我每天用６克，大概要到每天服用５０克才叫大量

From WebMD: https://www.webmd.com/vitamins/ai/ingredientmono-996/xylitol

When taken by mouth: Xylitol is commonly consumed in foods. It is possibly safe when used in chewing gums, candies, lozenges, toothpastes, and mouth rinses in amounts up to about 50 grams daily. It might cause diarrhea and gas in some people.

Taking high doses of xylitol is possibly unsafe. Using very high doses long-term might cause tumors.