Brief answer....explained below
Detailed answer....
Hello,
Thanks for the query.
Frankly speaking there is no generalised dietary advice which would work for everybody since influence of diet is unique to each person. Symptoms of IBS range from abdominal pain,diarrhoea,bloating,constipation etc.
Ideally you should prepare a food diary yourself and see which food increases your problem and which not. If you avoid a food and feel better,then you know that it is to be avoided in future.
In general you should avoid....
Large meals
Fried and fatty foods
Chocolates,nuts,coffee,alcohol,carbonated drinks etc
Avoid too much of fiber specially the insoluble fiber of skin of fruits and vegetables
Avoiding specially  gas producing vegetables like onion,broccoli,cauliflower,beans,garlic etc
Food and drinks with fructose and sorbitol etc
Try eating small meals and take 6-7 small meals rather than 3 large meals
Eat slowly and don't rush through your food.
I hope it helps,however you are most welcome to revert to me for any further query.
Best of luck
Thanks

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