Higher dietary glycaemic index, load up CVD mortality risk

A dietary pattern with increased glycaemic index (GI) and load (GL) appears to elevate the risk of death due to cardiovascular diseases (CVDs), suggests a study involving Chinese adults.

Specifically, the association with GL is more evident in men while that with GI is more prominent in women, according to the researchers, led by Long-Gang Zhao of the Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.

Zhao and colleagues carried out the research based on two prospective cohort studies in Shanghai. They used validated cohort-specific food frequency questionnaires to obtain dietary information. Hazard ratios (HRs) for mortality associated with GI and GL were then estimated using Cox regression model.

A total of 8,711 deaths in men and 10,501 deaths in women were recorded over median follow-up periods of 12.8 years for 59,770 men and 18.2 years for 74,735 women. After controlling for potential confounding, dietary GI (p=0.025), GL (p=0.001), and carbohydrate intake (p=0.001) all correlated with an increased CVD mortality risk. [Eur J Clin Nutr 2022;76:1142-1149]

In men, dietary GI correlated with a lower risk of total and cause-specific mortality in the second quartile as compared with the first quartile (all-cause mortality: HR, 0.89, 95 percent confidence interval [CI], 0.84‒0.95). Dietary GL correlated with a lower risk of cancer mortality but a higher risk of CVD mortality.

In women in the fourth quartile compared with the first quartile, dietary GI correlated with all-cause (HR, 1.10, 95 percent CI, 1.04‒1.06), cancer (HR, 1.12, 95 percent CI, 1.02‒1.23), and CVD (HR, 1.10, 95 percent CI, 1.00‒1.22) mortality.

“In subgroup and sensitivity analyses, our main results generally remained stable and robust,” the researchers said. “The results of the current study indicated positive associations between dietary GI, GL, and risk of CVD mortality in Chinese men and women, which were consistent with our hypotheses.”

In contrast, a study in Japan found potential inverse associations between dietary GI and GL and the risk of all-cause and noncancer/non-CVD mortality in men. However, the Nurses’ Health Study conducted in the US showed a higher risk of all-cause mortality with higher dietary GL. [Am J Epidemiol 2010;173:319-329; Br J Nutr 2014;112:2010-2017]

In the PREDIMED study, results showed an increased total mortality risk associated with GL only in participants aged <75 years with a high CVD risk. [PLoS One 2014;9:e107968]

On the other hand, epidemiological evidence on cause-specific mortality was limited. A study in Sweden found no associations between dietary GI, GL, and CVD mortality. The said Japan study reported an association between GI and CVD mortality in women but not in men. [Am J Clin Nutr 2007;85:1521-1526; Br J Nutr 2014;112:2010-2017]

“Generally, our study was consistent with previous studies that dietary GI and GL were associated with an increased risk of CVD mortality,” the researchers said.

“The underlying mechanism remains unclear and the impact of other dietary factors on associations between dietary GI, GL, and mortality need to be further explored,” they added.