Are Grapes Toxic/Poisonous to Dogs?

by admin on July 28, 2011

Self-evident fact, or baseless myth that grapes are bad for dogs?

Vets have a great deal of confidence in one another and if one vet says something it is not likely to be questioned by another, even though there may be no evidence to support the contention. Add to that the fear-mongering that vets like to engage in combined with their knee-jerk tendency to be suspicious of any feeding practice that incorporates foods other than commercial pet products, and you get a baseless myth that travels around the world before the relevant facts have even been looked into.

That’s what seems to have happened in the case of grapes and raisins supposedly being “poisonous/bad” to dogs.

Complicating factors are not considered

In reality, there are many possible causes for digestive distress or renal failure in dogs, including pre-existing renal dysfunction caused by routine misfeeding and certain medications.  When this happens after a dog has ingested grapes or raisins, we needn’t jump to the conclusion that grapes and raisins are bad for dogs, since there are other potential explanations.  Most dogs who present to a vet with difficulties after consuming grapes or raisins are commercially fed, and the combination of commercial foods with natural, raw or dehydrated foods of any kind can sometimes produce diarrhea and other symptoms even if a dog hasn’t consumed anything controversial.

Where’s the evidence that grapes are bad for dogs?

Among the troubling lack of evidence is the fact that no specific chemical constituent in grapes has ever been isolated as being poisonous to dogs, nor has the myth ever been subjected to anything resembling scientific scrutiny or study. If the claim is to be made that a food is harmfully or fatally toxic, then the specific chemical must be found, via necropsy and other investigative methods, to have been solely responsible for the death of a dog. Suspicion is not good enough, we must have proof or at least solid evidence, and we have neither in the case of grapes allegedly being poisonous to dogs.BL

Misleading use of language

What we have instead is a lot of specious extrapolation, wild speculation and erroneous thinking. Consider this statement on “According to the ASPCA, around 1989 a disturbing trend began to emerge from the AnTox Database used by its Animal Poison Control Center: nearly all the dogs reported to have eaten grapes or raisins developed acute renal (kidney) failure.”  Notice that the pool is limited to the dogs that were reported to the poison control center.  The reader is led to ignore the thousands of other raisin or grape-eating-dogs who either showed no symptoms at all or whose owners were not sufficiently paranoid to call the poison control center.
And we know that there are thousands of dogs who eat grapes and raisins with no ill effects because, despite the traction this myth has gotten, many thousands of dog owners still obliviously feed them to their dogs, or dogs get into them ‘accidentally’, with no negative consequences.  So, nothing gets reported in the multitude of cases that would serve to offset the rare few where sickness was experienced.  When the information is presented as it is in the Scopes article, however, it sets up a self-fulfilling opportunity for everyone to make causal connections where there really are none.
On another website, the author lumps raisins and grapes together, which is a mistake if truthful discovery of the facts is what is desired.  She further concedes that “the actual toxic component hasn’t been identified” and goes on to make the statement:  “the ASPCA has been tracking cases of animal poisoning since 1989 and has found that most dogs developed kidney failure.”  This was no random sample.  The group is self-selected based on the extent to which the owners buy into 1) the grape-toxicity myth, and 2) the veterinary belief system in general.  These owners tend to feed commercial foods and follow other harmful veterinary advice such as the medicating or over-medicating of symptoms, all of which leads to health problems, including renal and digestive dysfunction.  These factors cannot be ignored if we want objective information about why some dogs get sick when eating grapes and others do not.

Conflicts of interest

Also it should be noted that the pet poison control center obviously benefits from having more people think that innocent foods are poisonous, so they’re not going to expend any resources getting to the truth of the matter.  I’ll stop short of suspecting a conspiracy, because surely this agency gets plenty of business from legitimate poisonings (given the increasing existence of poisonous substances that dogs can get into) to waste their time trying to instill fear in grape-feeding dog owners.  Others are not so sure.  The fact remains that dogs in varying conditions will have different physiological responses to different potentially harmful influences.  It can’t be said that a dog who is misfed on commercial foods and who got sick or died after eating raisins or grapes did so from “grape poisoning” when his/her renal system was already compromised and perhaps on the verge of failure.

A real poison is a poison every time it is eaten

I know that thousands of owners still give their dogs grapes and raisins because the topic comes up all the time on feeding discussion boards.  It is common to hear people say that they feed grapes routinely, or they did so before they heard that it was harmful, OR that their dogs eat them on their own when they come across them, and show no negative effects.   That means that for every case of “grape poisoning” that has happened since the recording of such incidents began in 1999 (20 total, including 7 deaths), there have been thousands of other dogs who have eaten grapes and experienced NO negative reaction. If anyone looking at this issue wanted to really get to the bottom of it, they’d attempt to understand why the overwhelming majority of dogs who eat grapes DON’T get sick, and they’d look at the differences between these dogs and the ones who got sick.  Nobody’s doing that.  There is money to be made by allowing this stupid myth to stand, and there is NO money to be made by exposing it.  As in human medical research, MONEY is what determines what gets studied.

More self-serving propaganda

The Scopes report goes on: “These cases were noted all across the USA, with the amount eaten varying widely from a pound of grapes to as little as a single serving of raisins.”  From the paranoia that is being spread surrounding grapes, we would expect that one or two grapes might be enough to kill a dog. Yet here we have the worst case scenario being painted by Scopes, which admits that problematic quantities BEGIN at a full POUND of grapes. Any number of circumstances can be imagined where eating a full pound of grapes would cause a problem for a dog which would have nothing to do with grapes being fundamentally toxic to dogs. Regarding raisins, presumably by “single serving” they mean a serving size suitable for a human. Since raisins are a processed food that dogs would have no adapted ability to digest in large quantities, this might be enough to legitimately cause problems for a small or medium sized dog, particularly one that is kibble fed. This would not allow us to jump to the unrelated conclusion that grapes are toxic, and it doesn’t say a whole lot about raisins either except that they are another of the thousands of foods that are not appropriate for dogs.

Not everybody’s buying it

Fortunately, there are others doubting the party line about grape toxicity. Andrews and Liquorman of ran a survey of 130 dog breeders, vets and professional dog handlers. 130 to 0, not one of them had ever had or known of a dog that did more than wag and beg for more after eating raisins or grapes. Here’s the full debunking article:

Wild dogs eat grapes!

We have evidence of wild dogs eating grapes, wild and cultivated. People who live in wine country inhabited by coyotes report seeing coyote droppings full of grape seeds, for example. Grapes probably aren’t the first choice even for coyotes, but coyotes typically aren’t in a position to be choosy. However, they aren’t suicidal, either, even when hungry.  And they are close enough genetically to the domestic dog that we can assume what is toxic for one would be so for the other.  Grapes have also been found in wolf scats in various parts of the globe, and wolves are our dogs’ closest wild relatives.

Some dogs don’t even like grapes

My dog, like many dogs, doesn’t like grapes, even sweet, tender, seedless ones offered straight from the vine. I suspect this is because of the dense outer skin on grapes that is absent in other more bioavailable fruits like figs or melons, which are almost universally appealing to dogs. Dogs don’t have that much capacity for chewing and they lack the digestive chemistry for breaking down cellulose. We all know dogs that eat anything marginally edible that they come across, even things that their bodies will have trouble digesting. When trouble follows, it doesn’t necessarily mean the same effect will occur in all dogs eating that particular “food”.  And it also doesn’t mean that when a dog enjoys eating grapes that his food selection skills are compromised.

Wasteful fear mongering

Recently I saw a billboard in a small rural town in California that had been put up by the local animal shelter that said “Grapes are toxic to dogs”.  It is saddening to know that even with financial resources of shelters being strapped to the bone in the current economy, they are choosing to spend their money on perpetuating baseless vet-industry-generated myths rather than saving the lives of dogs.
The problem that grapes represent in dogs, if any truly exists, may be similar to that of peanuts in children.  For a few children, peanuts can cause sometimes fatal anaphylactic shock.  If keeping peanuts and peanut products out of the schools is necessary to protect these few susceptible  kids, it might be justifiable.  But the dog-grapes myth is like telling all children that eating peanuts is dangerous or fatal.  Before we did that, wouldn’t we need to account for the millions of children who eat peanut butter everyday without harm, and the millions of adults living right now who survived regular peanut-eating in childhood?
Telling dog owners that grapes are poisonous to dogs is irresponsible. You may rightly wonder, however, what the harm is in telling people not to feed grapes to their dogs.  Cautious dog owners will simply choose not to feed grapes. There’s nothing in grapes that dogs can’t get from other foods, so nothing will be lost, right?  Not necessarily.  We must consider the impact that fake warnings have on dog owners who are consequently unable to sort out what’s really dangerous from what’s hyped or imagined. There are plenty of hazards to dogs that owners need to be aware of which have been studied and legitimately identified, without inventing others.  The other negative by-product of a myth like this is the implication that average dog owners cannot possibly figure out what’s good or bad for dogs without the help of vets and other “experts”.  After all, there might be some danger lurking in the most innocent-appearing food, or so we are to think.  In the end, the biggest danger might be in allowing “experts” to do our thinking for us.
I had an interesting personal experience with the raisin/grape controversy this week when one of my clients’ dogs managed to get into a 24-ounce container of raisins.  The dog ate roughly half, and she’s a 10-pound Puggle (half Pug, half Beagle).  The owner was apparently unaware of the hype around raisins and dogs so she hadn’t fallen prey to the fear mongering.  So, she was able to keep her head and approach the situation with calmness and objectivity.  Within about 3 hours of eating the raisins, the dog exhibited some of the symptoms that some dogs are reported to experience — notably, shivering, vomiting and diarrhea.  The owner kept a close eye on the dog for 24 hours, did not feed her and watched for signs of the extreme weakness and urinary difficulty that indicate kidney problems.  The owner did not seek veterinary intervention and instead allowed the dog’s body to reject the food naturally.  Within 36 hours, the dog was completely normal.
It should be noted that the dog in question is young (<2 yrs) and had been properly raw fed for 3 months prior to the raisin eating incident.  Before that she had been fed high quality grain-free kibble.  We can probably assume that these factors most likely had some influence on the outcome.
Obviously I could not recommend that dog owners take the same approach in every situation.  To be perfectly honest, even I was nervous as I waited to hear how the dog was doing the next day.  But there is some useful info to be gleaned from this experience that may help others keep their cool in similar circumstances.  Firstly, it provides even more evidence that raisins can’t possibly be as deadly as they are being made out to be by vets and others.  The factors that are alleged to create the most unfavorable outcomes are the quantity eaten relative to the size of the dog.  In this case, the dog had eaten roughly 7% of her body weight in raisins!  If there was ever a situation where the hype would have us expecting the worst, this was it.  Another question to ponder is one that is not often considered:  is it possible that in cases where outcomes are bad (dog dies), did heroic veterinary intervention contribute in a negative way?  After all, we have very few, if any, reports of dogs dying without intervention after consuming raisins or grapes.  That might be due to the fact that when a dog dies without vet care, the death is not reported.  Or it may be that it just never happens, because dogs who are treated tend to die more often than those that go untreated.  We will likely never know, because once again it’s in nobody’s financial interest to find out.  The question deserves to be asked, however, because we know that when outcomes are good, it is typical for medicines to be credited arbitrarily.  When things don’t turn out so well, the sickness or ‘poison’ is blamed, also arbitrarily.  In both scenarios, it is beliefs and wishful thinking that people typically use to form conclusions, rather than logic, reason and evidence.
Often these kinds of situations are approached with a “better safe than sorry” attitude, which for most people means involving a vet.  But if we are to look objectively at the evidence and everything we know to be true, we might find that this is not a cautious approach at all, particularly when you factor in the reality that many people simply cannot afford the exorbitant financial cost of intervention.
Best wishes,
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Rose December 27, 2011 at 9:34 am

Thanks so much for this article. This is what I always believed despite the hype all over the Internet and my kids warning me not to feed my dogs grapes. I also thought the same thing about the study quoted on Snopes. I have four dogs and two of them love fruit of any kind. Occasionally I have treated all four of them to a few grapes and not one has ever been sick from it. I agree that the amount of grapes fed should be observed as too many grapes can cause gastrointestinal problems for anyone. I’m happy to have found at least one article with common sense about this subject.Thank you.

admin January 15, 2017 at 7:20 pm

Dear Anonymous,
I’d like to know where you get the information that “30%” of dogs are “sensitive” to grapes and raisins? A link would be appreciated. I disagree that the idea that questioning this myth is “negative fallout” from the “inconsistency of response”. The observation that all but a tiny minority of dogs have no problems eating grapes is completely appropriate and proper, and rightly leads people to conclude that grapes are not poisonous at all. If a poison is truly a poison, this needs to be established using the same scientific methods that have been used to identify and document poisons since time immemorial. This has not been done where grapes and raisins are concerned.

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