Funding for this research was provided by:
China Medical Board (Grant No. 16-262)
Received: 22 March 2020
Accepted: 9 February 2021
First Online: 1 March 2021
Ethics approval and consent to participate
: Written informed consent for CHNS was approved by the institutional review committees of the University of North Carolina at Chapel Hill and the national institute of Nutritional and Food safety, China Centre for Disease Control and Prevention.
: Not applicable.
: The authors declared that they have no competing interests.