Clinical variables
All 490 participants to the study had BMI ≥ 25 kg/m
2. Forty-five participants were stone formers (9.2%), whereas 445 had no history of kidney stones. Among non-stone former 30 received therapy for dyslipidemia, 99 for hypertension and 9 for diabetes. Among stone former 7 received therapy for dyslipidemia, 16 for hypertension and 3 for diabetes. Stone formers were older than non-stone formers and had higher serum concentrations of triglycerides. A slight increase of fasting glucose and AST were also found (Table
1). Considering the distribution of these alterations (Table
2), subjects with high serum concentrations of triglycerides, fasting glucose and AST were more frequently found in stone formers than stone-free subjects.
Table 1
Serum variables in stone formers and non-stone formers
N (M/F) | 45 (18/27) | 445 (137/308) |
Age (years) | 53 ± 10.9* | 48 ± 10.2 |
Body weight (kg) | 86.6 ± 15.01 | 86 ±16.57 |
BMI (kg/m2) | 31.8 ± 5.12 | 31.5 ± 4.98 |
Total serum cholesterol (mg/dl) | 211 ± 39.5 | 214 ± 38.4 |
Serum HDL (mg/dl) | 53 ± 14.5 | 56 ± 14.4 |
Serum LDL (mg/dl) | 133 ±39.3 | 138 ± 33.4 |
Serum triglycerides (mg/dl) | 146 ± 110.5¶ | 110 ± 67.1 |
Fasting serum glucose (mg/dl) | 102 ± 21.5† | 96 ± 14.2 |
Serum uric acid (mg/dl) | 5.2 ± 1.30 | 5.1 ± 1.39 |
Serum creatinine (mg/dl) | 0.79 ± 0.186 | 0.77 ± 0.16 |
Serum TSH (ng/ml) | 2.35 ± 1.268 | 2.23 ±1.49 |
Serum γGT (U/I) | 39 ± 36.1 | 30 ± 32.7 |
Serum AST (U/I) | 25 ± 12.6 † | 21 ± 8.1 |
Serum ALT (U/I) | 30 ± 19.6 | 26 ± 15.9 |
Waist circumference (cm) | 105 ± 12.0 | 101 ± 12.7 |
Arm circumference (cm) | 33 ± 4.4 | 34 ± 4.1 |
Wrist circumference (cm) | 17 ± 1.4 | 17 ± 1.8 |
Subcutaneous abdominal tissue (cm) | 3.2 ± 1.19 | 3.3 ± 1.12 |
Visceral abdominal tissue (cm) | 6.8 ± 2.52 | 6.2 ± 2.58 |
Systolic blood pressure (mmHg) | 132 ± 14.4 | 129 ± 13.7 |
Diastolic blood pressure (mmHg) | 81 ± 9.3 | 80 ± 9.1 |
MedDiet score | 7 ± 1.55 | 6.75 ± 1.63 |
Table 2
Frequency of subjects with alterated values of the explored variables in subjects with high BMI distinguished in stone formers and non-stone formers
Subject count | 45 | 445 |
Sex (M/F) | 18/27 | 137/308 |
BMI > 30 kg/m2
| 24 (53.3) | 233 (52.4) |
Total serum cholesterol >200 mg/dl | 27 (60) | 276 (62.1) |
Serum HDL <50 mg/dl in F or <40 mg/dl in M | 31 (68.9) | 339 (76.3) |
Serum triglycerides >150 mg/dl | 17 (37.7)‡ | 80 (17.9) |
Fasting serum glucose >100 mg/dl | 22 (48.8)* | 121 (27.2) |
Serum gGT > 24 U/I in F or >30 U/I in M | 19 (45.2) | 148 (36.5) |
Serum AST >30 U/I in F or >40 U/I in M | 7 (15.5)† | 28 (6.3) |
Serum ALT >35 U/I in F or >40 U/I in M | 11 (24.4) | 71 (16) |
Waist circumference >80 cm in F or >92 cm in M | 43 (95.6) | 426 (95.7) |
Subcutaneous abdominal tissue >4 cm | 10 (22.2) | 99 (22.9) |
Visceral abdominal tissue >4 cm | 40 (88.9) | 346 (77.8) |
Systolic blood pressure >130 mmHg | 16 (35.5) | 134 (30.1) |
Diastolic blood pressure >85 mmHg | 13 (28.9) | 84 (18.9) |
MedDiet score ≥ 9 | 8 (17.8) | 67 (15.1) |
Two hundred and fifty-seven subjects were obese (BMI ≥ 30 kg/m2): 9.3% of them were stone formers (n = 24). Two hundred and thirty-three subjects were overweight: similar to obese subjects, 9.0% of them were stone formers (n = 21). In both obese and overweight subjects, stone formers were older than non-stone formers.
Multinomial logistic regression confirmed that kidney stone production was associated with high fasting glucose (OR = 2.6, 95% CI 1.2-5.2, P = 0.011), AST (OR = 4.3, 95% CI 1.1-16.7, P = 0.033) and triglycerides (OR = 2.7, 95% CI 1.3-5.7, P = 0.01). A second multinomial logistic regression model also adjusted for VAT and SAT was used to investigate the association between kidney stone and abdominal obesity, confirming that kidney stone production was associated with high fasting glucose and triglycerides (data not shown).
The number of stone formers was higher in diabetic than non-diabetes patients (n = 6 [22.2% of diabetic patients] vs n = 39 [8.4% of non-diabetic patients], chi square = 5.8, DF = 1, p = 0.016). Conversely, stone disease was not associated with arterial hypertension (n = 15 [12.6% of hypertensive patients vs n = 30 [8.1% of normotensive patients]).
The analysis of non-diabetic subjects (n = 463) confirmed that stone formers were older than stone-free subjects (51 ± 10.3 vs 48 ± 10 yrs, p = 0.037). The number of patients with high fasting serum glucose (n = 16 [41% of stone formers] vs n = 97 [23.7% of stone free patients]; p = 0.019), AST (n = 6 [15.3%] vs n = 25 [5.9%]; p = 0.015) and tryglicerides (n = 16 [41%] vs n = 75 [17.7%]; p = 0.001) was higher in non-diabetic stone formers than stone-free subjects.
Among normotensive subjects (PA ≤ 130/80 mmHg, n = 371), stone formers were older than stone-free subjects (52 ± 11.2 [n = 30] vs 46 ± 9.7 [n = 341] yrs, p = 0.001). Subjects with high fasting serum glucose (n = 16 [53.3%], vs n = 76 [22.2%]; p = 0.001), AST (n = 6 [20%] vs n = 22 [6,5%]; p = 0.007) and tryglicerides (n = 13 [43.3%] vs n = 60 [17.6%]; p = 0.001) were more frequent in stone formers than stone free subjects.
The analysis of normotensive and non-diabetic subjects (n = 357) again showed that stone formers more frequently had high fasting serum glucose (n = 13 [48.1%], vs n = 66 [20%]; p = 0.001), AST (n = 5 [18.5%] vs n = 19 [5.8%]; p = 0.01) and tryglicerides (n = 12 [44.4%] vs n = 56 [17%]; p = 0.001).
Mediterranean diet
Mediterranean diet adherence was evaluated with a specific questionnaire. In our population n = 75 subjects were adherent to Mediterranean diet (Medscore ≥9) with a mean score of 6.8 ± 1.62. MedDiet score was not different in stone formers and subjects with no stone. However, the analysis of food frequency in Medscore questionnaire showed that stone formers had lower consumption frequency of olive oil and nuts, but higher consumption of wine compared with stone-free subjects (Table
3). Multinomial regression analysis observed that decreased risk of stone was associated with olive oil consumption whereas it increased in association with wine consumption (Table
4).
Table 3
Analysis of food frequency in Medscore questionnaire in stone formers and non-stone formers
N (M/F) | 45 | 445 |
Use of olive oil as main culinary lipid | 45 (100) | 443 (97.3) |
Olive oil ≥ 4 tablespoons | 11 (24.4) | 188 (42.5)* |
Vegetables ≥ 2 servings/day | 28 (62.2) | 252 (56.6) |
Fruits ≥3 servings/day | 8 (17.8) | 75 (16.9) |
Red/processed meats <1/day | 34 (75.5) | 293 (65.8) |
Butter, cream, margarine <1/day | 45 (100) | 431 (96.8) |
Soda drinks <1/day | 38 (84.4) | 377 (84.7) |
Wine glasses ≥7/week | 27 (60) | 138 (31)† |
Legumes ≥3/week | 2 (4.4) | 17 (3.8) |
Fish/seafoods ≥3/week | 2 (4.4) | 30 (6.7) |
Commercial sweets and confectionery <3/week | 30 (66.7) | 236 (53) |
Free nuts ≥1/week | 0 (0) | 51 (11.5)* |
Poultry more than red meats | 29 (64.4) | 259 (58.2) |
Use of sofrito sauce ≥2/week | 23 (51.1) | 245 (55.1) |
Table 4
Multinomial regression analysis of olive oil and wine consumption in stone formers and non-stone formers
Olive oil | | | | |
Stone formers | 6 (13.3) | 28 (62.2) | 11 (24.4) | |
Non-stone formers | 33 (7.5) | 221 (50) | 188 (42.6) | |
OR | 1 | 0.7 | 0.32 | |
95% CI | | 0.3-1.8 | 0.1–0.9 | |
p | | 0.46 | 0.036 | |
| Score 1 | Score 2 | Score 3 | Score 4 |
| No consumption | 1–2 glasses/week | 3–7 glasses/week | >7 glasses/week |
Wine | | | | |
Stone formers | 13 (30.2) | 4 (9.3) | 16 (37.2) | 10 (23.3) |
Non-stone formers | 189 (42.9) | 115 (26.1) | 83 (18.8) | 54 (12.2) |
OR | 1 | 0.51 | 2.8 | 2.7 |
95% CI | | 0.2–1.6 | 1.3–6.1 | 1.1–6.5 |
p | | 0.24 | 0.009 | 0.027 |
Considering only subjects without diabetes (n = 460), it was confirmed that stone formers consumed lower olive oil and nuts and greater quantity of wine compared with stone-free subjects: 10 (25.6%) stone formers vs 176 (41.5%) stone-free subjects consumed ≥4 spoons of olive oil in a day (p = 0.05); 23 (59%) stone formers and 130 (30.7%) stone-free subjects drank ≥7 glasses in a week (p = 0.001); no stone formers, but 49 (11.6%) stone free subjects ate nuts (p = 0.028).