November 6, 2025, 12:57 pm | Read time: 5 minutes
Many believe that good dog food must primarily contain one thing: as much meat as possible. “Grain-free” is often touted as a quality feature in advertising. But is that really true? Dog trainer Katharina Marioth, who focuses on both behavior training and dog nutrition, explains why carbohydrates are important for dogs and how diet affects behavior.
From Wolf to Family Dog
Although dogs originally descended from wolves, Katharina Marioth explains in a conversation with PETBOOK, this connection is often misinterpreted. “That was, like, a hundred million years ago. We humans also descend from our ancestors and eat completely differently today.”
In her practice, the dog trainer regularly observes connections between diet and behavior. “We deal a lot with aggression cases and over-excitement,” she says. Problems in the musculoskeletal system of young dogs are also not uncommon. Studies from England and Scandinavia have shown that excessive protein intake—meaning a diet with too much meat and too few carbohydrates—can negatively affect behavior. 1, 2
“Too much protein can stress the dog internally and burden the organs—liver, kidney, spleen. We know this from humans too,” Marioth explains. Therefore, she always asks about the food in cases of behavioral issues, without recommending specific brands. “If someone feeds raw, it can be great in individual cases. But what’s important is what else is added. The dose makes the poison.”
Why Carbohydrates Are Important
According to Marioth, carbohydrates are an underestimated but crucial component of dog food. They help in the formation of L-Tryptophan—an amino acid that contributes to the production of serotonin and dopamine in the brain. “These neurotransmitters promote relaxation and learning ability and lower the level of excitement,” she says.
But that doesn’t mean the dog should only get pasta. “The dose matters. A little vegetable or sweet potato often isn’t enough.” 3
Too Much Protein–Too Little Balance
If a dog is aggressive or overexcited, Marioth recommends reducing the protein content in the food. “I would give such dogs about 30 percent less protein,” she explains. “Dry or wet food should contain significantly less than 25 percent crude protein.”
Excessive protein intake can not only burden the organs but also change behavior. “People who eat low-carb for a long time often become more irritable—and it’s similar with dogs.” In the UK, there are now food varieties specifically developed for dogs with excitement or aggression problems. They don’t replace training but can help stabilize the dog.
Millet Is Particularly Suitable
A practical way to increase carbohydrate content is the targeted use of plant-based side dishes. “Millet is the best plant-based source of L-Tryptophan,” Marioth explains. “After two to three weeks, many dogs already show a positive change.” 4
If the dog doesn’t like millet, pasta or rice are good alternatives—even in gluten-free form, if necessary. “What’s important is that carbohydrates end up in the bowl,” the trainer emphasizes. “They can stabilize behavior, especially in insecure or very active dogs.”
“Grain-Free” Is Not a Quality Seal
Marioth considers the fact that many manufacturers advertise with buzzwords like “high meat content” or “grain-free” to be marketing. “It just sounds good and caters to stereotypes,” she says. Raw meat feeding is popular but expensive—and thus very lucrative for providers. “Moreover, pure meat feeding requires many additives to avoid deficiencies, especially in minerals.”
The comparison with the wolf is misleading: “Wolves in the wild don’t just eat meat but also roots, herbs, and other plant components,” she explains. Additionally, through domestication and changed gut flora, the domestic dog has little in common with the wolf. 5
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How to Recognize Good Food
In the end, it mainly depends on the dog, says the expert. “Is he doing well? Does he have a shiny coat, good stool quality, calm digestion, and balanced behavior? Then the food is probably right.”
However, if changes are noticed—such as restlessness, irritability, or physical complaints—the diet should be reviewed. “It’s best to get advice from someone who is truly neutral—like a qualified trainer or veterinarian without ties to manufacturers,” she advises.
Often, a small adjustment is enough to achieve a big effect:
“Diet alone doesn’t solve behavioral problems, but it can help manage them better.”
Signs of Unbalanced Diet in Dogs
- Frequent restlessness or aggression
- Excessive panting or constant tension
- Dull coat, flaky skin
- Digestive problems or varying stool quality
- Sudden learning or concentration weakness
Katharina Marioth: “If behavior or well-being changes, it’s worth looking in the bowl—the cause often lies there.”
You can see the entire interview with dog trainer Katharina Marioth in the video.
About the Expert
Katharina Marioth is the founder of the brand Stadthundetraining and the KEML principle. She is an IHK- and government-certified dog trainer and behavioral assessor for dangerous dogs in Berlin. In her daily business, she works closely with veterinarians, scientists, and other specialists on dog-related topics. With her knowledge and skills, she secured the title of Dog Trainer of the Year 2023 in the Sat.1 show “The Dog Trainer Champion.”