- May 4, 2010
- Posted by: Jonny Bowden
- Category: Myths and Truths
Consuming carbohydrates with a high glycemic index increases the risk of coronary heart disease in women, according to a new study in the Archives of Internal Medicine.
If you’ve read my book “Living Low Carb: Controlled Carbohydrate Eating for Long-Term Weight Loss” then you probably understand the meaning of glycemic index. If you haven’t read the book, here’s the executive summary on glycemic index: it’s a measure of how quickly food affects your blood sugar.
That’s important, because when your blood sugar rises quickly, the pancreas responds by squirting a hormone called insulin into the bloodstream. Insulin’s job description includes escorting that excess sugar out of the bloodstream as quickly as possible. When you’re not exercising a lot, that sugar winds up in your fat cells which is why insulin is nicknamed “the fat storage hormone”.
High-glycemic carbs are the ones you want to avoid in your diet. They’re the processed carbs and the carbs with high sugar content (sodas, desserts). Unfortunately, most grains or grain products (like breads, pastas and the like) are high-glycemic, even- believe it or not- some of the “whole grain” products on the market. Rice is high-glycemic (both white and brown), as are most cereals.
All these foods raise blood sugar quickly and keep it up there for a long time, increasing the odds that your insulin levels will also be high– and that’s pretty much a guarantee that you’ll put on weight. It’s also the reason I so often counsel against high-carb low-fat diets. (Fat has zero effect on blood sugar and insulin; protein affects blood sugar but not nearly as much as carbs do.)
Last week I told you about a study in which added sugar was shown to increase measures of risk for heart disease. This week there’s a different study with even more bad news for high-sugar consumption. In this study, the diets of over 47,000 Italian men and women were evaluated for both carbohydrate intake and for glycemic impact. (Remember, not all carbs have a big glycemic impact- almost all vegetables, as well as many fruits, have very low glycemic indexes.)
The one-fourth of women who consumed the most carbohydrates overall- regardless of whether they were high- or low-glycemic carbs- had approximately twice the risk of developing heart disease than the one-fourth who consumed the least amount of carbs.
But when the carbs were separated into “high” and “low” glycemic categories, it turned out that the increased risk for heart disease was coming only from the “high” glycemic carbs. Low-glycemic carbs didn’t increase the risk for heart disease at all.
Using the glycemic load- an even better measure of the effect of food on blood sugar- the researchers found that the one-fourth of women whose diet had the highest glycemic load had 2.24 times the risk of heart disease compared to the women with the lowest glycemic load diet.
You can find a complete listing of the glycemic index and glycemic load of every food ever tested here.
When will we finally figure out that it’s not fat that’s the greatest risk factor in the American diet? A much bigger risk is sugar. Low-fat diets are almost always, by definition, high-carb diets, and the vast majority of carbs that we consume are high-glycemic.
This study reinforces what i- and many of my colleagues- have been saying for years: Stop worrying so much about fat and start paying attention to sugar. If you consume a reasonable calorie diet (target weight x 10-12 for calorie goal), and get most of your carbs from low-glycemic vegetables and fruits, the percentage of fat in the diet doesn’t matter nearly as much as you might think.
But clearly the amount of carbs– especially high-glycemic ones- matters a lot.
Both for the state of your waistline and for the health of your heart.