Higher BMI associated with greater glycemic index effect
Another important analysis in the new report calculated the impact of a higher glycemic index diet among people with a body mass index (BMI) of less than 25 kg/m2 as well as higher BMIs.
Among people in the lower BMI subgroup, greater intake of high-glycemic-index foods showed slightly more incident primary outcome events. In contrast, people with a BMI of 25 or greater showed a steady increment in primary outcome events as the glycemic index of their diet increased.
People with higher BMIs in the quartile that ate the greatest amount of high-glycemic =-index foods had a significant 38% higher rate of primary outcome events, compared with people with similar BMIs in the lowest quartile for high-glycemic-index intake.
However, the study showed no impact on the primary association of high glycemic index and increased adverse outcomes by exercise habits, smoking, use of blood pressure medications, or use of statins.
The new report complements a separate analysis from PURE published just a few weeks earlier in the BMJ that established a significant association between increased consumption of whole grains and fewer CVD events, compared with people who had more refined grains in their diet, as reported by this news organization.
This prior report on whole versus refined grains, which Dr. Jenkins coauthored, looked at carbohydrate quality using a two-pronged approach, while glycemic index is a continuous variable that provides more nuance and takes into account carbohydrates from sources other than grains, Dr. Jenkins said.
PURE enrolled roughly 225,000 people aged 35-70 years at entry. The glycemic index analysis focused on 119,575 people who had data available for the primary outcome. During a median follow-up of 9.5 years, these people had 14,075 primary outcome events, including 8,780 deaths.
Analyses that looked at the individual outcomes that comprised the composite endpoint showed significant associations between a high-glycemic-index diet and total mortality, CVD death, non-CVD death, and stroke, but showed no significant link with myocardial infarction or heart failure. These findings are consistent with prior results of other studies that showed a stronger link between stroke and a high glycemic index diet, compared with other nonfatal CVD events.
Dr. Jenkins suggested that the significant excess of non-CVD deaths linked with a high-glycemic-index diet may stem from the impact of this type of diet on cancer-associated mortality.
PURE received partial funding through unrestricted grants from several drug companies. Dr. Jenkins has reported receiving gifts from several food-related trade associations and food companies, as well as research grants from two legume-oriented trade associations.
A version of this article first appeared on Medscape.com.