Is it fine to add flaxseed?

Please send the recipe, he likes dessert so this could be very helpful

I have a great muffin recipe to sneak in fiber, fruits and nuts (chop nut very tiny to make it easier for elderly to chew). These are soooo yummy and my 92 yr old mom loves them. Very moist. Her constipation is gone, and it doesn’t cause diarrhea.
Message me for recipe if you are interested.