The impact of substituting clarified butter with canola oil on the components of metabolic syndrome, fatty liver index, and insulin resistance among individuals diagnosed with metabolic syndrome: a quasi-experimental study

Abstract

Purpose

Clarified butter, contain harmful saturated and beneficial trans-fatty acids. Canola oil is a promising alternative to other oils for reducing saturated fat intake. This trial aimed to investigate the effects of replacing clarified butter with canola oil in patients with metabolic syndrome on various metabolic syndrome components, fatty liver index (FLI), and insulin resistance.

Methods

In this trial, 42 individuals with metabolic syndrome referred to the clinic in Imam Khomeini University Hospital in Urmia, Iran, were enrolled. The participants, who commonly consumed (3 to 8 serving per day) clarified butter, were instructed to follow a healthy diet and replace their consumption of clarified butter with an equivalent amount of canola oil for 3 months. To compare the differences of outcomes in the group, the paired samples T-test and cohen’s d effect size were applied. To analyze the changes in dietary intakes and Metabolic equivalent of task (MET), repeated measures of ANOVA was used.

Results

There was a significant decrease in fasting blood sugar (FBS) (< 0.001), triglyceride (TG) (0.003), and anthropometric measurements (< 0.001). Furthermore, significant reductions were observed in total cholesterol (TC) (< 0.001), low-density lipoprotein (LDL) (0.009), gamma-glutamyl transferase (GGT) levels (0.003), FLI (< 0.001), insulin levels (0.007), and homeostatic model assessment for insulin resistance (HOMA-IR) (0.002), and increase in quantitative insulin-sensitivity check index (QUICKI) (< 0.001). Unfavorably, there was a significant reduction in the high-density lipoprotein (HDL) (< 0.001).

Conclusion

The replacement of clarified butter with canola oil demonstrated potential benefits in improving metabolic syndrome.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-024-01453-z.

Highlights

Consumption of canola oil instead of clarified butter showed potential to improve the lipid profile, glucemic variables, anthropometric indices, and FLI of patients with metabolic syndrome.

The substitution of clarified butter with canola oil did not have a significant impact on blood pressure.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-024-01453-z.

Introduction

Metabolic syndrome is characterized by the co-occurrence of various metabolic abnormalities, including central obesity, insulin resistance, elevated triglyceride and cholesterol levels, high blood pressure, and reduced levels of high-density lipoprotein (HDL)-cholesterol [1–4]. The escalating prevalence and unfavorable clinical outcomes associated with metabolic syndrome, have positioned it as a substantial public health challenge in the contemporary era [5]. Its occurrence varies between 10% and 40% among different populations [6]. Numerous research studies have consistently demonstrated a powerful relationship between metabolic syndrome and a nearly twofold increase in the risk of cardiovascular disease [7]. According to earlier researchs, dietary and lifestyle modifications is more successful than pharmaceuticals in delaying the onset of the metabolic syndrome [8–11]. Metabolic stressors such as high-saturated-fat diets cause obesity, insulin resistance, and metabolic syndrome [12–14]. Considering this, the type of dietary fat takes on a critical role than their quantity in modulating the components of metabolic syndrome [15, 16]. Animal-origin fats are a kind of lipids, specially clarified butter or ghee, that consists of harmful saturated and beneficial trans-fatty acids [17]. In accordance with the definition provided by the International Dairy Federation, ghee is composed of approximately 65% saturated fatty acids (SFAs) and 33% monounsaturated fatty acids (MUFAs) [18–20]. Clarified butter is a commonly used fat in most parts of Iran, and for that reason, it may have a special impact on the health status of Iranian people [21, 22]. Recent studies have suggested a possible connection between SFAs and insulin resistance. However, it is important to note that certain other studies have indicated that reducing the intake of saturated fatty acids in the diet did not yield significant effects on insulin sensitivity in individuals with metabolic syndrome [23, 24]. These contrasting findings highlight the complexity of the relationship between saturated fatty acids and insulin sensitivity, and additional investigation is required to gain a deeper understanding of the underlying mechanisms [23, 24]. Contrary to expectations, a study has revealed that the butyrate present in butter has the potential to promote insulin sensitivity [25]. Furthermore, the CLA found in butter has demonstrated beneficial effects on metabolic diseases [25, 26]. These findings suggest that certain components of butter may have positive impacts on metabolic health. While some studies indicated that the consumption of animal lipids, due to their saturated fatty acid content, may elevate the risk of cardiovascular diseases, other research has revealed that trans-fatty acids present in dairy fat do not contribute to the increment of risk factors associated with cardiovascular diseases [17, 27, 28].

Several studies have uncovered that the consumption of vegetable oils connects to a decreased incidence of chronic heart disease and a decrease in risk factors related to metabolic syndrome components [29]. Canola oil is notable for its composition, which includes a low level (7%) of SFAs. It also contains significant amounts of MUFAs and (polyunsaturated fatty acids) PUFAs, specifically 61% oleic acid, 21% linoleic acid, and 11% alpha-linolenic acid (ALA) [30, 31]. The content of SFA in canola is lower (7%) compared to other commonly used oils including corn (25%), soybean (13.5%), sunflower seed (8.8), and olive oil (14.3%) [32, 33]. Additionally, canola oil possesses the highest concentration of n-3 fatty acids and MUFAs among the popular oil choices available [33]. Canola oil has immense potential to effectively replace other lipids in the diet, thereby reducing the consumption of saturated fatty acids [30]. Various therapeutic approaches have been explored for the treatment of metabolic syndrome, but an effective treatment option remains elusive. Based on the aforementioned background, the objective of this clinical trial is to evaluate the effects of substituting clarified butter with canola oil on metabolic syndrome components, fatty liver index, and insulin resistance in patients with metabolic syndrome.

Materials and methods

Study setting

The trial involved the participation of 42 adult patients who were newly diagnosed with metabolic syndrome at the time of the study and were guided to the gastrointestinal and liver clinic at Imam Khomeini University Hospital in Urmia, Iran.

Participants and sample size

To be eligible for participation, individuals had to meet the following criteria: be between 35 and 65 years of age, have a diagnosis of metabolic syndrome according to the International Diabetes Federation (IDF) guideline, and regularly consume 3 to 8 servings per day of clarified butter for cooking purposes. Participants with kidney disease, heart failure, psychiatric conditions, any form of cancer, pregnant or breastfeeding women were excluded from the study. The sample size for the study was determined based on the trial conducted by Tierney et al., taking into account the mean change of systolic blood pressure (effect size = 3.21) [34]. The values for 1-α/2 and 1-β were considered as 1.96 and 0.84, respectively. The formula utilized for determining the required sample size was as follows:

According to the mentioned formula, a sample size of 35 individuals was required. Taking into account approximately a 20% dropout rate, final sample size of 42 individuals was considered. The decision to choose the specific timeframe for the study was influenced by earlier research findings that had demonstrated the beneficial effects of modifying dietary fat in patients with metabolic syndrome [34]. The recruitment of participants took place between July and August 2023 following metabolic syndrome diagnosis. Metabolic syndrome was diagnosed according to the IDF guideline, which requires a person to have central obesity (> 94.5 cm in both genders) [35] along with any two of the following four additional factors:

1. A triglyceride level that is higher than or equal to 1.7 mmol/L (150 mg/dL).

2. Low levels of HDL-cholesterol, which are less than 1.03 mmol/L (40 mg/dL) in males and less than 1.29 mmol/L (50 mg/dL) in females (or undergoing specific treatment for these lipid abnormalities).

3. High blood pressure, indicated by a systolic blood pressure of 130 mmHg or higher, or a diastolic blood pressure of 85 mmHg or higher (or undergoing specific treatment for these blood pressure abnormality).

4. An elevated fasting plasma glucose level of 5.6 mmol/L (100 mg/dL) or higher after a period of fasting (or previously diagnosed type 2 diabetes) [36].

Study design

It was a quasi-experimental study conducted over three months. Measurements of lipid profile, glycemic varibales, blood pressure, anthropometric measurements, and fatty liver index were done before and after the intervention to determine the impact of the intervention. Dietary intake and physical activity assessment were conducted before the intervention and end of the each month.

Intervention

Prior to entering the study, each patient was required to provide written informed consent, indicating their voluntary agreement to participate after being fully informed about the study’s purpose, procedures, potential risks, and benefits. The participants were advised to substitute their consumption of claified butter or ghee with an equivalent amount of canola oil. In this study, a serving size of clarified butter or ghee was defined as 5 g. Participants were advised to eat according to the guidelines of the Food and Agriculture Organization for Iranian dietary recommendations [37]. The guidelines encourage consumption of vegetables, fruits, whole grains, legumes and dairy and low intake of fatty, salty and sugary foods and consumption of water and unsweetened beverages. In addition, the guidelines encourage maintaining a healthy weight and physical activity as well as hygienic food practices. Regular telephone follow-ups were conducted with the participants every week, during which reminders about using canola oil in the same amount as their previous clarified butter usage were provided. Additionally, reminders about adhering to the Iranian dietary guidelines were given. The duration of each call was approximately 20–30 min.

Measurements

A general questinnaire was employed to gather data regarding gender, age, educational background, and income.

Biochemical measurements

Blood samples were collected from patients at the baseline and end of the intervention after an overnight fast. A 5 mm venous blood specimen was drawn for biochemical assessments. These blood samples were then subjected to centrifugation at a speed of 4000 revolutions per minute for 10 min. The resulting serum samples were stored at -80˚ C until further biochemical examination.

To estimate serum fasting insulin levels, enzyme-linked immunosorbent assay (ELISA) kits from Pars Azmoon Co, Tehran, Iran, were utilized. The analysis of gamma-glutamyl transferase (GGT), lipid profile (total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL-c), and HDL-c), as well as fasting blood glucose levels, were performed using a BT1500 autoanalyzer from Biotecnica Instrument SpA, Rome, Italy.

To calculate homeostatic model assessment for insulin resistance (HOMA-IR) and quantitative insulin-sensitivity check index (QUICKI), the recommended formulas were employed [38, 39]. The laboratory personnel were unaware of the intervention method used.

Blood pressure

Blood pressure measurements were taken using a manual sphygmomanometer and the mean of two measurements was considered. The standard guidelines were used. For example blood pressure was measured after participants had rested for 5 min. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were recorded upon the detection of the first and last audible Korotkoff sounds, respectively. This method ensured accurate and reliable measurement of blood pressure levels in the study participants.

Fatty liver index

The likelihood of fatty liver occurrence was assessed based on the fatty liver index (FLI) formula. The FLI formula is as follows:

FLI = [e^(0.953 × loge(TC)) + 0.139 × BMI + 0.718 × loge(GGT) + 0.053 × WC − 15.745] ÷ [1 + e^(0.953 × loge(TC)) + 0.139 × BMI + 0.718 × loge(GGT) + 0.053 × WC − 15.745] × 100.

In this formula, TC represents total cholesterol, body mass index (BMI) represents body mass index, GGT represents gamma-glutamyl transferase, and waist circumference (WC) represents waist circumference. The FLI is calculated by substituting the respective values into the formula, and the resulting score is expressed as a percentage.

Anthropometric measurements

The height and weight measurements were taken using a digital scale and stadiometer with a precision of 0.1 cm and 100 g, respectively. During the measurements, participants wore minimal clothing and were barefoot. The BMI was performed using the following formula: dividing the weight in kilograms by the square of the height in meters (kg/m²). WC was measured immediately after the participant exhaled, using a flexible tape placed between the hip bones and the lowest rib. Care was taken to ensure that the tape was horizontal and did not compress the skin. To ensure reliability, the measurements were taken three times, and the average of the three was considered each time.

Dietary intake and physical activity assessment

To assess the intake of canola oil, clarified butter, other lipids, calorie, and other food groups such as cereal, dairy, vegetables, fruit, meat, and sugar, a dietary evaluation was conducted. This evaluation consisted of four 3-day 24-hour dietary recalls befor the study and each month during the study, where participants were asked to recall their intake for two non-consecutive days, with a day in between, and each time the mean intake over the three days was considered. Energy intake and servings of canola oil, clarified butter, and food groups were estimated using the food exchange list [40].

To evaluate physical activity levels, the metabolic equivalent of task (MET) questionnaire was utilized. This questionnaire helped assess the intensity and duration of various physical activities engaged in by the participants.

Primary and secondary outcomes

The primary objectives of our study were to assess changes in the components of metabolic syndrome, including WC, TG, fasting blood sugar (FBS), SBP, DBP, and HDL levels. These variables were considered as the primary outcomes of the study.

We also investigated secondary outcomes including TC, LDL levels, GGT, insulin levels, HOMA-IR, QUICKI, FLI, weight, and BMI. These secondary outcomes provided further insights into the changes and effects observed during the study.

Statistical analysis

The statistical analysis was performed using IBM SPSS Statistics software version 26 (IBM Corp., Armonk, NY). The p-value threshold of less than 0.05 was adopted to determine the statistical significance of the results. Prior to the intervention, the general characteristics of the individuals in the intervention group were described using measures such as mean and standard deviation. Additionally, categorial data was presented using frequency and percentage. To compare the differences of WC, Weight, BMI, TG, FBS, SBP, DBP, HDL, TC, LDL, insulin, GGT, FLI, HOMA-IR, and QUICKI from baseline to the end of study, the paired samples T-tests was used for evaluating statistical significance. Effect size was calculated using cohen’s d method for stimating clinical significane of variables change during study. Cohen’s d of 0.2 or greater is deemed a “weak” effect size, while a range of 0.2 to 0.5 indicates a “medium” effect size, and 0.5 to 0.8 represents a “strong” effect size. Using the Kolmogorov–Smirnov test, we assessed the normality of the continuous values. To analyze the changes in dietary intakes and MET at baseline, 1st, 2nd, and 3rd months, repeated measures of ANOVA was used.

Results

Forty-two of the 50 individuals who were eligible and enrolled in the study completed the study. Eight were lost to follow-up (Fig. 1). Consequently, the study was conducted with a total of 42 patients in the group. Table 1 shows the baseline characteristics of the subjects. Mean dietary intake data did not show significant differences in energy intake and food groups from baseline to the end of the study, as illustrated in Fig. 2.

Fig. 1.

The flowchart of study participants based on the CONSORT guidelines

Table 1.

Baseline characteristics of individuals with metabolic syndrome

Variable	Values
Age (years)	42.14 ± 6.8
Education (years)	14 ± 2.5
Monthly incomes (Million Tomans)	8.4 ± 5.7
Gender
Male	21 (50)
Female	21 (50)
FBS (mg/dl)	103.5 ± 9.8
SBP (mmHg)	127.1 ± 4.8
DBP (mmHg)	84 ± 3.5
Waist (centimeter)	107.4 ± 9.6
TG (mg/dl)	205.1 ± 62.5
HDL (mg/dl)	40.1 ± 4.7

Values are means ± SDs for continuous variables and frequency (%) for categorical variables

Fig. 2.

Changes in Calorie consumption, dietary intake, and physical activity of the participants with metabolic syndrome during the 12 wk. The P values demonstrate the effect of time (computed through the general linear model ANOVA for repeated measurements). MET, metabolic equivalent of task

Figure 3 shows the type of lipids consumed by individuals, both before and during the trial. As shown in Fig. 3, the amount of clarified butter and canola oil consumption before and after the study was significantly different. Consumption of canola oil was significantly higher at the end of the study compared to baseline (P < 0.001). Consumption of clarified butter was significantly lower at the end of the study compared to baseline (P < 0.001). About the other lipids consumption, there was no significant difference between before and during the study (P = 0.584). Also, when using the MET questionnaire, the results did not indicate any significant differences at the at the end of the study compared to baseline, as shown in Fig. 2.

Fig. 3.

Composition of lipids consumed by individuals before anf duing the 12 wk. The P values demonstrate the effect of time (computed through the general linear model ANOVA for repeated measurements)

Primary outcomes

Significant reductions were observed in the group at the end of the study compared to baseline for several key measures. Specifically, there was a significant decrease in serum levels of HDL (P < 0.001), FBS (P < 0.001), and TG (P = 0.003). Also, a significant reduction in WC was observed (P < 0.001). However, no significant changes were found in SBP (P = 0.082) and DBP (P = 0.127) (Table 2). Based on Table 2 and effect size amounts, there was medium effect size regarding SBP, DBP, and TG; and strong effect size regarding waist, HDL, and FBS.

Table 2.

Changes in anthropometric measurements, lipid profile, glycemic variables, fatty liver index, and blood pressure during the 12-week study in individuals diagnosed with metabolic syndrome (n = 42)

Variable	Before intervention	After intervention	P value*	Effect size γ (95% CI)
Weight (kg)	81.5 ± 7.1	77.9 ± 7	< 0.001	1.34 (0.91, 1.75)
Waist (centimeter)	107.4 ± 9.6	102.1 ± 8.4	< 0.001	1.42 (0.98, 1.84)
BMI (kg/m2)	28.5 ± 2.5	27.2 ± 2.5	< 0.001	1.30 (0.88, 1.70)
LDL (mg/dl)	120.8 ± 32	112.2 ± 29	0.009	0.42 (0.10, 0.73)
HDL (mg/dl)	40.1 ± 4.7	36.1 ± 4.9	< 0.001	1.51 (1.06, 1.96)
TG (mg/dl)	205.1 ± 62.5	192.5 ± 63.8	0.003	0.49 (0.16, 0.80)
TC (mg/dl)	180.6 ± 32.2	166 ± 33.5	< 0.001	0.77 (0.42, 1.11)
FBS (mg/dl)	103.5 ± 9.8	97.9 ± 10.1	< 0.001	0.97 (0.60, 1.34)
Insulin (mU/l)	15.4 ± 6.1	12.7 ± 6	0.007	0.43 (0.11, 0.75)
HOMA-IR	4 ± 1.7	3.11 ± 1.7	0.002	0.49 (0.17, 0.81)
QUICKI	0.31 ± 0.02	0.33 ± 0.03	< 0.001	-0.88 (-1.23, -0.52)
GGT (IU/l)	30.6 ± 12.1	28.2 ± 10.2	0.003	0.48 (0.16, 0.80)
FLI	77.2 ± 13.1	64.6 ± 17.7	< 0.001	1.53 (1.07, 1.97)
SBP (mmHg)	127.1 ± 4.8	126.4 ± 4.4	0.082	0.27 (-0.03, 0.58)
DBP (mmHg)	84 ± 3.5	83.5 ± 3.3	0.127	0.24 (-0.06, 0.54)

* P value Calculated using paired samples T-test. γ Effect size calculated by Cohen’s d method, CI: Confidence Interval

Secondary outcomes

Regarding the impact of the intervention on the lipid profile, a significant decrease was observed in TC (P < 0.001) and LDL cholesterol (P = 0.009). The results also indicated a significant reduction in GGT levels after the intervention (P = 0.003). In terms of glycemic variables, a significant decrease in insulin levels (P = 0.007), HOMA-IR (P = 0.002), and QUICKI (P < 0.001) was observed after the intervention compared to the pre-intervention stage. The study further concluded with a significant reduction in anthropometric measurements such as weight (P < 0.001) and BMI (P < 0.001). Also, replacing clarified butter with canola oil resulted in a significant decrease in the FLI (P < 0.001) (Table 2). There was medium effect size regarding GGT, HOMA-IR, insulin, TC, and LDL; and strong effect size regarding weight, BMI, and FLI (Table 2). Regarding the absolute value of Cohen’s d for QUICKI, because a reduction in QUICKI signifies an improvement in insulin resistance, there was a strong effect size.

Discussion

To date, there has been limited research exploring the potential impacts of substituting clarified butter with canola oil on clinical parameters among individuals diagnosed with metabolic syndrome. Our study aimed to fill this gap and demonstrated that substituting clarified butter with canola oil over a period of three months led to a significant improvement in various components of metabolic syndrome, fatty liver index, insulin resistance, and obesity. In the current clinical trial, the consumption of canola oil resulted in a noteworthy decrease in lipid profile, albeit an undesirable decrease in HDL levels. In a study conducted by Bowen et al., it was observed that incorporating canola oil into the diet led to a decrease in TC and LDL when compared to a diet rich in fatty acids typically found in Western diets [41]. In agreement with our results, Iggman et al., conducted a study demonstrating that rapeseed oil or canola oil had a rapid and clinically significant positive impact on serum lipoprotein profile, including a reduction in triglyceride levels, particularly in individuals with hyperlipidemia [42]. In line with our study, another trial showed that substituting 20% of daily energy intake from vegetable SFA with canola oil for five weeks led to a decrease in LDL levels [43]. Additionally, a previous trial demonstrated that replacing larger amounts of butter with canola or rapeseed oil resulted in a 29.5% reduction in LDL levels [44]. Also, in line with our results, a study by Maleki Sedgi et al. showed that replacing ghee or clarified butter with canola oil could reduce the levels of lipid profile, glycemic variables, and anthropometric measurements in patients with non-alcoholoic fatty liver disease [45]. A systematic review and meta-analysis study revealed that canola oil, when compared to other edible oils, significantly reduced TC, LDL, and TG levels. Additionally, it was found that canola oil was associated with a decrease in HDL levels [46]. Consistent with the findings of the present study, several other studies have also reported a decrease in HDL levels following the consumption of canola oil when compared to a high saturated fatty acid Western diet [47, 48]. These findings are consistent with our own study, highlighting the potential of canola oil to positively impact lipid profiles but undesirable reduction in HDL. Hodson et al. demonstrated that when total and saturated fat intake decreased and PUFAs or MUFAs intake increased, there was a decrease in HDL levels [49]. This effect may be attributed to the fact that a high dose of n-3 PUFAs, compared to saturated fat such as palmitic acid, could lead to a reduction in the expression of genes involved in HDL particle formation and maturation, including HDL apo-A1, ATP binding cassette A1, lecithin-cholesterol acyltransferase, and phospholipid transfer protein mRNA levels [50]. Superoxide dismutase and catalase are two antiperoxidative enzymes that canola oil possesses that have statin-like effects and lower cholesterol [51]. Furthermore, canola oil has significant quantities of tocopherols and stanols, and because of this and the fact that it contains α-tocopherols, supplementing with sterols and stanols derived from canola oil lowers LDL [52]. The metabolism of cholesterol can be disrupted by the phytosterols in canola oil. Plant sterols can replace cholesterol in intestinal micelles because of their structural similarity, reducing the absorption of cholesterol and increasing the excretion of cholesterol and its byproducts, such as bile salts [53]. Also, phytosterols suppress cholesterol esterase enzymes and minimize cholesterol intracellular esterification [54]. As previously stated, canola oil is rich in monounsaturated fatty acids and has minimal amounts of saturated fatty acids. It has been claimed that MUFA consumption increases insulin and lipoprotein lipase activity, leading to a reduction in TG levels [54]. Moreover, PUFAs have been found to inhibit TG synthesis and storage by suppressing the activity of lipogenic enzymes [55].

Additionally, the results of the current study demonstrated that incorporating canola oil into the diet led to improvements in glycemic control parameters (fasting blood glucose levels and insulin resistance). In a parallel design, randomized experiment conducted by Jenkins et al., it was also observed that a diet enriched with canola oil improved glycemic control in individuals with type 2 diabetes [56]. Based on the research conducted by Gustafsson et al. it was found that a diet primarily consisting of canola oil resulted in a notable decrease of 6% in fasting blood glucose levels compared to a diet containing over 15% saturated fatty acids in hyperlipidemic subjects [47]. Consistent with our findings, Nigam et al. conducted a study that revealed the positive impact of canola oil consumption on glycemic status in individuals diagnosed with non-alcoholic fatty liver disease [55].. Li et al. conducted a study where they investigated the effects of sinapine, the main phenolic acid found in canola oil, on mice. The results of their study demonstrated a noteworthy decrease in fasting blood glucose levels and HOMA-IR following supplementation with sinapine [57]. The mechanism that may explain these observations involves sinapine’s ability to decrease the levels of phosphorylated IRS-1 protein, thereby reducing insulin resistance [58]. In addition, sinapine has been found to suppress the expression of intestinal inflammatory factors by modulating the composition of the gut microbiota and upregulating GPR43 (G-protein-coupled receptor 43) [57].

Moreover, the intervention resulted in improvement of participants’ anthropometric indices. A 2019 systematic review and meta-analysis by Dehkordi et al. showed that the consumption of canola oil contribute to significant weight loss [59]. Moreover, subgroup analysis revealed that canola oil intake resulted in a reduction in waist circumference compared to a typical diet. Also the results of this study has highlighted the role of fatty acid storage and oxidation properties in weight control [59]. N-3 fatty acids have been found to be effective in managing obesity and also to have the ability to regulate the proliferation, differentiation, and apoptosis of adipocytes [60]. Furthermore, it is suggested that PUFAs may contribute to weight loss by influencing gene expression that promotes fat oxidation in adipose tissue, liver, and other organs, thereby reducing fat storage [61]. Also, canola oil has been demonstrated to enhance the sensation of fullness and reduce appetite by stimulating the release of cholecystokinin, a hormone known for its satiating effects on the ileum [62].

In the present trial, no significant changes were observed in blood pressure measurements. These findings align with a meta-analysis that, indicated that canola oil did not have a significant impact on blood pressure compared to other edible oils [46].

The findings of our trial revealed that the incorporation of canola oil into the diet exhibited a significant reduction in the fatty liver index, indicating a potential preventive effect on the development of fatty liver. This suggests that the consumption of canola oil may have a beneficial impact on reducing the incidence of fatty liver. In accordance with our study findings, a randomized, parallel, open-label design study conducted by Nigam et al. reported a notable and statistically significant improvement in hepatic steatosis following the consumption of canola oil [55]. This suggests that canola oil has the potential to effectively ameliorate the accumulation of fat in the liver.

The main advantage of our study was the utilization of a non-invasive and cost-effective approach for the prevention and treatment of metabolic syndrome. This dietary intervention method may potentially contribute to future prevention of this syndrome and its metabolic-associated diseases such as diabetes, cardiovascular diseases, and more. However, the study has certain limitations, including the absence of a control group and the inability to blind the participants due to the nature of the study design. Also, as this trial was conducted at a single site, the generalizability of the findings to other settings may be limited, and it is possible that the demographics of the participants do not accurately represent the typical average Iranian population.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Author contributions

The authors’ responsibilities were as follows: M. A. and F. M. S. conceived and designed the study and analysed the data; M. M. H provided material and technical support; F. M. S. wrote the manuscript; M. A. critically revised the manuscript for important intellectual content and M. A. had primary responsibility. All authors read and approved the final manuscript.

Funding

This trial supported by the Urmia University of Medical Sciences.

Data availability

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available because of privacy or ethical restrictions.

Declarations

Disclosure of potential conflicts of interest

The authors have no competing interests to declare that are relevant to the content of this article.

Research involving human participants

The intervention conducted in this study received approval from the Ethics Committee at Urmia University of Medical Sciences and was registered on the Iranian Registry of Clinical Trials website (www.irct.ir) under the registration number IRCT20170206032417N6.

Informed consent

Prior to entering the study, each patient was required to provide written informed consent, indicating their voluntary agreement to participate after being fully informed about the study’s purpose, procedures, potential risks, and benefits.

Transparency declaration

The lead author affirms that this manuscript is an honest, accurate, and transparent account of the studies being reported. The lead author affirms that no important aspects of the studies have been omitted and that any discrepancies from the studies as planned have been explained.