You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

The importance of the media in the way it influences our daily lives should never be underestimated. "You are what you eat" is a phrase that has been around for decades - and it is generally accepted by the public as being true. People even buy posters and wear T-shirts with it on. However - it isn't true.

The phrase "you are what you eat" implies that whatever you eat becomes an integral part of your body, therefore if you eat too much of something excess will accumulate in your body, if you eat an imbalance of nutrients your body will contain an imbalance of those nutrients , if you eat a nutrient-deficient diet your body will be deficient. 

It is true that some nutrients are essential and must be in the ration that you or your pet eats. Examples are some essential fatty acids, vitamins and minerals. If you or your pet eat a diet which does not contain these, signs of deficiency disease can develop. Fortunately we know enough about pet nutrition now that if you feed a complete balanced pet food produced by one of the main reputable pet food manufacturers it will contain all the essential nutrients that your pet needs. Deficiency disease could still occur if your pet is unable to eat, digest or absorb the nutrients in the food, but this is uncommon. (Please note - you can purchase pet foods which are labelled as being complementary. These foods are not complete, must be mixed with other foods to form a complete ration, and these may not contain all the essential nutrients that your pet needs.)

The reason why the phrase "you are what you eat" is NOT true is that the body is able to regulate how much of a nutrient it absorbs and keeps. In other words it does not retain everything that is in a foodstuff . I'll give you two good examples :

• Calcium is an essential mineral, and there are huge reserves in the body - in the form of the skeleton. Meat is deficient in calcium and if an exclusively meat ration is fed many pets (eg dogs, cats, reptiles) will develop signs of calcium deficiency - including thinning of the bones and fractures. If you feed a ration containing too much calcium however, the gut regulates how much is absorbed. Once the calcium content of a food exceeds a certain level, the greater the amount of calcium in the food, the less percentage of it is absorbed into the body and more is excreted in the faeces. In this way you or your pets are not "what you eat".
• Water soluble vitamins are essential nutrients which are easily absorbed from the food. However, excess water soluble vitamins are not retained, or stored in any great amounts in the body - they are excreted via the kidneys in the urine. So excess dietary intake (or supplementation) does not become an integral part of you or your pet's body. Another example of why you are not "what you eat"

Does this then mean that we can eat as much of whatever we want, and we can feed as much as we want to our pets without causing harm ? 

Sadly, for the gluttons amongst us (and amongst our pets!) the answer to this is NO. Although we all know individuals who eat huge volumes of food and remain thin, most of us and most of our companion animals cannot deal with excessive calorie intake, and will develop obesity. We also have difficulty in regulating some other nutrients, so excessive intake over requirements should be avoided otherwise disease might occur. I'll give you two examples of this :

• Cats fed high amounts of magnesium in their food are more likely to develop urinary tract disease called feline urologic syndrome (FUS) or feline lower urinary tract disease (FLUTD) which is caused by struvite crystals and stones forming in the urine. These crystals and stones contain magnesium as one of their chemical components.
• Too much dietary vitamin A (a fat-soluble vitamin) accumulates in the body and can cause serious bone disease in adult cats, and deformities such as cleft palate in developing fetuses. 

Conclusion : The phrase "you are what you eat" is only true in part.

Updated October 2013