The whole point of vitamin supplementation is to support the body’s nutrient needs—which means accounting for the bioavailability of the ingredients is really, really important. Scratching your head? We tapped Ritual’s Senior Scientist, Arianne Vance, MPH, for an easy-to-understand crash course on what, exactly, bioavailability means—and why you should care. Class has commenced!
What is bioavailability?
“In simple terms, bioavailability can be defined as the amount of an ingested dietary ingredient that is absorbed in the gut and made available for use or storage by the body,” explains Arianne. In other words, it’s a measure used to define the percentage of a nutrient (or ingredient) that actually gets absorbed into the body’s tissues. (1,2,3)
When it comes to food, Arianne notes that different forms of a nutrient can have different bioavailabilities. Take iron, for instance—there are two forms of iron commonly found in foods: heme and nonheme iron. Meat, seafood, and poultry contain both heme and nonheme iron, whereas nonheme iron is predominantly found in plants and iron-fortified foods. (4)
“Research has established that the absorption of nonheme iron is increased when consumed with vitamin C, but decreased when consumed with calcium, phytates, and some polyphenols,” says Arianne. “There are, however, certain forms of iron that may be less affected by the presence of such inhibitors. Ferrous bisglycinate is one example: It maintains good bioavailability, even in the presence of phytates.” (4,9)
What’s the relationship between bioavailability and absorption?
They’re pretty similar, actually: Absorption is the process of moving nutrients from the digestive system into the bloodstream, while bioavailability is the amount of a nutrient that reaches the body’s tissues after it is consumed. “In the context of nutrients and other dietary ingredients, bioavailability is similar to absorption,” says Arianne. “In order to show that a nutrient is bioavailable, we first have to show that it is able to be absorbed by the body.” (10)
Is there anything that affects bioavailability?
Yes. There are many factors that can impact the bioavailability of nutrients, from the chemical form of the nutrient and the presence (or absence!) of other food components, to individual factors like age and nutrient status. (7,8)