The Canine Ledger

The Seven Nutrients Homemade Diets Miss Most

Zinc, choline, copper, omega-3s, calcium, vitamin E and vitamin D. What two large recipe studies found, how short the recipes fell, and why it matters.

Written by thecanineledger

In 2013, researchers at UC Davis ran 200 published recipes for adult dogs through nutrient-analysis software, from books by veterinarians as well as websites. Their finding: “Only 3 recipes provided all essential nutrients in concentrations meeting or exceeding the NRC RA”, meaning the recommended allowance set by the US National Research Council (Stockman et al., JAVMA 2013).

Three out of two hundred. Two more met the NRC’s lower minimum requirement for every nutrient. Overall, “most (190/200 [95%]) recipes resulted in at least 1 essential nutrient at concentrations that did not meet NRC or AAFCO guidelines.”

While every recipe goes wrong in its own way, the gaps are not random. The same few nutrients come up short again and again, in different countries and against different standards. This page names them, shows how short the recipes fell, and explains why topping up one nutrient at a time is not the fix it looks like.

1. The list

The UC Davis study named the five most commonly deficient nutrients, and separately reported vitamins D and E. A 2017 Brazilian study of 82 recipes published in Portuguese that could be fed to dogs, scored against the European FEDIAF guidelines, found most of the same gaps (Pedrinelli et al., Journal of Nutritional Science 2017).

NutrientUC Davis 2013 (200 recipes, NRC)Brazil 2017 (82 recipes, FEDIAF)
Zinc69% short75.6% short
Choline64.5% short85.4% short
Copper54% short85.4% short
EPA + DHA (omega-3s)53.5% shortNot reported in the list
Calcium35% short73.2% short
Vitamin E45.1% short (of 175 recipes with full data)82.9% short
Vitamin DSee §2Among the nutrients furthest below the recommendation

Sources: the UC Davis text and Table 1; the Brazilian abstract. The 2017 study also found iron short in 68.3% of dog recipes, riboflavin in 65.8% and vitamin B12 in 61%.

Five of the seven were short in most or many recipes in both studies: zinc, choline, copper, calcium and vitamin E. The two studies used different standards, in different countries, with different recipe sources. That they agree is the point.

Our note: “Seven” is our framing, not either study’s. It is the five most common deficiencies UC Davis named, plus the two vitamins it reported separately.

2. Why we don’t print a vitamin D figure

The UC Davis paper reports that 102 of 167 recipes were too low in vitamin D. We have not put that number in the table.

A year after publication, the journal printed a correction. It says that “the value for the National Research Council recommended allowance of vitamin D in Table 1 on page 1502 and Table 3 on page 1503 is incorrect” (Correction, JAVMA 2014;245(2):177). The corrected value is well under half the one the paper’s tables used. (We are not printing either number: they are formulation targets, not something to dose from.) The correction does not say whether the deficiency count changes, but if the recipes were scored against the higher figure, the count is likely to be too high.

So vitamin D is on the list, because both studies flagged it. The 2017 study put it among the nutrients furthest below recommendation. But we are not printing a percentage we have reason to doubt.

Our note: We think the vitamin D deficiency counts were probably scored against the wrong, higher value, so we don’t print them.

3. How short is short?

Some recipes missed by a little. Many did not.

The UC Davis team counted recipes that did not reach even half the NRC recommended allowance. Among recipes short in each nutrient, that was the case for zinc in 55.1%, choline in 43.4% and vitamin E in 39.2%. (They also report this for vitamin D, but the §2 problem applies.)

Missing a nutrient by half is not a rounding error. It means the recipe, fed exactly, supplies half of what the dog is recommended to get, every day.

4. Why each one matters

We have kept this to what the sources say. None of these is something to diagnose at home.

NutrientWhat the source says
Choline“diets deficient in choline can cause weight loss and fat accumulation in the liver” (UC Davis 2013)
Vitamin D“vitamin D deficiency may cause substantial musculoskeletal abnormalities, particularly in growing puppies” (UC Davis 2013)
Zinc and vitamin E“clinical signs of deficiency may appear only after a prolonged period of feeding a deficient maintenance diet” (UC Davis 2013)
Calcium“calcium deficiencies have occurred when feeding high- or all-meat diets high in phosphorus and low in calcium” (Merck Veterinary Manual)
Zinc in plant-heavy recipes“phytate present in vegetable ingredients can bind to zinc and reduce its bioavailability” (Pedrinelli et al., BMC Veterinary Research 2021)
EPA + DHAThe NRC sets an adult recommendation; AAFCO does not. AAFCO’s 2014 profiles set an omega-3 minimum for growth only, finding no “scientific justification for setting minimum recommended concentrations for n-3 fatty acids for adult maintenance” (AAFCO 2014)

The EPA and DHA row is worth reading twice. Whether a recipe is “short” in omega-3s depends on which standard you hold it to. Against the NRC, half the UC Davis recipes were. Against AAFCO’s adult profile, there is no minimum to miss.

The quiet ones are the worry. A shortfall in zinc or vitamin E may take a long time to show. By then the dog has been eating the recipe for months.

→ The Calcium Problem: Why Meat-and-Rice Diets Break Bones

Our note: UC Davis lists EPA and DHA among the five most common deficiencies, but AAFCO sets no adult minimum. A shortfall here isn’t a definite problem.

5. Rotating recipes doesn’t fill the gaps

A common answer to all this is variety: no single meal has to be complete if the week balances out. The UC Davis team tested it.

“Many proponents of less structured recipes for home-prepared diets assert that although each day’s meal is not necessarily complete, rotation and variety will provide a balanced diet overall. Our analysis indicated that this assumption was unfounded because evaluation of 3 recipe groups, each of which comprised 7 separate recipes, did not eliminate deficiencies.”

The reason is in their next finding: “many recipes had similar deficiencies, with 14 nutrients provided at inadequate concentrations in at least 50 recipes.” Rotating recipes that share the same gaps just rotates the gaps.

6. Vets’ recipes did better, but not well

Recipes written by veterinarians had fewer and less severe deficiencies than those by non-veterinarians. All five recipes that met NRC values for every essential nutrient were written by veterinarians. Still, the authors note that “most of the veterinarian-written recipes had at least 1 nutrient deficiency.”

A recipe from a vet’s book is better odds than one from a forum. It is not the same as a recipe formulated for your dog.

7. Why you can’t fix them one at a time

Seeing a list like this, it is tempting to add a zinc tablet and some fish oil and call it done. We are deliberately not naming a product or giving an amount, because the list tells you where recipes usually fail, not where yours does or by how much.

Two problems sit underneath that temptation. First, the right amount of each nutrient depends on everything else in the bowl. Calcium has to be balanced against phosphorus, for example. Second, adding nutrients on a guess can overshoot. The UC Davis study found the opposite failure too: “Nine recipes surpassed the safe upper limit for vitamin D, and 6 surpassed the safe upper limit for the combination of EPA plus DHA.”

The UC Davis team’s own recommendation is the one we would give: recipes should “be obtained from or evaluated by board-certified veterinary nutritionists or veterinarians with advanced training in nutrition.”

→ How to Get a Properly Formulated Recipe (and What It Costs) · → Why Adding a Multivitamin Doesn’t Fix an Unbalanced Recipe

Our note: The UC Davis study used software from a company to analyse the recipes. We have read the full text on the journal’s site. Its footnotes name that company as the source of the software and of a proprietary nutrient database. The paper has no funding, disclosure or conflict-of-interest statement. So it doesn’t tell us whether any author had a business link to the company.

8. What we could not verify

Commonly saidWhat we found
“Homemade diets are missing protein”Not in these studies. No UC Davis recipe fell below the NRC protein recommendation. The gaps were in micronutrients.
“Variety balances it out”Tested and contradicted by UC Davis: rotating seven recipes did not remove deficiencies.
“A recipe by a vet will be complete”Not reliably. Most vet-written recipes had at least one deficiency, though fewer than others.
“61% of recipes are low in vitamin D”We are not printing it. The paper’s vitamin D reference value was later corrected (§2).
“These deficiencies make dogs ill”Possible, but not measured here. Both studies analysed recipes, not dogs. Neither shows how often dogs fed them become ill.

Sources

Always confirm with your vet before acting on anything on this page.