Is grain-free food good for dogs?

Interest in grain-free dog food is on the rise.

In our 2023 survey of over 1,500 dog owners, 27% said that one of the most important factors they consider when choosing dog food is whether or not it’s grain-free. 

Advocates say grain-free diets are gentler on dog's stomachs, and closer to their 'ancestral' diet, but the experts we spoke to said this isn't necessarily the case.

We asked Dr. David Gardner, professor of physiology at the University of Nottingham School of Veterinary Medicine and Science, and Dr. Teresa Hollands, senior lecturer in veterinary nutrition at the University of Surrey, for their expert insight to find out if grain-free dog food is all it's cracked up to be.

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What is grain-free dog food?

Grains are a type of seed that grows on grass-like plants called cereals. Common grains include corn, wheat, oats and barley. 

They are typically included in dog food as a source of carbohydrates - although they also contain many other essential nutrients. 

Grain-free dog food doesn't contain any grain, and typically has a lower volume of carbohydrates than dog foods that do contain grain. 

It may include carbohydrates from alternative sources, including vegetables and legumes such as sweet potatoes, lentils and peas. 

Grain-free food and digestive health

Grain-free advocates claim that grains are poorly tolerated by dogs.

They say that a number of dogs have grain allergies or intolerances, and therefore these foods upset their stomachs. 

They also suggest that there is anecdotal evidence that dogs with sensitive stomachs do better on grain-free diets, or that grain-free diets are more gentle on the stomach. 

However, there are a few issues with these claims. 

‘Grain allergies or intolerances are actually not that common in dogs,’ says Dr. Gardner. 'Diets including grain are generally quite well tolerated.’

According to the 2018 State of Pet Health Report from Banfield Pet Hospital, only around 0.2% of dogs have a food allergy. The most common food allergies in dogs are chicken, beef, and dairy. 

What's more, '‘Gentle on the stomach’ isn’t a term grounded in scientific literature or research.’ says Dr. Gardner. ‘Your dog’s digestive health is very unlikely to be improved by removing grain from their diet unless they have an allergy or intolerance.’ 

What about ‘ancestral’ diets?

Another claim made about grain-free diets is that they are superior because they are closer to a dogs ‘ancestral diet’ - i.e., the diet of a wolf. 

The ideas is that as wolves don't eat grain, it's more ‘natural’ to feed dogs grain-free diets, and therefore it's better for their health. 

However, there are a few different issues with these claims. 

Firstly, research such as this 2013 study published in Nature suggests that, compared to wolves, dogs have several genetic variations which make them better able to digest starchy carbohydrates, like grains. 

It has long been established that dogs produce amylase (the enzyme that breaks down starchy carbohydrates) in their small intestine and pancreas.

‘Although dogs do have the teeth and jaws of a carnivore, they have evolved to eat carbohydrates, including grains,’ said Dr Teresa Hollands, senior lecturer in veterinary nutrition at the University of Surrey. 

‘Remember that dogs have been domesticated for almost 30,000 years, during which time their genes have changed significantly.’

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Is there a link between grain-free food and heart disease in dogs?

In 2018, the US Food and Drinks Authority (FDA) reported that it was aware of a number of cases of a type of heart disease called canine dilated cardiomyopathy (DCM) in dogs not genetically predisposed to the disease. 

It noted that many of these dogs were on a grain-free diet which contained a high proportion of peas, lentils, and other legume seeds. 

One theory is that grain-free diets may lead to a taurine deficiency, which can be a trigger for the development of DCM.

However, the link may also be coincidental, or driven by another factor unrelated to the nature of the diet. DCM is a relatively common condition in dogs, so it makes sense that some dogs with DCM would be on a grain-free diet. 

In a 2021 statement on the investigation, the UK Pet Food Industry Association said: ‘The FDA currently has no definitive information indicating that diets under investigation are inherently unsafe […] and there is no information to suggest a similar problem in the UK or Europe.'  

The latest FDA statement in December 2022 stated it would not release any further updates unless there was a meaningful development.

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Should I feed my dog grain-free?

‘I personally wouldn’t feed my dog grain-free,’ Dr. Gardner told us, ‘as I don’t see any clear advantages. But that doesn’t mean that dogs can’t be healthy on a grain-free diet.’ 

On choosing the best food for your dog, Dr. Hollands said: ‘The most important thing is to monitor their health day-to-day. Are they sleeping, behaving, and passing stools normally? If so, it is unlikely that their diet is having a detrimental effect on their wellbeing.’

Talk to your vet before you make any dietary changes - including introducing, re-introducing, or removing grains from their diet. 

But the most important thing is that your dog's diet has all the nutrients they need, regardless of the ingredients. For this, look for a dog food labelled as 'complete', which means it will meet nutritional requirements. 

Unless your dog has an allergy or intolerance, you don't need to pay a premium for grain-free food. 

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