Why does my dog eat grass — and what does it mean for their gut?

At a glance

• Grass eating is normal in dogs — studies show up to 79% of dogs eat plants regularly
• Less than 25% of dogs vomit after eating grass, and fewer than 10% show signs of illness beforehand
• Frantic, repeated grass eating paired with vomiting can signal gut discomfort
• Fibre deficiency is one dietary reason dogs seek out grass
• Improving diet quality, particularly fibre content, reduces compulsive grass eating in many dogs

Why do dogs eat grass in the first place?

Most dogs eat grass simply because they want to. It is a normal, instinctive behaviour that has been documented in wolves and other wild canids. It is not automatically a sign of illness or nutritional deficiency.

A large survey published in Applied Animal Behaviour Science found that 79% of dogs had eaten plants at some point, with grass being the most common choice. Of those dogs, fewer than 10% appeared unwell before eating grass, and only around 22–25% vomited afterwards. That means the vast majority are doing it for reasons other than feeling sick.

The most plausible explanations fall into three categories: instinct, enjoyment, and fibre-seeking. Grass is rich in insoluble fibre, which adds bulk to digested food and moves it through the gut. If a dog's daily diet is low in fibre, the gut can feel sluggish — and grass becomes a quick fix. Understanding how gut health and diet connect helps explain why some dogs reach for the lawn more than others.

Does grass eating mean my dog has a gut problem?

Occasional, calm grass eating is not a gut problem. It becomes meaningful when the behaviour changes. If your dog is suddenly eating grass frantically, eating far more than usual, or consistently vomiting after, that pattern is worth paying attention to.

Possible gut-related reasons include:

• Gastric discomfort or excess gas — grass may help trigger vomiting to clear the stomach
• Constipation or slow gut motility — insoluble fibre from grass can help move things along
• Gut dysbiosis — an imbalance in the gut microbiome can drive unusual eating behaviours
• Dietary fibre deficiency — particularly common in dogs fed low-fibre, heavily processed foods

If your dog is eating grass compulsively, vomiting repeatedly, or showing other symptoms like bloating, diarrhoea, or weight loss, speak to your vet. Those combinations can point to underlying conditions that need proper investigation.

It is worth knowing that fibre plays a much bigger role in dog digestion than most people realise. The type of fibre matters too. Soluble fibre feeds beneficial gut bacteria. Insoluble fibre keeps transit time healthy. Many commercial dog foods under-deliver on both.

What does grass eating tell us about what dogs actually need in their diet?

When dogs seek out plant material, it often signals a gap in what their daily food provides. Grass is not a great source of nutrients — dogs cannot digest cellulose properly — but the act of seeking it out tells you something.

The two most common dietary gaps linked to grass eating are fibre and gut microbiome support. A dog whose gut bacteria are well-fed and diverse is less likely to show signs of digestive restlessness. Prebiotics, the non-digestible fibres that feed beneficial bacteria, are central to that. Chicory root is one of the best-researched prebiotics in dog nutrition — it contains inulin, a soluble fibre that selectively feeds good gut bacteria and supports regular digestion. Marleybones meals include chicory root alongside other gut-supportive ingredients like linseeds and chia seeds, specifically to address this kind of microbiome support.

Fresh, minimally processed food also retains more of the natural fibre structure found in ingredients. That matters because processing at high temperatures degrades fibre and destroys beneficial plant compounds. Marleybones uses a slow-cook-in-pack method that preserves the integrity of ingredients without requiring freezing or artificial preservatives.

When should I be worried about my dog eating grass?

Most grass eating requires no action at all. The situations that warrant a closer look are:

• A sudden increase in grass eating — especially if the dog previously showed little interest
• Eating grass followed by repeated vomiting in the same session
• Signs of illness before eating grass, such as lethargy, drooling, or stomach gurgling
• Grass eating paired with other digestive symptoms like loose stools, bloating, or gas
• Any change in eating behaviour that persists for more than a few days

Also consider what is on the grass. Pesticides, herbicides, and fertilisers are common in parks and gardens. If your dog eats treated grass frequently, that carries its own health risk separate from the behaviour itself. Rinse your dog's muzzle after walks in heavily treated areas.

Every dog is different — build your personalised Marleybones feeding and health plan tailored to your dog's age, size, and health requirements.

Can changing my dog's diet stop them eating grass?

For dogs eating grass because of a dietary gap, yes. Several small studies have reported that increasing dietary fibre reduced or eliminated compulsive plant eating in dogs. The mechanism is straightforward: a well-fed gut with diverse bacteria and adequate fibre is a settled gut. There is less reason to seek supplemental roughage from the garden.

The most effective dietary changes are increasing fibre variety (both soluble and insoluble), adding prebiotic ingredients, and switching to food that is more digestible overall. For dogs who eat grass repeatedly and show signs of gut imbalance, a higher-quality diet with genuine gut-supportive ingredients is often the most practical first step before considering supplements.

If diet changes do not reduce the behaviour within two to four weeks, consult your vet to rule out underlying conditions such as inflammatory bowel disease or parasites.

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FAQs

Is it safe for dogs to eat grass?

Yes, in most cases. Eating small amounts of untreated grass is harmless. The risk comes from grass that has been treated with pesticides, herbicides, or fertilisers. If you are unsure whether grass in a park or garden has been treated, it is safer to discourage the behaviour in those specific areas.

Why does my dog eat grass and then vomit?

Grass irritates the stomach lining and triggers the vomiting reflex in some dogs. This may be deliberate, particularly if the dog has gastric discomfort and is using grass to clear its stomach. However, only around 25% of dogs vomit after eating grass, so for most dogs it passes through without issue.

Do dogs eat grass because they are missing something in their diet?

Sometimes. Fibre deficiency is the most common dietary reason. Dogs fed low-fibre diets are more likely to seek out plant material. Gut microbiome imbalance is another factor. Improving diet quality, particularly fibre and prebiotic content, reduces grass-seeking behaviour in many cases.

Should I stop my dog from eating grass?

Not necessarily. If the grass is untreated and the dog is calm and healthy, there is no strong reason to intervene. If the behaviour is frantic, frequent, or paired with vomiting, it is worth addressing the potential dietary or health cause rather than simply stopping the behaviour without understanding it.

Can puppies eat grass too?

Yes, puppies eat grass for the same reasons as adult dogs. They are also more likely to eat things out of curiosity. The same safety rules apply: untreated grass in small amounts is fine, but monitor for repeated vomiting or signs of stomach upset, and check that the area has not been chemically treated.

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