Nutritional reductionists believe that they can formulate complete and balanced diets for dogs and cats. They create pet foods from ingredients that the ancestors of our dogs and cats did not have access to. The conditions under which the animal body was finely tuned over millions of years can give us insight into what is needed for its optimal functioning. Nutrition is far too complicated for people to figure out how to bypass Mother Nature.
Most people do not realize that there is very little correlation between the amount of a nutrient consumed and the amount that actually reaches the cells of the body (its bioavailability). The proportion of a nutrient that is digested, absorbed, and delivered to various tissues, in part, depends on the body’s need for that nutrient at that moment in time.
For example, the proportion of beta-carotene ingested that is actually converted to its active form (vitamin A) can vary by 8 fold in the same individual. The proportion converted also decreases with increasing doses, keeping the absolute amounts that are absorbed about the same. Calcium bioavailability can vary by 2 fold and iron bioavailability can vary by 19 fold! We can never know exactly how much of a nutrient to feed since we cannot predict how much will be utilized.
Furthermore, there are complex interactions between the individual nutrients in food. For instance, calcium decreases iron bioavailability by as much as 400%, while beta-carotene increases iron bioavailability by as much as 300%. If we compare a high calcium, low beta-carotene diet with a low calcium, high beta-carotene diet we could see a 1200% difference in iron absorption. Such interactions are common between all of the hundreds of nutrients found in foods. To complicate things further, nutrients not only affect each others absorption but they also influence each others affect on various systems on the body.
For the reductionist nutritionist, nutrition is hopeless. Even the smartest veterinary nutritionist armed with the most powerful super-computer cannot figure it out. Luckily, the wisdom of the body can handle the nutrition puzzle with no problem – assuming the body is provided with the raw materials it evolved consuming.
The best way to ensure that a pet is getting optimal nutrition is to mimic its ancestral diet as closely as possible. That’s why I recommend balanced raw diets for pets.