Hypertension: High sodium intake and low potassium intake leading to hypertension in six provinces of China

New research on current level of sodium and potassium intake and their associations with blood pressure (BP) in a large sample of Heilongjiang, Qinghai, Hebei, Sichuan, Jiangxi, Hunan provinces in China, led by The George Institute for Global Health (China), Chinese Centre for Disease Prevention and Control and Queen Mary University of London, has produced the following findings: 

• In the six provinces, the average salt intake was above 11g/d and potassium intake was less than 1.6g/day, with the sodium-to-potassium ratio as high as 5:1;
• WHO upper limit of 5g/d for salt intake was exceeded by 93.5% of the participants, and the potassium intake of nearly all the participants (99.0%) was below the WHO lower limit of 3.5 g/d;
• Each 1g increase in sodium intake was associated with increased systolic BP by 1.32 mm Hg; each 1g increase in potassium intake was associated with decreased systolic BP by 3.19 mm Hg; and each unit increase in sodium-to-potassium ratio was associated with an increase of systolic BP by 1.21 mm Hg.

The research was funded by the National Institute for Health Research and was published in Hypertension in Oct 2020. The data were collected from the baseline survey of Action on Salt China (ASC), covering an unprecedented over 5300 participants across six provinces of China. The study is the largest to date in measuring urinary sodium and potassium excretion using the most accurate method of 24-hour urine collection in China.

The researchers found that the average sodium intake was over 4300 mg/d (equivalent to 11.0 g/d salt), whereas the average potassium intake was under 1600 mg/d.  World Health Organization upper limit of 5 g/d for salt intake was exceeded by 93.5% of the participants, and the potassium intake of nearly all the participants (99.0%) was below the World Health Organization lower limit of 3.5 g/d. Over half participants had sodium intake above 4000 mg/d (10 g/d salt) and potassium intake under 1500 mg/d. As a result, the mean sodium-to-potassium ratio was as high as 5.0. The results are consistent with several recent studies, showing that the sodium and potassium intake presenting the sustained high sodium and low potassium situation in China.

The results also showed that a higher sodium intake, lower potassium excretion, and a greater sodium-to-potassium ratio were associated with a higher systolic BP and diastolic BP. That is, each 1g increase in sodium intake was associated with increased systolic BP by 1.32 mm Hg and diastolic BP by 0.34 mm Hg, whereas each 1g increase in potassium intake was associated with decreased systolic BP by 3.19 mm Hg and diastolic BP by 1.56 mm Hg. As a result, each unit increase in sodium-to-potassium ratio was associated with an increase of systolic BP by 1.21 mm Hg and diastolic BP by 0.44 mm Hg.

Evidence has shown that dietary sodium intake and potassium intake are associated with BP.  This study confirms the increasing trend of associations between sodium and potassium with increased BP.  Dr Yuan Li, senior research fellow of The George Institute for Global Health (China) and the first author of this paper said “high salt intake and low potassium intake lead to high prevalence of hypertension in China with 1 in 3 or 4 adults experiencing high BP. It is of great importance and urgency to adopt comprehensive strategies in salt reduction and potassium evaluation across the country to prevent and control hypertension, and thus to reduce the risks of occurrence of cardiovascular diseases. ”

Professor Puhong Zhang, Deputy Director of The George Institute for Global Health (China), also the first author of the paper said “the six provinces represented a broad range of geographic locations, i.e. east, middle and west regions in China. The results revealed that northern and rural region had relatively higher sodium intake than southern and urban regions, while the potassium intake and sodium-to-potassium ratio were similar in general. High salt and low potassium diet is common among Chinese population. Healthy diets including the consumption of potassium-rich foods such as fruits and vegetables should be more strongly recommended, and potassium-enriched salt substitutes should be recommended to the general population, in addition to the reduction of dietary salt intake.”

Feng J He, Professor of Global Health Research at Queen Mary University of London and Deputy Director of Action on Salt China said, “Action on Salt China (ASC) consists of 4 cluster randomized controlled trials (RCTs) which has been implemented in 2018-2019 in 6 provinces of China. These 4 RCTs include AppSalt-based salt reduction in primary school children and their families (AIS), home cook salt reduction intervention study (HIS), restaurant-based salt reduction intervention study (RIS) and community-based comprehensive salt reduction intervention study (CIS). The baseline survey results will provide robust evidence on the effectiveness of the salt reduction interventions.” Professor Graham A. MacGregor at Queen Mary University of London, who is the chairman of the World Action on Salt & Health (WASH) said that ASC study will provide important reference on diet and BP research for other developing countries with similar eating habits as China.

The corresponding author, Professor Xinhua Li, the former Party Chief of Chinese Centre for Disease Prevention and Control said that China has promoted salt reduction over the past decade through various initiatives such as the China Healthy Lifestyle for All campaign and a pilot salt reduction project in Shandong province. The efforts have facilitated the implementation of salt reduction action across the whole country toward the Healthy China 2030 goal of < 5 g/d. However, further efforts should be made to continue the salt reduction work, at the same time to address the issue of low potassium intake. This significant study highlighted the urgency of comprehensive strategies in salt reduction and potassium elevation in China, and it will play important role in improving dietary pattern in China in the context of Healthy China development. . 

This research was funded by the National Institute for Health Research (NIHR) (16/136/77)using UK aid from the UK Government to support global health research. The views expressed in this publication are those of the author(s) and not necessarily those of the NIHR or the UK government.