In a new study, researchers found a diet high in poor quality carbohydrates leads to a higher risk of heart attacks, strokes, and death.
The higher risks of a diet high in poor quality carbohydrates, called a high glycemic diet, were similar whether people had previous heart disease or not.
The research was conducted by a team at the University of Toronto and elsewhere.
In the study, a total of 137,851 people aged 35 to 70 years old were followed for about 9.5 years.
The research team used food questionnaires to measure the long-term dietary intake of participants and estimate the glycemic index (the ranking of food based on their effect on blood sugar levels) and glycemic load (the number of carbohydrates in food times its glycemic index) of diets.
There were 8,780 deaths and 8,252 major heart events recorded among the participants during the follow-up period.
The investigators categorized dietary intake of carbohydrates depending on whether specific types of carbohydrates increased blood sugars more than others (high glycemic index) and compared this index to the occurrence of heart disease or death.
Those people consuming a diet in the highest 20% of the glycemic index were 50% more likely to have a heart attack, stroke, or death if they had a pre-existing heart condition, or 20% more likely to have an event if they did not have a pre-existing condition.
These risks were also higher among those people who were obese.
The findings suggest that not all carbohydrate foods are the same.
Diets high in poor quality carbohydrates are associated with reduced longevity, while diets rich in high-quality carbohydrates such as fruit, vegetables and legumes have beneficial effects.
This study also makes it clear that among a diverse population, a diet low in both its glycemic index and load has a lower risk of heart disease and death.
Most fruits, vegetables, beans, and intact whole grains have a low glycemic index, while white bread, rice, and potatoes have a high glycemic index.
One author of the study is David Jenkins, a professor of nutritional sciences and medicine.