Consumption of nitrate containing vegetables and the risk of chronic kidney disease: Tehran Lipid and Glucose Study

Figures & data

Table 1. Baseline characteristics of participants according to the tertiles of NCV at baseline.

	Nitrate containing vegetables
	Tertile 1	Tertile 2	Tertile 3	p
Total NCV (g/day)
Range	<203	203-332	≥332
Median	146	261	428
Age (years)	35.3 ± 11.6	38.4 ± 12.1	40.4 ± 11.8	0.04
Male (%)	54.7	45.0	29.3	0.001
Body mass index (kg/m^2)	26.2 ± 0.2	26.4 ± 0.2	27.2 ± 0.2	0.018
Physical activity (Met-h/week)	34.1 ± 2.4	35.8 ± 2.4	40.4 ± 2.4	0.18
Smoking (%)	6.9	10.3	7.8	0.02
Education level (%)
Illiterate	1.2	1.6	2.3	0.13
Diploma	70.7	74.2	72.8	0.12
Academic	28.1	24.2	24.9	0.26
Systolic blood pressure (mm Hg)	108 ± 0.5	107 ± 0.5	106 ± 0.5	0.10
Diastolic blood pressure (mm Hg)	71.7 ± 0.4	71.2 ± 0.4	70.9 ± 0.4	0.44
Serum creatinine (mg/dL)	1.04 ± 0.01	1.05 ± 0.01	1.05 ± 0.01	0.48
eGFR (ml/min/1.73 m2)	83.5 ± 0.8	80.0 ± 0.8	76.6 ± 0.8	0.001
Creatinine clearance rate (ml/min)	96.7 ± 1.2	90.9 ± 1.2	85.8 ± 1.1	0.001
Chronic kidney disease (%)	9.9	15.1	21.7	0.001

Data are mean ± SE unless stated otherwise. Analysis of variance and chi-square test were used for continuous variables for non-continuous variables. NCV: Nitrate-containing vegetables.

Table 2. Mean dietary intakes of participants according to the tertiles of NCV.

	Nitrate containing vegetables
Dietary intake	Tertile 1	Tertile 2	Tertile 3	p
Total NCV (g/day)
Range	<203	203-332	≥332
Median	146	261	428
High-nitrate vegetables	8.8 ± 6.8	13.1 ± 10.6	24.5 ± 18.8	<0.001
Medium nitrate vegetables	4.9 ± 3.8	8.2 ± 4.2	14.9 ± 7.6	<0.001
Low-nitrate vegetables	141 ± 61	246 ± 64	444 ± 195	<0.001
Energy intake (kcal/day)	2389 ± 28	2258 ± 28	2301 ± 28	0.06
Carbohydrate (%)	57.4 ± 0.3	56.8 ± 0.3	58.2 ± 0.3	0.87
Fat (%)	31.4 ± 0.3	32.5 ± 0.2	31.3 ± 0.3	0.22
Protein (%)	13.4 ± 0.1	13.5 ± 0.1	13.8 ± 0.1	0.07
Total fiber (g/day)	35.7 ± 0.7	37.3 ± 0.7	39.4 ± 0.7	0.005
Potassium (mg/day)	3190 ± 38	3694 ± 37	4372 ± 38	<0.001

Data are shown as Mean ± SEM. To compare the dietary intakes of participants across tertiles of NCV general linear model was used with adjustment of sex, age, and energy intake. NCV: Nitrate-containing vegetables.

Table 3. Baseline association (Odds ratio and 95% CI) of chronic kidney disease according to tertiles of NCV categories.

	Nitrate containing vegetables
	Tertile 1	Tertile 2	Tertile 3	p for trend
Total nitrate containing vegetables
Model 1	1	1.31 (0.88–1.97)	1.50 (1.02–2.21)	0.04
Model 2	1	1.26 (0.84–1.91)	1.48 (1.00–2.14)	0.05
Model 3	1	1.18 (0.78–1.79)	1.26 (0.81–1.94)	0.34
High-nitrate containing vegetables
Model 1	1	1.09 (0.77–1.56)	1.43 (1.00–1.99)	0.03
Model 2	1	1.10 (0.77–1.58)	1.44 (1.01–1.97)	0.04
Model 3	1	1.11 (0.76–1.60)	1.48 (1.05–2.13)	0.05
Medium-nitrate containing vegetables
Model 1	1	1.12 (0.70–1.65)	1.15 (0.78–1.67)	0.56
Model 2	1	1.10 (0.72–1.63)	1.12 (0.77–1.65)	0.64
Model 3	1	0.80 (0.53–1.23)	0.85 (0.57–1.26)	0.58
Low-nitrate containing vegetables
Model 1	1	1.24 (0.83–1.86)	1.39 (0.91–2.22)	0.04
Model 2	1	1.24 (0.83–1.87)	1.38 (0.90–2.20)	0.08
Model 3	1	1.15 (0.75–1.75)	1.36 (0.88–2.12)	0.11

Model 1: Adjusted for age and sex, body mass index. Model 2: Additional adjustement for smoking, education, physical ativity, diabetes, and hypertension. Model 3: Additional adjustement for ditary intake of energy, fiber, and potassium. NCV: Nitrate-containing vegetables.

Table 4. The occurrence of chronic kidney disease according to tertiles of NCV categories after 3 years of follow-up.

	Nitrate containing vegetables
	Tertile 1	Tertile 2	Tertile 3	p for trend
Total nitrate containing vegetables
Model 1	1	0.90 (0.46–1.79)	1.12 (0.58–2.08)	0.64
Model 2	1	0.87 (0.44–1.71)	1.03 (0.54–1.96)	0.66
Model 3	1	0.84 (0.42–1.70)	0.93 (0.43–2.02)	0.81
High-nitrate containing vegetables
Model 1	1	0.95 (0.48–1.88)	1.63 (0.89–2.99)	0.09
Model 2	1	0.79 (0.39–1.61)	1.33 (0.71–2.49)	0.11
Model 3	1	0.76 (0.37–1.57)	1.23 (0.66–2.53)	0.23
Medium-nitrate containing vegetables
Model 1	1	0.72 (0.39–1.34)	0.74 (0.40–1.38)	0.51
Model 2	1	0.79 (0.42–1.48)	0.77 (0.41–1.47)	0.67
Model 3	1	0.82 (0.43–1.56)	0.78 (0.41–1.51)	0.31
Low-nitrate containing vegetables
Model 1	1	1.07 (0.55–2.08)	1.15 (0.60–2.19)	0.91
Model 2	1	1.00 (0.51–1.98)	1.07 (0.56–2.06)	0.96
Model 3	1	0.95 (0.44–2.00)	0.96 (0.47–1.95)	0.99

Model 1: Adjusted for age and sex, body mass index. Model 2: Additional adjustement for smoking, education, physical ativity, diabetes, and hypertension. Model 3: Additional adjustement for ditary intake of energy, fiber, and potassium. NCV: Nitrate-containing vegetables.