Ahmad Esmaillzadeh, Masoud Kimiagar, Yadollah Mehrabi, Leila Azadbakht, Frank B Hu, Walter C Willett, Fruit and vegetable intakes, C-reactive protein, and the metabolic syndrome, The American Journal of Medical Diet, Quantity 84, Situation 6, December 2006, Pages 1489–1497, https://doi.org/10.1093/ajcn/84.6.1489
ABSTRACT
INTRODUCTION
The time period metabolic syndrome, for the reason that work of Reaven (1), refers back to the state by which metabolic danger elements are clustered in individuals. This syndrome is rising as one of many main medical and public well being issues in the US (2) and worldwide (3–5), and individuals with this syndrome have an elevated danger of morbidity and mortality resulting from heart problems and diabetes (6, 7). In Tehran, Iran, >30% of adults (8) and 10% of adolescents (9) are affected. The dietary determinants of this syndrome stay to be recognized (10–12).
Though many research have investigated the function of fruit and vegetable intakes in power ailments (13–17), knowledge instantly relating intakes of fruit and greens to the danger of the metabolic syndrome are scant. Intakes of fruit and greens might cut back the danger of the metabolic syndrome by the helpful mixture of antioxidants, fiber, potassium, magnesium, and different phytochemicals. Fruit and greens have been proven to be related to a decreased danger of coronary coronary heart illness (18–20), however the mechanisms haven’t been properly understood. Systemic irritation, as evidenced by plasma C-reactive protein (CRP) concentrations, has been continuously steered as a doable mechanism by which food plan can have an effect on the event of power ailments (21–23). As lately reported, CRP might instantly have an effect on heart problems by a complement-mediated course of (24). Fruit and vegetable consumption might cut back the danger of coronary coronary heart illness partially by the reducing of CRP concentrations. Nonetheless, restricted knowledge exist concerning the affiliation of fruit and vegetable intakes with CRP (25, 26). This research was, due to this fact, undertaken to evaluate the affiliation of fruit and vegetable intakes with blood CRP concentrations and the prevalence of the metabolic syndrome amongst feminine academics aged 40–60 y residing in Tehran.
SUBJECTS AND METHODS
Topics
This cross-sectional research was carried out amongst a consultant pattern of feminine academics aged 40–60 y residing in Tehran chosen by a multistage cluster random sampling technique. A random pattern of 583 feminine academics had been invited to take part within the present research, and 521 girls agreed to take action. Contributors with a historical past of heart problems, diabetes, most cancers, or stroke had been excluded due to doable adjustments in food plan related to these situations. We additionally excluded topics who had left >70 gadgets clean on the food-frequency questionnaire (FFQ), who reported a complete each day vitality consumption outdoors the vary of 800–4200 kcal, and who had been taking medicines that might have an effect on serum lipoprotein, blood strain, and carbohydrate metabolism. These exclusions resulted in 486 topics for the current evaluation. This research was authorised by the analysis council of Nationwide Diet and Meals Know-how Analysis Institute, Shaheed Beheshti College of Medical Sciences, and written knowledgeable consent was obtained from every participant.
Evaluation of dietary consumption
Standard dietary consumption was assessed with the usage of a validated 168-item semiquantitative FFQ. All of the FFQs had been administered by a educated dietitian. The FFQ consisted of a listing of meals with commonplace serving sizes generally consumed by Iranians. Contributors had been requested to report their frequency of consumption of a given serving of every meals merchandise throughout the earlier yr on a each day (eg, bread), weekly (eg, rice and meat), or month-to-month (eg, fish) foundation. The reported frequency of consumption for every meals merchandise was then transformed to a each day consumption. Portion sizes of consumed meals had been transformed to grams by utilizing family measures (27). Complete vitality consumption was calculated by summing up vitality intakes from all meals.
We thought of fruit to be pears, apricots, cherries, apples, raisins or grapes, bananas, cantaloupe, watermelon, oranges, grapefruit, kiwi, strawberries, peaches, nectarines, tangerines, mulberry, plums, persimmons, pomegranates, lemons, pineapples, recent figs, and dates. Within the vegetable meals group, we included cabbage, cauliflower, Brussels sprouts, kale, carrots, tomatoes, spinach, lettuce, cucumber, combined greens, eggplant, celery, inexperienced peas, inexperienced beans, inexperienced pepper, turnip, corn, squash, mushrooms, and onions.
The reliability of the FFQ was evaluated in a randomly chosen 132 members (not included on this research) by evaluating nutrient consumption decided utilizing responses to the FFQ on 2 events 1 y aside (11, 12). The correlation coefficients for the repeatability of FFQ for fruit and greens had been 0.71 and 0.74, respectively. The FFQ additionally had excessive reliability for vitamins. For instance, the correlation coefficients had been 0.81 for dietary fiber and 0.85 for magnesium. Comparative validity was decided by comparability with intakes estimated from the common of twelve 24-h dietary remembers (one for every month of the yr). Preliminary evaluation of the validation research confirmed that vitamins generally present in fruit and greens had been reasonably correlated between these 2 strategies after whole vitality consumption was managed for. These correlation coefficients had been 0.69 for dietary fiber and 0.67 for magnesium consumption. The validity of the FFQ for assessing fruit and vegetable intakes was additionally good; the correlation coefficients for a comparability between the FFQ and detailed dietary remembers had been 0.61 for fruit and 0.57 for greens. General, these knowledge point out that the FFQ supplies moderately legitimate measures of common long-term dietary intakes.
Evaluation of anthropometric measures
Weight was measured to the closest 100 g with digital scales whereas the topics had been minimally clothed and never sporting sneakers. Top was measured whereas the topics had been standing and never sporting sneakers by utilizing a tape measure whereas the shoulders had been in a traditional place. Physique mass index (BMI) was calculated and expressed in kg/m2. Waist circumference was measured on the narrowest stage and that of the hip on the most stage over mild clothes with the usage of an unstretched tape measure and no strain to the physique floor; measurements had been recorded to the closest 0.1 cm. Because the measurements had been made, the members had been requested to take away belts and tight or unfastened clothes meant to change the form of the physique; the individual doing the measuring was requested to make sure that the tape had the right rigidity, neither too unfastened nor too tight. Though the narrowest level of the waist is simple to establish in most individuals, it was not evident in among the members due to both a considerable amount of belly fats or excessive thinness (28). Within the present research, when the narrowest level of waist was tough to establish (notably in overweight individuals), we measured waist circumference instantly under the tip of the bottom rib, as a result of, in most individuals, the narrowest level of the waist is on the lowest rib (28). To scale back subjective error, all measurements had been taken by the identical technician.
Evaluation of biomarkers
A blood pattern was drawn between 0700 and 0900 into evacuated tubes from all research members after they fasted in a single day for 12 h. Blood samples had been taken whereas the topics had been in a sitting place, in keeping with a typical protocol, and centrifuged inside 30–45 min of assortment. The evaluation of samples was carried out by utilizing Selectra-2 auto-analyzer (Important Scientific, Spankeren, Netherlands). Fasting plasma glucose was measured on the day of blood assortment with an enzymatic colorimetric technique utilizing glucose oxidase. Serum triacylglycerol concentrations had been assayed with the usage of triacylglycerol kits (Pars Azmoon Inc, Tehran, Iran) by enzymatic colorimetric checks with glycerol phosphate oxidase. HDL ldl cholesterol was measured after precipitation of the apolipoprotein B–containing lipoproteins with phosphotungstic acid. CRP concentrations had been measured by utilizing an ultrasensitive latex-enhanced immunoturbidimetric assay (Randox laboratory Ltd, Belfast, United Kingdom). The inter- and intraassay CVs for CRP had been 4.8% and seven.6%, respectively.
Evaluation of blood strain
For the measurement of blood strain, the members initially rested for 15 min. A professional individual then measured blood strain 3 instances with a typical mercury sphygmomanometer whereas the topics had been in a seated place; the imply of the three measurements was thought of to be the participant’s blood strain. The systolic blood strain was outlined as the looks of the primary sound (Korotkoff part 1), and the diastolic blood strain was outlined because the disappearance of the sound (Korotkoff part 5) throughout deflation of the cuff at a 2–3 mm per second decrement price of the mercury column.
Evaluation of different variables
Information on bodily exercise had been obtained by administering a pretested oral questionnaire to the members; bodily exercise was expressed as metabolic equal hours per week (MET-h/wk) (29). Further covariate data concerning age, smoking habits, menopausal standing, medical historical past, and present use of medicines was obtained by utilizing questionnaires.
Definition of phrases
Weight problems was outlined as a BMI ≥ 30 (30). Metabolic syndrome was outlined because the presence of ≥3 of the next parts as really helpful by the Nationwide Ldl cholesterol Schooling Program Grownup Remedy Panel III (ATP III) (31): 1) belly adiposity (waist circumference > 88 cm), 2) low serum HDL ldl cholesterol (<50 mg/dL), 3) excessive serum triacylglycerol (≥150 mg/dL), 4) elevated blood strain [≥130 (systolic)/85 (diastolic) mm Hg], and 5) irregular glucose homeostasis (fasting plasma glucose ≥ 110 mg/dL). Statistical strategies The Statistical Package deal for Social Science (model 9.05; SPSS Inc, Chicago IL) was used for all statistical analyses. The members had been categorized in keeping with quintiles of fruit and vegetable intakes. Important variations normally traits throughout quintile classes of fruit and vegetable intakes had been evaluated by utilizing one-way evaluation of variance with Tukey’s submit hoc comparisons. Chi-square checks had been used to detect any important variations within the distribution of topics throughout quintile classes with regard to qualitative variables. We decided age- and energy-adjusted means for dietary variables throughout quintiles of fruit and vegetable intakes by utilizing a normal linear mannequin (GLM). Evaluation of covariance with Bonferroni correction was used to match these means. Imply plasma concentrations of CRP had been computed throughout quintiles of fruit and vegetable intakes in numerous fashions. First, we adjusted for age (steady), BMI (steady), and waist circumference (steady). Within the second mannequin we moreover adjusted for smoking (sure or no), bodily exercise (steady), whole vitality consumption (steady), use of estrogen (sure or no), menopausal standing (sure or no), and household historical past of diabetes or stroke (sure or no). Lastly, we added dietary variables into the mannequin, together with proportion of vitality from fats, the mutual results of fruit or greens (all as steady variables), and intakes of ldl cholesterol, meat and fish, dairy merchandise, and complete and refined grains. Evaluation of covariance was used for comparability of imply CRP concentrations throughout quintiles. To find out the affiliation of fruit and vegetable intakes with the metabolic syndrome and its options, we used multivariable logistic regression fashions managed for age (y), vitality consumption (kcal/d), ldl cholesterol consumption, proportion of vitality from fats, cigarette smoking (sure or no), bodily exercise (in MET-h/wk), present estrogen use (sure or no), menopausal standing (sure or no), and household historical past of diabetes or stroke (sure or no). For dependent variables with which a big affiliation with fruit and vegetable intakes was noticed, we additional examined whether or not dietary patterns related to excessive fruit and vegetable intakes would clarify these associations by adjusting for intakes of complete grains, refined grains, dairy, and meat and fish. Within the third mannequin, we added CRP to the talked about covariates within the mannequin. We managed for BMI within the final mannequin to find out whether or not the associations had been mediated by weight problems. The percentages ratios estimated from logistic regression fashions in cross-sectional research will not be legitimate estimators of the speed ratios when the binary end result variable has a excessive prevalence (32, 33). Due to this fact, we used the system steered by Zhang and Yu (34) to right the adjusted odds ratios obtained from logistic regression to derive an estimate of affiliation that higher represents the true relative danger. In all multivariate fashions, the primary quintile of fruit and greens consumption was thought of as a reference. The Mantel-Haenszel extension check was carried out to evaluate the general pattern of odds ratios throughout rising quintiles of fruit and greens consumption.
RESULTS
The reported imply each day intakes of fruit and greens had been 228 ± 79 and 186 ± 88 g/d, respectively. The meals gadgets that contributed most to fruit intakes had been apples, cantaloupe, watermelon, grapes, and bananas, respectively, and those who contributed most to vegetable consumption had been onions, tomatoes, combined greens, lettuce, cucumber, and inexperienced beans, respectively.
Traits of the research members throughout quintile classes of fruit and vegetable intakes are proven in Desk 1. In contrast with members within the lowest quintile, these within the highest quintile of fruit consumption had been barely youthful, extra bodily energetic, and fewer prone to be overweight and had decrease anthropometric measures and a decrease prevalence of the metabolic syndrome. Equally, these within the highest class of vegetable consumption had decrease anthropometric measures and a decrease prevalence of weight problems and the metabolic syndrome and had been extra bodily energetic than had been these within the lowest class. No important distinction within the distribution of people who smoke and in present estrogen customers throughout quintile classes of fruit and vegetable consumption was noticed.
Age- and energy-adjusted means for dietary variables throughout quintile classes of fruit and vegetable intakes are introduced in Desk 2. Increased intakes of fruit and greens had been related to a more healthy food plan; these topics within the higher class additionally consumed much less ldl cholesterol, meat, and refined grains and extra dietary fiber and complete grains.
Imply plasma CRP concentrations throughout quintile classes of fruit and vegetable intakes are supplied in Desk 3. Each fruit and vegetable intakes had been inversely related to plasma CRP concentrations. After the statistical management for age, BMI, and waist circumference, imply plasma CRP concentrations throughout rising quintile classes of fruit had been 1.94, 1.79, 1.65, 1.61, and 1.56 mg/L (P for pattern < 0.01) and of greens had been 2.03, 1.82, 1.58, 1.52, and 1.47 mg/L (P for pattern < 0.01). This inverse affiliation remained important even after extra management for different potential confounding variables and dietary elements. Once we thought of fruit and vegetable intakes collectively, this affiliation was extra evident even after changes had been made for potential confounding variables and dietary elements (knowledge not proven). In contrast with these within the lowest quintile of fruit and vegetable intakes, topics within the highest class had decrease odds of getting the metabolic syndrome, even after CRP concentrations and way of life and dietary confounders had been managed for (Desk 4). After potential confounders had been managed for, topics within the highest quintile of fruit consumption had a 34% decrease and people within the highest quintile of vegetable consumption had a 30% decrease likelihood of getting the metabolic syndrome. Once we thought of fruit and vegetable intakes collectively, the protecting impact grew to become even stronger; these within the highest quintile had a 39% decrease danger (knowledge not proven). Nonetheless, all associations grew to become a lot weaker after we took the BMI into consideration (Desk 4). The identical outcomes had been obtained after we used Worldwide Diabetes Federation standards for the metabolic syndrome (not proven). After adjustment for potential confounding variables together with dietary elements and CRP, a big inverse pattern was noticed between fruit consumption and the likelihood of getting the metabolic syndrome options (Determine 1). Nonetheless, no important affiliation was noticed between consumption of fruit and a low HDL-cholesterol focus. Increased consumption of greens was additionally related to a decrease danger of metabolic syndrome options (Determine 2). In multivariate-adjusted fashions, topics within the higher quintile of vegetable consumption had decrease odds of getting the metabolic syndrome options. As for fruit, greater consumption of greens was not related to prevalence of low HDL ldl cholesterol. Nonetheless, when fruit and vegetable intakes had been thought of collectively, we noticed a touch important inverse affiliation (odds ratio for quintile 5 versus quintile 1: 0.95; 95% CI: 0.85, 0.99; P = 0.046) with the prevalence of low HDL ldl cholesterol.
DISCUSSION – “c reactive protein lowering foods”
Within the present research we noticed an inverse affiliation of fruit and vegetable intakes with CRP. We additionally discovered that greater intakes of fruit and vegetable had been related to a decrease danger of the metabolic syndrome. To our information, that is the primary research to instantly relate fruit and vegetable intakes with the metabolic syndrome. Lately, 2 medical trials (25, 35) and a couple of observational research (26, 36) have examined the affiliation of fruit and vegetable intakes with CRP, however the members had been restricted to males (25, 36) or the aged (26) and such an affiliation has not been noticed in girls. Nonetheless, the helpful results of fruit and vegetable intakes within the framework of dietary patterns had been reported beforehand, and it has been proven that dietary patterns wealthy in fruit and greens might cut back the danger of the metabolic syndrome (37, 38) and are related to decrease concentrations of inflammatory markers (39). We even have proven in a randomized medical trial that consumption of a DASH (Dietary Approaches to Cease Hypertension) food plan, ie, a food plan wealthy in fruit and greens, has helpful results on options of the metabolic syndrome (40). Esposito et al (41) confirmed that the Mediterranean food plan, which is wealthy in fruit and greens, lowers plasma markers of irritation and endothelial dysfunction.
A good affiliation of fruit and vegetable consumption with CRP and the metabolic syndrome could also be attributed to the wholesome way of life related to greater intakes of those meals. Nonetheless, the apparently protecting impact of fruit and vegetable consumption continued in multivariate fashions after recognized potential confounders had been accounted for. Second, some middleman occasions, together with dyslipidemia or elevated blood strain, might have led to adjustments in food plan and will due to this fact confound the affiliation between fruit and vegetable intakes and the metabolic syndrome. Nonetheless, such residual confounding results would are inclined to attenuate the danger estimates towards the worth of 1, as a result of topics with danger elements might be suggested to observe a nutritious diet wealthy in fruit and greens. Additionally, one might conclude that this affiliation is a results of the participation of extremely educated members in our research. Though academics in our group have the next socioeconomic standing than does the overall Iranian inhabitants, the members in our research have been chosen from 4 giant socioeconomically numerous districts of Tehran, which covers a broad vary of dietary habits. In contrast with different research which have been reported from Iran (11, 12, 42, 43), this report covers a variety of fruit and vegetable intakes. Given these traits, it’s unlikely that the entire associations between fruit and vegetable intakes and the metabolic syndrome in our research may very well be defined by this kind of bias. It is usually doable that the members in our research overestimated their intakes due to the comparatively giant variety of questions used to evaluate intakes of fruit and greens (≈30 questions for fruit and 22 questions for greens) in our questionnaire. Nonetheless, even when there was some overestimation of fruit and vegetable intakes, such overestimation is unlikely to bias the danger estimates.
Though the danger of each heart problems and sort 2 diabetes is mediated partially by tissue sensitivity to the results of insulin (44), no epidemiologic research has examined the affiliation of fruit and vegetable intakes with the insulin resistance syndrome or the metabolic syndrome. Within the present research, the prevalence and odds of getting the metabolic syndrome had been decrease in these with the next consumption of fruit and greens. Our findings are according to these of earlier research which have proven a protecting impact of fruit and vegetable intakes towards mortality (45), heart problems (18), and diabetes (46). One other cross-sectional research in younger adults additionally confirmed that individuals with the metabolic syndrome have considerably decrease intakes of fruit and greens than do these with no metabolic dangers (47). A portion of those cardioprotective results of fruit and vegetable intakes could also be mediated by the impact of their parts (eg, antioxidants) on inflammatory markers (23, 36). Nonetheless, few research have associated fruit and vegetable consumption to markers of irritation, notably in girls. We confirmed {that a} greater consumption of fruit and greens is related to decrease plasma concentrations of CRP. Though this favorable obvious impact of fruit and vegetable intakes was noticed in one other epidemiologic research in a Hispanic aged inhabitants (26), the outcomes of medical trials will not be constant. Watzl et al (25), in a 4-wk randomized managed medical trial in wholesome nonsmoking males, confirmed that consumption of 8 each day servings of carotenoid-rich fruit and greens considerably decreased plasma CRP concentrations in contrast with those that consumed 2 each day servings. In distinction, Freese et al (35), in a 6-wk randomized managed research of wholesome topics aged 19–52 y, noticed no distinction in inflammatory markers, together with CRP, between those that consumed a food plan offering 810 g fruit and greens per 10 MJ (2390 kcal) and people who consumed an isocaloric food plan offering 196 g fruit and greens per 10 MJ (2390 kcal). Nonetheless, though the interpretation of those intervention research is difficult by the completely different age ranges of the topics studied and by the quick period of the interventions, it seems that the long-term consumption of fruit and greens is extra essential than is the short-term consumption of those meals on the modulation of markers of irritation.
Consuming ≥5 servings of fruit and greens each day is really helpful to scale back the danger of power ailments (48). Information from the Nationwide Meals Consumption Survey in Iran have proven decrease intakes of fruit and greens by Iranians than these really helpful (42). Within the present research, topics within the prime quintile of fruit and vegetable consumption consumed 362 g fruit/d and 279 g greens/d. The imply fruit and vegetable intakes in our research had been 228 and 186 g/d, respectively; these intakes are greater than these reported kind Finland in The Seven Nations Examine (49) and decrease than these reported for American males within the Diet Standing Survey in Massachusetts (50). Within the Well being Professionals Comply with-Up Examine and the Nurses’ Well being Examine (51) and within the Framingham Coronary heart Examine (52), the consumption of fruit and greens was ≈5 servings/d and within the Ladies’s Well being Examine the consumption was 6 servings/d (18). Nonetheless, it needs to be saved in thoughts that a few of these research, like our research, didn’t embrace potato within the vegetable group (52). Contemplating the favorable affiliation of fruit and vegetable consumption with the metabolic syndrome and inflammatory markers, it appears probably that an elevated consumption of those merchandise will significantly cut back the danger of metabolic issues.
Our findings have to be interpreted whereas contemplating some limitations. First, we used cross-sectional knowledge to evaluate the affiliation of fruit and vegetable intakes with the metabolic syndrome. Though a direct potential affiliation between fruit and vegetable intakes and the metabolic syndrome has not but been reported, many research have proven a potential affiliation between fruit and vegetable intakes and danger elements associated to the metabolic syndrome. Second, as a result of we used an FFQ to evaluate dietary intakes, misclassification was a serious concern in our research, as it’s in all epidemiologic research. Third, diets wealthy in fruit and greens had been related to a more healthy way of life, which can not have been precisely captured and managed in our evaluation and, thus, might have resulted in residual confounding. Fourth, the danger estimates obtained in our research weren’t adjusted for glycemic load, a dietary agent that has been proven to correlate with each CRP (53) and the metabolic syndrome (54). Nonetheless, the associations we noticed had been unlikely to be confounded considerably by dietary glycemic load as a result of the in depth changes we made had minimal results on the chances ratios. Fifth, topics with recognized power ailments had been excluded from the research. These exclusions might have decreased the probability of discovering important tendencies within the odds of getting metabolic dangers throughout quintile classes of fruit and vegetable consumption. Sixth, this research included solely girls. Iranian girls behave in another way with metabolic syndrome than do males. The prevalence of the metabolic syndrome amongst girls in Iran is nearly twice that in males (8) and, of all girls on this planet, Iranian girls have the best prevalence (3). Seventh, we didn’t embrace potato within the vegetable group as a result of current research have proven that potato consumption can enhance the danger of diabetes (55); due to this fact, suggestions to incorporate potatoes as a vegetable might not be warranted (26). Nonetheless, inclusion of potato as a vegetable on this research attenuated the associations however they remained important.
In conclusion, this research confirmed that greater intakes of fruit and greens had been related to a decrease danger of the metabolic syndrome; the decrease danger could also be the results of decrease CRP concentrations. These findings assist present dietary suggestions to extend intakes of fruit and greens as a major safety measure towards heart problems. Our outcomes additionally present additional proof for the speculation {that a} excessive consumption of fruit and greens is related to decreased plasma concentrations of inflammatory markers.
We thank the members of this research for his or her enthusiastic assist. Not one of the authors had any private or monetary conflicts of curiosity.
AE and LA designed the research, collected and analyzed the info, and wrote the manuscript. MK supervised the analysis. YM served as an advisor for the analysis. FBH and WCW commented on this work and helped put together the manuscript.
FOOTNOTES
REFERENCES
“c reactive protein lowering foods”