If you have not been eating meat protein for a long time, it takes a while for the gastro-intestinal tract to adapt. Go slow. Small amounts at first. What you are experiencing is not unusual.
You can try chicken soup. The protein will be dilute. I cup per day to start. Add a few shreds of chicken meat to it after a few days if you are digesting the broth well. If you make your own, you only need a couple of legs with backs attached. Celery, carrot, onion, spice of choice. Freeze serving sizes so you don't have to concern yourself with it going off.
Also fish soup.
There are some delicious recipes for various types of recipes easy to find on line for using fish as a soup base.
It all depends on how many ingredients you have available and the adventurousness of your palate.
More than a couple of weeks..... Vegetarians have a very hard time introducing meat protein to the diet. It makes them sick because the enzymes required from the pancreas have gone on 'holiday'. It takes a couple of months of very slow introduction in order to ramp up production.
If your vegetarian diet was low fat, then the gall bladder action is also going to be somewhat lazy. You can test this by downing a shot glass of high quality olive oil. If that manages to go through without adverse symptoms, then that's great.
If you check history, the inmates of the concentration camps (not saying here that you are like that but it's a matter of perspective) died after liberation when the Americans started feeding them a protein and fat rich diet to try to save their lives. Of course you won't die if you all of a sudden start to eat significant amounts of meat, but as you discovered, it is very uncomfortable and makes you feel terrible. A more gradual introduction of proteins and fats were required. For these people, calories were more important than ideal nutrition. So that part of the story does not apply to you.
25 years of no meat or fish etc. is a long time so you can't expect the body to adapt rapidly.
No meat or poultry, but I still did eat fish, that is, when I could get access to it.
I remember reading an article many years ago, about how necessary fat is for a healthy brain.
We always used butter,and I have never bought anything, that said, fat free.
Thank you, soooo much for this information, if I could, I would give you a hug, cat and all.
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