Why Does My Dog Eat Grass?

Why is your dog eating grass? We get this question often in the pet store. If you sometimes catch your dog munching on grass, you’re not alone. It’s a surprisingly common behaviour. We’ve had customers assume that their dogs were doing it to annoy them. Others hypothesized that it was because their pets lacked fiber. But what does the research really say about why dogs eat grass?

Are there safe alternatives or ways to address it if you’d rather your dog skip the lawn buffet? Here’s a deeper dive into what we know, and what you can do.

What Research Reveal About Grass-Eating in Dogs

According to research, dogs eating grass is very common. For domestic dogs, a 2007-2008 self-reported owner study surveyed the plant eating habits of dogs.

“Of 3340 surveys returned, 1571 met enrollment criteria. Overall, 68% of dogs were reported to eat plants on a daily or weekly basis with the remainder eating plants once a month or less. Grass was the most frequently eaten plant by 79% of dogs.”¹

Does Grass Eating Mean My Dog Is Sick or Have to Vomit?

In the study we mentioned above, “Only 9% were reported to frequently appear ill before eating plants and only 22% were reported to frequently vomit afterwards.”¹ 

This suggests that for most dogs, grass-eating is not tied directly to illness or stomach upset.
In another controlled study, beagles fed a diet enriched with fermentable fiber (fructooligosaccharides, or “FOS”) which influences stool softness did not increase grass-eating when compared to a “standard diet” group.
The FOS diets did induce watery feces; however, grass eating was reduced among dogs with looser stools.

“The dogs spent less time eating grass and demonstrated fewer grass eating events when they had a mild gastrointestinal disturbance compared with when they produced normal stools, suggesting that they did not use grass to self-medicate a diarrhoeal gastrointestinal disturbance.”²
Another study by Bjone “deflates the theory that dogs eat grass as an emetic as there were only five vomiting events for 709 grass eating events across all 12 dogs and all 18 testing sessions (similar to the results of Sueda et al., 2005).”

Is My Dog’s Grass Eating Evolutionary?

Wild dogs and wolves have been shown from other research material to have plant matter in their poop. A field observation showed that “intentional consumption of grass by wolves has also been documented” (Murie, 1944, Stahler et al., 2006).

Grass is largely indigestible for dogs.

Anecdotally, you’d find that the raw food diet proponents (which we are) suggest an ancestral diet similar to those for wild dog populations.

Is Grass Eating Related to Fiber or Diet?

One commonly held theory is that dogs eat grass to boost fiber intake. Some experts argue that when a dog’s diet lacks adequate roughage, they may instinctively turn to grass for extra bulk to help digestion.

However, this theory has mixed support. The FOS study only evaluated GI disturbance, not dietary fiber motivation. However, the results seemed to challenge the idea that fiber deficiency alone drives the behaviour. More research is necessary.

Does Hunger Influence Grass-Eating Behaviour?

The Bjone et al. study on “Grass eating patterns in the domestic dog, Canis Familiaris” found patterns that suggest “that grass eating is influenced by satiety and time of day.”³ The dogs were less interested in eating grass when they were satiated.

Do Dogs Eat Grass to Self-Medicate or Deworm?

So far, we did not come across any study that suggested that this was the case for dogs.

In wolves, “after observing blades of grass wrapped around intestinal worms in wolf scats, Murie (1944) suggested that grass might have a scouring effect in removing worms.”¹

It was noted that there is a possibility that chimpanzees use non-nutritional plant eating to “have a purging effect on intestinal nematodes (Huffman and Canton, 2001)”¹

The study suggests that “controlled, laboratory studies could be performed with domestic dogs to determine whether or not plant eating reduces intestinal parasites in this species.”¹

Facts: Why Dogs Eat Grass

Several theories attempt to explain why dogs eat grass, but most remain unproven. Some behavioural experts hypothesize that dogs may simply enjoy the texture or taste of grass, or that boredom plays a role. These explanations have not been validated by controlled research but remain common interpretations among owners and trainers.

In Vancouver, anecdotally, some dogs eat soil in early spring, likely because of strong-smelling organic fertilizers such as fish emulsion. While this observation is common, it has not been formally studied.

Bjone et al. in their small study found that “the dogs did not demonstrate a statistically significant preference for eating either couch or kikuyu grass.”³ This weakens the idea that dogs intentionally select specific plants for taste or medicinal benefits. Although field observations of wild canids show occasional consumption of various plants, there is no evidence that domestic dogs engage in targeted medicinal plant use.

There is still no consensus on why dogs eat grass. The behaviour appears to depend on the individual dog and context. However, research findings do support a few trends:

1. Grass eating is extremely common in domestic dogs, occurring in roughly 79% of dogs surveyed in large-scale studies, though its biological purpose is still unknown.
2. The Bjone study found a trend that satiated dogs were less likely to eat grass, but this study involved a very small sample, and results were not uniform across all dogs.
3. In the same study, some dogs showed increased grass eating in the morning before meals, but this pattern was not consistently statistically significant.

Anecdotally, some owners report reduced grass-eating after switching to a more balanced or nutrient-rich diet (kibble or raw-fed), but this relationship has not been demonstrated in published research.

What You Can Do If You Prefer Your Dog Stops Eating Grass

If you’d like to discourage the behaviour, or at least make it safer, here are some practical steps with owner-friendly tips:

1. Make sure your dog is eating the appropriate amount of food.
2. Feed your dog first thing in the morning if it tends to eat grass during your walk before its meals
3. Make sure your dog’s diet is balanced, nutritious that may reduce the impulsive need to graze.
4. Introduce greens or vegetables at home to satisfy any “green cravings”.
5. A good workout or exercise for your dog will build appetite and may reduce boredom related to grass eating.
6. If grass-eating becomes frequent, obsessive, or is accompanied by vomiting/other symptoms, consider a vet check to rule out nutritional deficiencies or gastrointestinal issues.

Natural Supplement & Dietary Alternatives. Can They Help?

If you want to give your dog a healthier “green fix,” you might consider (with your vet’s approval):

• Steamed or pureed dog-safe veggies: spinach, kale, parsley, broccoli. Softening them helps dogs digest fibers better than raw veggie or grass blades.
• Fiber-rich foods or supplements: to support smooth digestion without relying on indiscriminate grass consumption.

Note: These supplements below do not have evidence showing they reduce grass-eating. Their use is for general wellness only.

• Safe herbal/vegetable-based supplements: some owners add dog-appropriate green powders, chlorophyll supplements, or plant-based nutrients.
  • Milk thistle for liver support
  • Slippery elm bark for digestion upset.
  • Wheat grass and barley grass for vitamins and minerals

These alternatives may satisfy any instinctual craving for green plant matter — but they don’t guarantee your dog will stop grazing.

When Grass Eating Could Be Problematic

Though grass-eating is usually harmless, there are scenarios where it could pose a risk.

• Treated lawns or gardens: If grass has been sprayed with pesticides, herbicides, or other chemicals, ingestion can be dangerous.
• Contamination risks: Grass may be contaminated with animal feces (parasite risk, parvovirus or other bacteria).
• Compulsive or excessive grass eating: If your dog seems to graze obsessively, vomits often after, or shows signs of illness (lethargy, loss of appetite, diarrhea), that’s worth a vet visit.

FAQ: Why Dogs Eat Grass

References

1. Characterisation of plant eating in dogs by Karen Lynn Chieko Sueda, Benjamin Leslie Hart, Kelly Davis Cliff https://www.sciencedirect.com/science/article/abs/pii/S0168159107001827?  
2. Reduction in grass eating behaviours in the domestic dog, Canis familiaris, in response to a mild gastrointestinal disturbance by Samantha J. McKenzie, Wendy Y. Brown, Ian R. Price https://www.sciencedirect.com/science/article/abs/pii/S0168159109003311?
3. Grass eating patterns in the domestic dog, Canis familiaris by S.J. Bjone, W.Y. Brown and I.R. Price https://www.une.edu.au/staff-profiles/ers/wbrown/files/bjone-brown-price-grass-eating20patterns-raan-2007.pdf