Phaseolus vulgaris species such as pinto, black and dark red kidney beans with white rice are classic food combinations in many areas of the world, especially in the Caribbean, Latin America, Middle East, and Mediterranean . Epidemiological studies show associations with increased bean consumption and decreased rates/prevalence of chronic diseases including type 2 diabetes [1–3]. In the United States, the Centers for Disease Control estimate that 25.8 million people, or approximately 8% of the population, have type 2 diabetes mellitus . A disproportionate number of Hispanics (11.8%) and African Americans (12.6%) are affected by this disease .
Diet and lifestyle changes are the first intervention steps recommended by leading health agencies to prevent and control type 2 diabetes [5, 6]. Despite the known benefits of diet and lifestyle change, there is often poor adherence to dietary recommendations [7–10]. In fact, difficulty meeting diabetic dietary guidelines is a frequently reported concern , particularly among Hispanic [11–14] and African American type 2 diabetes populations [15, 16]. Two adherence barriers often mentioned are exclusion of culturally familiar foods from counseling and diet education materials and the perceived inability to eat the same foods as the rest of the family, e.g. beans and rice [11, 12, 16].
Beans are known functional foods that are low in fat and high in fiber, vegetable protein, folate, iron, magnesium, zinc, omega-3 fatty acids, and antioxidants [1–3]. They also contain phytate and phenolic compounds that may function in similar ways to α-glucosidase or α-amylase inhibitor type 2 diabetes medications like the oral hypoglycemic agent acarbose .
Beans have a low glycemic index (GI) which by definition means they produce a relatively low rise in blood glucose after a meal [17–19]. In contrast, high GI items like long grain white rice can cause postprandial glycemic elevations that are damaging to vascular tissues and other organs [20, 21]. Regular white rice consumption has also been linked to an increased risk of type 2 diabetes . Few studies have looked at the acute effects of P. vulgaris or common beans on glycemic response as part of traditional meals or in combination with other foods [17, 19, 20, 23].
Since elevated blood glucose is a significant contributor to cardiovascular risk, these findings have important implications for chronic disease risk reduction beyond type 2 diabetes [5, 21]. Emphasizing the continued inclusion of culturally familiar beans in the therapeutic diets of persons with type 2 diabetes may decrease postprandial glycemic variability, maintain vascular health, and improve dietary compliance and thus quality of life, especially for immigrants and minorities [9–11, 24]. We hypothesized that pinto, black, and dark red kidney beans in combination with long grain white rice would equally reduce postprandial glycemic response in adults with type 2 diabetes.