Never heard this before and it sounds incorrect.
The digestive system works best with a good level of fiber and non-concentrated foods.
We are omnivores so can digest both meat and vegetables.
What you are suggesting sounds non-scientific and probably based on some spurious opinions.
What damages the body appears to be too much fat, sugar and salt.
On top of this people can get immune system reactions to various food proteins like gluten.
With irritable bowel syndrome this is linked also to stress. With this condition you could invent
any theory you like and not be able to prove it one way or the other.
So I doubt the benefit of what you are sharing as I have experience in my family of people
who suffer from these conditions and what does or does not work for them.
Actually he is the one who is correct and you are the one who is in error.
This is the only factual info you presented in your post:"What damages the body appears to be too much fat, sugar and salt.
On top of this people can get immune system reactions to various food proteins like gluten."
And even this is a very simple way of viewing the issue. Its like saying what damages a car is bad gas. But it goes a lot deeper then that.
And everyone knows that to much salt and fats and sugar is no good for the body anyway.
Your just parroting waht the health industry wants you to know.
I had IBS. i am 100% cured. Not in remission, but cured, for over 20 years. Please take the time to read my posts in the sister thread to this one.
I would tell you how to do it, to help your family with IBS, but no disrespect to you, I would probably be wasting my time with your attitude.
I actually get paid for the info I have been putting out here, and many people have come to a new level and understanding of higher health thanks to my training, experience and what God has revealed to me in prayer.
It is obvious by your comments your living a lifestyle that you think is conducive to good health, but you are almost definitely not. That is your business. May the Lord show you the way.
But do not mislead others. Your hurting them.
My advice: best thing you can do is ask questions rather then parroting something that is not true.