Walnuts are not considered healthy treats for dogs. While nuts are a good-for-you snack that's rich in nutrients for humans, it's best to keep this particular snack to yourself. The dangers of walnuts for dogs range from tummy trouble to serious conditions like toxicity. Here's what you need to know before you offer walnuts to your dog.

Are Walnuts Safe for Dogs?

Walnuts can make your dog sick, especially if too many are eaten. If your dog happens to steal a walnut that fell off your kitchen counter, it's probably not going to hurt them. However, it's best to avoid letting your dog eat walnuts for a few reasons:

Toxic Mold

Walnuts are susceptible to a particular type of black mold that can prove extremely toxic to canines. Any walnuts that have been collected outdoors from trees are unsafe for pets. While it's less likely to occur in high-quality walnuts that you might find at the grocery store, they have a high moisture content and can thus start growing fungi at any stage during their growth process, from harvest to the store shelf (whether they're shelled or not).

Some fungi that grow on walnuts produce metabolites called mycotoxins, which are considered to be carcinogenic, while others produce tremorgenic mycotoxins, which can cause tremors and seizures. While it's possible to boil walnuts and thoroughly dry them to remove any potential mold, it might not be worth the effort for dogs, as there are plenty of other treats that are safe to eat as-is.

Black Walnuts

A specific type of walnut that's particularly toxic to dogs is the black walnut. These nuts are native to Northeastern United States and Canada, and are toxic for both dogs and horses (but, interestingly, not cats). Note, however, that the walnuts sold in stores are typically English walnuts, not black walnuts.

What Happens if Your Dog Eats Walnuts

If your dog does accidentally ingest either a moldy walnut or black walnut, symptoms to watch out for include vomiting, tremors, and seizures. Contact your veterinarian immediately because this condition can be fatal if left untreated, especially in a small dog, puppy, or geriatric dog. Plain, store-bought walnuts themselves aren’t necessarily toxic to your dog in small quantities (assuming they don't contain any black mold). However, too many walnuts can be harmful for other reasons.

Fat Content

Generally speaking, human foods like walnuts that are high in fat can upset your pooch's stomach and lead to the usual symptoms of tummy troubles, including vomiting and diarrhea. In some cases, however, consuming walnuts can lead to the development of more serious conditions like pancreatitis or gastroenteritis. Pancreatitis is an inflammation of the pancreas that can be either acute or chronic, while gastroenteritis occurs when the gastrointestinal tract (particularly the stomach and intestines) becomes inflamed. Both of these conditions, especially pancreatitis, can be very serious, or even fatal for your dog.

Salt and Other Additives

Another reason to keep walnuts away from your dog is that, along with their high fat content, prepackaged walnuts can also contain additives like salt or other seasonings that can be harmful to our pets. Large amounts of salt can make a dog very sick.

Gastrointestinal Obstruction

Since walnuts are one of the larger varieties of nuts, they can not only be difficult for Fido to digest but can potentially cause serious gastrointestinal blockages, particularly in smaller breeds. These blockages often require surgery and could be fatal if not addressed right away. Additionally, if your dog happens to eat a shelled walnut there's a higher possibility of the shell causing an obstruction.

Choking Hazard

Choking is another risk, as many dogs swallow food without chewing it, and the round shape of a walnut makes it more likely to become stuck in an overly eager dog's throat.

Are There Health Benefits of Walnuts for Dogs?

Experts say our canine counterparts can't take full advantage of the health benefits of nuts because digestive systems don't handle nuts as well as ours do. Tree nuts like walnuts, almonds, and hazelnuts are full of vitamins and minerals, healthy fats, protein, and fiber, which have been proven to have health benefits in humans. Fresh walnuts, in particular, are packed with protein, antioxidants, and omega oils. Unfortunately, our four-legged friends cannot reap the same benefits.

The other issue is that even if Rover could take advantage of some of the health benefits of walnuts, the negative impact of their fat content will override them. To put it into perspective, an ounce of walnuts contains about 18 grams of fat, and an average 30-pound dog should only be consuming about 14 grams of fat total per day. And combined with the possibility of any form of fungi, the risks of walnuts outweigh the potential benefits.

Are Other Nuts Safe for Dogs?

Generally speaking, veterinarians don't recommend nuts for dogs as they're nutritionally unnecessary and risky. You should never offer your dog macadamia nuts, as they are considered to be particularly toxic for dogs.

The only "nuts" that are considered to be somewhat less harmful to dogs in small amounts are peanuts and cashews. These nuts all contain nutrients like fiber and protein but still can carry a risk of causing stomach distress or intestinal blockage. Plus, you have to be especially careful with any nuts that contain flavorings like salt.

If you do choose to offer your dog nuts, be sure these treats only make up a very small percentage of your pet's overall calorie intake. Your dog should obtain almost all of their calories from balanced foods specifically formulated for a dog's dietary needs. Excessive treats and fatty foods can cause dogs to become overweight, which may lead to or exacerbate conditions such as diabetes and arthritis.