In a comprehensive study by the Lancet,
19 year old Chinese are now the tallest in Asia, overtaking 19 year old South Koreans. Young Koreans and Chinese are now above 175cm or 5 foot 9 inches. I bet a lot of Korean nationalists would be annoyed, because previously Koreans were taller than Chinese, therefore proof that Koreans had so-called 'superior Korean genetics'. But Chinese youths are now taller than Korean youths. Japanese are still shorter than Koreans/Chinese, and to me one factor is that Japanese simply have less protein in their diets, and they like eating smaller meals than Koreans and Chinese.
That is not the reason. You are not going to get much taller simply supplementing your diet like that. The reason Chinese are always going to be taller than Japanese (if you ignore technological enhancement or surgery) is simply due to genetics.