Dietary Dogma: The latest dust-up over low-carb diets

Have you seen the headlines? Low-Carb Diet Reduces Heart Risk Factors!  A new study (summarized here on Science Daily) finds that low-carb diets are more effective than low-fat diets in reducing the amount of inflammatory markers and saturated fats in the blood.  That's right: even though a low-carb diet may contain more saturated fats, you may have more fat in your bloodstream if you follow a low-fat diet.

But hang on, where is that study that just crossed my desk a couple of weeks ago? Ah yes, here it is: Researchers at the University of Maryland found that people on the Atkins diet (50% fat) experienced increased cholesterol and inflammatory markers, compared with those on South Beach (30% fat) and Ornish (10% fat) diets.

(Incidentally, the first story got approximately ten times as much attention in the media and blogosphere than the second.)

But with conflicting scientific studies being released monthly, who are we to believe? How do we make good decisions about how to eat?

Part of the story is in the details. The first (pro-Atkins) study involved patients with metabolic syndrome (a pre-cursor to diabetes), in which metabolism is altered by insulin resistance. People with metabolic syndrome respond differently to carbohydrates, transforming them more readily into blood (and body) fat. These results are consistent with other studies (such as the one I blogged about here) finding that low-glycemic diets seem to be most helpful for people with diabetes and metabolic syndrome (but not as effective for others). 

The second (anti-Atkins) study specifically looked at the weight maintenance phase.  There are several studies showing that people on the Atkins diet experience improved cholesterol and triglycerides. But weight loss, by any means, is likely to improve cardiovascular markers such as blood fats and inflammation.  The researchers designed this study to look at the effects of various diets when the (otherwise healthy) subjects maintained their weights. And, indeed, it appeared that the high-fat diet had several undesirable effects, consistent with previous studies such as this one.

So, where does all this leave you? Livin' la vida low-carb or doing the low-fat lambada?  As noted in yesterday's post on salt, you can probably find some research study to support whatever position you want to take. Here's my two cents' worth:

1. Do what works.  The pros and cons of various diet styles notwithstanding, the most important thing is to maintain a healthy weight. If a low-carb diet is the only way for you to do it, then the possible risks are probably justified. 

2. Consider your health history. If you are diabetic or have metabolic syndrome and have weight to lose, a lower-carb diet may be a better choice.  If you are otherwise healthy and are simply trying to maintain a healthy weight, a moderate-fat, controlled-calorie diet may be the best choice.

3. Monitor your risk factors.  Regardless of which dietary dogma you ascribe to, have your cholesterol, triglycerides, and inflammation markers (CRP) tested on an annual or bi-annual basis.

4. Don't over-simplify.  I think an underlying truth in all of this conflicting research is that looking at diets only in terms of macronutrients (fats, proteins, or carbohydrates) is overly simplistic.  All fats are  not the same: Trans fats are highly inflammatory and atherogenic while monounsaturated fats are the opposite. Similarly, a diet rich in low-glycemic carbs like vegetables and legumes is not going to have the same negative effects as a diet high in high-glycemic carbs like rice cakes and white bread.  Even proteins are not all equivalent: chicken liver, for example, is quite inflammatory (because of its high arachidonic acid content) while tuna is anti-inflammatory.

One of the reasons I use Nutrition Data for my own research and diet planning is that it offers so much more detail about what you are eating. In addition to showing you macronutrient ratios, you also see the inflammation factor, the estimated glycemic load, and many other tools that can help you find a balanced, healthy, and effective diet strategy.