Question
Could you explain bioavailability in simple terms? I see this word used sometimes in relation to food and healthy eating.
Jole
Answer
Bioavailability can refer to both: how much of a nutrient in a specific food may be available to our body and once inside the body, how much of the nutrient our body will be able to absorb and use. I will illustrate through some examples, as follows.
When you pick up a processed food package with a nutrition label, you see numbers that tell you how much of the different nutrients the food has. Well, these numbers are in no way completely true or the most accurate representation of how much of the nutrient you will get or your body will be able to use. For example, if people see that a certain food offers 5 grams of protein, they think they are getting 5 grams of protein. However, that protein amount may not be fully available to you, to begin with depending on how the food was processed and prepared. Food companies are supposed to show the final number after processing but this is not guaranteed, and they can be using numbers the food would have had before it got processed. The problem with this is that processing, like refining grains or cooking foods at high temperatures, can change the chemical form and function of nutrients. Basic cooking, for example, can make some nutrients more “available,” while it can make others less “available.” Foods may also have other compounds in them that make the nutrients they have unavailable for our body to use; imagine it like locking down the nutrients.
That is problem number one. The second problem is what happens when the food or nutrients actually enter our body. Using the above example, let’s assume that the food item will actually provide you with the full 5 grams of protein that it claims to offer. Your body may not be able to digest or assimilate all of that protein from the food for many different reasons. This happens a lot with various vitamins and minerals especially. People take supplements for example and think that they are getting the numbers of the nutrients found on the bottle’s label, but that is completely not the case. How well a human body extracts a nutrient and how it uses it depends on numerous factors, including the person’s health, quality of the food, what it is eaten with, the form of the nutrient, etc.
In this discussion, supplements are especially troublesome because different forms of vitamins and minerals have completely different bioavailability. For example, magnesium comes in several different forms. Some, like magnesium citrate, have high bioavailability of around 90 percent, while others, like magnesium oxide, have low bioavailability of around 4 percent.
So the point about bioavailability for our everyday use and practical application in everyday life is that we can not base our food choices on numbers alone, as these are always estimates at best. Secondly, for optimal health and from a holistic perspective, we should never be eating by counting any numbers anyway. Rather, as I explain in many of my healthy eating resources, we should focus on eating the right foods in amounts that are best for our lifestyle and health needs.
The more you eat the right foods, this being whole plant foods, the more you provide your body with the most nutrient-dense foods, and the more you are able to maintain a healthy body that can regulate itself best to extract any and all the nutrients it needs from its food. On the other hand, the more we eat processed foods and use supplements, the more we interfere with our body’s proper function and its ability to extract and regulate its nutrient levels most optimally.
For more information about this topic, and why we cannot eat by numbers for optimal health and weight, please refer to my book Healing & Prevention Through Nutrition.