There is old saying that says that changing food on a dog can make it sick to its stomach. And that if you want to change the dog's food, you need to slow introduce it by mixing it in increasing percentages with the old food until he is eating only the new food.

However, in my experience, this doesn't seem to be the case. My wife's dog used to get whatever was on sale when he was a puppy and never showed any problems. His diets has since stabilized so his dry food doesn't change much, but we do switch the wet food every now and then based what's on sale (he only gets a spoonful or 2 of wet food with every meal so it diet is mostly dry food). All of the other dogs I've had have not shown any sign of problems after an abrupt diet change.

My parents, however, always subscribed to this idea, so they religiously get the same food all of the time and in the rare cases the switch, slowly introduce it over a several week period.

So my question is there any truth to this idea or is it a old wives tail?

  • 1
    Customer loyalty? I'm sure the food companies have a part to play in this but can't tell if it's true or fast at all.
    – Salketer
    Commented Oct 10, 2013 at 13:12
  • Pet food companies are loyal to no one. They can change their formulas without needing to update the label for six months according to this article from 2008: naturalnews.com/024768_food_pet_changes.html I can't remember where I heard it more recently, but the cheaper brands tend to change their formula depending what ingredients are available at the lowest prices
    – Cuthbert
    Commented Oct 10, 2013 at 19:56

4 Answers 4


I think it's a myth. My sister has two dogs: a Labrador and a French Mastiff. She often modifies their diet to give them equal proportions of calcium and protein as required. She always switches between food types and brands and it has never created any problems at all.

I have been in touch with few dog owners who feed their dogs the same way; they have never had any problems due to it.

But avoid doing so when they are puppies. Puppies take a little more time to adjust in food changes and can react negatively.

My sister's Labrador disliked the food change when he was a puppy but now he doesn't care and eats what we serve.

  • 1
    The puppy aspect is a good one. Is that a quote from a source? Commented Oct 10, 2013 at 14:52
  • @psubsee2003 its from personal experience. Commented Oct 10, 2013 at 16:47

I worked at a Pets Hotel for a few months and saw a lot of dogs with upset stomachs (diarrhea) when their owner didn't leave their own food. The default food for when the owner doesn't provide their own is Science Diet: Sensitive Stomach.

I know that there are a variety of other factors that could affect a dog's stomach in that setting (like being separated from their owner for a lengthy period of time), but a sudden change in diet certainly doesn't help.

That said, I would always follow a 10-day rule. You exchange an extra 10% of the dog's normal diet with new food each day for 10 days. This will allow your dog the time he/she needs to adjust to the new food.

Doctors Foster and Smith say you should make changes slowly for the following reason:

Normal bacteria in the intestine help your dog or cat digest food. A sudden change in food can result in changes to the number and type of bacteria and their ability to help digest food. These changes can lead to intestinal upset. Therefore, your pet must be switched to a new food slowly.

The concept is similar to a vegetarian starting to eat meat again. They're going to be sick for a few days while their body learns to process the new bacteria.


I don't think there is any truth in that saying. That saying applies to cats (mostly). I've had a dog for about 6 years now and we have always been changing his food and he has never had problems due to that.

Also take a look at : How often should i change dog foods?. It says here that dog foods can be changed every 3 months.

As salketer said:

I'm sure the food companies have a part to play in this [...]


It definitely is breed dependent too. My huskies cannot have food switched on them randomly or they get sick to their stomachs with runny diarrhea. This makes things particularly difficult when dealing with my older husky (she will be four in September) who gets sick of her food after a week or two. My younger one who is only six months old can only have hills science diet for puppies or she is sick with diarrhea nonstop.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.