What is Bioavailability?
Bioavailability, in the context of nutrition, describes the availability of nutrients to be absorbed into our body and to nourish us. The more bioavailable a nutrient is, the more benefit we receive from it. Bioavailability differs from person to person, and depends on a variety of things such as the health of one’s digestive tract, the types of foods being eaten and the combination of foods being eaten.
Why is the concept of bioavailability important?
The concept of bioavailability helps us understand the importance of getting the most benefit out of the foods we choose to eat. Food labels tell us which nutrients are found in a particular food: fats, protein, carbs, vitamins and minerals. However, what we really need to figure out is how many of these nutrients are actually being absorbed and utilized by our body? Once we have a better understanding of bioavailability, we can make better choices around the foods we eat, and increase the likelihood that we will benefit our health from each food.
What types of things affect bioavailability of nutrients?
The bioavailability of nutrients is determined by the nutrient content of a food; whether or not the food has been processed, and how processed it is; a person’s individual health and the health of their digestive system; other foods that are eaten at a particular meal or are a part of one’s diet; and the presence of anti-nutritional factors (from Grain Fields Australia).
As we know, processed foods are often stripped of their nutrients and then fortified or enriched, meaning certain nutrients are added back in. Enrichment means adding back in the original nutrients that were lost during processing, whereas fortifying means adding in additional nutrients not found in the original food but thought to be beneficial to health. Many foods are enriched and/or fortified, including breads, crackers, cereals and even milk or juice. When nutrients are added back into foods, studies have shown that they become less bioavailable to our body. This is why I encourage people to eat whole foods instead of processed foods. That boxed cereal may boast loads of protein and fiber and iron, but how much of it is actually getting into our body and benefiting our health? It’s hard to know for sure, but definitely not as much as if we ate a grain cereal we prepared ourselves and added some fresh fruit and nuts to it.
Each person’s individual state of health can also significantly affect bioavailability of nutrients. Someone with a very healthy digestive system, regular bowel movements, and highly functioning metabolism will absorb many more nutrients than someone who commonly experiences abdominal pain or bloating after meals, soft stools or constipation, or has other symptoms that may indicate a food allergy, such as gas, acne, headaches, or overall discomfort after eating certain foods. This is why it is so important to be in tune with your body and try to figure out the cause of any digestive discomfort you may experience. A lifetime of soft stools or excessive gas is not just “something that runs in the family” or “how it will always be”. Diet and nutrition are so important for overall health, and these may be signs that you have a digestive issue that needs attention. Altering diet to improve digestion will allow more nutrients to be absorbed into your body, which creates more balance, better health, and helps prevent disease.
Certain food combinations can also affect bioavailability of nutrients. For example, the fat-soluble vitamins (A, D, E & K) need fat to be properly absorbed. People who have trouble absorbing fats, such as those who have ulcerative colitis, Crohn’s disease, or cystic fibrosis, may also have trouble absorbing these vitamins, meaning they are not as bioavailable to them despite being present in the foods they are consuming. Remember when I talked about the importance of eating the entire egg, not just the egg white? This is partly because so many nutrients found in the egg white need the yolk in order to be properly absorbed into our body.
Things like sugar, alcohol and caffeine can also change bioavailability of nutrients, in that they attach to certain vitamins and minerals and carry them right out of our body before we can utilize them for our health. Many alcoholics are found to be undernourished for this reason, as well as those who consume too much caffeine or too many sugary foods and drinks.
Some things to think about…
It all comes back to eating whole foods. Whole foods are not processed, they are better for our digestive system and our health, they contain the proper balance of macronutrients and micronutrients, and they help balance our blood sugar, reduce cravings, achieve a healthy weight, create a balanced body overall. Remember, we obtain energy from macronutrients (fats, protein and carbs), and we are able to actually USE the energy because of the micronutrients (vitamins and minerals). Some foods that people often consume but may not realize that bioavailability of nutrients could be low include protein powder or protein shakes; Vitamin Water; processed energy bars; cereals that claim to be packed with fiber; and fortified or enriched wheat breads.
This is just a brief overview but I hope it helps you understand bioavailability a bit better!