Refined carbohydrates increase heart disease risk

white bread

Intact carbohydrates – whole grains and starchy vegetables – are more healthful than refined carbohydrates like white rice and white flour products, since they remain rich in micronutrients and fiber.  Carbohydrates’ influence on heart disease was recently investigated based on glycemic index.   The glycemic index (GI) evaluates the blood glucose response per gram of carbohydrate in particular foods on a 1-100 scale.  Glycemic load (GL) is a similar ranking, but is thought to be more meaningful because it takes into account the carbohydrate content of a certain portion size of each food rather than a fixed number of grams of carbohydrate. In general, most refined carbohydrate foods, devoid of fiber to slow down absorption of sugars, are higher in glycemic index than unrefined foods. For example: high GI foods include sugar, white bread, and sweetened breakfast cereals; low GI carbohydrate foods include many whole grains, fresh fruits, beans, and vegetables.1  White potatoes, although they are a whole plant food, are also high in GI and GL, and potato consumption of even one serving per day is associated with increased risk of type 2 diabetes.2

Foods with a high glycemic index (or glycemic load) produce dangerous spikes in blood glucose. Diets including large quantities of high GL foods increase the risk of diabetes, breast cancer, colorectal cancer, endometrial cancer, and overall chronic disease.3

The current study followed subjects in Italy for 8 years, divided them into four groups according to intake from high GI and high GL foods, and recorded incidence of coronary heart disease. In women, the groups with the greatest intake of high GI foods were at 68% greater risk of heart disease than those with the lowest intake. Analyzing by glycemic load revealed an even more pronounced effect - women with the highest intake of high GL foods were more than twice as likely to develop heart disease compared to women with the lowest intake - a 124% increase in risk.4

Curiously, in this study, a similar pattern was not seen in men. The researchers noted that triglyceride and HDL levels were more sensitive to GI and GL in women than in men, but they are not sure why. However, a recent and similar study performed in men did find an increased risk of heart attack in men with the highest GI and GL food intake. In any case, most high GL foods are calorie-rich and nutrient-poor, and do not have a place in a health-promoting diet.5

Eating according to nutrient density automatically keeps the glycemic load of your diet low - the low GL carbohydrate sources are also the most nutrient rich – vegetables, beans, and fresh fruits, followed by whole grains and starchy vegetables.

 

References:

1. Foster-Powell K, Holt SHA, Brand-Miller JC. International table of glycemic index and glycemic load values: 2002. Am J Clin Nutr 2002;76:5-56.

2. Halton TL, Willett WC, Liu S, et al. Potato and French fry consumption and risk of type 2 diabetes in women. Am J Clin Nutr. 2006 Feb;83(2):284-90.

3. Barclay AW, Petocz P, McMillan-Price J, et al. Glycemic index, glycemic load, and chronic disease risk--a meta-analysis of observational studies. Am J Clin Nutr. 2008 Mar;87(3):627-37.

Gnagnarella P, Gandini S, La Vecchia C, Maisonneuve P. Glycemic index, glycemic load, and cancer risk: a meta-analysis. Am J Clin Nutr. 2008 Jun;87(6):1793-801.

4. Sieri S, Krogh V, Berrino F, et al. Dietary glycemic load and index and risk of coronary heart disease in a large italian cohort: the EPICOR study. Arch Intern Med. 2010 Apr 12;170(7):640-7.

5. Mursu J, Virtanen JK, Rissanen TH, et al. Glycemic index, glycemic load, and the risk of acute myocardial infarction in Finnish men: The Kuopio Ischaemic Heart Disease Risk Factor Study. Nutr Metab Cardiovasc Dis. 2009 Oct 14. [Epub ahead of print]

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Comments (7) Read through and enter the discussion with the form at the end
susan - May 4, 2010 5:58 PM

great article!what about organic whole grain air popped popcorn?what if you mixed low GI vegetables and legumes with a higher GI food-would it not bring down the GL?

Michael - May 5, 2010 9:46 AM

I am curious if the GI/GL matters as much with whole, healthy foods as it does with refined foods. There are many whole foods with high GI (watermelon, carrots, potatoes, etc) that I always considered healthy because of all of the fiber and phytochemicals in them and their low caloric density. I really don't like making my food choices any more complicated than nutrient per calorie density.
Is it worth paying attention to GI with whole foods? Is the GI of potatoes really the issue or is it the fat that it's typically consumed with and the way it's cooked?

Matt Stone - May 5, 2010 10:15 AM

No Michael, it's not worth paying attention to the GI or GL of whole foods. They are always packaged with what is needed to metabolize them correctly.

Deana Ferreri - May 5, 2010 10:18 AM

Susan,
Popcorn scores about 70 on the GI, and scores low in ANDI compared to other whole grains like quinoa, oats, and brown rice. Mixing low GI vegetables with high GI foods would bring down the overall GL of a meal, but keep in mind that this study didn't look at GL of meals, it looked at the quantity of high GL foods that were consumed. Higher GL most often means less nutrient dense.

Michael,
I agree. Many of the whole foods with high GI like watermelon and carrots have low GL because their total carbohydrate content is low. Potatoes are an exception - their carbohydrate content is high - and their nutrient density is low compared to other vegetables, even other starchy vegetables. Nutrient density is definitely the most important factor to look at.

StephenMarkTurner (formerly Steve) - May 5, 2010 10:21 AM

I believe that originally rating carrots as high GI was a mistake, plus they are not that high in calories, so I think the actual load is pretty low.

SMT

PS Is there any way to turn off the darn spell check? It is very annoying.

Dean - May 20, 2010 11:14 AM

No mention of sample size, or really much else. The fact that there was no association among men doesn't elicit confidence, and another study saying that it does it for men too only makes everything more coherent. I did look at the Finnish study the author notes, and it's not an amazingly high
sample size nor is it a particularly significant correlation among the people of normal weight. This to me suggests that the results are half baked at best.

Martha - May 3, 2012 5:11 AM

I am new to the information you are sharing here. When it comes to size charts, I am considered morbidly obese, thought I don't look it but I am fat. Would you name the main foods that I need to stay away from. I am thinking, like all other healthy eating habit plans that it's the white stuff. Things like flour, white bread, pasta, sweet cereal, would I be correct?

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