An expert recommendation on salt intake and blood pressure management in Chinese patients with hypertension: A statement of the Chinese Medical Association Hypertension Professional Committee

Abstract

The occurrence of hypertension is influenced by combined actions of genetic and environmental factors. Among environmental factors, high salt intake is considered as one of the most important and critical dietary factors. High salt intake is closely related to the incidence and mortality of cardiac and cerebrovascular events, as well as ventricular hypertrophy, renal damage, and other target organ damages. The existing data show that the daily sodium salt intake of Chinese population is significantly higher than that of European and American populations, and it generally exceeds the standard. Therefore, sodium and potassium intake in patients with hypertension should be actively assessed to carry out targeted treatment, which is an important strategy in blood pressure management. According to the characteristics of high prevalence of hypertension, high sodium salt intake, and low blood pressure control rate in China, Chinese Medical Association Hypertension Professional Committee believes that it is necessary to promote salt restriction and formulate the assessment of salt intake and clinical process of blood pressure management according to the current status of sodium intake.

1. INTRODUCTION

The occurrence of hypertension is influenced by combined actions of genetic and environmental factors. Among environmental factors, high salt intake is considered as one of the most important and critical dietary factors. In terms of the global death due to cardiovascular diseases, 1.65 million cases are attributed to excess sodium salt intake per year.1 The INTERSALT (international salt) study2 has shown that individual salt intake is significantly associated with blood pressure; if 24‐hour sodium excretion (reflecting sodium intake) decreases by 100 mmol, systolic and diastolic blood pressure decrease by 6.0 and 2.5 mm Hg, respectively. In 2013, the BMJ (British Medical Journal) published a new meta‐analysis of 36 randomized controlled trials in European and American countries about salt restriction lowering blood pressure, and the effect of salt restriction on blood pressure was clarified. The results showed that salt restriction was effective in blood pressure management in patients with hypertension and normal blood pressure; it could lower blood pressure by 3.4/1.5 mm Hg on average. The higher the blood pressure, the more significant the antihypertensive effect.3 High salt intake is closely related to the incidence and mortality of cardiac and cerebrovascular events, as well as ventricular hypertrophy, renal damage, and other target organ damages. Some recent studies have suggested that low sodium salt intake (less than 3 g/day) may also increase cardiovascular risk.4, 5, 6 However, the conclusions of these studies are disputed by international academic circles. In view of one of the World Health Organization's (WHO) Global Action Plan (2013‐2020) for the Prevention and Control of Chronic Diseases, the salt intake relatively should decrease by 30%. In 2011, the Canadian Ministry of Health developed Canada's limited sodium salt intake strategy. The sodium salt intake was expected to be reduced by 5 g/day till 2016 on average, and it was expected to reduce the cost of treatment for 1 million hypertensive patients per year.7 In 2006, WHO recommended the sodium intake of less than 5 g/day (sodium chloride) as a population nutrient intake goal.8 The guidelines for prevention and control of hypertension in China (2010) also pointed out that each person's sodium salt intake gradually dropped to <6 g/day9, 10; the systolic blood pressure was expected to decrease by 2‐9 mm Hg. The existing data show that the daily sodium salt intake of Chinese population is significantly higher than that of European and American populations, and it generally exceeds the standard. In most parts of China, the average sodium salt intake per person is more than 12 g/day, and the intake of people in the northern part of China is up to 12‐18 g/day,11 which is obviously higher than the WHO‐recommended level of ＜5 g/day. Excessive dietary sodium salt intake and/or low potassium intake have/has become an important risk factor for hypertension in Chinese populations. Therefore, sodium and potassium intake in patients with hypertension should be actively assessed to carry out targeted treatment, which is an important strategy in blood pressure management. According to the characteristics of high prevalence of hypertension, high sodium salt intake, and low blood pressure control rate in China, Chinese Medical Association Hypertension Professional Committee believes that it is necessary to promote salt restriction and formulate the assessment of salt intake and clinical process of blood pressure management according to the current status of sodium intake.

Salt restriction first involves the assessment of salt intake. The 24‐hour urinary sodium determination has been used as the gold standard for assessing sodium intake. However, this method is not suitable for nonhospitalized patients because of the problems of 24‐hour urine collection, tedious operation, and long‐time collection. Therefore, its extensive application is limited. At present, in addition to 24‐hour urinary sodium determination, another method has been developed for assessing sodium intake by determining spot urinary sodium/creatinine, which makes it easier to assess sodium intake. Japan has used a spot urine method to predict 24‐hour urinary sodium, and the formula has been included in the guidelines for hypertension. Therefore, establishing a formula for estimating spot sodium intake to predict 24‐hour urine excretion of sodium in Chinese hypertensive population helps in the rapid assessment of sodium intake and guides an antihypertensive strategy in clinical practice. Two methods for assessing sodium intake are combined, and a more appropriate treatment is provided to the patients with a definite diagnosis of medium‐to‐high sodium salt intake.

1.1. Standards of salt restriction for hypertensive patients

The WHO12 and European Guidelines for Hypertension recommend a sodium salt intake of less than 5 g/day. The guidelines for hypertension in China, Japan, and the United States recommend a sodium salt intake of less than 6 g/day.9, 13, 14

1.2. Definitions of different salt intake

Under normal conditions, 98% sodium is excreted through kidneys. Therefore, dietary sodium intake is calculated routinely by determining 24‐hour urinary sodium. The daily salt intake is calculated according to the proportion of sodium chloride in table salt (99%) and the specific gravity of sodium in sodium chloride (g). That is, daily salt intake (g) ≈ urine sodium concentration (mmol/L) × urine 24‐hour volume (L) ÷ 1000 × 58.5 (g/mol); 100 mmol sodium is equivalent to 5.85 g sodium chloride (≈6 g).

Definitions of salt intake in this recommendation:

1. Normal salt intake: NaCl <6 g/day is equivalent to sodium intake <2.36 g/day. (24‐hour urinary sodium excretion <100 mmol)

2. Moderate salt intake: NaCl >6‐12 g/day is equivalent to sodium intake >2.36‐4.72 g/day (24‐hour urinary sodium excretion = 100‐200 mmol);

3. High salt intake: NaCl >12 g/day is equivalent to sodium intake >4.72 g/day (24‐hour urinary sodium excretion >200 mmol).

1.3. Target blood pressure for control

General hypertensive population: <140/90 mm Hg.

Elderly hypertensive population (≥80 years old): <150/90 mm Hg.15, 16

1.4. Hypertensive population recommended salt assessment

Patients with certain clinical characteristics are considered as hypertensive patients with salt sensitivity in view of the difficulty of performing diagnostic procedures in salt‐sensitive hypertension; the effect of high salt intake on blood pressure is estimated, and targeted treatment is performed.

The primary hypertensive population recommended the assessment of salt intake includes the following:

Incipient hypertensive patients, elderly hypertensive patients, or obese hypertensive patients; infants with birth weight <3.05 kg,17, 18 or premature infants (gestational age <37 weeks),19, 20 or infants with macrosomia (birth weight >4.0 kg)21; resistant hypertensive patients; women with a history of hypertensive disorder complicating pregnancy22; hypertensive patients with high nocturnal blood pressure (nondipper blood pressure except obstructive sleep apnea syndrome) accompanied by fast nocturnal heart rate (average heart rate >75 beats/min); hypertensive patients with a family history of cardiovascular and cerebrovascular diseases, or hypertensive patients living in the northern part of China whose blood pressure does not reach the target with a single drug; and patients with chronic kidney disease (CKD).

1.5. Salt assessment and recommendation process of lifestyle intervention

*When preparing to take low sodium salt, the renal function and serum potassium level should be assessed (Figure 1). If serum potassium is ≥5.0 mmol/L or creatinine is ≥177 µmol/L, the common table salt is still used, but lifestyle needs to include salt restriction.

Figure 1.

Salt assessment and recommendation process of lifestyle intervention

1.6. Salt assessment and recommendation process of drug treatment

Patients with moderate and high sodium intake cannot comply with dietary control, or patients with high blood pressure cannot be effectively controlled or reach the standard by lifestyle intervention; for them, appropriate and targeted drug therapy can be administered according to the status of salt intake. Before or during the course of drug therapy, cardiac function, renal function, and balance of water and sodium should be assessed; the selection of drug is based on the intake status of sodium and potassium (Figure 2).

Figure 2.

Salt assessment and recommendation process of drug treatment

Note:

1. Diuretic, CCB (calcium channel blockers), RASI [rennin angiotensin system inhibitors, ACEI (angiotensin enzyme converter inhibitor) or ARB (angiotensin receptor blocker)], or β‐receptor blocker is optional, but RASI is preferred; other drugs can also be selected according to clinical features (such as CCB or diuretic can be selected for isolated systolic hypertension).

2. Low‐dose diuretic: 12.5 mg/day hydrochlorothiazide, 1.25‐1.5 mg/day indapamide.

3. Fixed combination: RASI +CCB or RASI +diuretic.

4. Reach the target: office blood pressure <140/90 mm Hg.

Recommendations for the aforementioned hypertensive patients, on the basis of the determination of routine blood pressure and urine sodium, are as follows:

1. In the treatment of resistant hypertension, renal hypertension, secondary hypertension with adrenal cause, and OSAS should be excluded.

2. Hypertensive patients with CKD [estimated glomerular filtration rate <30 mL/(min 1.73 m²)] should be careful while taking low sodium/potassium salt, thiazide diuretic, and aldosterone antagonist. If needed, it is recommended to be applied under the guidance of hypertensive professionals and renal physicians.

3. For hypertensive patients with sodium chloride intake >6 g/day, other cardiovascular risk factors and target organ damage should be examined and assessed to facilitate integrated blood pressure management.

This process is performed based on the assessment of effective salt intake. It is recommended that salt intake (including determination of 24‐hour urinary sodium or determination of urinary sodium, creatinine, and other indicators by calculating spot urine sodium; salt intake is calculated by referring to the gender, age, and other parameters) should be assessed in the qualified medical institutions during the integrated management of blood pressure. The assessment of salt intake is more appropriate for patients with incipient hypertension and resistant hypertension, as well as the aforementioned population, to carry out targeted salt restriction management in lifestyle and the selection of antihypertensive drugs.

Written by Ningling SUN, Hongyi Wang

Writing committee: Xiaoping Chen, Shaoli Chu, Qiuyan Dai, Wenhui Ding, Ningyuan Fang, Yingqing Feng, Guosheng Fu, Lijun Guo, Ling Han, Longfu Jiang, Yinong Jiang, Guangping Li, Yong Li, Yuming Li, Huiliang Liu, Wei Liu, Jianjun Mou, Peili Bu, Weichong Qian, Guohai Su, Gang Sun, Ningling Sun, Yingxian Sun, Yuemin Sun, Jianhong Tao, Hongyi Wang, Meng Wei, Haiying Wu, Meixiang Xiang, Liangdi Xie, Rui Xu, Xinjuan Xu, Xiaowei Yan, Xinhua Yin, Liangrong Zheng, Zhiming Zhu.

CONFLICT OF INTEREST

We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.

Sun N, Mu J, Li Y; Working Committee of Salt evaluation, Blood Pressure Management, Chinese Medical Association Hypertension Professional Committee, Hypertension Group, Chinese Society of Cardiology . An expert recommendation on salt intake and blood pressure management in Chinese patients with hypertension: A statement of the Chinese Medical Association Hypertension Professional Committee. J Clin Hypertens. 2019;21:446–450. 10.1111/jch.13501