Table 2 General characteristics of included studies in the systematic review and meta-analysis

Huang J

2024

USA [24]

cross-sectional

24 h-Recall

General population

N = 2108

M = 1044

F = 1064

Mean age: 53.9

1. Risk of low-eGFR

2. Correlation with eGFR

1. Highest vs. lowest adherence: OR = 2.070; 95%CI, 1.12, 3.82

2. Significant negative correlation between DII and eGFR.

Gender, age, race, education level, poverty index, hypertension, diabetes, smoking, and drinking.

6/9

Guo M

2024

China [26]

cross-sectional

24 h-Recall

Middle-aged and elderly populations

N = 23,175

M=-

F=-

Mean age: 60

1. Risk of CKD

2. Risk of low-eGFR

1. Highest vs. lowest adherence: OR = 1.08; 95%CI, 1.05, 1.10

2. Highest vs. lowest adherence: OR = 1.16; 95%CI, 1.13, 1.19

Race, age, sex, education level, smoking status, PIR, BMI, albumin, glucose, glycosylated hemoglobin, ALT, AST, serum iron, potassium, cholesterol, triglycerides, BUN, uric acid, hypertension, coronary heart disease, congestive heart failure, stroke, arthritis, cancer, and diabetes.

7/9

Guo C

2023

China [27]

cross-sectional

24 h-Recall

Patients with type-2 diabetes mellitus

N = 7974

M = 4131

F = 3843

Mean age: 59.5

Risk of CKD

Highest vs. lowest adherence: OR = 1.67; 95%CI, 1.29, 2.17

Age, sex, ethnicity, smoking, drinking, body mass index (BMI), triglyceride (TG), total cholesterol (TC), metabolic equivalents (METs), energy intake, hypoglycemic medications, hypertension, and cardiovascular disease (CVD).

7/9

Moludi

2022

Iran [34]

cross-sectional

FFQ

General population

N = 9824

M = 4610

F = 5214

Age: 35–65

Risk of CKD

Highest vs. lowest adherence: OR = 1.92; 95%CI, 1.52–2.42

Age, gender, smoking status, BMI, place, education level, and physical activity, HEI, kidney stone, diabetes, and high blood pressure.

5/9

Lin

2021

China [35]

cross-sectional

FFQ

Women with diabetes, prediabetes and normal glucose

N = 2644

F = 2644

Mean age: 55.3

1. Risk of low-eGFR

2. Correlation with eGFR

1a. Highest vs. lowest adherence in diabetes: OR = 15.519; 95%CI, 1.373, 175.377

1b. Highest vs. lowest adherence in prediabetes: OR = 2.413; 95%CI, 0.688, 8.461

1c. Highest vs. lowest adherence in normal blood glucose participants: OR = 1.439; 95%CI, 0.250, 8.300

2. Significant negative correlation between DII and eGFR in patients with diabetes. But no significant correlation in patients with pre-diabetes and normal glucose.

Age, BMI, current smoking, alcohol intake and exercise, systolic BP, diastolic BP, glucose, LD, HDL, triglyceride, cholesterol

7/9

Mazidi

2018

USA [16]

cross-sectional

24 h-Recall

General population

N = 21,649

M= -

F= -

Age: ≥18

1. Risk of CKD

2. Risk of low-eGFR

3. Association with eGFR

4. Association with Cr

5. Association with uric acid

1. Highest vs. lowest adherence: OR = 1·23; 95%CI, 1.10, 1.35

2. Highest vs. lowest adherence: OR = 1·29; 95%CI, 1·03, 1·62

3. Significant decrease in mean eGFR across increasing E-DII quartiles.

4. Nonsignificant increase in mean Cr across increasing E-DII quartiles.

5. Significant decrease in mean uric acid across increasing E-DII quartiles.

Blood glucose, blood pressure, BMI, diabetes, hypertension status

6/9

Wang

2022

USA [36]

cross-sectional

24 h-Recall

Diabetes

N = 4264

M = 2241

F = 2023

Age: >20

1. Risk of low-eGFR

2. Risk of DKD

1. Highest vs. lowest adherence: OR = 1.57; 95%CI, 1.10, 2.26

2- Highest vs. lowest adherence: OR = 1.64; 95%CI, 1.24, 2.17

Age, sex, race, educational level, marriage status, family poverty income ratio, smoking status, drinking status, physical activity level, hypertension and BMI.

6/9

Qu

2024

USA [37]

cross-sectional

24-hour dietary recall

General population

N = 18,070

M = 8906

F = 9164

Age: ≥ 20

1. Risk of CKD

2. Risk of low-eGFR

1. Highest vs. lowest adherence: OR = 1.24; 95%CI, 1.11, 2.64

2. Highest vs. lowest adherence: OR = 1.71; 95%CI, 0.95, 1.63

Age, sex, race, education level, marital status, PIR, BMI, smoking status, physical activity, diabetes, hypertension and energy

6/9

Zeng

2023

USA [38]

cross-sectional

24-hour dietary recall

Adults Aged

50 Years and Older

N = 12,090

M= -

F= -

Age: ≥ 50

Risk of low-eGFR

Highest vs. reference adherence: OR = 2.08; 95%CI, 1.30–2.86

Age, sex, body mass index, race/ethnicity, education, ratio of family income to poverty, smoking, physical activity, hypertension, diabetes, and daily intakes of total plain water, total energy, and sodium.

7/9

Xu Z

2024

USA [39]

cross-sectional

24 h-Recall

CKD patients

N = 2488

M: 1183

F: 1304

Mean age: 67.11 ± 15.56

1. Risk of higher CKD Stages

2. Correlation with eGFR

1- Highest vs. reference adherence: OR = 2.29; 95%CI, 1.42, 3.71

2. Significant negative correlation between DII and eGFR.

Age, gender, race, education level, poverty income ratio (PIR), marital status, body mass index (BMI), metabolic equivalent (MET) score, drinking, smoking, history of hypertension, history of diabetes, cotinine, systolic blood pressure, diastolic blood pressure, total triglycerides, and total cholesterol

7/9

Vahid

2023

Luxemburg [25]

cross-sectional

FFQ

General population

N = 1404

M = 654

F = 750

Age: 25–79

1. Correlation with eGFR

2. Correlation with uric acid

1. No Significant correlation between DII and eGFR.

2. No Significant correlation between DII and uric acid.

Age, gender, birth country, marital status, education, job, income, IPAQ scoring, current smoking

6/9

Bondonno

2020

Australia [52]

Cohort

(10 years)/ cross-sectional

FFQ

Older women

N = 2644

F = 2644

Mean age: 55.3

Correlation with eGFR

Significant negative correlation between DII and eGFR both at the baseline and after 10 years.

Age, energy intake, treatment code (calcium or placebo), BMI, smoking status, physical activity, alcohol intake, diabetes status, use of antihypertensive medication, prevalent ASVD, statin use, and use of NSAIDs for joint pain

7/9

Tajik

2019

Iran [40]

cross-sectional

FFQ

Elderly population

N = 221

M = 65

F = 161

Mean age: 67 ± 5.7

1. Correlation with eGFR

2. Association with Creatinine

1. No Significant correlation between DII and eGFR.

2. No significant association between mean Cr and DII.

Energy intake, age, sex, BMI, smoking status, physical activity, hypertension, diabetes, use of lipid-lowering medication, angiotensin II receptor blockers (ARB) and angiotensin-converting enzyme inhibitor (ACEI), steroidal and non- steroidal anti-inflammatory medications.

6/9

Xu H

2015

Sweden [41]

cross-sectional

7-d food records

Elderly population

N = 1942

M = 1520

F = 422

Age: 70–71

Correlation with eGFR

Significant negative correlation between DII and eGFR.

Energy intake, age, sex, smoking status, physical activity, hypertension, diabetes, use of lipid-lowering medication, and whether the participants were from the Uppsala Longitudinal Study of Adult Men or the Prospective Investigation of Vasculature in Uppsala Seniors, BMI, CRP

7/9

Rouhani

2018

Iran [42]

cross-sectional

FFQ

CKD patients

N = 221

M= -

F= -

Mean age: -

1. Risk of higher CKD Stages

2. Association with eGFR

3. Association with Cr

4. Association with BUN

1. Highest vs. lowest adherence: OR = 2.12; 95%CI, 1.05, 4.26

2. No significant association between mean eGFR and DII.

3. No significant association between mean Cr and DII.

4. No significant association between mean BUN and DII.

Socioeconomic status, height and weight, systolic and diastolic blood pressure

5/9

Alkerwi

2015

Luxembourg [22]

cross-sectional

SQ-FFQ

General population

N = 1352

M= -

F= -

Age: 18–69

1. Correlation with Cr

2. Correlation with uric acid

1. No Significant correlation between DII and Cr

2. No Significant correlation between DII and uric acid.

Age (continuous), sex, education level (primary, secondary or tertiary), smoking status (smoker or non-smoker), physical activity in metabolic equivalents-h/week

5/9

Farhangi

2018

Iran [23]

cross-sectional

SQ-FFQ

Candidates of CABG surgery

N = 454

M = 332

F = 122

Age: 35–80

1. Correlation with Cr

2.Correlation with BUN

1. Significant positive correlation between DII and Cr in male patients, but not in female patients.

2. Significant positive correlation between DII and BUN in male patients, but not in female patients.

Age, gender, BMI, educational attainment and presence of diabetes and myocardial infarction

5/9

Bavi Behbahani

2022

Iran [43]

cross-sectional

FFQ

Atherosclerosis patients

N = 320

M = 171

F = 149

Age: ≥ 20

1. Correlation with Cr

2. Correlation with BUN

1. No Significant correlation between DII and Cr.

2. No Significant correlation between DII and BUN.

Age, sex, energy intake, physical activity, race, BMI, WC, marital status, and education.

5/9

Rodgers

2024

Spain [50]

Case-control

SQ-FFQ

Cases: kidney stone formers.

Controls: individuals with no history of kidney stone.

N = 160 (Cases:97, Controls:63)

M = 111

F = 49

Mean Age: 47

1. Correlation with Cr

2. Correlation with uric acid

1. No Significant correlation between DII and Cr.

2. No Significant correlation between DII and uric acid.

Sex, age and for the statistically significant predictors of the univariate analyses

6/9

Carrasco-Marín

2024

UK [44]

cross-sectional

24 h dietary recall

Healthy adults

N = 66,978

M = 30,852

F = 36,126

Age: 37–73

1. Correlation with Cr

2. Correlation with uric acid

1. Significant negative correlation between DII and Cr.

2. No Significant correlation between DII and uric acid.

Age, sex, deprivation, smoking, alcohol consumption, physical activity, and BMI.

6/9

Kizil

2016

Turkey [45]

cross-sectional

3-day

dietary recall

Hemodialysis patients

N = 150

M = 68

F = 82

Mean age: 57.5 ± 12.4

Association with Cr

No significant association between mean Cr and DII.

Gender, education level, and marital status.

3/9

Lu

2024

USA [46]

cross-sectional

24 h-Recall

patients with hypertension

N = 17,294

M = 8642

F = 8652

Mean age = 59.78 ± 0.18

Risk of CKD

Highest vs. lowest adherence: OR = 1.38; 95%CI, 1.15,1.65

Age, gender, race, education, family income, smoking status, alcohol intake, and diabetes.

6/9

Rivera-Paredez

2024

Mexico [47]

cross-sectional

SQ-FFQ

patients with hypertension

N = 2098

M = 32.4%

F = 67.6%

Mean age = 47

Correlation with eGFR

Significant negative correlation between DII and eGFR.

Age, smoking, drinking, physical activity, hypertension, BMI, glucose, lipids, and blood pressure

6/9

Rui

2024

USA [48]

cross-sectional

24 h-Recall

patients with DM

N = 2712

M = 32.4%

F = 67.6%

Mean age = 47

Risk of DKD

Highest vs. lowest adherence: OR = 0.9; 95%CI, -0.6, 2.4

Age, gender, race, education level, PIR, BMI, waistline, total energy intake, HbA1c, FPG, Ualb, Ucr, BUN, SUA, TC, TG, HDL, LDL, ALT, AST, Hypertension, MetS, taking prescription for hypertension, taking prescription for to lower blood sugar, Taking prescription for cholesterol

7/9

Huang Y

2024

USA [53]

cross-sectional

24 h-Recall

General population

N = 25,167

M = 48.3%

F = 51.7%

Mean age = 49.2

Risk of CKD

Highest vs. lowest adherence: OR = 1.56; 95%CI, 1.34, 1.82

Age, gender, race/ethnicity, body mass index, smoking status, poverty status, education levels, alcohol consumption, leisure time physical activity, history of diabetes.

6/9

Guo L

2024

USA [49]

cross-sectional

24 h-Recall

General population

N = 40,388

Without CKD:

M = 50.42%

F = 49.58%

Mean age = 44.99

With CKD:

M = 43.20%

F = 56.80%

Mean age = 60.84

Risk of CKD

Highest vs. lowest adherence: OR = 1.24; 95%CI, 1.12, 1.37

Sex, age group, race, education, marital status, BMI, smoking, and drinking status, hypertension, and diabetes.

6/9

Li

2024

USA [51]

Cohort

(19 years)

24 h-Recall

General population

N = 23,099

M= -

F= -

Age = ≥ 18

Risk of CKD

Highest vs. lowest adherence: HR = 1.36; 95%CI, 1.23–1.51

Systolic blood pressure (SBP), total cholesterol (TC), age, education, BMI, serum creatinine, smoking habit, sex, and race.

6/9