Effects of acupuncture on gut microbiota and short-chain fatty acids in patients with functional constipation: a randomized placebo-controlled trial Tekijä Xiang-Yun Yan, Jun-Peng Yao, Yan-Qiu Li, Xian-Jun Xiao, Wan-Qing Yang, Si-Jue Chen, Tai-Chun Tang, Yu-Qing Yang, Liu Qu, Yu-Jun Hou, Min Chen, Ying Li