How to Follow a Recipe Exactly, and Why Substitutions Aren't Small
Most owners given a formulated recipe change it within months. What two owner studies found, which changes matter, and how to cook it as written.
Written by thecanineledger
This page carries no advertising, and nothing on it is for sale.
The veterinary nutrition service at Tufts surveyed owners whose dogs had been given a custom home-cooked recipe. Of the 30 surveys that included a full diet history, “only four (13%) demonstrated exact adherence to home-cooked diet recipes” (Johnson et al., Journal of Small Animal Practice 2016, abstract).
These were not careless owners. They were clients of a veterinary nutrition service, the most common reason they cooked was their dog’s medical needs, and “Most respondents liked and continued to feed a home-cooked diet.” They simply stopped following the recipe.
While getting a recipe formulated is the hard part to arrange, following it is the hard part to keep up. A formulated recipe is balanced only as written. This page sets out what owners change, why the changes matter more than they look, and how to cook the recipe as it was designed.
1. What owners change
A Brazilian study asked 46 owners how they were preparing recipes prescribed by a university veterinary nutrition service (Oliveira et al., Journal of Nutritional Science 2014). The answers show where recipes drift.
| What they did | How many |
|---|---|
| Admitted changing the recipe (“increasing, reducing, changing or eliminating some ingredients”) | 14 of 46 (30.4%) |
| Weighed ingredients on a kitchen scale | 7 of 46 (15.2%) |
| Measured by eye, with no specific amounts | 17 of 46 (36.9%) |
| Added the exact amount of meat, starch or vegetables | 23 of 46 (50.0%) |
| Used the prescribed amount of oil or salt | 12 of 46 (26.1%) |
| Left out the vitamin, mineral or amino acid supplements | 13 of 46 (28.3%) |
| Added a food the dog liked better when it left some | 10 of 46 (21.7%) |
The rest of the owners used the volume guide in the prescription (22 of 46, 47.8%).
Only 30.4% said they had changed the recipe. The other rows show that many more were not making it as written.
The Tufts nutritionists describe the same pattern from their own clinic. Cailin Heinze, a board-certified veterinary nutritionist, writes that “A common change that was made was adjusting or leaving out the supplements, which can result in a very unbalanced, unhealthy diet” (Tufts Petfoodology, 2023, vet-school blog, not peer-reviewed).
→ Balancing Premixes: What They Do, and the Evidence Gap
2. Why a small change isn’t small
A formulated recipe is a calculation. Every ingredient is there for a reason, and the supplements are sized to fill the gaps the other ingredients leave. Change one ingredient and the gaps move.
The Brazilian authors put it simply: “an adequate recipe can be made inadequate if the owner changes the ingredient composition.” And they note the catch: “The owner, however, is not always able to evaluate the effect of these changes on the final nutritional composition of the food.”
Heinze gives three kinds of change that matter.
Swapping one ingredient for a similar one. “For example, if the same volume or weight amount of sweet potatoes are used instead of white potatoes in a recipe, that will result in a ~60% increase in calories.” Two foods that look interchangeable in the kitchen are not interchangeable in the calculation.
Changing how it’s cooked. “different cooking methods result in differing nutrient amounts. So, changing cooking methods – boiling instead of baking, using a crockpot to cook all ingredients together instead of cooking them separately as stated in a recipe – or swapping ingredients can have big effects on the nutrient profile of a diet.”
Adjusting portions by cutting one thing. Owners trying to change their dog’s weight “Often they do this by decreasing or leaving out the fat ingredients, decreasing the carbohydrates only, or only increasing the protein or fat.” That changes more than calories. It can “dramatically change the nutrient profile of the diet.”
Cutting the oil is the one the Brazilian study saw most: “More than 50 % of the owners specifically restricted or even omitted the soyabean oil and salt from their dogs’ diets.” In a formulated recipe, the oil is often there to supply essential fatty acids. Heinze: “fat will usually be added separately as well to meet essential fatty acid requirements.”
Our note: Oil in a formulated recipe is often there for essential fatty acids. We have no source on why salt is included.
3. Why recipes are hard to follow in the first place
Some drift isn’t the owner’s fault. Many published recipes are too vague to follow exactly.
The UC Davis study of 200 published recipes found that “Most (184 [92%]) recipes contained vague or incomplete instructions that necessitated 1 or more assumptions for the ingredients, method of preparation, or supplement-type products” (Stockman et al., JAVMA 2013). The researchers had to decide things like how much fat was in “ground beef”. When their calculations and the laboratory results differed, one possible reason they gave was “the amount of fat drained and discarded during preparation of ground meat.”
A Brazilian study of recipes published in Portuguese found that “Most recipes (48 %) had no precise determination of ingredients and quantities” (Pedrinelli et al., Journal of Nutritional Science 2017).
A formulated recipe should not leave you guessing. If yours does, that is a question for whoever wrote it, not a gap to fill yourself.
→ The Seven Nutrients Homemade Diets Miss Most
4. How to cook it as written
We are not giving amounts, substitutions or products here. Those belong to your recipe and the person who formulated it.
Weigh, if your recipe gives weights. Only 15.2% of the Brazilian owners used a scale. Heinze notes that it “can be a challenge to increase volume measurements accurately by small amounts”, which is one reason gram amounts are easier to keep consistent.
Make it exactly, including every supplement, every time. Heinze: “it is absolutely essential that you make the recipe exactly as the nutritionist designed it, including all the supplements in the specified amounts!”
Cook it the way the recipe says. If you want to use a slow cooker or batch-cook differently, tell the nutritionist before you start, so they can account for it.
Ask before you swap anything. “Never change a recipe without talking to the nutritionist who formulated it!” That includes a brand of supplement, a cut of meat, or a vegetable your shop has run out of.
If your dog won’t eat part of it, call rather than adjust. In the Brazilian study, dogs most often disliked the vegetables, the liver, or the supplements. Heinze: “If your pet is not eating the diet well, talk to the nutritionist who formulated the diet for options.”
If your dog is gaining or losing weight, don’t cut one ingredient. Ask the nutritionist or your vet to adjust the whole recipe.
Book the follow-up. The Tufts study’s conclusion stresses “importance of recipe adherence and necessity for follow-up after diet formulation with a board-certified veterinary nutritionist.” It also found that “many dogs required recipe modifications”. A recipe is meant to be checked and adjusted, by the person who wrote it.
Our note: Some recipes are written in cups on purpose. Follow the units your recipe gives.
Our note: If an ingredient is unavailable, ask your nutritionist before you swap.
5. Variety is not a fix
Some owners rotate recipes deliberately, on the theory that a varied diet balances itself out over a week. That isn’t the same as changing a formulated recipe, but it is often offered as a reason not to worry about exactness. The UC Davis team tested the theory on unformulated recipes and found it “unfounded”: rotating through seven recipes “did not eliminate deficiencies.”
If you want variety, ask the nutritionist for more than one formulated recipe.
Our note: We read only the abstract of the Tufts study, because the full text is not open access.
6. What we could not verify
| Commonly said | What we found |
|---|---|
| “Small swaps don’t matter” | Contradicted. A same-amount swap of sweet potato for white potato raises calories by about 60%, per Heinze. |
| “Cooking method doesn’t change nutrients” | Contradicted. “different cooking methods result in differing nutrient amounts” (Heinze). |
| “Most owners follow the recipe they’re given” | Not in the studies. 13% exact adherence at Tufts; many changes in the Brazilian survey. |
| “Leaving out the oil makes it healthier” | Not in a formulated recipe. Fat is usually added to meet essential fatty acid needs (Heinze). |
| How much harm recipe drift causes | Not measured. Neither owner study tested whether the changes made dogs ill. |
Sources
- Johnson LN, Linder DE, Heinze CR, Kehs RL, Freeman LM. J Small Anim Pract 2016;57(1):23–27. ⚠️ abstract read; full text not open access
- Oliveira MCC, Brunetto MA, da Silva FL, Jeremias JT, Tortola L, Gomes MOS, Carciofi AC. J Nutr Sci 2014;3:e23: owner survey, 46 dogs, read in full on PMC
- Stockman J, Fascetti AJ, Kass PH, Larsen JA. JAVMA 2013;242(11):1500–1505
- Pedrinelli V, Gomes MOS, Carciofi AC. J Nutr Sci 2017;6:e33
- Heinze CR. What Nutritionists Wish You Knew: 5 Homecooked Diet Mistakes & Misconceptions (Tufts Petfoodology, 2023): vet-school blog, not peer-reviewed. The page carries an author disclosure, including employment by the Mark Morris Institute
Always confirm with your vet before acting on anything on this page.