Friday, December 10, 2004

Carbohydrates, Cholesterol, and Other Kernels

Save for my Apple Pie, which is rare fare on The Fanatic's Menu, it's dawned on me that a number of my recent posts are carbohydrate-rich, giving the impression that my diet is carbohydrate-rich, leading to the presumption that (at least through a filter of South Beach, Atkins, Barry Sears, et al.) my body is wide, my blood vessels narrow, and my time on this planet limited. Thanks to mirrors and modern blood-letting technology, I can attest to wide vessels, slender tenders, and the promise of longevity. I've asked myself ... how can I be a walking testament to the virility of an anti-Atkins camp? I think the answer lies in the type of carbohydrates I eat. And to do them justice, Atkins, Sears, and Agatston (South Beach Diet) all address this issue. It isn't so much that eating fewer carbohydrates (which, by default, equates to eating more protein and fat) makes us healthier. It's that the type of carbohydrates we eat, the highly-processed, easily (and speedily) digestible, nutrient-poor starches we begin and end our days with are wrecking havoc with our girth ... not to mention our blood lipid profiles.

This isn't news. There are lots of text books and popular diet books and research studies and MDs with web pages that espouse the benefits of eating foods closer to their natural, un-processed state. They describe, some in meticulous detail, why these foods are better for us than the likes of, say, a soft pretzel or a bowl of corn flakes.

Yet people battling high cholesterol and taking doses of statins will turn to me questioningly when I suggest that their morning bagel is more likely the culprit behind their over-200 mg/dl cholesterol1 than their weekend scrambled eggs. It seems intuitive to equate the cholesterol (and saturated fat) we eat with the cholesterol in our bloodstream, and to an extent it does play a role. The association between sugar or starch and cholesterol may be more mystifying2 but, in fact, can powerfully impact our blood lipid profile. And the more processed those sugars and starches are, or the higher their rank on the glycemic index scale, the greater elevating effect they have on cholesterol. (Researchers in a recent study in the American Journal of Clinical Nutrition found they could lower women's LDL cholesterol up to 10% by feeding them foods with a low glycemic index.3)

What exactly is glycemic index (GI)? And how can you use it to lower your cholesterol? Simply, GI is a measure of how fast a food you eat is broken down, and consequently, how high that food can send your blood sugar (blood glucose) after you eat it. A low GI is preferable to a high GI. There are lots of resources on the web for GI. One I like is on David Mendosa's site.

His table is helpful because it lists not only the GI rank of a food, but takes into account how much of a food people typically eat. For instance, carrots have a moderately high GI, but since there is so little carbohydrate in one carrot (the amount a person typically eats), you'd have to eat 8 of them to equal the glycemic impact of one small, 3.5 inch, bagel (the amount a person typically eats - well, maybe in some parts of the world).

This post ended up being longer than I planned. I really only wanted to say that although I write about and enjoy foods with a high-carb signature, they don't make up the bulk of my diet. And I'm attentive to a food's GI when preparing meals, much to the FRE's chagrin.


1 Since I implied that a cholesterol level of over 200 mg/dl is high, I thought I'd post the US National Institutes of Health general cholesterol recommendations (pdf file):

2 For those with a technical interest:
When we eat sugar or starch, it's digested into a 6-carbon glucose molecule. This 6-carbon glucose can be broken down further into a 2-carbon acetate fragment (a reaction from which we derive a little energy). This 2-carbon acetate fragment is used for various purposes. It can be broken down further into carbon dioxide gas and water (a process from which we derive a whole lot of energy) ... or (if we don't need energy because we're sitting at a computer not moving more than our eyes and a few fingers) it can be used to make cholesterol and other fats. Thus, an influx of these acetate fragments from ingestion of lots of high-GI foods can drive the production of cholesterol.

3 Sloth B, Krog-Mikkelsen I, Flint A, Tetens, I, Bjorck I, Vinoy S, Elmstahl H, Astrup A, Lang V, Raben A. No difference in body weight decrease between a low-glycemic-index and a high-glycemic-index diet but reduced LDL cholesterol after 10-wk ad libitum intake of the low-glycemic-index diet. Am J Clin Nutr. 2004. Aug;80(2):337-347.

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