When shopping for supplements, you’re likely to come across terms like “digestion” and “absorption” and, chances are, you know what they mean as they relate to nutrition.
There’s another term you might encounter: bioavailability.
Frequently used pharmacology and nutritional science, bioavailability is a term that has a knack for stumping consumers. Is it just a fancier way of saying “absorption?” We did the heavy lifting and deciphering of scientific definitions for you, let’s take a look.
Digestion vs. Absorption vs. Bioavailability
While these three terms are similar and play big roles in the world of nutrition, they do not mean the same thing.
Digestion: the chemical and/or mechanical breakdown of food into smaller parts.
The mouth and stomach exhibit both kinds of digestion. For example, if you eat a sandwich…
– Your saliva’s enzymes begin the breakdown of carbohydrates (chemical digestion), and your teeth crush and grind the sandwich bits to change their consistency and shape making it easier to swallow and for further digestion.
– Once in the stomach, hydrochloric acid continues to breakdown proteins while your stomach churns to smash the food further.
Absorption: the movement of nutrients from your digestive tract (mainly the small intestine) to your bloodstream.
Now that your sandwich has been broken apart into tiny bits, your small intestine can now absorb carbohydrates, proteins, fats, vitamins, and minerals.
What nutrients don’t get absorbed? A great example, in this case, would be the fiber–in fact, it doesn’t get digested either! It makes its way through the small intestine and into the large intestine absorbing water along the way.
Bioavailability: the nutrients that were absorbed into the bloodstream and have made their way into your body’s cellular processes.
In other words, nutrients that have “high bioavailability” are ones that your body is able to use and benefit from more efficiently.
Your sandwich, in general, is bioavailable; it satiates your appetite, it provides you with energy–immediate and stored–and gives you sources of protein, carbohydrates, and fats.
Supplements can be a bit trickier as they are typically isolated nutrients.
Factors Affecting Bioavailability
Knowing the bioavailability of a nutrient or specific brand of supplements can give you confidence when choosing whether or not to consume it. From the definitions above, we can see that it’s possible for a supplement to be easily digested and absorbed. The question then becomes…does it actually make its way to your cells in proper “shape” to do its job?
It is for this reason that most reputable supplement companies use research to guide their formulations and manufacturing processes and, in some cases, perform clinical trials to determine just how bioavailable their products are.
In a perfect world, the bioavailability of a nutrient would be the exact same for everyone under any condition whether internal or external. Unfortunately, this isn’t the case, and it can vary from person to person.
Here are some factors that can affect bioavailability:
- Personal physiological factors
- The presence of certain illnesses and diseases
- If the supplement is taken with other medications or supplements
- Whether the supplement is taken with food or without food
- The age of the person
- The metabolic rate of the person
Not only can bioavailability be affected by the body and physiology of the person taking the supplement, but it can also be affected by the properties of the supplement itself and its environment.
For instance, the physical properties of the supplement (e.g., whether it is in tablet or liquid form) can affect bioavailability.
Other chemical factors include:
- Formulation of the supplement
- How it interacts with water or fat-based molecules (i.e., insolubility or solubility)
- How well it can withstand the pH levels in the stomach and digestive tract
The Main Takeaway
When it comes to supplementation, bioavailability is perhaps one of the most critical aspects to consider.
While you’ll be hard-pressed to find a brand that will openly boast that its products have low bioavailability, you are now armed with the knowledge to ask or to investigate on your own.
Don’t know where to start? Asking your primary care physician if you should be supplementing with a specific nutrient is the best place to start. After, get their recommendations on which supplements/brands are known for having high bioavailability.