Study design and Participants
In this double-blinded (participants and investigator), placebo-controlled and single center trial 100 Type 2 diabetes patients were recruited from endocrinology and metabolism clinics of Golestan Hospital of Ahvaz Jundishapur University of Medical Science, Iran in 2017-2018 (Fig 1).
Inclusion criteria : Patients with DM (no more than five years since diagnosis); aged 30- 60 years; with gastrointestinal symptoms; body mass index (BMI) range between 25 to 35 kg/m2; without systemic diseases, thyroid disease, kidney disorder; not pregnant and lactating women; were not taking any dietary supplements or antioxidants, and immunosuppressant and anti-inflammatory agents. Exclusion criteria : Noticeable change in the dose of medications and treatment of diabetes, the ones were refusing to continue the participation in the study, and the subjects who had less than 90% compliance with dill capsules.
Diagnosis of DM was done based on the American Diabetes Association guidelines. Patients with FBS ≥126 mg/dl or 2-hour glucose) 2 hpp (≥ 200 mg/dl or HbA1c ≥ 6.5% were diagnosed as diabetes mellitus (20).
Fifty two patients were excluded from study (because of not meeting inclusion criteria such as gastrointestinal symptoms and not accepting to participate). Forty eight patients were randomly assigned to two groups of intervention (n = 24) or placebo (n = 24), for 8 weeks. Randomization was done using the computer-generated random numbers by a third person to reduce the bias. The third person were generated a random block in blocks of 4. The naming of Dill or placebo bottles were done according to random numbers. odd or even numbers were allocated randomly to groups A or B. Multi-part questionnaire including demographic data (age and sex), anthropometric indices, dietary intake, medication, diabetes duration (in years), physical activity, gastrointestinal symptoms was obtained from subjects. During each visit, every patient was given dill supplement or placebo for 4 weeks and throughout these weeks, consumption of supplements or placebo by the patients was ensured through phone calls or text messages. The compliance of patients was checked by counting the capsules remaining. Patients were excluded from study if had consumed less than 90 % of prescribed capsules.The protocol of this study was approved by the Ethics Committee of Ahvaz Jundishapur University of Medical Sciences (Ethical Code: IR.AJUMS.REC.1396.623) and this study was registered in the Iranian Registry of Clinical Trials website (IRCT20120704010181N12) which is available at: http://irct.ir/user/trial/20288/view. Written informed consent was obtained from all participants.
Supplement and placebo prescription
After confirmation the Anethum Graveolens (dill) herb by the botanist, dried leaves were milled to powder. Capsules containing 1 g of dill powder were provided by the Faculty of Pharmacy, Ahvaz Jundishapur University of Medical Sciences. In this study, starch was used as placebo. The intervention and control groups received either 3 capsules of 1 gr dill or placebo three times per day after each meal (breakfast, lunch and dinner) for 8 weeks. The placebo and dill capsules were matched with together in terms of size, taste, color and shape.
Assessment of demographic data, anthropometric indices and food intake
Dietary intakes were investigated with a 24-h food recall for 3 days (2 week days and 1 weekend day), and dietary intake was analyzed by software Nutritionist 4 specified for Iranian foods. Aanthropometric indices (weight, height, BMI) were measured by a trained researcher (nutritionist) at baseline and after the 8-week intervention. Weight (Seca, Germany) was measured while the patients wore light clothing and no shoes with 0.1-kg accuracy for weight. Height was measured using a stadiometer (Seca) with 0.5-cm accuracy without shoes. BMI was calculated (weight in kilogram divided by the square of the height in meter). Physical activity level was evaluated by the Persian and short form of the International Physical Activity Questionnaire (IPAQ) and presented in Met-Min/week. The participants were asked not to change their ordinary dietary intake and physical activity during the intervention.
Assessment of gastrointestinal symptoms
The assessment of gastrointestinal symptoms was done by questionnaire at the baseline and end of the study (21). This questionnaire was included gastrointestinal symptoms such as gastroesophageal reflux, esophageal motility disorders, dyspepsia, gastric motility disorders and colonic motility disorders.
The numbers 0, 1 and 2 indicate the severity of gastrointestinal symptoms. 0: the patient hadn't gastrointestinal symptoms, 1: patient had occasional gastrointestinal symptoms, and 2 ≤: the patient had permanently gastrointestinal problems.
Biochemical assays
Fasting blood samples (5 ml) were collected from all participants at the beginning and end of the study and were immediately centrifuged (3000×g, 10 min, 4ºC). Blood samples were poured into anticoagulant tubes in order to extract serum samples and sent to the lab in cool boxes. All samples were stored at − 70 °c until biochemical analyses. Serum glucose, TG, HDL and TC was measured by the standard enzymatic methods using Pars Azmoun kit (Tehran, Iran). Serum insulin was measured by human insulin enzyme-linked immunosorbent (ELISA) kit (mombind). Insulin resistance was estimated according to the Homeostasis Model Assessment (HOMA) calculated as: HOMA-IR = fasting concentrations of glucose (mg/dL) × fasting insulin (μU/mL) / 405 (22). Friedewald formula was used for calculation of LDL (23):
LDL-c (mg/dL) = TC (mg/dL) − HDL-c (mg/dL) − TG (mg/dL)/5 (VLDL), VLDL =TG (mg/dl)/5
Serum markers of oxidative stress such as total antioxidant capacity (TAC) and malondialdehyde (MDA) were measured by reliable spectrophotometric methods using Zell Bio GmbH kit (Germany). Serum levels of hc-CRP were measured by enzyme-linked immunosorbent assay (ELISA) kits (Diagnostics monobind).
Sample size calculation
The sample size (95% confidence interval and 80% power) was computed according to Mobasseri and coworkers’ study (24) and considering LDL-C as the main outcome. Sample size was 21 subjects for each group. 24 subjects were computed in per group with withdraw 10%.
Outcomes
In this study, LDL-C was considered as the primary outcome. Also, the secondary outcomes measurements were glycemic parameters, other factors of lipid profile, some antioxidant and inflammatory markers and gastrointestinal symptoms.
Statistical analysis
All statistical analysis was performed using SPSS 25. All data were reported as mean ± standard deviations (SD) for quantitative variables or number (percentage) for qualitative variables. Normal distribution of data was checked using Kolmogorove-Smirnov test. Paired sample t-test was also used to compare the results within groups post-intervention. Independent sample t-test was done to compare the results between the two groups (placebo and intervention). Also, Independent T-test was used to identify differences between two groups at the end of study. Analysis of covariance (ANCOVA) was used to identify any differences between two groups at the end of study, adjusting for baseline values and covariates. Also, Chi square test was done for statistical analysis of qualitative variables. P-value of less than 0.05 was considered statistically significant in all analyses.