not sure why it's not listed.
But for constipation I make sure to add some ground flax meal, or chia seeds to my foods.
I add a pinch of ground flax to my shakes. And chia seeds I add a teaspoon to my oatmeal, or yogurt with granola, or a sprinkle in peanut butter to dip my apple slices in. I also try and eat a grapefruit a few times a week. These in combination seem to help me.