Anti-Hypertensive Effect of a Solar Salt Diet in Elderly Hypertensive Patients: A Preliminary Randomized, Double-Blind Clinical Trial

Seung Ha Baek; Ju Won Ahn; Hye-Ree Lee; Soo Hyun Cho; Jung-Ha Kim

doi:10.15384/kjhp.2015.15.3.98

Korean J Health Promot > Volume 15(3); 2015 > Article

Baek, Ahn, Lee, Cho, and Kim: Anti-Hypertensive Effect of a Solar Salt Diet in Elderly Hypertensive Patients: A Preliminary Randomized, Double-Blind Clinical Trial

Original Article

Korean Journal of Health Promotion 2015;15(3):98-106.

Published online: December 19, 2015

DOI: https://doi.org/10.15384/kjhp.2015.15.3.98

Anti-Hypertensive Effect of a Solar Salt Diet in Elderly Hypertensive Patients: A Preliminary Randomized, Double-Blind Clinical Trial

Seung Ha Baek¹, Ju Won Ahn¹, Hye-Ree Lee², Soo Hyun Cho¹, Jung-Ha Kim¹

¹Department of Family Medicine, Chung-Ang University Hospital, Chung-Ang University College of Medicine, Seoul, Korea

²Department of Family Medicine, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea

Corresponding author：Jung-Ha Kim, MD, PhD Department of Family Medicine, Chung-Ang University Hospital, Chung-Ang University College of Medicine, 102 Heukseok-ro, Dongjak-gu, Seoul 06973, Korea
Tel: +82-2-1800-1114, Fax: +82-2-6264-8272 E-mail: girlpower219@cau.ac.kr

Financial support was provided by the Ministry of Knowledge and Economy through a regional technology innovation program.

Received March 09, 2015 Accepted July 07, 2015

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

ABSTRACT

Background

High sodium and/or low mineral intake are known to be associated with elevated blood pressure. It has been reported that substituting low-sodium, mineral-rich salt for refined salt lowers blood pressure (BP). And solar salt is emerging as a low sodium high mineral salt for a healthy diet in Korea. Therefore, this double-blind, randomized, and placebo-controlled trial was conducted to explore changes in BP from substituting refined salt with solar salt among hypertensive elderly subjects.

Methods

Forty-three hypertensive and institutionalized elderly individuals aged 65 years or older were enrolled. Thirty-eight subjects (88.4%) completed the study. Subjects were provided with either a solar salt- or refined salt-based diet for eight weeks.

Results

Systolic BP decreased significantly in the solar salt-based diet group after 2, 4, and 8 weeks when compared to the refined salt-based diet group. And, diastolic BP was lowered significantly in the solar salt-based diet group compared to that in the refined salt-based diet group after 8 weeks. In addition, urinary sodium/po-tassium, and angiotension converting enzyme activity decreased significantly in the solar salt-based diet group compared to the refined salt-based group. Urinary potassium excretion was significantly increased in the solar salt-based diet group.

Conclusions

These results may provide clinical evidence that solar salt has beneficial effects on BP in elderly patients. And, people such as Koreans, who do not consume enough minerals, may experience a greater anti-hypotensive effect by using solar salt. However, further large-scale studies are necessary.

Keywords: Hypertension, Blood pressure, Aged, Salt, Randomized controlled trial

Figure 1.

Flowchart of the study design and study subjects. BP, blood pressure.

Figure 2.

(A) Changes in systolic and diastolic blood pressures with intake of solar or refined salt over eight weeks. P-values were calculated using Wilcoxon rank sum test and Wilcoxon signed rank test. (B) The rate of change in ACE activity with intake of solar (least square mean [SE]: -15.45 [16.13]) or refined salt (least square mean [SE]: 34.09 [14.82]) before and after the study. P-values were calculated using ANCOVA. ACE, angiotensin converting enzyme; SE, standard error.

Table 1.

Clinical characteristics of the subjects at baseline

	Solar salt (n=18)	Refined salt (n=20)	P^a
Age, y	79.5 (75-88)^b	80.0 (77-84)^b	0.520
Body mass index, kg/m²	24.4 (19.9-25.8)^b	23.8 (19.2-25.3)^b	0.270
Sex			0.170
Male	9 (64.29)^c	5 (25.00)^c
Female	9 (36.00)^c	15 (75.00)^c
Blood pressure, mmHg
Systolic	127.5 (121-140)^b	129.0 (122-136)^b	0.300
Diastolic	74.0 (70-94)^b	76.0 (70-88)^b	0.610
Pulse rate, beat/min	75 (70-82)^b	72 (69-78)^b	0.250
Geriatric functional assessment, score
MMSE-K	21 (13-23)^b	20 (12-23)^b	0.380
K-ADL	4.0 (2-7)^b	4.0 (1-8)^b	0.610
S-IADL	29.5 (20.0-38)^b	32 (30-38)^b	0.470
GDS	4.0 (3-5)^b	5.0 (4-5)^b	0.440
Antihypertensive medication	13 (72.2)^c	14 (66.6)^c	0.980
Diuretics	2 (15.38)^c	1 (7.14)^c
Calcium channel blockers	12 (92.31)^c	13 (92.86)^c
ACE inhibitors or ARBs	8 (61.54)^c	6 (42.86)^c
Beta-blockers	2 (15.38)^c	3 (21.43)^c
Medical history
Cardiovascular disease^d	8 (44.44)^c	9 (42.86)^c	0.990
Diabetes mellitus	8 (44.44)^c	6 (28.57)^c	0.760
Dyslipidemia	2 (11.11)^c	1 (4.76)^c	0.590
Dementia	6 (33.33)^c	7 (33.33)^c	1.000
Osteoporosis	3 (16.67)^c	7 (33.33)^c	0.290

Abbreviations: MMSE-K, mini-mental state examination-Korean version; K-ADL, Korean activities of daily living; S-IADL, Seoul- instrumental activities of daily living; GDS, global deterioration scale; ACE, angiotensin converting enzyme; ARB, angiotensin receptor blocker.

^aCalculated using a Wilcoxon rank sum test, Fisher’s exact test or χ

²-test.

^bMedian (25-75%).

^cNumber (%).

^dCerebral infarction, cerebral hemorrhage, myocardial infarction, angina or atherosclerosis.

Table 2.

Changes in nutrient intake by the w weighing method after 8 weeks

	Solar salt (n=18)		P_a	Refined salt (n=20)		P^a
	Pre (baseline)	Post (8 wk)	P_a	Pre (baseline)	Post (8 wk)	P^a
Calorie intake, kcal	1,299.06	1,324.52	0.770	1,271.91	1,355.25	0.120
	(1,142.71-1,729.12)^b	(1,011.63-1,732.43)^b		(1,044.55-1,503.03)^b	(1,178.77-1,475.32)^b
Protein, % energy	16.61 (15.27-18.87)^b	16.48 (14.53-17.78)^b	0.770	17.94 (16.24-19.70)^b	17.01 (16.15-17.62)^b	0.160
Fat, % energy	19.92 (15.20-22.37)^b	20.87 (14.97-23.08)^b	0.090	20.60 (19.41-23.85)^b	22.00 (18.87-23.03)^b	0.930
Carbohydrate, % energ	gy 63.14 (58.72-69.44)^b	62.65 (58.81-70.36)^b	0.640	62.30 (55.77-63.82)^b	60.97 (58.90-64.98)^b	0.650

^aCalculated using a Wilcoxon signed rank test.

^bMedian (25-75%).

Table 3.

Changes in study outcomes of solar- or refined salt-based diet after 8 weeks^a

	Solar salt (n=18)			Refined salt (n=20)
	Pre (baseline)	Post (8 wk)	P^b	Pre (baseline)	Post (8 wk)	P^b
Body mass index	24.4 (19.9-25.8)	24.8 (19.8-26.0)	0.820	23.8 (19.2-25.3)	23.9 (19.5-25.8)	0.750
Blood pressure, mmHg
Systolic^c	127.5 (121-140)	110 (102-120)	0.007	129.0 (122-136)	128.5 (120-136)	0.930
Diastolic	74.0 (70-94)	69.0 (66-74)	0.090	76.0 (70-88)	78 (72-88)	0.930
Pulse rate, beat/min	75 (70-82)	77 (70-82)	0.720	72 (69-78)	72 (69-76)	0.830
Antihypertensive medication	13 (72.2)	10 (55.6)	0.300	14 (70.0)	15 (75.0)	0.730
Glucose tolerance index
Fasting glucose, mg/dL	95.0 (90-110)	93.5 (86.0-131.0)	0.770	90.5 (83.0-97.5)	90.0 (82.0-100.0)	0.410
Fasting insulin, μIU/mL	9.24 (6.22-12.79)	8.18 (6.54-11.72)	0.310	9.20 (6.77-12.24)	9.40 (6.74-11.74)	0.900
HOMA-IR Lipid profile	2.30 (1.35-3.32)	2.33 (1.43-3.93)	0.280	2.25 (1.79-3.04)	2.27 (1.82-3.42)	0.900
Total cholesterol, mg/dL	184 (156-221)	166 (132-201)	0.080	169 (158.5-201.5)	164 (143-194)	0.620
Triglyceride, mg/dL	142.5 (11.20-220.0)	141 (105-270)	0.920	135.5 (101.5-157.5)	116 (101-156)	0.230
HDL-cholesterol, mg/dL	34.6 (32.0-43.1)	36.55 (32.60-43.75)	0.670	33.45 (30.60-45.70)	34.0 (32.0-46.3)	0.170
Renal function test
Blood urea nitrogen, mg/dL	14.5 (10.3-16.2)	12.85 (11.00-15.25)	0.920	13.45 (10.10-18.40)	12.47 (10.90-15.80)	0.860
Creatinine, mg/dL Electrolyte	0.9 (0.8-1.3)	0.8 (0.7-1.25)	0.530	0.9 (0.8-1.0)	0.9 (0.8-1.0)	0.780
Serum sodium, mEq/L	138 (138-140)	138.5 (136.0-142)	0.530	137.5 (136.0-140)	140 (136-142)	0.110
Serum potassium, mEq/L	4.2 (4.0-4.5)	4.45 (3.80-4.60)	0.030	4.00 (3.80-4.35)	4.05 (3.80-4.20)	0.320
Urinary sodium, mEq/L	80 (57-109)	94 (46-121)	0.890	88 (54-118)	86.5 (49.0-120)	0.460
Urinary potassium^c, mEq/L	30 (24-32.5)	36.5 (30.5-49)	0.008	25.5 (17-38)	23.5 (14.5-36.5)	0.340
Urinary sodium/potassium^c	2.34 (1.97-3.64)	2.07 (1.25-3.21)	0.040	2.67 (2.20-4.59)	3.44 (2.47-4.39)	0.520

Abbreviations: HOMA-IR, homeostasis model assessment of insulin resistance; HDL, high density lipoprotein.

^aValues are presented as median (25-75%) or N (%).

^bCalculated using a Wilcoxon signed rank test or χ

²-test within each group.

^cStatistical significance at P<0.05 according to a Wilcoxon rank sum test for comparing % change between two groups.

REFERENCES

1.. Fields LE, Burt VL, Cutler JA, Hughes J, Roccella EJ, Sorlie P. The burden of adult hypertension in the United States 1999 to 2000: a rising tide. Hypertension 2004;44(4):398-404.

2.. McCarty CA, Berg RL, Rottscheit CM, Dart RA. The use of dietary supplements and their association with blood pressure in a large Midwestern cohort. BMC Complement Altern Med 2013;13:339.

3.. Safar ME, Temmar M, Kakou A, Lacolley P, Thornton SN. Sodium intake and vascular stiffness in hypertension. Hypertension 2009;54(2):203-9.

4.. Hu G, Jousilahti P, Peltonen M, Lindström J, Tuomilehto J. Urinary sodium and potassium excretion and the risk of type 2 diabetes: a prospective study in Finland. Diabetologia 2005;48(8):1477-83.

5.. He FJ, MacGregor GA. A comprehensive review on salt and health and current experience of worldwide salt reduction programmes. J Hum Hypertens 2009;23(6):363-84.

6.. Meneton P, Jeunemaitre X, de Wardener HE, MacGregor GA. Links between dietary salt intake, renal salt handling, blood pressure, and cardiovascular diseases. Physiol Rev 2005;85(2):679-715.

7.. Houston M. The role of magnesium in hypertension and cardiovascular disease. J Clin Hypertens (Greenwich) 2011;13(11):843-7.

8.. Sacks FM, Svetkey LP, Vollmer WM, Appel LJ, Bray GA, Harsha D, et al. Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. DASH-Sodium Collaborative Research Group. N Engl J Med 2001;344(1):3-10.

9.. Gilleran G, O'Leary M, Bartlett WA, Vinall H, Jones AF, Dodson PM. Effects of dietary sodium substitution with potassium and magnesium in hypertensive type II diabetics: a randomised blind controlled parallel study. J Hum Hypertens 1996;10(8):517-21.

10.. Geleijnse JM, Witteman JC, Bak AA, den Breeijen JH, Grobbee DE. Reduction in blood pressure with a low sodium, high potassium, high magnesium salt in older subjects with mild to moderate hypertension. BMJ 1994;309(6952):436-40.

11.. China Salt Substitute Study Collaborative Group. Salt substitution: a low-cost strategy for blood pressure control among rural Chinese. A randomized, controlled trial. J Hypertens 2007;25(10):2011-8.

12.. Sarkkinen ES, Kastarinen MJ, Niskanen TH, Karjalainen PH, Venäläinen TM, Udani JK, et al. Feasibility and antihypertensive effect of replacing regular salt with mineral salt -rich in magnesium and potassium- in subjects with mildly elevated blood pressure. Nutr J 2011;10:88.

13.. Lee KD, Park JW, Choi CR, Song HW, Yun SK, Yang HC, et al. Salinity and heavy metal contents of solar salts produced in Jeollanamdo province of Korea. J Korean Soc Food Sci Nutr 2007;36:753-8.

14.. Chobanian AV, Bakris GL, Black HR, Cushman WC, Green LA, Izzo JL Jr, et al. Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. National Heart, Lung, and Blood Institute; National High Blood Pressure Education Program Coordinating Committee. Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Hypertension 2003;42(6):1206-52.

15.. Paik HY. Dietary Reference Intakes for Koreans (KDRIs). Asia Pac J Clin Nutr 2008;17(Suppl 2):416-9.

16.. Korean Ministry of Health, Welfare, and Family Affairs & Korea Centers for Disease Control and Prevention. The Korean National Health and Nutrition Examination Survey - KNHANES IV (2007). Seoul. 2008;[Accessed December 12, 2014].. http://knhanes.cdc.go.kr.