Bioavailabilty & Why Sources Matter
Absorption is more important than amount
We’ve written a lot about AAFCO. Despite our critique of their appropriateness for fresh foods, we believe this group plays an important role. After all, without AAFCO guidelines, pet food manufacturers could put whatever they wanted into dog food. So if you think that kibble is bad now, imagine what it would be like if AAFCO didn’t exist.
However, AAFCO guidelines are not made for real foods, and today we dive into the main reason why, bioavailability. This is a topic that’s important to how we think about Cedric and Edith’s food. Though it sounds scientific, bioavailability just means how much of a nutrient can actually be used by the body. Before that here is a new, simple recipe to use with All Pups Seasoning!
AAFCO and pet food
AAFCO was originally formed in 1909. It’s main function was to ensure animal feeds met a certain threshold of quality for farmers. By the 1980s the pet food industry grew large and manufacturers were making all sorts of wild claims. AAFCO was the most logical organization to set rules. They standardized nutrition profiles and required minimum crude analysis. These were all good initiatives that helped to keep many millions of dogs safe from eating substandard food. (Sawdust used to be a common ingredient in dog food.)
However, at some point, the pet food industry started to infiltrate and influence AAFCO. We’ve shared public records of officials objecting to industry representatives being on executive committees in the organization. Furthermore, because the organization is over 100 years old and covers a wide variety of species from farm animals to fish in addition to pets, they move extremely slowly. The last meaningful update to AAFCO dog food guidelines occurred over 10 years ago.
Ultimately, the guidelines are limited in scope. There are no guidelines for weight loss, senior dogs, or medical conditions. Renal, senior and other “prescription” diets are made at the discretion of the manufacturers and vary widely. Fresh, real food nutrition is not given any consideration in their guidelines at all. In fact vitamin B9 in AAFCO guidelines is listed as folic acid, the synthetic form of folate!
Why AAFCO numbers don’t work for real food
When we first started formulating AAFCO-balanced real food for Cedric and Edith, we couldn’t believe how hard it was. We were sitting there with spreadsheets and nutrition databases thinking, how can this be so hard? We’re using real food. High-quality stuff, the kind of ingredients people have been feeding dogs for thousands of years. But the numbers wouldn’t line up. (We also found numerous mistakes in the leading pet food formulation software.)
Zinc and copper were always difficult to get right. No matter what we did, we couldn’t hit the AAFCO minimums without stuffing so much of certain ingredients into each recipe that it threw everything else off. So we started asking a question that changed everything for us: where do these numbers actually come from?
What did dogs eat before AAFCO?
Nutrient minimums in AAFCO are based on the ingredients that kibble manufacturers use, which are synthetic vitamins and inorganic minerals. Zinc oxide. Copper Oxide. Ferrous sulfate. These are cheap additives that get sprayed onto processed food to make the nutritional math work on paper.
But dogs didn’t eat zinc oxide for the first 15,000 years of domestication. They ate animals. They ate scraps. They ate whatever was around. And they were fine. So when we couldn’t hit the AAFCO zinc number without using tons of oysters (literally the highest zinc food on earth), something didn’t add up.
The bioavailability problem
This is where it gets interesting. Minerals in forms like zinc oxide and copper oxide are incredibly stable compounds. They are the end result of numerous chemical reactions over long periods of time. This stability is great for shelf life, but terrible for digestion. Your dog’s body has to work extra hard to break them apart and absorb the zinc or copper inside. Studies show dogs only absorb about 20-30% of the zinc from zinc oxide.
Zinc from oysters is a completely different situation. It comes bound to proteins, and dogs (and people) are able to absorb far more of it. The same is true for copper from organ meat vs copper oxide (which dogs absorb as little as 5-15% of). Other examples include iron from meat vs ferrous sulfate, and selenium from seafood vs sodium selenite. According to research on canine absorption, selenium from food sources has as much as a 4-times higher absorption rate than sodium selenite. However, not all natural vitamins and minerals are more bioavailable. Vitamin C for example is the same whether it comes from a lab or broccoli. Some forms of synthetic vitamins are actually more potent including iodine and several B vitamins. (Some researchers believe food aids in absorption and utilization, but this research is still far from definitive.)
But for many nutrients it does make a big difference. AAFCO says your dog needs 20mg of zinc per 1000 kcal. But that number was set assuming your dog is eating zinc as a supplement and absorbing a fraction of it. If your dog is eating zinc from oysters and real meat, they need far less than 20mg / 1000 kCal. They’re getting more out of less because the source actually works with their bodies.
Once we understood this about zinc, we started questioning everything.
Anton Beynen has written extensively about canine nutrition, and one of the things that jumped out to us from his research was the calcium-to-phosphorus ratio. Every canine nutritionist treats the Ca:P ratio like gospel. It has to be between 1:1 and 2:1 or your dog is in danger. But when you actually look for the evidence supporting that specific ratio in adult dogs, there’s almost nothing there. Beynen himself has pointed out that the calcium requirement for adult dogs is actually quite low.
That was another turning point for us. If the “rules” don’t even have strong evidence behind them, what about all the other beliefs? How many of these rules and beliefs are based on solid science, and how many are just conventions that nobody has bothered to challenge? Another example we previously covered was the poor research around avocado toxicity in dogs. The original source for the claim was an anecdotal report of two dead dogs that were taken to an animal hospital in Nairobi, Kenya. This anecdotal report somehow made it as a primary source for a European research paper that has over 100 citations. This is an example of why research should be read with skepticism.
The carbohydrate conundrum
AAFCO requires extremely specific amounts of minerals. You need exactly this much zinc, this much copper, this much selenium, down to the milligram. Miss any of them and you can’t call your food “complete and balanced.”
But carbohydrates? Dogs have zero dietary requirement for carbohydrates. Zero. Yet AAFCO doesn’t set a maximum. You can legally make a dog food that’s 70% carbohydrate and still call it complete and balanced. Even though increasing refined carbohydrate intake in dogs (like the kind in kibble) is associated with worse health outcomes, including higher blood sugar, increased inflammation, and greater risk of chronic disease.
AAFCO guidelines and nutritionists obsesses over minerals down to fractions of a milligram. They use targets calibrated for synthetic forms of vitamins and minerals, some of which dogs barely absorb, yet completely ignore the macronutrient that’s doing the most damage in commercial diets. We find that many dogs do well with some COMPLEX carbohydrates. But most dogs today are getting the majority of their energy from refined carbs, and that’s just not what serves them best over the long term.
Introducing The Dog’s Table Standard
We don’t ignore AAFCO. We think nutrient requirements are important. After all dogs need zinc, copper, selenium, vitamin D, and all the rest. The question is how much, and from what source.
We recently updated our nutrition calculator to take every AAFCO requirement and adjusts it based on published bioavailability data for whole food sources. When you feed your dog zinc from oysters instead of zinc oxide, they need less of it because they absorb more. When you feed iron from liver instead of ferrous sulfate, it’s the same thing. Vitamin E from sunflower seeds is up to twice as potent as the synthetic dl-alpha form that kibble uses.
Going forward, every one of our recipes will meet or exceeds AAFCO requirements when you account for how much of each nutrient a dog actually absorbs. Not what’s listed, but what their body can use. We are calling this The Dog’s Table Standard.
That’s the difference between creating products for good-looking labels and creating products for healthy dogs.
Why this matters for you
If you’re cooking for your dog and worrying about whether the food is “balanced enough,” you’re probably doing better than you think. In general, whole food ingredients are more bioavailable than the processed meals and synthetic additives in commercial food.
If someone tells you homemade food can’t be balanced without a synthetic vitamin pack, ask them which form of zinc they’re basing that on. The answer matters a lot more than most people realize.
All the best,
Joelle & R.A.