Monday, July 04, 2005

Opinion Versus Evidence

One thing that bugs me is when "medical writers" or "science editors" write things without backing up their statements with references to studies or data.

Case in point - in today's Toledo Blade, science editor Michael Woods ends his article, "How to adopt anti-inflammatory way of living" with this sentence: Nobody is certain about those popular low-carb/high protein diets, but some evidence suggests that they increase invisible inflammation.

Invisible inflammation is what the American Heart Association calls "low grade inflammation" and the marker for it is C-Reactive Protein (CRP) in the blood. The AHA website provides us with information about how important a marker the CRP may be in our risk for a heart attack - Most studies show that the higher the hs-CRP levels, the higher the risk of developing heart attack. In fact, scientific studies have found that the risk for heart attack in people in the upper third of hs-CRP levels is twice that of those whose hs-CRP is in the lower third.

So, elevated CRP is an important risk factor we should consider for our long-term health. Many believe that certain foods help the body reduce inflammation. Mr. Woods includes a list in his article:
  • Fatty fish like salmon, mackerel, and sardines
  • garlic
  • onions
  • almost all green vegetables
  • nuts (especially walnuts and almonds) and beans
  • fruits and berries (especially deeply colored items like blueberries, oranges, tomatoes, and cantaloupe)
  • herbs (especially rosemary, oregano, and parsley)
  • spices (especially ginger, turmeric, clove, and cinnamon)
  • certain beverages (especially green, white, and black tea and red wine)
  • olive and canola oil
  • cocoa

So far so good, except, last time I looked, all of the above foods are not only allowed on a low-carb diet to lose weight (except oranges) and a controlled-carb approach to maintaining weight, they're strongly encouraged! (and yes, oranges are fine later in a low-carb diet and controlled-carb approaches)

So, what's this assertion that low-carb may increase infalmmation coming from? Here are the foods that he lists that increase inflammation:

  • fatty meats
  • high-fat dairy products
  • foods cooked at high temperatures, including many fried foods, fast foods, and snack foods such as French fries, hamburgers, and potato chips

I hear you saying hmmm.

Here is where I say, let's take a look at the evidence rather than take his word for it, OK? To do so requires that we find dietary comparisons where a low-carb diet versus a low-fat diet were investigated and researchers actually measured CRP as part of the study.

Do such studies exist? Yes.

Last September, in the American Journal of Medicine, researchers from the University of Pennsylvania compared a low-fat diet to a low-carb diet for six months. They assessed weight loss and compared changes in lipoprotein subfractions and C-reactive protein levels.

Their finding? C-reactive protein levels decreased modestly in both diet groups. However, patients with a high-risk baseline level (>3 mg/dL, n = 48) experienced a greater decrease in C-reactive protein levels on a low-carbohydrate diet (adjusted difference = -2.0 mg/dL, P = 0.005), independent of weight loss.

So, a low-carb diet had a better result on CRP in those following a low-carb diet who had the greatest risk at the start of the study - regardless of how much weight they lost.

Are there any other studies that find similar improvements?

In May 2004 the International Journal of Obesity published a study from Australian researchers that compared a conventional, low-fat diet (30% or less fat) with a low-carb diet and included CRP levels are part of the analysis of the two dietary approaches.

Their finding? Both diets significantly increased HDL cholesterol concentrations and decreased fasting insulin, insulin resistance, sICAM-1 and CRP levels.

So again, we find evidence that suggests that low-carb diets can decrease markers for inflammation.

The AHA maintains that [n]o one knows for sure what causes the low-grade inflammation that seems to put otherwise healthy people at risk. However, the new findings are consistent with the hypothesis that an infection -- possibly one caused by a bacteria or a virus -- might contribute to or even cause atherosclerosis.

Can your diet affect the CRP levels in your blood? Sure they can, and eating the foods on the list he included to help reduce inflammation are all good bets, not only because they may help reduce inflammation, but because they're all just can't go wrong with fresh blueberries, olive oil or wild salmon!

Will eating fatty meats and regular dairy product increase CRP markers? They might, they might not - low-carb diets do not require you to eat either, but if you do include some occassionally, remember, the evidence shows that an overall low-carb dietary approach does not increase CRP - and that's from the evidence.

I highly doubt an occassional burger is going to do such harm that you can't enjoy one now and then - and heck, what's a burger without a nice slice of natural cheddar? Use common sense in your food choices - eat a varied, nutrient-dense selection of foods and work with your physician to ensure your blood tests are on track for good health!

Happy 4th of July! I'm off to enjoy a cheeseburger and a big salad for lunch myself!

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