What is bioavailability and why is it important to you and your health?

Bioavailability is a term that should be important to you if you are not already aware of it.  Although the concept of bioavailability deals with complex processes in biochemistry, physiology, and anatomy, you do not have to be a scientist or a physician to understand its value to you and your health. 

If you take dietary supplements or medications, then bioavailability is important because it refers to how much of an active ingredient, e.g., vitamin C or a drug, that your body utilizes in the bloodstream and/or the target cells in relationship to how much of it you consume.  The active ingredient refers to the particular nutrient, phytonutrient, compound, molecule, or element that you are taking for a particular purpose.  It could be a product that has multiple active ingredients, such as a multivitamin and mineral.  For example, if you take 1,000 mg of calcium citrate and its bioavailability is 50%, then that means that your body will be able to utilize 500 mg of calcium. Prior to considering the concept of bioavailability, you may have thought that you absorb (and utilize) the entire amount of any active ingredient you take, but in almost every case that is false. The bioavailability of an active ingredient is also very different between what you take by mouth versus by injection or intravenously.

Several factors contribute to the bioavailability of an active ingredient.  For example, your diet, your health status, your exercise or activity level, if you happen to be overweight or obese, if you use alcohol, tobacco, or illicit drugs, your age, your microbiome, and your genes can influence the bioavailability of an active ingredient.  Fat-soluble compounds, such as turmeric, curcumin, and vitamins A, D, E, and K, typically have low bioavailability.  Water-soluble compounds, such as sugars, salts, vitamin C, and all of the B vitamins, typically have high bioavailability.

Typically, everything that we eat or drink gets combined into what are called micelles.  When we eat fat-soluble compounds, the body’s digestive and small intestine phases cause the formation of micelles that allow these substances to be absorbed into the bloodstream to be utilized by our cells in a complex transporting process.  You may be wondering what a micelle is.  See Figure 1 for a representation of a micelle.  A micelle is a very important molecule that is formed with a fatty acid that has the active ingredient, e.g., curcumin or vitamin D, on the inside of the molecule surrounded by an outer shell of fatty material.  This outer layer helps the active ingredient get into the bloodstream.  Additionally, these molecules are covered with a water film, essentially making them water-soluble and more bioavailable.  Only water-soluble substances that can permeate this water film are directly absorbed by the small intestine.

Figure 1.  A graphical representation of a micelle

Given the background context of what bioavailability is and how your body utilizes what you consume, what does that mean for you when you want to purchase a dietary supplement?  First, remember that any dietary supplement that contains a fat-soluble ingredient, e.g., curcumin or vitamins A, D, E, or K, will commonly have low bioavailability, unless it has been formulated with a technology that uses micelles to enhance the active ingredient’s absorption.  You will have to read the product description to look for terms like “micelle” or “nanoencapsulation,” as these are terms used to refer to a formulation process to improve bioavailability.  If you do not see these words describing the product, then chances are that product has a low bioavailability.  If the product contains water-soluble ingredients like salts (e.g., sodium or potassium), sugars (e.g., glucose or mannose), vitamin C, or the B vitamins, then the use of this same type of technology is not as crucial, but it would still help the overall bioavailability of the product.

The bottom line for your health is that active ingredients that have been formulated with a technology that utilizes micelles to enhance the bioavailability are more effective.  Your body will better absorb active ingredients with high bioavailability, which means that you get the most for your health and your dollar.  Whenever possible, I recommend that you take products that utilize micelles to improve the bioavailability of the active ingredients to maximize their effectiveness.   All other factors being equal, the higher the bioavailability of the active ingredient, the more your body absorbs it, and the better it is for your health and wellbeing.