Despite the lack of textual evidence, scholars of Chinese medicine believe the custom of taking tonic foods on the first day of winter may derive from a passage in the Canon of Internal Medicine which says: "Unless vital essences are built up in the winter, sickness is inevitable in the spring."
立冬進補何時開始成為一種習俗？典籍雖無明文記載，但許多中醫界人士相信，是受了中國重要醫學典籍「內經」上說「冬不藏精，春必病瘟」這句話的影響。