Dietary fiber intake and its association with diabetic kidney disease in American adults with diabetes: A cross-sectional study

Table 1 Population characteristics by categories of dietary fiber intake

Variables	Total	Dietary fiber intake, g/1000 kcal/d			P value
		T1 (≤ 6.4)	T2 (6.5-10.0)	T3 (≥ 10.1)
N	6032	1978	2000	2054
Age (yr), mean (SD)	61.1 (13.5)	58.3 (14.2)	61.8 (13.3)	63.0 (12.6)	< 0.001
Sex, n (%)					< 0.001
Male	3140 (52.1)	1146 (57.9)	1011 (50.5)	983 (47.9)
Female	2892 (47.9)	832 (42.1)	989 (49.5)	1071 (52.1)
Race/ethnicity, n (%)					< 0.001
Non-Hispanic white	2210 (36.6)	799 (40.4)	789 (39.5)	622 (30.3)
Non-Hispanic black	1481 (24.6)	626 (31.6)	465 (23.2)	390 (19.0)
Mexican American	1126 (18.7)	237 (12.0)	355 (17.8)	534 (26.0)
Others	1215 (20.1)	316 (16.0)	391 (19.6)	508 (24.7)
Educational level (yr), n (%)					< 0.001
< 9	1067 (17.7)	265 (13.4)	288 (14.4)	514 (25.0)
9-12	2406 (39.9)	863 (43.6)	801 (40.1)	742 (36.1)
> 12	2559 (42.4)	850 (43.0)	911 (45.6)	798 (38.9)
Marital status, n (%)					0.013
Married or living with a partner	3649 (60.5)	1164 (58.8)	1190 (59.5)	1295 (63.0)
Living alone	2383 (39.5)	814 (41.2)	810 (40.5)	759 (37.0)
Family income, n (%)					0.340
Low	2151 (35.7)	706 (35.7)	682 (34.1)	763 (37.1)
Medium	2453 (40.7)	795 (40.2)	836 (41.8)	822 (40.0)
High	1428 (23.7)	477 (24.1)	482 (24.1)	469 (22.8)
BMI (kg/m2), mean (SD)	32.3 (7.4)	33.1 (7.9)	32.5 (7.3)	31.5 (6.8)	< 0.001
Smoking status, n (%)					< 0.001
Never	3029 (50.2)	893 (45.1)	952 (47.6)	1184 (57.6)
Former	2032 (33.7)	601 (30.4)	749 (37.5)	682 (33.2)
Current	971 (16.1)	484 (24.5)	299 (14.9)	188 (9.2)
CHD, n (%)	607 (10.1)	192 (9.7)	206 (10.3)	209 (10.2)	0.807
Hypertension, n (%)	3942 (65.4)	1281 (64.8)	1316 (65.8)	1345 (65.5)	0.780
Calorie consumption (1000 kcal/d), mean (SD)	1.9 (0.9)	2.1 (1.0)	1.9 (0.9)	1.7 (0.7)	< 0.001
Protein consumption (g/1000 kcal/d), mean (SD)	41.2 (13.3)	40.4 (14.7)	40.9 (12.6)	42.2 (12.5)	< 0.001
Dietary fiber (g/1000 kcal/d), median (IQR)	8.2 (5.7, 11.4)	4.7 (3.7, 5.7)	8.1 (7.3, 9.0)	13.1 (11.3, 16.1)	< 0.001
Dietary supplements taken, n (%)	3300 (54.7)	981 (49.6)	1105 (55.2)	1214 (59.1)	< 0.001
Family history of diabetes, n (%)	3840 (63.7)	1276 (64.5)	1265 (63.2)	1299 (63.2)	0.632
Duration of diabetes (yr), median (IQR)	8.0 (3.0, 15.0)	8.0 (3.0, 15.0)	9.0 (3.0, 15.0)	9.0 (4.0, 16.0)	< 0.001
Insulin use, n (%)	1160 (19.2)	384 (19.4)	378 (18.9)	398 (19.4)	0.900
Glucose-lowering drugs use, n (%)	4092 (67.8)	1237 (62.5)	1393 (69.7)	1462 (71.2)	< 0.001
HbA1c (%), mean (SD)	7.2 (1.7)	7.3 (1.9)	7.2 (1.7)	7.2 (1.7)	0.404
FPG (mmol/L), mean (SD)	8.6 (3.4)	8.7 (3.6)	8.6 (3.2)	8.5 (3.3)	0.088
FINS (μU/mL), median (IQR)	14.1 (8.5, 23.9)	15.3 (8.9, 26.1)	14.3 (8.5, 23.9)	13.3 (8.2, 21.9)	< 0.001
HOMA-IR, median (IQR)	5.1 (2.8, 8.9)	5.4 (3.0, 10.1)	5.1 (2.9, 8.9)	4.8 (2.7, 8.1)	< 0.001
TC (mmol/L), mean (SD)	4.8 (1.2)	4.9 (1.3)	4.8 (1.2)	4.8 (1.2)	< 0.001
ALT (U/L), median (IQR)	22.0 (16.0, 30.0)	22.0 (16.0, 31.0)	21.0 (16.0, 29.0)	22.0 (17.0, 29.0)	0.191
AST (U/L), median (IQR)	23.0 (19.0, 28.0)	23.0 (19.0, 28.0)	23.0 (19.0, 28.0)	23.0 (19.0, 28.0)	0.231
SUA (µmol/L), mean (SD)	344.4 (94.4)	352.5 (99.4)	343.4 (92.2)	337.6 (90.9)	< 0.001
BUN (mmol/L), median (IQR)	5.0 (3.9, 6.8)	5.0 (3.9, 6.4)	5.4 (3.9, 6.8)	5.4 (3.9, 6.8)	< 0.001
sCr (µmol/L), median (IQR)	79.6 (63.6, 97.2)	80.4 (67.2, 99.0)	79.6 (64.5, 97.2)	76.0 (61.9, 95.5)	< 0.001
ACR (mg/g), median (IQR)	12.9 (6.8, 40.6)	12.5 (6.7, 43.5)	13.1 (6.8, 43.8)	12.9 (6.8, 35.9)	0.487
eGFR (ml/min/1.73 m2), mean (SD)	83.3 (24.3)	83.9 (25.0)	82.4 (24.1)	83.7 (23.9)	0.103
Hemoglobin (g/dL), mean (SD)	13.9 (1.6)	14.0 (1.7)	13.8 (1.6)	13.7 (1.6)	< 0.001
Systolic blood pressure (mmHg), mean (SD)	132.0 (20.1)	131.4 (19.8)	132.0 (20.1)	132.7 (20.4)	0.124
Diastolic blood pressure (mmHg), mean (SD)	69.3 (13.5)	70.9 (13.5)	69.3 (13.5)	68.0 (13.2)	< 0.001
DKD, n (%)	2316 (38.4)	765 (38.7)	803 (40.2)	748 (36.4)	0.048

ACR: Albumin creatinine ratio; ALT: Alanine aminotransferase; AST: Aspartate aminotransferase; BMI: Body mass index; BUN: Blood urea nitrogen; CHD: Coronary heart disease; DKD: Diabetic kidney disease; eGFR: Estimated glomerular filtration rate; FINS: Fasting plasma insulin; FPG: Fasting plasma glucose; HbA1c: Glycosylated hemoglobin; HOMA-IR: Homeostasis model assessment of insulin resistance; sCr: Serum creatinine; SUA: Serum uric acid; TC: Total cholesterol.

Table 2 Association of covariates and diabetic kidney disease risk

Variables	OR (95%CI)	P value
Age (yr)	1.04 (1.04-1.05)	< 0.001
Sex, n (%)
Male	1 (reference)
Female	0.93 (0.84-1.03)	0.178
Race/ethnicity, n (%)
Non-Hispanic white	1 (reference)
Non-Hispanic black	1.11 (0.97-1.27)	0.115
Mexican American	0.80 (0.69-0.93)	0.003
Others	0.72 (0.62-0.83)	< 0.001
Educational level (yr), n (%)
< 9	1 (reference)
9-12	0.97 (0.84-1.12)	0.651
> 12	0.73 (0.63-0.85)	< 0.001
Marital status, n (%)
Married or living with a partner	1 (reference)
Living alone	1.45 (1.31-1.61)	< 0.001
Family income, n (%)
Low	1 (reference)
Medium	0.96 (0.85-1.08)	0.466
High	0.62 (0.54-0.72)	< 0.001
BMI (kg/m2)	1.00 (0.99-1.01)	0.605
Smoking status, n (%)
Never	1 (reference)
Former	1.34 (1.20-1.51)	< 0.001
Current	1.08 (0.93-1.25)	0.328
CHD, n (%)
No	1 (reference)
Yes	2.16 (1.82-2.56)	< 0.001
Hypertension, n (%)
No	1 (reference)
Yes	2.24 (2.00-2.52)	< 0.001
Calorie consumption (1000 kcal/d)	0.83 (0.78-0.89)	< 0.001
Protein consumption (g/1000 kcal/d)	1.00 (1.00-1.00)	0.965
Dietary fiber consumption (g/1000 kcal/d)	0.98 (0.97-0.99)	< 0.001
Dietary supplements taken, n (%)
No	1 (reference)
Yes	1.06 (0.95-1.17)	0.313
Family history of diabetes, n (%)
No	1 (reference)
Yes	1.04 (0.93-1.16)	0.487
Duration of diabetes (yr)	1.04 (1.03-1.04)	< 0.001
Insulin use, n (%)
No	1 (reference)
Yes	2.32 (2.03-2.64)	< 0.001
Glucose-lowering drugs use, n (%)
No	1 (reference)
Yes	1.03 (0.92-1.15)	0.576
HbA1c (%)	1.15 (1.11-1.18)	< 0.001
FPG (mmol/L)	1.06 (1.04-1.07)	< 0.001
FINS (μU/mL)	1.00 (1.00-1.00)	0.132
HOMA-IR	1.01 (1.00-1.01)	< 0.001
TC (mmol/L)	0.95 (0.91-0.99)	0.012
ALT (U/L)	1.00 (0.99-1.00)	0.019
AST (U/L)	1.00 (1.00-1.00)	0.816
SUA (µmol/L)	1.00 (1.00-1.01)	< 0.001
Hemoglobin (g/dL)	0.81 (0.79-0.84)	< 0.001

ALT: Alanine aminotransferase; AST: Aspartate aminotransferase; BMI: Body mass index; CHD: Coronary heart disease; FINS: Fasting plasma insulin; FPG: Fasting plasma glucose; HbA1c: Glycosylated hemoglobin; HOMA-IR: Homeostasis model assessment of insulin resistance; SUA: Serum uric acid; TC: Total cholesterol.

Table 3 Association between dietary fiber and diabetic kidney disease

Variable	Total, n	Events, n (%)	Model 1		Model 2		Model 3
			OR (95%CI)	P value	OR (95%CI)	P Value	OR (95%CI)	P value
DF intake (g/1000 kcal/d)	6032	2316 (38.4)	0.97 (0.96-0.98)	< 0.001	0.97 (0.96-0.98)	< 0.001	0.97 (0.96-0.98)	< 0.001
Tertile groups (g/1000 kcal/d)
T1 (≤ 6.4)	1978	765 (38.7)	1 (reference)		1 (reference)		1 (reference)
T2 (6.5-10.0)	2000	803 (40.2)	0.96 (0.84-1.10)	0.544	0.97 (0.84-1.11)	0.642	0.97 (0.84-1.12)	0.674
T3 (≥ 10.1)	2054	748 (36.4)	0.78 (0.68-0.90)	0.001	0.79 (0.68-0.91)	0.001	0.79 (0.68-0.92)	0.002
P for trend				< 0.001		0.001		0.002

Model 1 was adjusted for age, sex, race/ethnicity, educational level, marital status, and family income. Model 2 was adjusted for all covariates in Model 1 in addition to smoking status, coronary heart disease, hypertension, calorie consumption, and protein consumption. Model 3 was adjusted for all covariates in Model 2 plus the duration of diabetes, insulin use, and glycosylated hemoglobin, homeostasis model assessment of insulin resistance, total cholesterol, alanine aminotransferase, serum uric acid, hemoglobin levels. DF: Dietary fiber.