Anti-inflammatory diet consumption reduced fatty liver indices

The aim of this study was to assess the association between dietary inflammatory index (DII) and non-invasive markers of liver status in adults. This cross-sectional study was performed on 8520 adults, recruited in Ravansar Non-Communicable Diseases (RaNCD) cohort study, western Iran. The DII score was calculated based on participants’ dietary intakes obtained from Food Frequency Questionnaire (FFQ). Fatty Liver Index (FLI) score was calculated by anthropometric measurements and some non-invasive markers of liver status. Linear regression models were applied to estimate the associations and adjust the possible confounding factors. A greater DII score was significantly associated with higher energy intake, body mass index (BMI), body fat mass (BFM), blood pressure, and FLI (P < 0.001). Participants with the highest DII score had a significantly higher consumption saturated fat, trans fat and red meat than those in the lowest quartile (P < 0.001). After adjustments of age and sex, participants in the highest quartile of the DII score had a greater risk of FLI (β: 0.742, 95% CI: 0.254, 0.601). More pro-inflammatory diet in participants was associated with a higher FLI. The DII score was positively associated with non-invasive liver markers. Thus, having an anti-inflammatory diet can help balance liver enzymes, reduce obesity, and decrease fatty liver.

The association of fatty liver index with dietary inflammatory index. Crude and multivariableadjusted linear regression analysis was used to investigate the effect of several factors on FLI (Table3). We found a significant association between the DII scores and FLI, with one-point increment in the DII score, on average the risk of having FLI increased by 13 (95% CI, 0.076 to 0.181). In the crude and multivariable-adjusted model with one-point increment in the physical activity, on average the risk of having FLI decreased by 6 (95% CI, − 0.076 to − 0.056) and 2 (95% CI, − 0.030, − 0.016), respectively. We also found a significant association between FLI and BMI, with one-point increment in the BMI, on average the risk of having FLI increased by 23 in the crude and 35 in the adjusted models.
After adjustments of age and sex (Model 1, Table 4) and after adjustments of BMI, WC, and physical activity (Model 2, Table 4), participants in the highest quartile of the DII score had a greater risk of FLI (β: 0.742 and Table 1. Baseline characteristics, anthropometric and biochemical of participant's factors according to the dietary inflammatory index score. AST aspartate transaminase, ALT alanine aminotransferase, BFM body fat mass, BMI body mass index, DII dietary inflammatory index, FLI fatty liver index, GGT gamma-glutamyltransferase, TG triglycerides, SBP systolic blood pressure, DBP diastolic blood pressure, VFA visceral fat area, WC waist circumference, WHR waist hip ratio. *Analysis of variance (ANOVA), P < 0.05. www.nature.com/scientificreports/  Table 3. Association between selected variables and fatty liver index by linear regression analysis. *Adjusted for current smoker, use alcohol, FBS and lipid profile (LDL-C, HL-C, TG and total cholesterol).  www.nature.com/scientificreports/ β: 0.497, respectively) than those in the lowest quartile. Figure 1 shows a positive association between DII and liver markers.

Discussion
Our findings showed that a higher pro-inflammatory diet in participants was associated with a higher FLI. The DII score was positively associated with the non-invasive liver markers (ALT, AST, and GGT), suggesting that diet-induced inflammation may increase liver disorders. We found a positive association between FLI and BMI, WC and BFM in crude and adjusted models. While this finding supports the idea that inflammation is induced by adiposity, the association may be bidirectional. In the study of Cantero et al. 13 , a positive association between the DII and FLI has also been observed, as it reveals that higher inflammation and fewer adherences to the Mediterranean diet were related with a higher degree of liver disorders in obese individuals.
In the current work, the level of inflammatory markers was not measured. However, given that the obesity is an inflammatory condition and the rise in BMI is associated with an increase in the DII score (Q1 = 26.97 vs. Q4 = 27.90), subsequently the association between DII and inflammatory conditions is inferred. A study by Fong et al. (2006) observed association between different diet-quality scores including the alternative healthy eating index (AHEI), healthy eating index (HEI), and the alternate Mediterranean diet index (aMED) with inflammatory markers such as CRP and IL-6 22 . Sureda et al. (2018) reported that low adherence to the Mediterranean dietary pattern (MDP) was directly associated with a worse profile of plasmatic inflammation markers including adiponectin, Leptin, TNF-α, plasminogen activator inhibitor 1 (PAI-1), and high-sensitivity C-reactive protein (hs-CRP) 23 .
The present study revealed that more pro-inflammatory diet in the participants was associated with higher energy intake, red meat, saturated fat, trans fat, cholesterol, MUFA, and PUFA. Previous studies have shown that healthy food is inversely related to inflammation 1,2 and also several trial and meta-analysis studies have reported association between enough intake of vitamin C, vitamin E, antioxidants, and fiber with lower levels of inflammatory markers 3,4,6,7 . On the other hand, associations between DII and metabolic syndrome (MetS) components including high TG and low HDL-C concentrations, high blood pressure, glucose intolerance, central obesity, CVD, and liver cancer have been reported to be related 2,24-26 . Overall, the mentioned studies' results are in line with our findings in the hypothesis that diet is an important factor in the inflammation process 13,24 .
In the crude and adjusted models with increasing physical activity, inflammation was reduced. A cohort study with a ten-year follow-up showed physically active participants at baseline had lower CRP and Il-6 levels,  www.nature.com/scientificreports/ which remained stable over time 27 . There are other studies reporting an inverse association of physical activity with inflammatory markers [28][29][30] . The liver has many functions within the body including amino acid synthesis, carbohydrate metabolism, cholesterol linkage, protein degradation, the manufacture of TG, and the major part of lipoprotein synthesis 31 . Currently, there is no effective treatment for NAFLD; therefore, many researches have recently focused on finding biomarkers for a prediction of liver disorders particularly NAFLD. FLI is a combination of four components: BMI, WC, TG, and GGT. Thus, calculating the FLIis simple, with an accurate and cost effective method 14 . According to the components of the FLI (including anthropometric measures, liver enzymes, and blood lipid), its increasing could be a type of inflammation and setting an anti-inflammatory diet can keep balance the FLI.
The main strength of our study is the large sample size. This study faced several limitations; firstly, not being able to evaluate the inflammatory markers. Therefore, we suggest that these markers be examined in future studies. Secondly, due to the cross-sectional nature of the study, it is not possible to infer causality and more studies are needed. In addition, because of the large sample size, more of the relationships were statistically significance which should not be over-emphasized if there is no clinical significance. Third, FFQ are containing some degree of recall bias. However, we used the validated dietary questionnaire for calculation of DII, thus diet was investigated through face-to-face interviews, which may have reduced measurement error. Although, the diet may change over time and we are unable to measure the changes; longitudinal studies evaluating these associations are needed to determine causality. Fourth, liver fat was not directly measured, i.e. magnetic resonance spectroscopy (MRS) or magnetic resonance imaging (MRI).

Conclusion
Our study findings indicated that more pro-inflammatory diet in participants was associated with higher FLI. The DII score was also positively associated with non-invasive liver markers (ALT, AST, and GGT). We found a positive association between FLI with BMI, WC, BFM and energy intake, red meat, saturated fat, trans fat, cholesterol, MUFA, and PUFA. Therefore, it was concluded that having an anti-inflammatory diet can help balance liver enzymes, reduce obesity, and decline body fat mass and also related co-morbidities like the fatty liver.

Methods
Study population. This was a cross-sectional study based on baseline data from Ravansar Non-Communicable Disease (RaNCD) prospective study in western Iran in 2020. The RaNCD study is part of a prospective epidemiological research study in Iran (PERSIAN). Ravansar is a district with urban and rural areas located in the west of Iran and in Kermanshah province with a population of about 50,000. The initial phase data was collected in 2014, and 10,000 adults between the ages of 35 and 65, being registered as permanent residents of Ravansar, were included in this cohort study. RaNCD study methodology and design with details have been published in 2019 32 . Participants included all subjects from the first phase of the RaNCD study. For this study, the exclusion criteria were as follows: pregnancy, patients with hepatitis B, hepatitis C, cancer, hypertension, thyroid disorder, and the case that their information was incomplete (Fig. 2). www.nature.com/scientificreports/ were completed by trained experts. Demographic information and personal habits were completed face-to-face in the digital cohort questionnaire.

Ethics approval. The Ethics
Anthropometry measurements. We used the Bio-Impedance Analyzer BIA (Inbody 770, Inbody Co, Seoul, Korea) to measure body weight with a precision of 0.5 kg and BSM 370 (Biospace Co, Seoul, Korea) to measure height with the precision of 0.1 cm. Body composition components including BMI, Body fat mass (BFM), visceral fat area (VFA), Waist hip ratio (WHR), and WC were measured by BIA. WC also was measured with a flexible measuring tape at a level midway between the lowest rib margin and the iliac crest.
Blood pressure. We measured blood pressure using a manometer cuff and stethoscope from both arm in the seated position and after ten minutes of rest for two times from each arm with an interval of five minutes. Then a mean of both systolic and diastolic blood pressure was reported.
Biochemical factors. Serum  Assessment of DII. Dietary information derived from the Food Frequency Questionnaire (FFQ) was applied to calculate the DII scores for subjects. Shivappa et al. found that 45 food items were associated with one or more of the inflammatory including Interleukin-1b (IL-1b), Interleukin-6 (IL-6), Tumor Necrosis Factora (TNF-a), C-reactive protein (CRP), or anti-inflammatory markers including Interleukin-4 (IL-4) and Interleukin-10 (IL-10). They scored the inflammatory potential for each food parameter according to whether it increased inflammatory or decreased anti-inflammatory markers (+ 1), whether it decreased inflammatory or increased anti-inflammatory markers (−1), or if it had no effect (0) on the level of inflammatory or anti-inflammatory markers. They calculated global mean and standard deviation for each of the 45 food parameters based on 11 data sets from 11 countries in different parts of the world 9 .
To calculate the DII score for each subject, we subtracted the "standard global average" from the value consumed per person and then divided by the "global standard deviation" to obtain the Z score for each food parameter. We used the global means ± SDs from the Shivappa et al. study 9 . Afterwards, we converted these values to a centered percentiles score to minimize the risk of skewness. The inflammatory score for each of the food parameters was calculated via this method, and then the inflammatory score of all parameters was summed to calculate the overall DII score which could be positive or negative. More positive DII scores indicate more pro-inflammatory diets, while more negative scores imply more inti-inflammatory diets 9,33 . Finally, DII scores were classified into four groups (quartile) to investigate the association between the different variables. The first and fourth quartiles had the lowest and highest DII scores, respectively. Statistical analysis. All analyses in this study were performed using Stata version 14.2 software (Stata Corp, College Station, TX, USA), which is available from: (https:// downl oadbu ll. com/ porta ble-stata corp-stata-14-2-free-downl oad/). General characteristics, anthropometric indices, and biochemical factors of participants across quartiles of the DII score were reported as mean ± standard deviation for continuous variables and as percentages for qualitative variables. The normality was checked using the Kolmogorov-Smirnov test. To compare differences across DII quartiles, we used the one-way ANOVA test. Analysis of linear regression was conducted to determine associations between FLI and the DII score and other risk factors adjusted for smoking and alcohol use. Additionally, linear regression was applied to determine the associations between FLI across quartiles of the DII score for adjusting the following confounding factors: age, sex, BMI, WC, and physical activity. Variables with p-value < 0.2 in univariable analysis were entered into multivariable linear model. For statistical analyses, a p-value of < 0.05 with 95% confidence intervals (CIs) was considered significant.