A note on the burden of proof: I am often asked for further studies to ‘prove’ that rotational diets have no benefits – except the burden of proof lies with the individuals who claim rotational diets have benefits, and if they cannot produce evidence to support their claims (that rotational dieting somehow prevents allergies, improves the microbiome or ‘balances’ the diet) then it simply means they are false. Unfortunately we cannot debunk something that doesn’t have any evidence begin with. For this reason, this post has limited references, but I have updated some of the content here to help pet owners discern the claims they hear online and linked back to other relevant posts to provide further information on the topics covered here. For more information on the burden of proof, see my Instagram post below:
Some people believe rotating diets is how we should feed pets. They believe this because they claim it will reduce the supposed “negative impacts” of feeding one diet, provide variety for their pet and reduce the potential to develop allergies to a food.
Let’s unpack this. There are so many myths associated with this type of feeding that it’s important to consider each of these claims and determine if they have evidence:
Claim 1: You should not feed one diet everyday, because no food is complete and balanced
This is mainly because pet owners have been led to believe that feeding the same complete and balanced diet every day for the life of their pets is somehow damaging – in fact, this claim stems from the opinion that kibble has all the nutrition ‘cooked out’. This couldn’t be further from the truth, as a complete and balanced diet is defined as a diet that meets the minimum and maximum requirements of vitamins, minerals, protein, and fat for the intended life stage of a pet. When a diet is formulated, losses and gains of specific nutrients are taken into account, and supplements are added to replace anything lost in cooking, processing or storage. This guarantees that no supplements need to be added to your pet’s diet to meet the crucial requirements that are needed for your pet to survive.
Unfortunately however, we do know that feeding a highly variable diet is actually more damaging in that if the diet is not always balanced, we can create what is called a “Swiss cheese effect” where all the different deficiencies add up over time to cause illness. We know that 95% of homecooked pet food recipes found online and in textbooks are deficient in one or more nutrient – and by rotating multiple deficient diets at any one time, you’ll only end up with something being deficient all the time. This simply isn’t the case for commercial foods, but we have different issues there – if we mix two balanced diets, we are likely to end up with excesses and deficiencies due to the way the nutrients interact.
Claim 2: Rotating diets creates a diverse microbiome
When frequently changing diets, diarrhea often results. This is actually due to a shift in the microbial population in the gut; the types of microbiota in the gut depends on the types of foods the pet consumes and is adapted to that diet. For example, pets that consume high levels of animal protein will have more proteolytic bacteria than those who do not. So, when a new food is introduced this shift occurs quite rapidly when changing diets, and this has a profound effect on the microbiome – it essentially causes the old microbiome to die off and be replaced with brand new microorganisms. With this in mind, we can see how simply changing diets all the time isn’t necessarily going to be maintaining a ‘diverse’ microbiome, but potentially just causing a lot of GI distress for your pet.
In the same way, we need to think if a diverse microbiome is something we even want – there’s little evidence to suggest a ‘diverse’ microbiome is what you want, considering this would simply mean you have many different types of organisms (some pathogenic and some symbiotic) in the gut but this doesn’t necessarily confer a benefit. Really what we want is a microbiome that is relatively balanced, stable and has lower concentrations of pathogenic bacteria.
Claim 3: Helps to avoid your pet being affected by a recall
This to me is wild. Recalls are relatively rare, but even if this was your intention, feeding multiple different diets in rotation with no record of batches and dates of when the product was consumed, will make it near impossible for you to trace if your pet has been affected by a recall. It also means if you ever notice your pet has an issue, it’s going to be very difficult to narrow down which of the multiple diets you feed is the culprit.
The safest method of avoiding recalls is feeding a diet that follows strict quality control standards and the WSAVA guidelines. Do not use a diet that touts zero recalls as this can simply mean they don’t perform QC testing to voluntarily recall their foods before they harm pets.
Claim 4: Pets like and need variety
Cats and dogs have significantly less tastebuds than we do, and experience flavour in a very different way to us; they generally prefer texture, temperature and smell when selecting their food not so much the actual flavour. Flavours in pet foods is usually more of a way to appeal to pet owners rather than pets, because apart from the differences in smell the pet probably doesn’t even recognise the difference in taste. Cats in fact, will refuse to eat if they can’t smell their food and often won’t eat things straight out of the fridge because the smell is so dulled. Again, because we as humans would become bored if we ate the same thing, pet owners extend this same belief to their pets; humans eat a wide variety of foods as they cannot get a balanced diet from one specific food unlike pets, and still majority of the global population suffers from at least one deficiency of vitamins or minerals whether they know it or not. Multivitamins for humans are really meant to be used with a balanced diet anyway, so the argument that we have variety and eat a perfectly balanced diet yet don’t suffer any ill effects is actually false; we also have the benefit of our foods being fortified with nutrients to try and avoid us developing nutrient deficiencies so we don’t naturally have complete and balanced diets anyway, so arguing this is a moot point.
Claim 5: Rotating diets prevents allergies
Allergies develop with exposure to an allergen. With pets, providing them access to a wide variety of protein sources and diets actually increases their chances of developing unusual allergies, and making treatment (finding a novel or new protein for them to safely consume) very difficult. Sometimes the term used is a sacrificial protein; this means by feeding your pet one thing only and they then suddenly develop an allergy to it, we can ‘sacrifice’ that protein and use something different which is not an allergen – if the pet has been exposed to lots and lots of different diets and proteins, not only do we not have a ‘safe’ protein source for them to eat, we also may find it extremely difficult to actually diagnose what is causing the allergy. So, it’s actually better for allergic pets to eat one thing until they can’t, rather than over-exposing them and changing their diet. It’s also important to note that many “limited ingredient” diets contain traces of various protein sources and can actually contribute to allergies in pets by exposing them to multiple allergens, so the claim that simply mixing and matching diets will prevent allergies is downright false. To date, we have no evidence of any diet regimen that ‘prevents’ food allergies in humans or any other animal.
When should you change your pet’s diet?
• Entering a new lifestage: if your puppy or kitten is now an adult, or your adult is now a senior, consider switching foods.
• New diagnosis: if your pet has been recently diagnosed with a new disease or disorder, speak with your vet or a nutritionist on what diet would best manage their condition
• Allergies: if your pet has been diagnosed with a true food allergy, then you will need to switch to a hydrolysed or truely novel protein diet
• Current diet is not ideal for your pet: if your vet has recommended changing the diet, your pet is under or overweight, your pet is not thriving, they are experiencing frequent gastrointestinal upsets or their coat appears dull and dry you will need to switch diets
Bibliography
Davies RH, Lawes JR, Wales AD. Raw diets for dogs and cats: a review, with particular reference to microbiological hazards. J Small Anim Pract. 2019;60(6):329-339. doi:10.1111/jsap.13000
https://doi.org/10.1016/j.cvsm.2021.01.002
https://www.fda.gov/animal-veterinary/animal-health-literacy/complete-and-balanced-pet-food
https://www.aaha.org/trends-magazine/publications/homemade-pet-food-guidance/
https://vetnutrition.tufts.edu/2017/01/food-allergies/
https://tails.com/blog/2016/02/29/do-dogs-get-bored-of-their-food/
https://www.akc.org/expert-advice/nutrition/accounting-taste-probing-mysteries-dogs-find-delicious/