Effect of a Phytochemical-Rich Diet on Cardiovascular Risk Factors in Type 1 Diabetes

Researchers investigated the relationship between dietary phytochemical index (DPI) and specific cardiovascular risk factors among young adults with type 1 diabetes mellitus (T1DM). They found that DPI scores indicating a higher dietary intake of phytochemically rich foods were associated with lower probability of cardiovascular risk factors, including dyslipidemia and high fasting blood glucose (FBG). The results of their study were published in BMC Cardiovascular Disorders.

The cross-sectional study enrolled 261 individuals aged 18 to 35 years with type 1 diabetes (T1D) at Tehran University of Medical Sciences in Iran. The participants included 99 men and 162 women with an average body mass index (BMI) of 23.4±3.3 kg/m².

The investigators collected information including dietary intake, general demographics, anthropometric measurements such as BMI and waist circumference, blood pressure, and blood samples following 12 to 14 hours of nighttime fasting to measure blood glucose and lipid levels, total antioxidant capacity, activity of glutathione peroxidase, and superoxide dismutase.

The International Physical Activity Questionnaire was used to assess physical activity levels and calculate metabolic equivalents based on frequency and duration of the activity.

Following adjustments for multiple confounding variables, patients in the highest tertile of DPI had an 88% decreased likelihood (P trend=.02) of fasting hyperglycemia, an 81% decreased likelihood (P trend=.03) of low levels of high-density lipoprotein (HDL), and a 98% decreased likelihood (P trend=.04) of a high ratio of low-density lipoprotein (LDL) to HDL. Participants in the higher tertile of DPI demonstrated significantly lower systolic blood pressure (P trend=.04) and LDL (P trend=.03) compared with those in the lower tertile.

Although other studies have found inverse associations of DPI to anthropometric measurements and blood biomarkers of oxidative stress, the researchers did not identify any other relationships between DPI and other cardiovascular risk factors such as anthropometric measurements and antioxidant levels in this study in patients with T1D.

DPI is a quantitative index calculated as the percentage of phytochemical energy intake within a person’s total energy intake. Phytochemicals are mainly found in plant-derived foods including fruits, vegetables (except potatoes), soy, teas, spices, nuts, seeds, legumes, olives and olive oil, and whole grains.

Phytochemicals, which have anti-inflammatory and antioxidant benefits, are inversely associated with chronic diseases such as cardiovascular disease, diabetes, and cancer. Antioxidant properties of phytochemicals may reduce oxidative stress, which is a factor that contributes to hypertension.

Phytochemicals also influence carbohydrate metabolism and improve FBG by stimulating pancreatic insulin production, stimulating hepatic glycolysis and glycogenesis, affecting intracellular signaling pathways and gene expression, and inhibiting intestinal glucose absorption and carbohydrate digestion.

Phytochemical flavonoids increase the production of endothelial nitric oxide, which in turn vasodilates blood vessels and lowers arterial pressure. Thus, flavonoid phytochemicals affect oxidative stress and reduce the risk of developing hypertension.

The cross-sectional nature of this study limited the ability to make cause-and-effect observations. Another inherent limitation involved the DPI itself because phytochemical-rich foods such as green and black teas and spices were not included in this study due to their lack of energy content. A third limitation included the lack of consideration of the type of phytochemical foods consumed. For example, 2 different diets with varying phytochemical foods may result in the same DPI calculation, but these different phytochemical food sources might have potentially different benefits.

The study authors conclude, “The strength of this study is investigating…dietary intake of patients with T1DM who are at high risk of several diabetic complications.” They add, “More studies are warranted to corroborate the present findings.”

Reference

Delshad Aghdam S, Siassi F, Nasli Esfahani E, et al. Dietary phytochemical index associated with cardiovascular risk factor in patients with type 1 diabetes mellitus. BMC Cardiovasc Disord. 2021;21(1):293. doi:10.1186/s12872-021-02106-2