you expected they would.

This article also illustrates another issue: the effect of preconceptions by the scientists doing the study. Most people today think thin is good. They think eating a low-fat diet is good, especially if it's vegetarian.

And the title of this article is "Inflammation and Infection Do Not Promote Arterial Aging and Cardiovascular Disease Risk Factors Among Lean Horticulturalists." In other words, they're saying, "Well, these risk factors might not work if the rest of your lifestyle is healthy, like being thin and eating a plant-based diet."

They could just as easily have said, ". . . Among Tobacco-Using Hunters With High Parasite Loads," or "Well, these risk factors might not work if you smoke, eat meat, and have a lot of worms."

Many people read only the titles of articles, and perhaps the abstracts. So any biased generalizations made there can mislead a lot of people. It takes much longer to plow through the full text of an article. But sometimes it's necessary to learn what it really shows.