| ARTICLE INFO | ABSTRACT | |
| ORIGINAL ARTICLE | Background: The present study aimed to investigate the association between dietary acid load and depression among Iranian women. Methods: This case–control study was conducted on 110 women with depression and 220 healthy controls recruited from two psychiatric clinics in Tehran, Iran. Dietary intake over the previous 12 months was assessed using a validated semi-quantitative food frequency questionnaire (FFQ) consisting of 168 items. Dietary acid load was calculated using two established indices: Potential Renal Acid Load (PRAL) and Net Endogenous Acid Production (NEAP). The association between dietary acid load and depression was evaluated using multivariate logistic regression models in crude and adjusted analyses. The adjusted model was controlled for potential confounders, including energy, physical activity, history of depression, smoking status, periods of unemployment, occupational status, and body mass index (BMI). Results: Participants in the highest quartile of PRAL and NEAP had significantly higher odds of depression compared to those in the lowest quartile. In the fully adjusted model, the odds ratio (OR) for depression was 3.52 (95% CI: 1.64–7.54; P for trend <0.001) for PRAL and 4.07 (95% CI: 1.86–8.89; P for trend <0.001) for NEAP. Conclusion: Higher dietary acid load, as measured by PRAL and NEAP, was associated with increased odds of depression in women. However, due to the case–control design, causal inferences cannot be established. Further prospective studies are warranted to confirm these findings. | |
| Article history: Received: 2 Jul 2025 Revised:7 Jun 2026 Accepted: 21 Jun 2026 |
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| *Corresponding author: hoseinzade.mahdie@gmail.com Department of Nutrition, School of Public Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. Postal code: 8915173160 Tel: +98 35 38203232 |
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| Keywords: Depression; Depressive disorder; Acid-base equilibrium; Dietary acid load; Potential renal acid load; Net endogenous acid production. |
| Table 1. Characteristics of study participants according to the patients and controls and quartiles of the PRAL score. | ||||||||
| Variables | Health status | PRAL quartiles | ||||||
| Control | Case | P-valuea | Q1 | Q2 | Q3 | Q4 | P-valueb | |
| Body mass index (kg/m2) | 26.43±5.51 | 26.45±5.13 | 0.98 | 27.25±5.72 | 27.14±6.02 | 25.69±4.71 | 25.63±4.79 | 0.08 |
| Physical activity (MET-h/week) | 38.58±4.93 | 36.94±5.45 | 0.006 | 38.75±4.38 | 37.72±5.57 | 38.81±6.02 | 38.88±4.28 | 0.05 |
| Years of education | 12.20±4.56 | 11.24±4.27 | 0.070 | 12.16±4.32 | 11.37±4.61 | 11.95±4.68 | 12.07±4.34 | 0.67 |
| History of depression | 22(10) | 33(30) | <0.001 | 22(10) | 33(30) | 22(10) | 33(30) | <0.001 |
| Marital status | ||||||||
| Single | 67(30.3) | 32(29.1) | 0.24 | 21(26.5) | 20(24.1) | 26(31.3) | 32(36.6) | 0.45 |
| Married | 143(64.7) | 67(60.9) | 56(68.3) | 58(69.9) | 51(61.4) | 45(54.2) | ||
| Divorced or widowed | 11(5) | 11(10) | 5(6.1) | 5(6) | 6(7.2) | 6(7.2) | ||
| Smoking status | ||||||||
| Non smoker | 209(94.6) | 98(89.9) | 0.11 |
80(76.6) | 79(95.2) | 75(90.4) | 73(89) | <0.001 |
| Smoker | 12(5.4) | 11(10.1) | 2(2.4) | 4(4.8) | 8(9.6) | 9(11) | ||
| Periods of unemployment | ||||||||
| House worker | 98(44.3) | 65(59.1) | 0.007 | 44(53.7) | 46(55.4 | 39(47) | 34(41) | 0.23 |
| ≤6 months in the last 5 years | 104(47.1) | 32(29.1) | 6(7.3) | 9(10.8) | 5(6) | 12(14.5) | ||
| More than 6 months in the last 5 years | 19(8.6) | 13(11.8) | 32(39) | 28(33.7) | 39(47) | 37(44.6) | ||
| Job | ||||||||
| Employee | 42(19.4) | 12(11.3) | 0.014 | 18(22) | 13(16.3) | 11(13.6) | 12(15.2) | 0.10 |
| Self-employed | 32(14.8) | 16(15.1) | 8(9.8) | 12(15) | 11(13.6) | 17(21.5) | ||
| Students | 38(17.6) | 9(8.5) | 7(8.5) | 8(10) | 17(21) | 15(19) | ||
| House worker & retired | 104(48.1) | 69(65.1) | 49(59.8) | 47(58.8) | 42(51.9) | 35(44.3) | ||
| ::::as char::::acteristics are very similar according to the NEAP score, baseline characteristics are only presented according to the PRAL score quartiles; a: Obtained from Chi-squared test and independent t-test for categorical and continuous variables, respectively; b: Chi-squared test for qualitative variables and ANOVA test for quantitative variables. Continuous and categorical data are presented as mean ± SD and frequency (percentage), respectively. | ||||||||
| Table 2. Dietary daily intakes (mean±SD) of participants according to the PRAL quartiles. | |||||
| P-valuea | Q4(N=83) | Q3(N=83) | Q2(N=83) | Q1(N=82) | Variables |
| <0.001 | 19.95 ± 25.29 | -7.49 ± 4.60 | -19.45 ± 3.79 | -49.73 ± 23.53 | PRAL (mEq/d) |
| <0.001 | 51.20 ± 10.34 | 36.58 ± 3.44 | 29.70 ± 3.89 | 22.30 ± 5.15 | NEAP (mEq/d) |
| <0.001 | 3060.6 ± 1216.5 | 2530 ± 953.6 | 2411.8 ± 843.5 | 2872.6 ± 1209.5 | Energy intake(kcal) |
| 0.003 | 58.85 ± 0.09 | 61.42 ± 0.07 | 61.57 ± 0.06 | 63.42 ± 0.08 | Carbohydrate(g) |
| 0.01 | 16.13± 0.09 | 14.35± 0.02 | 13.97 ± 0.02 | 13.70 ± 0.02 | Protein(g) |
| 0.36 | 27.78± 0.09 | 28.08 ± 0.07 | 26.87 ± 0.06 | 25.86 ± 0.07 | Fat(g) |
| <0.001 | 26.02 ± 21.83 | 23.87 ± 8.14 | 24.98 ± 7.86 | 38.42 ± 14.72 | Fibre (g/d) |
| <0.001 | 327.09 ± 283.77 | 247.23 ± 116.19 | 258.84 ± 140.79 | 281.22 ± 171.87 | Cholesterol (mg/d) |
| 0.009 | 27.91 ± 17.57 | 22.04 ± 12.27 | 21.53 ± 8.97 | 24.48 ± 13.42 | SFA (mg/d) |
| 0.031 | 29.56 ± 16.43 | 23.97 ± 13.51 | 23.49 ± 12.08 | 26.46 ± 16.19 | MUFA (mg/d) |
| 0.024 | 24.64 ± 15.54 | 18.97 ± 11.24 | 18.81 ± 10.84 | 21.97 ± 17.89 | PUFA (mg/d) |
| <0.001 | 16.10 ± 8.36 | 11.80 ± 4.23 | 11.24 ± 4.26 | 13.22 ± 5.39 | Zinc (mg/d) |
| <0.001 | 2050.12 ± 1008.65 | 1559.73 ± 549.76 | 1498.32 ± 561.61 | 1774.75 ± 734.91 | Phosphorus (mg/d) |
| <0.001 | 4084.45 ± 1608.45 | 4041.48 ± 1349.23 | 4374.48 ± 1343.74 | 6317.21 ± 2521.29 | Potassium (mg/d) |
| 0.002 | 1156.88 ± 483.75 | 1054.02 ± 435.91 | 1051.15 ± 390.96 | 1286.86 ± 463.54 | Calcium (mg/d) |
| <0.001 | 515.09 ± 364.49 | 403.56 ± 143.23 | 397.07 ± 137.06 | 508.32 ± 218.18 | Magnesium (mg/d) |
| 0.13 | 4444.20 ± 2542.79 | 3725.79 ± 2141.43 | 3801.80 ± 2013.87 | 3927.35 ± 1909.09 | Sodium (mg/d) |
| <0.001 | 1349.35 ± 767.60 | 1536.64 ± 911.56 | 1523.93 ± 771.45 | 2758.91± 2105.37 | Vitamin A (RAE/d) |
| <0.001 | 146.90 ± 78.15 | 188.94 ± 91.10 | 218.65 ± 76.35 | 388.59± 196.43 | Vitamin C (mg/d) |
| <0.001 | 2.42 ± 1.20 | 2.15 ± 0.75 | 2.16± 0.76 | 3.17 ± 2.02 | Vitamin B6 (mg/d) |
| <0.001 | 654.40 ± 307.98 | 559.02 ± 222.31 | 549.04 ± 204.30 | 710.06 ± 290.59 | Folate (μg/d) |
| 0.37 | 5.26 ± 5.29 | 3.80 ± 2.47 | 3.91 ± 3.18 | 8.57 ± 39.17 | Vitamin B12 (mg/d) |
| Food groups (g/1000 kcal) | |||||
| <0.001 | 362.74 ± 209.21 | 478.13 ± 258.63 | 520.66 ± 202.64 | 944.69 ± 448.73 | Fruits |
| <0.001 | 231.08 ± 128.01 | 313.59 ± 152.43 | 368.82 ± 166.08 | 537.38 ± 259.33 | Vegetables |
| 0.008 | 39.72 ± 65.03 | 25.17 ± 17.88 | 19.79 ± 17.54 | 24.66 ± 72.22 | Red meat |
| 0.23 | 10.56 ± 17.10 | 10.13 ± 16.36 | 6.65 ± 9.70 | 8.45 ± 8.68 | Fish |
| 0.08 | 405.43 ± 261.12 | 406.67 ± 297.79 | 408.29 ± 226.20 | 492.98 ± 249.22 | Dairy |
| 0.15 | 29.78 ± 25.53a | 65.94 ± 52.73 | 67.73 ± 49.17 | 81.17 ± 57.78 | Legumes and nuts |
| 0.13 | 102.34 ± 154.29 | 78.86 ± 107.67 | 64.05 ± 70.97 | 70.11 ± 97.49 | Whole grains |
| <0.001 | 608.40 ± 322.87 | 446.84 ± 244.37 | 380.67 ± 222.67 | 362.15 ± 28.76 | Refined grains |
| 0.65 | 19.35 ± 15.72 | 22.36 ± 20.79 | 23.32 ± 19.02 | 22.45 ± 66.25b | Sugars |
| 0.28 | 62.16 ± 86.94 | 56.41 ± 120.89 | 66.46 ± 129.02 | 37.47 ± 61.09 | Sugar-sweetened beverages (ml/day) |
| 0.28 | 656.59 ± 482.61 | 730.91 ± 598.87 | 887.20 ± 498 | 859.19 ± 510.70 | Tea and coffee |
| PRAL: Potential renal acid load; NEAP: net endogenous acid production; SFA: Saturated fatty acid; MUFA: Monounsaturated fatty acid; PUFA: Polyunsaturated fatty acid; ::::as char::::acteristics are very similar according to the NEAP score, baseline characteristics are only presented according to the PRAL score quartiles; a: ANOVA test was used. | |||||
| Table 3. The OR (95%CI) of depression across quartiles of PRAL and NEAP. | ||||
| Dietary acid load score | Cases (N) | Crude | Model I | Model II |
| PRAL (mEq/day) | ||||
| <-27.2 | 27 | 1 | 1 | 1 |
| -27.2 to -13.6 | 20 | 1.21 (0.58-2.52) | 1.31 (0.62-2.77) | 0.95 (0.42-2.14) |
| -13.5 to 1.61 | 30 | 2.16 (1.07-4.34) | 2.30 (1.13-4.67) | 2.59 (1.19-5.60) |
| ≥2.21 | 43 | 4.11 (2.07-8.16) | 4.03 (2.02-8.03) | 3.52 (1.64-7.54) |
| P-trend | <0.001 | <0.001 | <0.001 | |
| NEAP (mEq/day) | ||||
| <27.2 | 16 | 1 | 1 | 1 |
| 27.2 to 27.9 | 20 | 1.31 (0.62-2.75) | 1.33 (0.63-2.81) | 1.14 (0.51-2.55) |
| 34.4 to 37.7 | 31 | 2.45 (1.21-4.97) | 2.38 (1.17-4.84) | 2.12 (0.96-4.66) |
| ≥42.9 | 43 | 4.43 (2.21-8.88) | 4.23 (2.10-8.52) | 4.07 (1.86-8.89) |
| P-trend | <0.001 | <0.001 | <0.001 | |
| PRAL: Potential renal acid load; NEAP: OR: Odds ratio; NEAP: Net endogenous acid production; Model I: Adjusted for energy intake; Model II: Model I + adjusted for physical activity, history of depression, smoking status, periods of unemployment, job and BMI; Logistic regression was used. | ||||
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