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Glycemic Index, Glycemic Load, and Cardiovascular Disease and Mortality
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This study assessed the impact of high glycemic index on cardiovascular risk and mortality in a geographically diverse population distributed across five continents and including Western and non-Western countries with low, middle, and high incomes. Over a median of 9.5 years, data were obtained from 137,851 participants aged 35 to 70 years. Country-specific questionnaires were used to determine dietary intake. In an adjusted analysis that divided participants by whether they had preexisting cardiovascular disease (CVD), there was an association between consumption of a diet with a high glycemic index and an elevated risk of a cardiovascular event or death from any cause in both groups. Individuals who consumed a diet with a high glycemic index also had a higher risk of death from cardiovascular causes. Similar findings were found for glycemic load for participants with preexisting CVD, but not for those without preexisting CVD.
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These data suggest that diverse individuals who consume diets with a high glycemic index have an elevated risk of CVD and death.
abstract
This abstract is available on the publisher's site.
Access this abstract nowBACKGROUND
Most data regarding the association between the glycemic index and cardiovascular disease come from high-income Western populations, with little information from non-Western countries with low or middle incomes. To fill this gap, data are needed from a large, geographically diverse population.
METHODS
This analysis includes 137,851 participants between the ages of 35 and 70 years living on five continents, with a median follow-up of 9.5 years. We used country-specific food-frequency questionnaires to determine dietary intake and estimated the glycemic index and glycemic load on the basis of the consumption of seven categories of carbohydrate foods. We calculated hazard ratios using multivariable Cox frailty models. The primary outcome was a composite of a major cardiovascular event (cardiovascular death, nonfatal myocardial infarction, stroke, and heart failure) or death from any cause.
RESULTS
In the study population, 8780 deaths and 8252 major cardiovascular events occurred during the follow-up period. After performing extensive adjustments comparing the lowest and highest glycemic-index quintiles, we found that a diet with a high glycemic index was associated with an increased risk of a major cardiovascular event or death, both among participants with preexisting cardiovascular disease (hazard ratio, 1.51; 95% confidence interval [CI], 1.25 to 1.82) and among those without such disease (hazard ratio, 1.21; 95% CI, 1.11 to 1.34). Among the components of the primary outcome, a high glycemic index was also associated with an increased risk of death from cardiovascular causes. The results with respect to glycemic load were similar to the findings regarding the glycemic index among the participants with cardiovascular disease at baseline, but the association was not significant among those without preexisting cardiovascular disease.
CONCLUSIONS
In this study, a diet with a high glycemic index was associated with an increased risk of cardiovascular disease and death. (Funded by the Population Health Research Institute and others.).
Additional Info
Disclosure statements are available on the authors' profiles:
Glycemic Index, Glycemic Load, and Cardiovascular Disease and Mortality
N. Engl. J. Med 2021 Feb 24;[EPub Ahead of Print], DJA Jenkins, M Dehghan, A Mente, SI Bangdiwala, S Rangarajan, K Srichaikul, V Mohan, A Avezum, R Díaz, A Rosengren, F Lanas, P Lopez-Jaramillo, W Li, A Oguz, R Khatib, P Poirier, N Mohammadifard, A Pepe, KF Alhabib, J Chifamba, AH Yusufali, R Iqbal, K Yeates, K Yusoff, N Ismail, K Teo, S Swaminathan, X Liu, K Zatońska, R Yusuf, S Yusuf, PURE Study InvestigatorsFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
Cardiology
This analysis, drawing on data from multiple populations globally, confirms earlier reports that diets with higher glycemic index and glycemic load are associated with higher risks of cardiovascular disease. Also as seen earlier, the excess risk was strongest in participants who were already overweight or obese. This finding is likely to be causal because such diets have adverse effects on indicators of glucose and lipid metabolism. These new data highlight the importance of carbohydrate quality. Practically, this means keeping consumption of refined grains, potatoes, and sugar low for optimal cardiometabolic health; replacing these foods with whole grains or healthy unsaturated fats is an easy way to accomplish this.
Primary Care
Glycemic Index and Cardiovascular Health
The glycemic index (GI) is a rating of how fast sugar from a food is absorbed into the bloodstream after consumption. Glycemic load (GL) takes into account the amount of sugar consumed. For example, watermelon has a sugar with a high GI (72) but most of watermelon is water. Although watermelon has a high GI, you would have to eat about three watermelons to consume enough sugar for a high GL.
Foods that have a high GI and GL pack a lot of sugar into a small package, like chocolate cake, juices, processed foods, or fluffy white bread. In fact, fluffy white bread is given a GI of 100 and provides the maximum score for the GI “bread” scale. Fluffy white bread is similar to cotton candy. It is made from bleached white flour (sugar) without fiber and is absorbed into the blood stream very quickly. You can also assess the GI of bread by squishing it in your fist to make a ball. The smaller the ball, the more sugar and less fiber.
Why Are High Glycemic Index Foods Bad for Health?
A fast rise in blood sugar results in insulin release where high insulin spikes can also result in rebound hypoglycemia and insulin resistance (see figure). Recurring spikes in insulin is similar to banging your thumb with a hammer 100 times. Eventually you lose feeling (insulin resistance) and you have to hit your thumb harder (more insulin) to feel it. This gradual build-up of insulin resistance leads to metabolic dysfunction, inflammation, weight gain, fatty liver, and plaque development. The goal is to flatten the curves by eating fiber-rich foods.
Rakel, D. Integrative Medicine. 4th ed. Elsevier, Inc.; 2018.
What This Study Showed
Data from the PURE study was used to evaluate glycemic index food intake for 137,851 people across diverse geographic and economic countries over 9.5 years. Those in the highest GI eating group had a hazard ratio of 1.51 for major cardiovascular events and death. The risk was higher in those with a high body mass index.
What to Recommend
To keep it simple, encourage high-fiber, whole foods with protein from roots and fish. But if someone does not have access to these foods, I like to recommend 1 tbsp of psyllium (or any soluble fiber) in 8 to 10 oz of water before meals to lower the GI of the meal. This will also lower HbA1c by 0.58%.1
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