6 Nutrients in Pet Food that Can Harm Your Cat

By Lorie Huston, DVM on Sep. 12, 2014

Sick Cat? See if Your Pet Food Has the Right Amount of these 6 Nutrients

By Lorie Huston, DVM

Cats are just like people when it comes to food — they need a diet that is rich in nutrients. But be careful. There are some essential ingredients and nutrients that can actually do more harm than good for cats if fed in excess amounts. Pay extra attention to these ingredients in your cat's food.


Being carnivores, cats require a higher level of protein than dogs, especially when it comes to animal-based protein. However, cats with renal disease benefit from a diet that contains an easily digestible protein source rather than one that contains excess levels of poor quality protein. 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 formation of bladder stones. While the problem is more commonly seen in dogs, both dogs and cats can suffer these effects.


Sodium is crucial for cats 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 cat's diet can negatively impact the heart, kidneys, and nervous system. In fact, cats 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 cat thirsty, resulting in an increased volume of urine being produced. An excess level of sodium in the diet can even cause your pet 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.

Calcium and Phosphorus

Calcium and phosphorus are other nutrients that can have a deleterious effect if fed in excess to cats. Of particular importance is the ratio of calcium to phosphorus in the cat food. An abnormally high level of either nutrient may alter the proper ratio and have a negative effect on bones.

Additionally, calcium and phosphorus intake is an important consideration for cats with illnesses like kidney disease. Cats 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.

Vitamin D

Feeding abnormally high levels of vitamin D can result in increased calcium levels, causing a number of adverse symptoms in cats 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 cat’s diet is that it should be balanced and complete. No one diet is right for all cats. Young growing kittens have different nutritional needs than do mature cats. Likewise, cats with medical issues may require modifications to their diet. Always consult your veterinarian for advice on what is best to feed your pet. Your veterinarian knows your cat’s individual needs and can help you determine which diet is most appropriate based on those needs.

Image: Goodluz / via Shutterstock

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Lorie Huston, DVM


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