High Dietary Insulin Index Linked to Increased Risk of Metabolic Unhealthiness – A recent study published in the journal Scientific Reports investigated the connection between dietary insulin index (DII) and dietary insulin load (DIL) with metabolic health (MH) status and the levels of brain-derived neurotrophic factor (BDNF) and adropin in the blood of Iranian adults.
Background
Obesity and overweight have become increasingly prevalent worldwide. Obesity is associated with various health problems, including insulin resistance, hypertension, and hypertriglyceridemia. However, not all obese individuals have metabolic abnormalities.
Globally, 7.27% of adults with obesity are metabolically healthy, while almost 20% of metabolically unhealthy (MU) adults have normal weight. A recent study estimated that 17.2% of the adult Iranian population is metabolically unhealthy normal weight (MUNW).
In addition to genetic factors, various elements, including cardiorespiratory fitness, lifestyle, chronic stress, and adipose tissue function, play crucial roles in determining MH status. Insulin resistance, which leads to chronic inflammation, is also linked to MH status. As a result, diets that raise blood sugar levels increase the risk of insulin resistance.
DII measures the postprandial insulin secretion after consuming common foods compared to an isoenergetic reference food. DIL accounts for the DII of each food and its energy content.
BDNF, a member of the neurotrophic growth factor family, helps reduce the risk of type 2 diabetes mellitus (T2DM), cardiovascular disease (CVD), obesity, hyperglycemia, metabolic syndrome (MetS), and dyslipidemia. Additionally, adropin, a short peptide hormone produced in various organs, including the heart and liver, has been linked to metabolic disorders. Interestingly, dietary components affect this protein.
Previous studies have established the association between DII and DIL with metabolic disorders, including T2DM and obesity. A higher DIL increases the risk of insulin resistance. No population-based studies have been conducted to evaluate how DII and DIL are linked to adropin and serum BDNF in relation to MH among Iranian adults.
Study Methodology
This cross-sectional study involved 600 adults from Isfahan, an Iranian city, recruited in 2022 using a multistage cluster random sampling method. To select a representative sample of the general adult population with diverse socioeconomic statuses, adults working in 20 schools, including teachers, principals, assistants, school managers, crews, and other staff, were considered.
A total of 527 adults met the eligibility criteria and were included in the study. Food frequency questionnaires (FFQs) were used to assess participants’ long-term dietary intake. The food insulin index (FII) was used to analyze insulin levels in participants two hours after consuming a 1000 kJ meal. FII values for each food were obtained from previous studies.
In this study, participants were divided into two groups: MH and MU. Participants with two or more risk factors, including fasting glucose level ≥ 100 mg/dL, antidiabetic drugs, abnormal HDL-c and serum triglyceride levels, systolic/diastolic blood pressure ≥ 130/85 mmHg, antihypertensive drugs, and C reactive protein (CRP) level > 90th percentile, were categorized as MU.
Study Findings
The average age of the participants was 42 years, and approximately 54% were men. Around 43% of the cohort was MU. This study found that adhering to a diet with a high DII increased the odds of MU in the study population. However, no significant association between DIL and metabolic health status was observed.
Higher DII was associated with increased blood pressure, while moderate DIL was significantly linked to hypertriglyceridemia. Notably, no significant association between DII and DIL with adropin and serum BDNF was observed. These findings have been attributed to the insulinogenic effects of a diet with high DII and DIL. This diet type could enhance postprandial insulin and insulin resistance.
Recommendations
Individuals with normal weight or obesity/overweight are advised to reduce their consumption of foods with high DII. This will improve diet quality, consequently reducing the burden of metabolic diseases and enhancing quality of life. Limiting or avoiding consumption of foods like refined grains, sugar, potatoes, and desserts that influence insulin response is essential.
Conclusions
This study also has some limitations, including the use of self-administered FFQs for dietary assessment, which increases the risk of misclassifications and biases. There is a possibility of unknown or unmeasured confounders that could impact the results. Furthermore, 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 BD
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