Look at the plant on the left – where is its most vulnerable spot? Right next to the root! It’s similar to your hair in that respect. A healthy root system does not affect the weakness of the hair near the root itself. Imagine pulling on the plant – it’s most likely to break at its weakest point – right above the root. Your hair is no different.
You can have healthy roots, but weak hair that breaks off, particularly at the root. This is almost always from processing with chemicals, dyes, hair irons or hair dryers. Here is a helpful video on why hair breaks off and a few suggestions.