According to the FDA (Food and Drug Administration), bioavailability represents the proportion and speed with which a nutrient, or part of it, is capable of being absorbed and available for use in its place of action (in this case, the blood).
The first step to make a nutrient bioavailable is to release it from the “matrix” of the food and convert it into a chemical form that can be absorbed by the digestive mucosa, so it depends on proper chewing and an adequate enzymatic function of the digestive system. For example, to be able to process the glucose present in rice, we must chew that rice and digest it with the enzymes. The same happens to assimilate proline (an amino acid present in chicken proteins), or to process omega 3 fatty acids present in fish oil.
Although there is theoretical bioavailability, there are many factors that can modify it, which must be taken into account when designing the recipe of a food that is assimilable and useful for our pets.
Without delving into it, but to give you an idea of the complexity of the matter, we will enumerate some of those factors that can modify the bioavailability of a nutrient:
- Cooking of the ingredient (Boiled or baked?).
- Origen of the ingredient (Animal or vegetal source?).
- Chemical form of the nutrient (Organic or inorganic?).
- Interactions with other ingredients and nutrients (for example, vitamin C increases the bioavailability of iron, so iron is better processed when provided together).
- Interactions with drugs (for example, the use of antibiotics can decrease the assimilation of zinc).
- Changes in the diet (changing from one recipe to another can alter the digestive mucosa, without causing external symptoms, but affecting for several weeks the bioavailability of the nutrients that are swallowed).
- State of the digestive mucosa (for example, having a lower acid secretion in the stomach hinders the assimilation of vitamin B12).
- Physiological states (in times of growth and lactation, nutrients are better assimilated).
- Pathological states (for example, having Helicobacter pylori, frequent in the case of ulcers and gastritis, also affects the bioavailability of vitamin B12).
- Individual factors such as race, sex, age and level of physical activity also have an impact.
If you want to delve into the other parameters that define the quality and nutritional effectiveness of an ingredient, check biological value and digestibility.