During my time in Guide Dogs I encountered a training school that had recently changed around 180 dogs from cereal-based dry food to raw feeding and among other benefits, the dogs were better able for their work. Exactly how or why may still elude us today but we have a lot more answers than we did ten years ago. The literature is rife with studies documenting the power of food to alter, stoke or soothe human behaviour. Unsurprisingly, we are finding the majority of these compounds work in a similar fashion in dogs. In this seminar, we discuss the many nutritional issues with ultra-processed food for negatively impacting behaviour in dogs. Of all aspects in this respect, the gut microbiota is perhaps the most important. We all know 90% of our serotonin comes from our gut but less of us know this process is managed by the gut flora. You mess them up, you get less happy chemicals. But they are not the only thing we should consider. From vitamins and minerals to protein (where we touch upon the tryptophan delusion), the role of carbs/sugar, fats and chemicals, we take a trip through a number of fascinating canine nutrition works that highlight how important each of these points are to the mental stamina in your dog. We conclude with some baseline tips on what you might do should you be faced with a dog exhibiting negative behaviour.