Hello and thanks for the query.
To prevent and treat gastritis and peptic ulcers, a light and wholesome diet is best. This differs from a normally wholesome and balanced diet in that some foods and drinks which may strain the digestive system are left out. 

Beverages to be avoided if you have gastritis or peptic ulcers
alcohol, coffee, carbonated drinks like colas.

Foods to be avoided if you have gastritis or peptic ulcers
Milk products 
A proper diet for the treatment of gastritis or ulcers should not include whole milk, cream or sour cream with a fat content of over 20%.

Meats 
For those who suffer with gastritis or peptic ulcers (and anyone who wants to be more healthy) fatty, smoked or cured meats should be left out of the diet. 

Fish 
Types of fish like eel, herring and salmon as well as smoked fish of any sort, dried or otherwise preserved fish or fish products should not be consumed if you have gastritis or peptic ulcers. 

Potatoes and vegetables 
Avoid any potato dishes which have been prepared using oil, including chips (French fries, pommes frites, wedges, etc.) and crisps (i.e. potato chips) if you have gastritis or an ulcer (and in general). 

Also potato salad containing bacon, mayonnaise or excessive oil should not be part of your diet. There are also several types of vegetable which are difficult to digest: cabbage, leeks, onions, mushrooms, peppers, olives, pickles, cucumber, horseradish and beans.

Likewise candy, sweets and sugar in general should not be part of your diet if you have gastritis and/or an ulcer as well as spices, especially those which have been dried or are in powdered form. 
What not to include in your diet if you suffer from gastritis or 

peptic ulcers
As noted above, you should avoid all fats (including high-fat soups or sauces) both during and after your gastritis/ulcer treatment. Hard-cooked eggs and any other high-fat food which contains eggs (such as mayonnaise) should not be part of your diet. Don't eat roasted, fried or grilled foods and avoid foods which were prepared using bacon or onion. 

What you can and should eat and drink during and after treating gastritis and/or a peptic ulcer

If you suffer with gastritis, it's a good idea to eat foods that you can tolerate; i.e. foods and drinks which do not lead to diarrhoea, the build-up of uncomfortable gas, abdominal pain or nausea. You should also avoid foods that cause you to feel too full or cause heartburn.

This includes light wholesome foods which are low in fat, mild in taste, lean and properly prepared. Dairy products such as yoghurt are effective against gastritis as they inhibit the reproduction of the H. pylori bacteria.

Easily digestible vegetables such as carrots, fennel, turnips, cauliflower, XXXXXXX peas, beans, tomatoes, zucchini and XXXXXXX leafy salad. For seasoning you should try to include freshly dried spices, mild vinegar (e.g. balsamic), lemon juice and a little salt. XXXXXXX marmalades and honey are the best sweeteners. 

If you have sweet tooth and suffer from gastritis, it's best to avoid refined baked goods and stick with whole-grain or fruit cakes (without whipped toppings or frosting) and cookies. For the preparation of your food we recommend boiling, steaming or baking in foil. 

The optimal drinks include any sort of tea, mild coffee, grain coffee, mineral water without gas, vegetable juices as well as diluted fruit juices.

Please keep in mind that a more wholesome diet such as the one outlined above does not have a direct therapeutic effect in the treatment of gastritis or ulcers, rather it is more tolerable for the digestive system and so easier to metabolise. 

 It's also very important to remember that a reduction in stress as well as a balanced lifestyle which includes some physical activity are essential in the treatment of such disorders of the digestive system. 

Five important diet tips for gastritis / peptic ulcer sufferers

1. Eat several small meals rather than a few large meals.

2. Try to take your time when you eat – don't rush! 

3. Chew thoroughly. 

4. Avoid eating foods that are either too hot or too cold. 

5. Regularly take s vitamin supplement, in particular vitamin B12, and detoxify the digestive system. In addition, fasting (e.g. juice fasting) can be beneficial for the body as natural vitamins and minerals can better be absorbed without the strain placed on the stomach by carbohydrates.
6. Avoid snacking late in night.
I hope to have answered your query in detail however you may revert to me for any further query.
Best of luck.
Thanks

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