The amount of  fiber the human body need is exactly zero.

does human need fiber>?
Yes, fiber is an essential part of a healthy diet. It helps with digestion, weight management, and reducing the risk of chronic diseases.
How fiber helps with digestion
Bowel movements: Fiber supports regular bowel movements and reduces constipation.
Healthy colon: Fiber provides energy for the intestinal microbiome, which promotes a healthy colon.
How fiber helps with weight management
Feeling full: Fiber can help you feel full, which can help you avoid excessive food intake and aid in weight loss.
How fiber helps reduce the risk of chronic diseases
Heart disease: Fiber can reduce the risk of heart disease.
Type 2 diabetes: Fiber can help manage blood sugar levels, which is important if you have diabetes.
Some cancers: Fiber can reduce the risk of colon cancer and some other cancers.
The recommended amount of fiber for most adults is between 22 and 34 grams (g) per day, depending on age and sex.

If you "need" fiber, why do you shit it out?