Associations of Dietary Salt and Its Sources with Hemoglobin A1c in Patients with Type 2 Diabetes Not Taking Anti-Diabetic Medications: Analysis Based on 6-Month Intervention with a Moderate Low-Carbohydrate Diet

Figures & data

Table 1 Hemoglobin A1c and Cardiovascular Risk Factors at Baseline and Their Changes During 6 Months by Sex

	Men (n = 138)				Women (n = 107)
	Baseline	6 Months	Changes	P	Baseline	6 Months	Changes	P
Age	60.0 ± 11.0				61.8 ± 10.4
Duration of diabetes (month)	26.9 ± 52.8				23.2 ± 51.3
Body mass index (kg/m^2)	25.5 ± 3.5	24.7 ± 3.4	−0.8 ± 1.2	< 0.001	25.1 ± 4.1	24.3 ± 4.0	−0.8 ± 1.3	< 0.001
Hemoglobin A1c (%)	8.3 ± 1.7	6.7 ± 0.7	−1.5 ± 1.6	< 0.001	7.8 ± 1.5	6.9 ± 0.7	−0.9 ± 1.3	< 0.001
Hemoglobin A1c (mmol/mol)	66.7 ± 18.3	50.0 ± 8.0	−16.7 ± 17.2	< 0.001	61.8 ± 16.9	51.6 ± 7.6	−10.2 ± 14.0	< 0.001
Plasma glucose levels (mmol/l)	8.16 ± 2.05	6.99 ± 1.28	−1.17 ± 1.72	< 0.001	7.66 ± 2.44	6.77 ± 1.39	−0.94 ± 1.72	< 0.001
Fasting insulin levels (pmol/l)	52.4 ± 32.4	45.7 ± 31.2	−6.7 ± 23.5	< 0.001	58.4 ± 42.3	53.3 ± 43.7	−5.1 ± 29.0	0.014
LDL-cholesterol (mmol/l)	3.42 ± 0.91	3.24 ± 0.78	−0.18 ± 0.96	0.030*	3.47 ± 0.80	3.18 ± 0.75	−0.28 ± 0.85	0.001
HDL-cholesterol (mmol/l)	1.30 ± 0.28	1.42 ± 0.31	0.13 ± 0.23	< 0.001	1.53 ± 0.39	1.63 ± 0.36	0.10 ± 0.23	< 0.001
Triglycerides (mmol/l)	1.83 ± 2.44	1.39 ± 1.06	−0.44 ± 1.89	< 0.001	1.49 ± 0.91	1.26 ± 0.76	−0.23 ± 0.63	0.001
Systolic blood pressure (mmHg)	140 ± 20	132 ± 13	−8 ± 18	< 0.001	138 ± 17	127 ± 10	−10 ± 17	< 0.001
Diastolic blood pressure (mmHg)	84 ± 13	81 ± 11	−3 ± 14	0.001	79 ± 11	74 ± 8	−5 ± 11	< 0.001*
Anti-hypertensive medications		46%				45%
Lipid-lowering medications		22%				36%

Notes: Change was defined as the level after 6 months minus the level at baseline. *Paired t-test was used, and Wilcoxon test was used for the others.

Abbreviations: LDL, low-density lipoprotein; HDL, high-density lipoprotein.

Table 2 Changes in Macronutrients, Total Salt and Its Sources at Baseline and Their Changes During 6 Months by Sex

	Men (n=138)				Women (n=107)
	Baseline	6 Months	Changes	P	Baseline	6 Months	Changes	P
Total energy (kcal)	2285 ± 753	1846 ± 521	−439 ± 660	< 0.001	1745 ± 431	1553 ± 342	−192 ± 438	< 0.001
Carbohydrate (g/day)	285 ± 94	170 ± 58	−115 ± 104	< 0.001	230 ± 67	166 ± 43	−64 ± 71	< 0.001
% Carbohydrate	50.8 ± 9.7	37.8 ± 11.5	−13.0 ± 11.3	< 0.001	52.6 ± 7.7	43.5 ± 9.3	−9.1 ± 9.7	< 0.001
Protein (g/day)	80 ± 24	82 ± 28	2 ± 26	0.797	68 ± 15	70 ± 18	3 ± 19	0.180
% Protein	14.2 ± 2.4	17.7 ± 3.3	3.5 ± 3.7	< 0.001	15.8 ± 2.5	18.2 ± 2.9	2.4 ± 3.3	< 0.001
Fat (g/day)	70 ± 30	76 ± 32	6 ± 33	<0.001	58 ± 21	64 ± 23	6 ± 23	0.022
% Fat	27.3 ± 7.0	36.5 ± 9.6	9.2 ± 10.4	< 0.001	29.8 ± 6.9	36.2 ± 8.0	6.5 ± 8.5	< 0.001
Total salt intake (g/day)	10.58 ± 3.08	9.65 ± 2.83	−0.92 ± 3.53	0.003*	8.93 ± 1.99	9.03 ± 2.05	0.10 ± 2.28	0.635*
Salt by source (g/day)
Soy sauce	2.53 ± 1.21	2.35 ± 1.20	−0.19 ± 1.51	0.228	2.06 ± 1.03	2.21 ± 1.05	0.14 ± 1.38	0.232
Table salt	1.85 ± 0.94	1.78 ± 0.97	−0.08 ±1.20	0.552	1.59 ± 0.77	1.56 ± 0.77	−0.03 ± 0.91	0.378
Miso	1.03 ± 0.83	0.90 ± 0.73	−0.14 ± 0.98	0.246	0.99 ± 0.82	1.07 ± 0.86	0.09 ± 0.99	0.097
Chinese noodles	0.53 ± 1.05	0.23 ± 0.49	−0.30 ± 1.11	0.003	0.24 ± 0.67	0.14 ± 0.35	−0.10 ± 0.77	0.625
Chinese noodles with soup	1.17 ± 1.78	0.65 ± 1.08	−0.53 ± 1.91	0.006	0.51 ± 1.04	0.29 ± 0.65	−0.22 ± 1.27	0.188
Udon	0.32 ± 0.84	0.17 ± 0.43	−0.14 ± 0.81	0.109	0.13 ± 0.28	0.19 ± 0.45	0.06 ± 0.52	0.646
Bread	0.63 ± 0.54	0.51 ± 0.50	−0.12 ± 0.53	0.005	0.68 ± 0.53	0.57 ± 0.46	−0.11 ± 0.59	0.035
Fish and roe processed foods	0.75 ± 0.66	0.74 ± 0.73	0.00 ± 1.00	0.579	0.55 ± 0.50	0.69 ± 0.59	0.14 ± 0.78	0.053
Meat processed foods	0.52 ± 0.48	0.68 ± 0.59	0.17 ± 0.61	0.002	0.37 ± 0.41	0.43 ± 0.41	0.06 ± 0.52	0.152
Salty snacks	0.10 ± 0.22	0.03 ± 0.08	−0.06 ± 0.22	0.004	0.12 ± 0.24	0.04 ± 0.09	−0.08 ± 0.25	0.001
Pickled vegetables	0.38 ± 0.50	0.44 ± 0.64	0.06 ± 0.75	0.893	0.27 ± 0.44	0.32 ± 0.45	0.05 ± 0.56	0.362

Notes: Change was defined as the level after 6 months minus the level at baseline. *Paired t-test was used, and Wilcoxon test was used for the others.

Table 3 Associations of Changes in Total Salt Intake with Changes in Hemoglobin A1c (%) in All Patients and Patients by Tertile of Reductions in Carbohydrate Intake by Sex

	Regression Model
	Model 1			Model 2			Model 3
	β	SE	P	β	SE	P	β	SE	P
Men
All patients (n = 138)	0.107	0.035	0.003	0.024	0.033	0.466	0.025	0.039	0.520
ΔC1-patients (n = 46)	0.019	0.032	0.561	0.019	0.033	0.566	0.023	0.033	0.490
ΔC2-patients (n = 46)	−0.052	0.052	0.326	−0.045	0.052	0.401	−0.035	0.058	0.549
ΔC3-patients (n = 46)	0.168	0.023	0.010	0.102	0.072	0.162	0.130	0.079	0.107
Women
All patients (n = 107)	0.070	0.051	0.176	−0.032	0.049	0.524	−0.019	0.056	0.734
ΔC1-patients (n = 36)	−0.003	0.030	0.912	−0.026	0.032	0.423	−0.008	0.036	0.815
ΔC2-patients (n = 36)	−0.072	0.075	0.344	−0.077	0.075	0.314	−0.075	0.078	0.343
ΔC3-patients (n = 35)	0.047	0.028	0.109	0.039	0.145	0.204	1.96×10^−4	0.150	1.000

Notes: Model 1: adjusted for age plus Δbody mass index (BMI). Model 2: adjusted for age, ΔBMI plus Δcarbohydrate (g/day). Model 3: adjusted for age, ΔBMI plus Δtotal energy (kcal). ΔC1 - 3 patients: Patients were stratified by tertile of reductions in carbohydrate intake. In men, reduction in carbohydrate intake was greatest in ΔC3-patients (224 ± 91 g/day) followed by ΔC2-patients (106 ± 19 g/day) and ΔC1-patients (16 ± 42 g/day) in descending order. In women, reduction in carbohydrate intake was greatest in ΔC3-patients (142 ± 59 g/day) followed by ΔC2-patients (56 ± 16 g/day) and ΔC1-patients (5 ± 25 g/day) in descending order.

Abbreviation: SE, standard error.

Table 4 Associations of Changes in Salt from Sources with Changes in Hemoglobin A1c (%) in Men (n = 138)

Salt by Sources	Regression Model
	Model 1			Model 2			Model 3
	β	SE	P	β	SE	P	β	SE	P
ΔSoy sauce	0.063	0.086	0.466	−0.036	0.073	0.624	−0.065	0.083	0.432
ΔTable salt	0.258	0.105	0.016	0.062	0.094	0.516	0.103	0.105	0.330
ΔMiso	−0.094	0.135	0.481	−0.024	0.112	0.931	−0.148	0.123	0.231
ΔChinese noodles	0.383	0.117	0.001	0.155	0.107	0.148	0.246	0.115	0.034
ΔChinese noodles with soup	0.229	0.067	0.001	0.099	0.061	0.109	0.144	0.066	0.032
ΔBread	0.419	0.238	0.080	−0.001	0.210	0.996	0.196	0.226	0.386
ΔUdon	−0.347	0.154	0.026	−0.215	0.131	0.104	−0.273	0.143	0.059
ΔFish and roe processed foods	0.031	0.129	0.808	0.044	0.108	0.684	−0.031	0.119	0.797
ΔMeat processed foods	0.470	0.205	0.024	0.291	0.175	0.100	0.159	0.205	0.439
ΔSalty snacks	1.177	0.569	0.040	0.819	0.482	0.091	0.987	0.527	0.063
ΔPickled vegetables	0.137	0.173	0.429	0.064	0.146	0.661	0.134	0.159	0.403

Notes: The change in hemoglobin A1c and total salt and its sources (Δ) was defined as the level after 6 months minus the level at baseline. Model 1: adjusted for age plus Δbody mass index (BMI). Model 2: adjusted for age, ΔBMI plus Δcarbohydrate (g/day). Model 3: adjusted for age, ΔBMI plus Δtotal energy (kcal).

Abbreviation: SE, standard error.

Table 5 Associations of Changes in Salt from Sources with Changes in Hemoglobin A1c (%) in Women (n = 107)

Salt by Sources	Regression Model
	Model 1			Model 2			Model 3
	β	SE	P	β	SE	P	β	SE	P
ΔSoy sauce	0.010	0.085	0.908	−0.703	0.076	0.343	−0.046	0.082	0.573
ΔTable salt	−0.057	0.129	0.662	−0.041	0.114	0.722	−0.142	0.123	0.252
ΔMiso	0.303	0.116	0.010	0.230	0.104	0.029	0.257	0.111	0.023
ΔChinese noodles	−0.002	0.157	0.991	−0.104	0.139	0.459	0.020	0.149	0.891
ΔChinese noodles with soup	−0.054	0.096	0.576	−0.086	0.084	0.307	−0.041	0.091	0.655
ΔBread	0.291	0.197	0.144	0.191	0.176	0.280	0.215	0.188	0.257
ΔUdon	0.238	0.225	0.294	−0.103	0.209	0.822	0.090	0.218	0.680
ΔFish and roe processed foods	−0.081	0.153	0.596	−0.096	0.134	0.479	−0.181	0.146	0.217
ΔMeat processed foods	−0.052	0.227	0.820	−0.182	0.200	0.366	−0.312	0.222	0.163
ΔSalty snacks	0.918	0.473	0.055	0.161	0.449	0.722	0.747	0.452	0.101
ΔPickled vegetables	0.107	0.208	0.608	0.209	0.184	0.257	0.228	0.198	0.254

Notes: The change in hemoglobin A1c and total salt and its sources (Δ) was defined as the level after 6 months minus the level at baselineModel 1: adjusted for age plus Δbody mass index (BMI). Model 2: adjusted for age, ΔBMI plus Δcarbohydrate (g/day). Model 3: adjusted for age, ΔBMI plus Δtotal energy (kcal).

Abbreviation: SE, standard error.