[Fungi]

That depends on the individual. Don't forget, legumes such as lentils, chick peas and a myriad of others. they are easy to incorporate into your diet, but people are unwilling to eat "healthy." Again, it is simply a case of culture.

Consider the Indian diet; it is full of legumes and their national dish is "dal," lentils cooked in innumerable ways, all great and all with flavor and fiber.

[Harmless Teddy Bear]

Changing your diet suddenly and having your body protest is not a matter of culture but a matter of what your guts are used to.

Does not matter really how you switch it up, going from vegetarian to carnivore will result in intestinal distress. Just going from a store bought diet to one that is partly foraged will give some trouble.

So just switch a bit at a time. In about a month you should be fully acclimated to your new way of eating.