Uhhh... I know this thread has been dead a while, but I need to make these points before someone takes any of this silly advice and makes everything worse.
Tomatoes are no good for gastritis. Nor is anything fatty. I've seen people recommended tomato soup, carbonara, peanut butter sandwiches... Please ffs... If you don't understand the condition, do not make a suggestion. I know people want to help but stabbing around in the dark is no good.
Gastritis is best treated with bland, non acidic foods. That means no cheese, no cheddar cheese, Mac and cheese, butter and cheese pasta, cheese on toast... also to be avoided are other dairy products or things that are acidic, high in fat or sugar. This includes tinned rice pudding, ice cream, "crunchy nut cornflakes with full fat milk" (as someone wanted above), biscuits, "Hawaiian toast (toast with ham, a slice of pineapple, topped with cheese and grill)"
Bland diet means bland. No sauces, mayonnaise, seasonings, no nothing.
Cucumber can cause reflux, so I wouldn't bother with that either.
NO SUGAR!!
Avoid breads, choose rice, whole grains, unseasoned corn chips.
Stick to grilled chicken, high omega fish, nuts, pulses, boiled potatoes. Eat small portions. Drink plenty of water. No fizzy stuff.
A little bit of marmite is good to put back the folic acid and b12 that you tend to become deficient in when you have gastritis.
The only seasoning you need to have is a little pinch of salt when you read some of the stuff written in these threads when they're written by kind hearted people without any clue of what they're talking about.
No offense intended, but at least 60 percent of the advice here is guaranteed to exacerbate the symptoms of gastritis.
Omeprizole btw is probably the only certainty to aid anything. Somebody said above it made their gut feel like a brick. That's not normal.
This medicine closes up the tubes that produce and feed acid into the stomach, thereby reducing the acidity there. The only sensation you should experience is relief from reflux and the burn that characterises the symptoms that lead to a diagnosis of gastritis. Nothing more.
If you feel like a brick after taking it, please do consider its cause may be something else and avoid saying anything that may put others off it. It could be the difference between a bout of gastritis that can last days or years. Proper care and treatment is the only way to resolve it.
If you have a diet that's too rich in gluten, saturated fat, sugar, lactose, caffeine, alcohol, hot spice and acidic ingredients, then you're at higher risk of being symptomatic of gastritis. Same goes if you over eat, eat at irregular times, fast too much to lose weight.
Just have a healthy balanced diet, eat at normal times and you'll probably avoid any instances of gastric distress.
If you do ever get it, stick to chicken, both, water, leafy greens, apple sauce and whole grains. Your symptoms will abate in days rather than weeks.
I am not a doctor, but I am qualified by having experience of this condition and have been hospitalised more than once.