This is probably the commonest query any pediatrician gets asked in their practice.
Surprisingly the answer to this question is very variable even amongst the pediatricians.
Here is what the present scientific evidence suggests
1. Do not starve your child. While this may reduce the immediate loose stools, it will make them weaker and more prone to recurrent diarrhea.In fact, the American Academy of Pediatrics states that 'most children should continue to eat a normal diet including formula or milk while they have mild diarrhea.'
2. For mild diarrhea, avoid any significant changes in diet.
3. Dehydrated children require rehydration (replacement of lost fluid). After being rehydrated, many children will be able to resume a normal diet.
4. Most children with diarrhea tolerate full-strength cow's milk products. It is not necessary to dilute or avoid milk products (except in children with known allergies to cow's milk).
5. Recommended foods include a combination of complex carbohydrates (rice, wheat, potatoes, bread), lean meats, yogurt, fruits, and vegetables.
6. Foods to avoid include fatty foods, very sweet juices & carbonated (fizzy) drinks as these are more difficult to digest.Do not start any new foods (that the child has not taken previously) during a diarrhea episode. During vomiting, avoid the temptation to feed large quantities of food/ drink. Give small frequent clear fluids/ soups/ ORS every few minutes to avoid dehydration.
Here is what you need to do
For mild diarrhea in children below 6 months, continue breast feeding/ formula feeding.
For older children, increased intake of clear fluids like coconut water, ORS, and a normal diet would help. Many children develop mild and temporary lactose intolerance. Continuing dairy foods may make the diarrhea last longer, but it can also allow a faster return to a regular diet. Hence milk intake may be temporarily restricted if there are explosive stools, lots of redness around the anus, and excessive gas, stomach pain etc. It would be appropriate to let your pediatrician suggest this rather than doing this routinely each time a child has diarrhea. You may add easily digestible foods like banana, apples (not juice), rice, khichdi, daal (Pulses), yogurt/ curd, potato (not fried), and toast.
Finally, remember that a full appetite is often the last behavior to return after any illness. Children should be allowed to take their time returning to their normal eating habits. No specific diet is recommended for diarrhea, but children usually tolerate bland foods better.
While lots of ready to drink ORS are available in the Western Countries (like Pedialyte), however the same is not easily available in India. Electral ready to drink ORS solution is now available in green apple and mango flavor at some of the larger cities.