The Ketogenic Diet is not supposed to be a long-term diet. Partly because little is genuinely known about the long-term effects. There still isn’t enough research into the long-term effects. Most of the studies have not been conducted for an extended period of time. There are very few studies in Dogs or Cats.
Most of the longer studies have been on those undergoing treatment for cancer or epilepsy, which does not translate to a healthy human, never mind a healthy dog or cat, and certain side effects of the ketogenic diet can be considered worth it when dealing with both of those conditions.
What we do know so far about the long-term effects of the Ketogenic Diet is concerning in both human and rat studies.
In one study 12-week study on rats, the researchers found that those fed the Ketogenic Diet had compromised Cancellous and Cortical Bone mass and degraded mechanical strength in the hind limbs.
In a retrospective, observational cohort study of 68 patients undergoing Ketogenic Diet Therapy; 8.8 % of patients got one or more long-bone fractures, two of which were acquired after a mild trauma; the causes of the other fractures were unknown/ nontraumatic. Another 8.8 % also had kidney stones during the treatment.
The researchers concluded that the patients had a low normal bone mineral density, which could further decrease, and that patients need to be monitored for kidney stones and hypercalciuria.
In a 60 day study on male rats fed a ketogenic diet that was 5.66 percent carbs, 86.19 percent fat, and 8.15 percent protein. The researchers did find some reasons to be concerned, mainly metabolic acidosis, anemia, and decreasing plasma antioxidant activity. While, Liver and Kidney function remained normal, despite the significant increase in lipid peroxidation activity. It was only a 60 day study. and more research is definitely needed in regards to the impact on liver and kidney health.
Several studies have shown that the Ketogenic diet can slow growth in children. In one such study with 24 children, they found that the Ketogenic Diet resulted in a decline in the linear growth rate of children. There have been several other studies that had the same or similar results.
It is important to note that when patients are put on ketogenic diet therapy, they have a team of specialists. The diet is carefully formulated to make sure they are still receiving the proper amount of vitamins and minerals.
Ultimately this makes them an apt comparison to complete and balanced Ketogenic Diets for Dogs, as they are formulated to meet AAFCO Nutrient Guidelines.
Several studies have also shown that a High-Fat diet can alter the gut microbiome, and not necessarily for the better. In one study with 12 children specifically, they found that a high-fat diet can lower the amount of Bidfidobacteria and increase the amount of Escherichia coli. While not necessarily harmful in small amounts, it can be a cause of dysbiosis when present in abundance, and we are slowly recognizing the importance of gut health and its impact on health.
Why we need to be careful.
Our pets don’t live as long as we do. The effects we have seen on humans in particular and mice to a lesser extent could be significantly worse for our pets, especially puppies.
These effects might be acceptable to a pet undergoing treatment for health conditions that respond well to a Ketogenic Diet. The possible side effects are ultimately unacceptable for normal, healthy dogs or puppies.
Some of these risks, such as the increase of Kidney Stones, should be especially worrying for dogs that have previously had kidney stones or a breed that is highly susceptible to kidney stones. The possible effects of the ketogenic diet on growing puppies need to be fully explored.
These effects are largely not even discussed in the broader literature around the ketogenic diet because, one, the side effects are worth it when dealing with cancer or epilepsy, and two, most studies concentrate on the benefits, not the side effects.
AAFCO Complete and Balanced and Feeding Trials are Inadequate
These foods are formulated to be complete and balanced diets according to AAFCO Nutrient standards. Some of them may have possibly even conducted feeding trials. It needs to be noted that most pet foods don’t conduct feeding trials.
However, the Ketogenic Diet is vastly different than most pet foods available, which makes it even more important that they conduct feeding trials on healthy dogs, not just dogs that have health conditions that may react positively to a ketogenic diet.
I reached out to 3 different companies and only one responded. The company that I communicated with when I asked if they conducted any AAFCO Feeding Trials they first said that they don’t offer any free trials. They later claimed that their formulations were validated on around 120 dogs over 6 years. They claimed they conducted independent feeding trials, but did not say whether they were conducted on dogs undergoing treatment or whether they were normal healthy dogs. They ignored the question as to whether they were AAFCO Approved Feeding Trials. Based on the first response, I and any reasonable person would be skeptical of their clams.
Even if they did conduct a feeding trial, there is still the issue, as some of you may know, that AAFCO feeding trials are inadequate in actually assessing the long-term impact of a food. An AAFCO Feeding trial is only 26 weeks and consists of a minimum of 8 dogs, only 75% of which must finish the trial. They do a minimum number of tests.
- Physical Examination
- Packed Cell Volume
- Serum Alkaline Phosphate
- Serum Albumin
- All Medication and the reason for its use must be recorded.
How do Dog Foods Fail a feeding trial?
- More than 25% dogs drop out
- They fail if there are signs of nutritional inadequacy or toxicity
- Side note no ones really knows for sure how long it really takes for a deficiency to occur. For example for Vitamin A it would require checking the Vitamin A stores in the liver to actually see if the diet is deficient.
- No dog loses more than 15% or gains more than 10% of its weight
- Average Hemoglobin no less than 14 g/fl (no individual less than 12/dl)
- Average PCV is less than 42 % (no individual less than 36%)
- Average Albumin is less than 2.8 g/Dl no individual less than 2.4 g/Dl)
- Average Serum Alkaline Phosphate is less than 150U/L
- Note the levels cannot be greater than the colony average plus 2.33 times the standard of error
These tests wouldn’t discover some of the possible side effects of feeding a ketogenic diet long-term. It might not detect the increased risk of bone fractures. It might not detect the increased risk of kidney stones. It might not detect changes in the gut microbiome.
Feeding trials for ketogenic diets need to fully evaluate the risk of kidney stones. They need to evaluate how it impacts growth of puppies. They need to evaluate how it impacts bone density.
Reasons to be Concerned
Unfortunately, the Ketogenic Diet is currently popular; This is not a good thing for dogs.
Everyone knows there are owners who will put their dogs on a Ketogenic Diet for reasons not related to the health of their pets, just as people put dogs and cats on vegan diets.
Everyone knows there are owners who won’t rotate their pets on and off of the diet. The companies claim you don’t need to rotate off of the diet because they are complete and balanced, so you can “feed them Keto for life”.
Everyone knows there are owners who will place a puppy on the food not knowing that it might potentially impact their puppies growth.
The companies do claim after all that it is suitable for all life stages. It should be noted that some of them do not include the statement for large breed puppies.
It is possible that ketogenic diet might be beneficial for breeds that evolved eating a diet higher in fat, but that isn’t the case for most dog breeds.
Detecting the Issues
If a dog gets kidney stones or breaks a leg due to low bone mineral density, it probably won’t be linked to the diet by the owner or veterinarian. How many dogs would it take for the average veterinarian to notice a pattern? It will take hundreds if not thousands of dogs before it is linked specifically to dogs or cats being fed a Ketogenic Diet long term. Especially when most owners and veterinarians are not aware of these effects.
Dogs have a vastly shorter period of growth, so the effects of slowed or stunted growth in a puppy will end up having a more significant effect. Slowed or stunted growth that will likely not be noticed until it has already significantly impacted their growth, and unlike humans, there won’t be time for the puppy to catch up. This could have long-term repercussions. This is something that the companies need to fully investigate before proudly saying that you can feed a “Ketogenic Diet to Puppies after weaning”.
Ketogenic Diet for Dogs And Cancer
The Ketogenic diet is commonly recommended for dogs with cancer. While some of the research does show a positive effect, some of the research shows no effect, and with certain cancers research shows that it may actually make it worse. Additionally, some research does show that some cancer cells can utilize ketones as a secondary energy source.
Ketogenic Diet for Dogs And Epilepsy
While in humans, the ketogenic diet has had some success in managing epilepsy, when it comes to dogs, the effects are significantly less consistent, but it also hasn’t been very well studied.
What Needs to be Done?
This is a situation when there should be a prescription. Owners shouldn’t be able to place their pets on the diet willy nilly. The companies selling these diets should be putting controls in place to prevent people from putting their dog on a Ketogenic Diet when there is no medical need. Instead of placing the food in retail stores, they should be limiting it to veterinary offices where it can be more controlled. Retail store owners must be vigilant in educating consumers who want to feed their dogs a Ketogenic Diet and the importance of rotating their dogs on and off a ketogenic diet.
Retail store owners and veterinarians do need to do a better job period of encouraging owners to rotate foods more often. ie not keeping the dog on the same food for months and years at a time.
One Recent Study found that owners were feeding the same food for a minimum of 182 days (6 Months) a max of 3558 days (9.5 Years) with the median being 814.5 days (2.31 Years). One owner did not report the length of time while the other remaining owner said several years.
The companies are trying to help. There are some health conditions that respond well to a ketogenic diet, and it’s a good thing that they are being made for those dogs that might be able to benefit from a ketogenic diet.
Its possible that rotating your dog on and off the ketogenic diet could be beneficial,, but at the same time the ketogenic diet could end up doing more harm than good.
The companies need to conduct long-term feeding trials that go well beyond AAFCO standards. They need to conduct studies on normal, healthy dogs; not just those being treated for medical conditions that respond well to the Ketogenic Diet. They need to actually investigate the impact of the Ketogenic Diet on the growth of puppies. They need to truly investigate the long-term effects on organ function. They need to investigate whether it will put dogs at an increased risk of bone fractures or kidney stones. They need to do a better job of encouraging owners to rotate dogs on and off of the ketogenic diet.
As the saying goes, all things in moderation. The discussions around the ketogenic diet, all ignore the possible side effects of the diet, probably because the advocates are only focusing on the potential positive aspects of the diet and because there hasn’t been much research investigating the impacts on bone health.
Ultimately there are several risks and a lot of unknowns at this point. Caution should be exercised before placing your pet on a Ketogenic Diet. As pet parents we need to demand that these companies do more research into the long-term effects of feeding a Ketogenic Diet.
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Xu X, Ding J, Wu X, et al. Bone microstructure and metabolism changes under the combined intervention of ketogenic diet with intermittent fasting: an in vivo study of rats. Exp Anim. 2019;68(3):371-380. doi:10.1538/expanim.18-0084