by Craig Weatherby
Ever since William Dufty’s book Sugar Blues brought the issue to light in 1975, heart disease has been linked ever more closely to diets high in sugars and “junk” starches such as white flour.
At the time, Dufty’s argument was received coolly by doctors… even though his warnings were based on sound research.
And evidence amplifying Duffy’s clarion call has only grown over the intervening decades.
Numerous studies now link sugary, starchy diets to cardiovascular disease, while others link them to diabetes, gallbladder disease, and breast cancer (Beulens JW et al. 2007; Sieri S et al. 2007; Barclay AW et al. 2008).
Diets high in carbohydrates—specifically, sugars and rapidly absorbed starches like white flour—raise heart disease risk in several ways.
Glycemic Index vs. Glycemic Load… what’s the difference?
A food’s glycemic index (GI) number reflects the rapidity with which the sugars and starches it contains raise blood sugar levels.
Anyone with diabetes can tell you that a GI of 70 or more is considered high, a GI of 56 to 69 is medium, and a GI of 55 or less is deemed low (Mendosa D 2008).
However, as our friend David Mendosa explains on his great diabetes Web site, a food’s GI number tells you only how rapidly the body turns its particular mix of carbohydrates into blood sugar… because it doesn't account for the amount found in a normal serving.
In contrast, a food’s glycemic load (GL) number considers both the GI of a food’s particular mix of carbohydrates, and the amount of that mix found in a normal serving.
Accordingly, compared to its GI number, a food’s GL number is now considered a more accurate measure of its actual impact on blood sugar levels.
For example, the carbohydrate mix in wild blueberries from eastern Canada—like the ones we offer—has a high GI (53). But there aren't a lot of carbohydrates in a serving of those wild blueberries, so their glycemic load (5) is quite low (Mendosa D 2008).
A GL of 20 or more is considered high, a GL of 11 to 19 is medium, and a GL of 10 or less is rated as low (Mendosa D 2008).
Chiefly, they raise blood levels of glucose, inflammation, and triglycerides while lowering blood levels of protective HDL (“good”) cholesterol and generating pro-inflammatory free radicals.
Now, the results of a large epidemiological study from Italy support the idea that sugary, starchy diets pose a risk to heart health… and suggest that such diets pose the greatest risk to women.
Unfairly perhaps, starchy diets appeared to be much less dangerous to men… probably due to differences in the way members of each gender process dietary carbohydrates.
The carbohydrates that the new study linked to higher heart risks among women are ones that the body turns into blood sugar (glucose) very rapidly.
Such foods are said to have a high “glycemic index” or GI… and the biggest villains are foods with a high “glycemic load” or GL.
A food’s GL ranking encompasses both the rate at which a food’s carbohydrates get converted into blood sugar, and the amount of carbohydrates found in a normal serving.
For more on this subject, see our “Glycemic Index vs. Glycemic Load” sidebar.
New Italian study links sugary, starchy diets to higher heart risk in women
A team of Italian researchers from Milan compared the self-reported diets of 47,749 Italian adults—15,171 men and 32,578 women—to their health outcomes over a period of almost eight years (Sieri S et al. 2010).
The scientists calculated the participants’ total carbohydrate intakes as well as the average glycemic index of the foods they consumed, and the glycemic loads of their diets.
By the midway point of the study, 463 (158 women and 305 men) had developed coronary heart disease.
The one-fourth of women who consumed the most carbohydrates overall had approximately twice the risk of heart disease as the one-fourth who consumed the least.
When these carbohydrates were separated into high- and low-glycemic-index categories, higher intake of high-GI foods was linked to higher risk of coronary heart disease, but low-GI foods were not.
As the authors wrote, “Thus, a high consumption of carbohydrates from high-glycemic index foods, rather than the overall quantity of carbohydrates consumed, appears to influence [raise] the risk of developing coronary heart disease” (Sieri S et al. 2010).
The one-fourth of women whose diet had the highest glycemic load had 2.24 times the risk of heart disease compared with the one-fourth of women with the lowest glycemic load.
In contrast, neither high total carb intakes, diets rich in high-GI foods, nor high-GL diets were associated with higher heart disease rates in men.
The authors hypothesized that this could be because the particular adverse changes associated with eating lots of high-GI carbohydrates—such as increased blood triglyceride levels—are stronger risk factors for heart disease in women than in men.
However, men should not consider sugary, starchy diets safe, both because they promote diabetes and because the adverse changes they produce are not good for either gender.
It may be that the particular blood fat changes produced by high-GL diets do cardiovascular damage more slowly in men than in women.
And as the Italians said, “…further prospective studies are required to verify a lack of association of a high dietary glycemic load with cardiovascular disease in men.”
- Barclay AW, Petocz P, McMillan-Price J, Flood VM, Prvan T, Mitchell P, Brand-Miller JC. Glycemic index, glycemic load, and chronic disease risk--a meta-analysis of observational studies. Am J Clin Nutr. 2008 Mar;87(3):627-37. Review.
- Beulens JW, de Bruijne LM, Stolk RP, Peeters PH, Bots ML, Grobbee DE, van der Schouw YT. High dietary glycemic load and glycemic index increase risk of cardiovascular disease among middle-aged women: a population-based follow-up study. J Am Coll Cardiol. 2007 Jul 3;50(1):14-21. Epub 2007 Jun 18.
- Mendosa D. Revised International Table of Glycemic Index (GI) and Glycemic Load (GL) Values - 2008. Accessed at http://www.mendosa.com/gilists.htm
- Sieri S, Krogh V, Berrino F, Evangelista A, Agnoli C, Brighenti F, Pellegrini N, Palli D, Masala G, Sacerdote C, Veglia F, Tumino R, Frasca G, Grioni S, Pala V, Mattiello A, Chiodini P, Panico S. 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.
- Sieri S, Pala V, Brighenti F, Pellegrini N, Muti P, Micheli A, Evangelista A, Grioni S, Contiero P, Berrino F, Krogh V. Dietary glycemic index, glycemic load, and the risk of breast cancer in an Italian prospective cohort study. Am J Clin Nutr. 2007 Oct;86(4):1160-6.