There is widespread consensus that lowering your saturated fat intake (animal fats, milk fats, cheese, cream, butter, etc) lowers your 'bad' LDL cholesterol.
What is less well-known is that increasing your fiber intake also lowers LDL. Why?
That second point is important, and is probably why you can't just take a fiber supplement to get this benefit. You have to get fiber from the source: plant food.
In fact, according to one study, just increasing your fiber can lower LDL as much as 30% in one week. That's about the effect of a statin drug.
Going from a meat-heavy to a plant-heavy diet helped me drop my LDL from 127 to 61. Without meds. I've had plenty of patients with similar improvements.
So, how do you lower LDL?
Learn what foods to eat, and what not to eat. Check out recipes and cookbooks that can help.