Findings of present study indicated a reduction risk of high blood pressure and MetS with higher adherence to DPI after adjustment the wide range of possible confounder variables. Decrease the risk of abdominal obesity was associated higher DPI follow-up independent of variables including age, sex and total energy intake. Women with most conformity of DPI had lower odds of MetS and participants with high BMI had lower risk of MetS in a higher DPI. These findings remained significant after full adjustment for confounders. Few studies have examined relationship between DPI with MetS and its risk factors. Therefore, this study aimed to investigate the relationship between DPI with odds of MetS and its components in a large sample of Iranians adults as Middle Eastern countries.
Findings of this study showed a diet with higher DPI were associated with less risk of high blood pressure and MetS. Former publications have manifested a higher amounts of vegetables and fruits [32, 33], whole grains [34, 35], nuts [36, 37], legume [38], is inversely associated with a reduction of hypertension. Another studies have shown that consumption of phytochemical abundant foods may prevent hypertension [39, 40]. Data of Korean adults aged ≥ 19 years discover higher intakes of phytochemical-rich foods are associated with a lower prevalence of MetS. These findings may be ascribed to synergistic effects of phytochemicals, variations their types and their antioxidant and anti-inflammatory properties[39–41]. A longitudinal study on adults stated an increasing energy intake from phytochemicals-rich foods precludes weight gain and adiposity [42]. Another cross-sectional study on 54 adults 18–30 years reported that DPI score was inversely related to WC (25). Protective role of phytochemicals against WC may be mediated by inhibitory role of some polyphenols in proliferation of pre-adipocytes, reduce adipogenesis, and stimulate lipolysis [43, 44]. In this study we found a significant reverse relationship between abdominal obesity and conformity DPI which was consistent with above studies but this relevance did not last long after further adjustments for confounders.
In the present study, one of the beneficial effects of highest compliance of DPI was reduced incidence of MetS in women. A cross sectional study showed a lower risk of the MetS among women with higher intakes of fruit and vegetables [45]. Another study, found moderate and high fruit intake could alleviate MetS in women [46]. Some studies have also reported that phytochemicals that found in food sources could improve lipid metabolism in middle-aged women especially with menopause [47, 48]. Several possible mechanisms that could explain the inverse relationship between MetS and DPI in women include decrease plasma concentrations of C-reactive protein, protection of cellular components against oxidative stress and inflammation, modulate estrogen in women, inhibits blood coagulation and increased intake of antioxidant vitamins such as vitamin A and C [49–52].
A review study presented higher doses of phenolic compounds could have a beneficial effects on the risk factors of MetS (33). Laboratory studies indicated that phytochemicals by their structural diversities, bioavailability, distribution and metabolism can have various effects on human health [53, 54]. In our study, mean score of DPI and also consumption of coffee and tea in women was somewhat higher than men which can probably be attributed to alleviate risk of MetS according to aforesaid explanation
Current study reveals that participants with high BMI had lower risk of MetS in a higher DPI compared with lower. Obesity and insulin resistance are among the most important risk factors of MetS [55]. Evidence available has shown phytochemical compounds may act through regulate insulin production and secretion and protect pancreatic β-cells from oxidative stress and induction of GLUT4 membrane activity [56–58].
There is little research on whether different adherence of phytochemical-rich diet has various interactions in subjects stratified by gender and BMI hence, this finding needs to be confirmed with well-conducted studies.
We actually wanted to make people in different quartiles more similar and homogeneous in terms of confounding factors, and we neutralized the effect of this effective factor in the quartiles so that we could better see the possible relationships. In another way, there is little research on whether different adherence of phytochemical-rich diet has various interactions in subjects stratified by gender and BMI. Hence, These findings need to be confirmed with well-conducted studies.
This study had several strengths and limitations. Population-based design was the most important strength of this study. Dietary intakes were assessed with a validated questionnaire. A major limitation of cross-sectional design of this study was that it could not determine the direction of relations. Probability of not considering all possible confounder factors was another. Types of phytochemicals available in coffee and tea as rich sources phytochemicals that have not been considered. Dietary phytochemicals quality of participants in the same DPI was not determined in term of variations of intake foods containing phytochemicals. Few studies conducted on the relationship between DPI and MetS with its risk factors.