6 Nutrients in Pet Food that Can Harm Your Dog

By Lorie Huston, DVM on Sep. 12, 2014

Sick Dog? Check to See if Your Pet Food Has the Right Amount of these 6 Nutrients

By Lorie Huston, DVM

Just like people, when it comes to food dogs need a diet that is rich in nutrients. There are, however, some essential ingredients and nutrients that can actually do more harm than good for dogs if fed in excess amounts. Pay extra attention to these ingredients in your dog's food.



Even though dogs are omnivores, protein is an essential part of any dog food. Ideally, the protein should come from an easily digestible source, especially for dogs with renal disease. Poor quality protein not only causes issues for metabolism and digestibility, it can lead to weight loss, nausea, vomiting, and diarrhea.



Magnesium, though a necessary nutrient, is certainly a nutrient that can cause illness, sometimes severe and life-threatening. When fed in excess amounts, magnesium can have a negative impact on both the nervous system and heart, causing symptoms such as weakness, paralysis, cardiac arrest, respiratory depression, coma, and even death. Magnesium can also contribute to the formation of bladder stones. While both dogs and cats can suffer these effects, the problem is more commonly seen in dogs than in cats.


Calcium and Phosphorus

Calcium and phosphorus are two other nutrients that can have a deleterious effect if fed in excess to dogs. Of particular importance is the ratio of calcium to phosphorus in the dog food. An abnormally high level of either nutrient may alter the proper ratio and have a negative effect on bones. This is especially true in the case of large breed dogs that are in their growth phase.

Additionally, calcium and phosphorus intake is an important consideration for dogs with illnesses like kidney disease. Dogs with such illnesses will have different requirements depending on the stage of disease and the individual animal. An excess of either calcium or phosphorus can lead to a progression of kidney disease as well as contribute to the formation of bladder stones.


Sodium is crucial for dogs in a numbers of ways — it helps regulate blood pressure, aids in the transmission of nerve impulses, and is partially responsible for maintaining the balance between acids and bases in the body. Despite this, excessive sodium found in a dog's diet can negatively impact the heart, kidneys, and nervous system. In fact, dogs with heart and kidney disease should have their sodium intake strictly monitored, as excess levels can cause progression of these diseases.

Excessive sodium can also make your dog thirsty, resulting in an increased volume of urine being produced. An excess level of sodium in the diet can even cause your dog to become dehydrated if enough water is not consumed to counter the amount of water being lost as the body tries to flush out the excess sodium.


Vitamin D

Feeding dogs abnormally high levels of vitamin D can result in increased calcium levels, causing a number of adverse symptoms involving the kidneys, gastrointestinal tract, nervous system, and cardiovascular system.

How Do I Know How Much is Too Much?

The most important thing to remember about your dog’s diet is that it should be balanced and complete. No one diet is right for all dogs. Young growing puppies have different nutritional needs than do mature dogs. Likewise, dogs with medical issues may require modifications in the diet. Always consult your veterinarian for advice on what is best to feed your pet. Your veterinarian knows your dog’s individual needs and can help you determine which diet is most appropriate based on those needs.

Image: Kittibowornphatnon /  via Shutterstock

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Lorie Huston, DVM


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