Recent Scientific Reports The study investigated the association between dietary insulin index (DII) and dietary insulin load (DIL) with metabolic health (MH) status and serum levels of neurotrophic factor (BDNF) and adropin in Iranian adult population.
Record
Currently, the global prevalence of obesity and overweight has increased significantly. Obesity has been associated with many health-related issues, such as insulin resistance, hypertension, and hypertriglyceridemia. It should be noted that not all obese people have metabolic abnormalities.
Globally, the prevalence of metabolically healthy adults with obesity is 7.27%, while metabolically unhealthy (MU) adults of normal weight is nearly 20%. A recent study estimated the prevalence of metabolically unhealthy normal weight (MUNW) among the adult Iranian population to be 17.2%.
In addition to genetic factors, many factors, such as cardiorespiratory fitness, lifestyle, chronic stress, and adipose tissue function, play an important role in determining MH status. Insulin resistance causing chronic inflammation is also associated with MH status. Therefore, diets that increase blood sugar levels increase the risk of insulin resistance. The DII indicates postprandial insulin secretion after ingestion of a common meal compared to an isoenergetic reference meal. DIL provides the DII of each food and its energy.
BDNF is a member of the neurotrophic factor family, which facilitates the reduction of risk for type 2 diabetes mellitus (T2DM), cardiovascular disease (CVD), obesity, hyperglycemia, metabolic syndrome (MetS), and dyslipidemia. In addition, adropin is a small peptide hormone that is expressed in many organs, including the heart and liver, and has been associated with metabolic disorders. Interestingly, this protein is affected by dietary components.
Previous studies have demonstrated the relationship between DII and DIL with metabolic disorders, including T2DM and obesity. An elevated DIL increases the risk of insulin resistance. No population-based studies have been conducted to assess how DII and DIL relate to serum adropin and BDNF in relation to MH in Iranian adults.
About the study
This cross-sectional study recruited a total of 600 adults in 2022 from Isfahan, a city in Iran. These participants were selected based on the multistage random sampling method. To select the general adult population of different socioeconomic statuses, adults working in 20 schools were examined, including teachers, principals, assistants, principals, crews, and other staff.
A total of 527 adults met the eligibility criteria and were ultimately included in this study. Food frequency questionnaires (FFQ) were used to assess participants’ long-term dietary intake. The food insulin index (FII) was used to analyze participants’ insulin levels after 2 h of consuming a 1000 kJ meal. The FII of each food was obtained from previous surveys.
In this study, participants were divided into two groups, namely, MH and MU. Participants with two or more risk factors including fasting glucose level ≥ 100 mg/dL, antidiabetic medications, abnormal serum HDL-c and triglyceride levels, systolic/diastolic blood pressure ≥ 130/85 mmHg, antihypertensive medications, and C-reactive protein (CRP ) level > 90th percentile, were grouped into MU.
Study findings
The average age of the participants was 42 years and approximately 54% were male. Approximately 43% of the cohort was MU. This study observed that following a high DII diet increased the odds of MU in the study population. However, no significant association was observed between DIL and metabolic health status.
A higher DII was associated with increased blood pressure, while moderate DIL was significantly associated with hypertriglyceridemia. Notably, no significant correlation was observed between DII and DIL with serum adropin and BDNF. These findings have been attributed to the insulinogenic effects of a diet high in DII and DIL. This type of diet could enhance postprandial insulin and insulin resistance.
Normal weight or obese/overweight individuals are advised to reduce their consumption of high DII food. This will raise the quality of nutrition and subsequently reduce the burden of metabolic diseases and improve quality of life. Eating foods such as refined grains, sugar, potatoes and desserts that affect insulin response should be avoided or limited.
According to the results of the current study, a previous study reported a significant association between DII and insulin resistance, and higher DIL was associated with an increased risk of insulin resistance. The contradictory findings of this study with previous studies could be due to differences in the age range of participants, study design, meal preparation in different societies, and varied assessment tools used for analysis.
conclusions
This study also has some limitations, including the use of a self-administered FFQ for dietary assessment, which increases the risk of misclassifications and biases. There is a possibility of the presence of unknown or unmeasured confounding factors that could affect the results. Additionally, causality could not be determined due to the cross-sectional nature of the study.
Despite the limitations, this study highlighted the association between DIL and DII with metabolic health status and adropin and BDNF in Iranian adult population. A larger DII increases the risk of hypertension and MU. Interestingly, no relationship was found between DIL and metabolic health.
