The results showed an inverse and significant association between adherence to RFS and risk of Hypertriglyceridemia, insulin resistance, and abdominal obesity. In this study, there was a significant association between NRFS and Hypertriglyceridemia, and also we found an inverse relationship between NRFS and HDL. There was no statistically significant relationship between other cardiovascular risk factors with RFS and NRFS.
According to our Knowledge, the present study is the first study to investigate the relationship between RFS and NRFS with cardiovascular risk factors. So, further prospective or intervention research is needed to confirm whether the association truly represents a cause–effect relationship.
To supporting our findings, a cross sectional study including 1008 adults in Korea found women with higher RFS and PA have lower risk of abdominal obesity(30). In another cross sectional study of Australian adults, it was observed in men, RFS was significantly inversely associated with systolic blood pressure (SBP) and diastolic blood pressure (DBP) and there was no associated between RFS and BP in women. Contrary to our results RFS was not significantly associated with obesity in both men and women(31). In a Prospective Cohort study of Korean Adults who were followed from 2001 to 2014, it was observed the incidence of metabolic syndrome in the 5th RFS quintile group significantly decreased compared to the 1st quintile group after adjusting for age and energy intake in women, but after adjusting for additional covariates this association disappeared(32).
There are also many reports on other different healthy dietary patterns such as DASH diet and Mediterranean diet and cardiovascular risk factors that we expect our findings are similar to these mentioned studies because the components of the RFS, based on the consumption of fruits, vegetables, grains, dairy products, and fish, are similar to these dietary patterns. In a cross sectional study including 6874 older adults in Spain, Participants with better adherence to the Mediterranean diet, Compared with low adherence, had significantly lower average TG levels, BMI, and WC(33). In another cross sectional study conducted in Iran, being in the higher category of the Mediterranean diet score was associated with lower WC, TG, hs-CRP, and higher HDL-C. Also, adherence to the DASH diet was associated with lower DBP, insulin levels, and hs-CRP(34). As can be seen, following the DASH diet also lowers BP, which is because the DASH diet emphasizes reducing salt intake, but does not measure salt intake in RFS. In contrast, in some clinical studies, the DASH diet had no effect on improving insulin sensitivity and TG(35)(36)
RFS seems to be associated with reduced cardiovascular risk factors such as TG, insulin resistance, and WC due to high amounts of fruits and vegetables, whole grains, and low-fat dairy products. fruit and vegetables contain a wide range of potentially cardio protective components such as fiber, folate, nitrate, vitamins, and flavonoids. Dietary flavonoids act via different mechanisms of action to reduce cardiovascular risk factors. They reduce oxidative stress, modify lipid levels, and regulate glucose metabolism(16). Whole grains, fruits and vegetables are high in soluble and insoluble fiber. Soluble fiber slows gastric emptying and increases satiety and regulates cholesterol and blood sugar(2, 37). The intestinal microflora ferments the indigestible carbohydrates in cereals into short-chain fatty acids (acetate, butyrate, and propionate), which are effective in reducing body weight, FBS, BP, and TG and increasing HDL(2).
On the other hand, NRFS seems to be associated with increased cardiovascular risk factors due to high consumption of red and processed meats, saturated fats, refined carbohydrates, and a variety of sweetened foods.
In a study conducted in Japan, participants who ate high amounts of meat and fat, had higher WC, BMI, BP, and blood lipid profile(38). Although the results of some studies contradict this(39), the results of a meta-analysis study showed that total, red, and processed meat intake is positively associated with metabolic syndrome(40). Red meat contains high amounts of saturated fat and heme-iron. Iron is a strong pro-oxidant, which can damage tissues such as pancreatic beta cells. So, a high iron level can impair glucose metabolism and decrease insulin levels(41, 42). Nitrate used as a preservative in processed meat can be change into nitrosamines. Nitrosamine have been shown to be toxic to pancreatic cells and lead to insulin resistance(43, 44).
It was observed that a diet high in sugar and refined carbohydrates increases TC, TG, LDL, the ratio of TC/HDL(45), glucose, HOMA-IR and insulin levels. It also increases the expression of enzymes involved in fat synthesis, reduces the expression of enzymes effective in lipolysis and increases the accumulation of fat in the body(23). In contrast, in another study conducted on Iranian women, diets lower in carbohydrate were not associated with overweight, obesity and cardiovascular risk factors(46).
The current study had some limitations. Due to the cross-sectional design, we could not evaluate causality between the RFS and cardiovascular risk factors. use of FFQs can result in under- or over-reporting of food intake. Our study was conducted only on obese and overweight women, so we cannot attribute the results to the whole community. only the RFS was used to evaluate the dietary quality, and no instruments were used for assessing other nutrients(47).
This study also has several strengths. this study is the first to show the relationship between RFS and cardiovascular risk factors in adult women. The number of study participants was relatively high and known potential confounding factors were measured and controlled for in the analysis.