It can be very frustrating. I've learned around certain people to just keep my trap shut. There are so many friends and family members I wish would listen to some of my suggestions, but they won't and think I'm a kook for making the 180 degree turn I've made in the way I choose to nourish myself. I grew up in my parents bar and grill and my sister is a chef and I had a dream of being a pastry chef.
The best way to show them is to lead by example.