Table 2. Dietary intake of micro-nutrients and DR.
| Author, year | Association | Study Design | Quality | Dietary Factor | Sample Size | DR outcome type | Confounders adjusted for | Statistical methods | Main Findings |
|---|---|---|---|---|---|---|---|---|---|
| Antioxidants | |||||||||
| Carotenoids | |||||||||
| Tanaka, 2013 | Protective | Prospective | 10 | Carotenoids | 978 | Incidence | Age, sex, BMI, HbA1c, duration of diabetes, treatment by insulin, treatment by oral hypoglycemic agents without insulin, systolic blood pressure, LDL Cholesterol, HDL cholesterol, triglycerides, smoking, alcohol, physical activity, total energy intake, proportions of dietary protein, fat, carbohydrate, saturated fatty acids, n-6 PUGA and n-3 PUFA, cholesterol & sodium | Multivariate Cox Regression | Highest Intake Quartile (Q4) vs lowest Intake Quartile (Q1), HR: 0.52 (0.33–0.81) |
| Mayer-Davis, 1998 | NS | Cross Sectional | 9 | Carotenoids (B-Carotene) | 387 | Prevalence | Age, duration of diabetes, ethnicity, glycosylated hemoglobin, hypertension, caloric intake, gender & insulin use. | Multivariable logistic regression | No significant associations with DR (Data not reported) |
| Sahli, 2016 | NS | Cross Sectional | 9 | Carotenoids (Lutein) | 1430 | Prevalence | HbA1c, blood pressure, duration of diabetes, race, total energy consumption & study center | Multivariable logistic regression | Intake Q3 vs Q1, OR: 1.54 (0.96–2.47) Intake Q4 vs Q1, OR: 1.41 (0.87–2.28) |
| Sasaki, 2015 | NS | Cross Sectional | 8 | Carotenoids (B-Carotene) | 379 | Prevalence | Energy Intake | Data not reported | No significant associations with DR (Data not reported) |
| Vitamin C | |||||||||
| Tanaka, 2013 | Protective | Prospective | 10 | Vitamin C | 978 | Incidence | Age, sex, BMI, HbA1c, duration of diabetes, treatment by insulin, treatment by oral hypoglycemic agents without insulin, systolic blood pressure, LDL Cholesterol, HDL cholesterol, triglycerides, smoking, alcohol, physical activity, total energy intake, proportions of dietary protein, fat, carbohydrate, saturated fatty acids, n-6 PUGA and n-3 PUFA, cholesterol & sodium | Multivariate Cox Regression | Intake Q4 vs Q1, HR: 0.61 (0.39–0.96) |
| Mayer-Davis, 1998 | Risk | Cross Sectional | 9 | Vitamin C | 387 | Prevalence | Age, duration of diabetes, ethnicity, glycosylated hemoglobin, hypertension, caloric intake, gender & insulin use. | Multivariable logistic regression | Intake 9th Decile vs 1st Quintile, OR: 2.21 (p = 0.011) |
| Millen, 2004 | NS | Cross Sectional | 8 | Vitamin C | 1353 | Prevalence | Total energy intake, race, duration of diabetes, serum glucose, hypertension, BMI, waist-hip ratio, smoking, alcohol, drinking status, plasma triacylglycerol, plasma cholesterol, hematocrit value, prevalent coronary heart disease, diabetes treatment group, &use of oral hypoglycemic agents or use of insulin | Multivariable logistic regression | Intake Q4 vs Q1, OR: 1.4 (0.8–2.4) |
| Sasaki, 2015 | NS | Cross Sectional | 8 | Vitamin C | 379 | Prevalence | Energy Intake | Data not reported | No significant associations with DR (Data not reported) |
| Vitamin E | |||||||||
| Mayer-Davis, 1998 | Risk (in insulin non-taking subjects) | Cross Sectional | 9 | Vitamin E | 387 | Prevalence | Age, duration of diabetes, ethnicity, glycosylated hemoglobin, hypertension, caloric intake, gender & insulin use. | Multivariable logistic regression |
Insulin Subjects: No Association Non-Insulin taking Subjects: Intake 10th Decile vs 1st Quintile, OR: 3.79 (p<0.02) |
| Tanaka, 2013 | NS | Prospective | 10 | Vitamin E | 978 | Incidence | Age, sex, BMI, HbA1c, duration of diabetes, treatment by insulin, treatment by oral hypoglycemic agents without insulin, systolic blood pressure, LDL Cholesterol, HDL cholesterol, triglycerides, smoking, alcohol, physical activity, total energy intake, proportions of dietary protein, fat, carbohydrate, saturated fatty acids, n-6 PUGA and n-3 PUFA, cholesterol & sodium | Multivariate Cox Regression | Intake Q4 vs Q1, HR: 0.84 (0.51–1,40) |
| Millen, 2004 | NS | Cross Sectional | 8 | Vitamin E | 1353 | Prevalence | Total energy intake, race, duration of diabetes, serum glucose, hypertension, BMI, waist-hip ratio, smoking, alcohol, drinking status, plasma triacylglycerol, plasma cholesterol, hematocrit value, prevalent coronary heart disease, diabetes treatment group & use of oral hypoglycemic agents or use of insulin | Multivariable logistic regression | Intake Q4 vs Q1, OR: 1.4 (0.8–2.3) |
| Sasaki, 2015 | NS | Cross Sectional | 8 | Vitamin E | 379 | Prevalence | Energy Intake | Data not reported | No significant associations with DR (Data not reported) |
| Vitamin D | |||||||||
| Millen, 2016 | NS | Cross-Sectional | 9 | Vitamin D | 1305 | Prevalence | Race, duration of diabetes, HbA1c & hypertension | Multivariate Logistic Regression | Intake Q4 Vs Q1, OR: 1.20 (0.76–1.89) |
| Alcubierre, 2015 | NS | Case-Control | 8 | Vitamin D | Case: 139 Ctrl: 144 |
Prevalence | NIL | Chi-Squared | No significant associations with DR (p = 0.93) |
| Calcium | |||||||||
| Alcubierre, 2015 | NS | Case-Control | 8 | Calcium | Case: 139 Ctrl: 144 |
Prevalence | NIL | Chi-Squared | No significant associations with DR (p = 0.65) |
| Sodium | |||||||||
| Roy, 2010 | Risk (For DME) NS for DR |
Prospective | 10 | Sodium | 469 | Progression & Incidence | Total caloric intake, age, sex, physical exercise, glycated hemoglobin, oleic acid intake, protein intake, carbohydrate intake & hypertension | Multivariable Logistic Regression | No significant associations with DR For DME, Intake Q4 Vs Q1, OR: 1.43 (1.10–1.86) |
| Horikawa, 2014 | NS | Prospective | 10 | Sodium | 978 | Progression& incidence | Age, Sex, BMI, HbA1c, diabtes duration, LDL cholesterol, HDL cholesterol, log-transformed triglycerides, insulin treatment, treatment by lipid-lowering agents, current smoking, alcohol intake, energy intake, sodium intake & physical activity | Multivariable Cox Regression | Intake Q4 Vs Q1, HR: 1.10 (0.75–1.61) |
| Cundiff, 2005 | NS | Prospective | 8 | Sodium | 1412 | Progression | Energy Intake | Spearman Correlation | Sodium in mg/kcal against DR progression rate, r = 0.02 (p = 0.47) |
| Engelen, 2014 | NS | Cross-Sectional | 7 | Sodium | 1880 | Prevalence | Age, sex, BMI, smoking, urinary potassium excretion, antihypertensive medication, total energy intake, physical activity, sat fat intake, protein intake, fibre intake & alcohol intake | Multivariable Logistic Regression | Per 1g/day increase in dietary salt intake, OR: 1.00 (0.96–1.04) |