Bioavailability is the proportion of a nutrient the human body is able to absorb and use. You might think that when you eat an apple every iota of vitamin A, every antioxidant, and every mineral it contains is used by your body with total efficiency, but that’s not exactly the case.
Bioavailability and Nutrient Absorption in the Body
Digestion is the mechanism by which the human body processes the nutrients from food. Digestion is a complex sequence of events and small inefficiencies can lead to larger problems down the line. Enzymes, organ health status, and even how well you chew your food can affect digestive system efficiency. How well the digestive system operates can directly affect the bioavailability of the nutrients in food, and, in turn, affect important processes like enzyme production and organ function. It’s all interconnected.
Before the body can use a nutrient, it must separate that nutrient from the food it’s contained within. This process begins in the mouth with chewing and is assisted by the enzymatic action of saliva. It continues in the digestive tract where food is broken down into macronutrients and micronutrients. Nutrients are absorbed by the intestinal lining, transferred into the bloodstream, and distributed for use or storage.
Macronutrients vs. Micronutrients
Nutrients can be separated into two basic categories—macronutrients and micronutrients. Macronutrients include carbohydrates, proteins, and dietary fats. They’re required in large amounts and necessary for tissue growth and providing the body with energy. Macronutrients are highly bioavailable and may be up to 90% utilized.
Micronutrients include vitamins, minerals, antioxidants, and certain phytochemicals; examples include iron, iodine, vitamin A, and folate. The bioavailability of micronutrients varies widely. Though the body only needs them in trace amounts, they’re critical.[6, 7] Enzymes and hormones are responsible for the body’s most important processes. Imagine the negative health effects if micronutrients weren’t available to facilitate enzyme or hormone production.
Of all the micronutrient deficiencies, magnesium seems to be the most widespread. Magnesium deficiency has been linked to problems such as diabetes, hypertension, dementia, and osteoporosis.[8, 9, 10, 11]
Factors That Affect Bioavailability
Nutrient bioavailability may vary from one person to the next. Two different people can consume the exact same nutrient in the exact same form yet their bodies may absorb and use different quantities of that nutrient. There are a multitude of factors that influence individual absorption. In the case of vitamin B-12, if a person lacks intrinsic factor, a protein in the gut that helps the body absorb and use vitamin B-12, the vitamin will simply pass right through. Other factors that affect bioavailability include…
Because bioavailability is heavily dependent upon the digestive process, a digestive system operating at less than optimal efficiency may not be, and probably isn’t, able to fully absorb and use all the nutrients it encounters. Nutrients in food may be absorbed at a rate as low as 20% or as high as 98%. Crohn’s, IBS, and other inflammatory bowel conditions can severely impact the body’s ability to capture nutrients.
Age is among the most influential factors that affect bioavailability. Unfortunately, at least half of the children worldwide age 6 months to 5 years suffer from micronutrient deficiencies. Without the right micronutrients in the right amounts, development can be affected and early infancy (0-6 months) and childhood (6-24 months) are two of the most critical periods of development. It’s one more reason to encourage breastfeeding; human breast milk is naturally rich in bioavailable nutrients.
Some nutrients, when consumed together, support each other’s bioavailability. For example, calcium is best absorbed when it’s consumed alongside magnesium. Consuming vitamin C with plant-based, iron-rich food enhances the bioavailability of iron. This is why a varied, balanced diet is so beneficial; a variety of foods equates to a diverse selection of micronutrients that support and enhance each other.
Orotates, which are highly bioavailable natural salts, were described in the 1970s by German researcher Hans Nieper. He recognized orotates as a component of a natural system of electrolyte carriers responsible for distributing minerals throughout the body. Binding dietary minerals such as magnesium, zinc, potassium, lithium, and calcium to orotic acid can improve their bioavailability.
Conversely, some micronutrient combinations interfere with each other. Tannins, which are polyphenols present in tea and wine, reduce the absorption of iron. Found in nuts and seeds, phytic acid is an antinutrient that binds to nutrients and blocks absorption.
Why Is Bioavailability Important?
Bioavailability has an especially big impact on cellular metabolism. Your body has an incalculable number of cells and each of those cells is a living, breathing, functional organism with a metabolism and a purpose. Red blood cells have a different function than lung cells, which have a different function than brain cells. What all those cells have in common, however, is that they need the right nutrients in order to do their job.
Real Nutrition vs. Synthetic Nutrients
Whole, real, organic food is the best source of nutrition. A properly balanced diet should provide all the macronutrients and micronutrients the body requires. It sounds simple but it will require planning and won’t happen by accident. Sometimes, life gets in the way and rigorous adherence to a balanced diet isn’t completely achievable at all times. While they’re not a replacement for food, nutritional supplements can help fill the gap between the nutrients you consume and the nutrients your body needs.
The best nutritional supplements offer plant-sourced nutrients. There is a difference between the vitamins and minerals naturally found in an orange, and the vitamins and minerals synthetically produced in a lab and used to fortify cereal. I only recommend organic, food-sourced supplements made in the United States by reputable brands who are transparent about their methods and adhere to the highest industry standards.
- V. Srini Srinivasan. Bioavailability of Nutrients. Journal of Nutrition. April 1, 2001.
- Nutrient bioavailability – getting the most out of food. European Food Information Council. Food Today. May 2010.
- Ertek, S, et al. “Relationship Between Serum Zinc Levels, Thyroid Hormones and Thyroid Volume Following Successful Iodine Supplementation.” Hormones (Athens, Greece). 9.3 (2010): 263–8. Web. 24 Aug. 2016.
- Van Campen R, Glahn P. Micronutrient bioavailability techniques: Accuracy, Problems and limitations. Field Crops Research. Jan 1999.
- Demystifying nutrition: the value of food, vitamins and supplements. Longwood Seminars, March 5, 2013. Harvard Health Publication.
- Lena Davidsson, Marjorie Haskell. Bioavailability of micronutrients: Stable Isotope techniques to develop effective food-based strategies to combat micronutrient deficiencies. Food and Nutrition Bulletin. Vol 32, 2011.
- What are proteins and what they do. Genetics Home Reference. U.S. National Library of Medicine.
- Micronutrients. World Health Organization.
- Durlach J, Collery P. Magnesium and potassium in diabetes and carbohydrate metabolism. Review of the present status and recent results. Magnesium. 1984;3(4-6):315-323.
- Altura BM, Altura BT. Interactions of Mg and K on blood vessels-aspects in view of hypertension. Review of present status and new findings. Magnesium. 1984;3(4-6):175-94.
- Glick JL. Dementias: the role of magnesium deficiency and an hypothesis concerning the pathogenesis of Alzheimer’s disease. Med Hypotheses. 1990;31:211-225.
- Dietary Supplements: What You Need to Know. National Institutes of Health.
- Micronutrient Facts. Centers for Disease Control and Prevention.
- Nancy F. Krebs. Bioavailability of Dietary Supplements and Impact of Physiologic State: Infants, Children and Adolescents. The Journal of Nutrition. April, 2001.
- Gibson RS, Perlas L, Hotz C. Improving the bioavailability of nutrients in plant foods at the household level. Proc Nutr Soc. 2006 May;65(2):160-8.
- Hallberg, L, M Brune, and L Rossander. “The Role of Vitamin C in Iron Absorption.”International journal for vitamin and nutrition research. Supplement = Internationale Zeitschrift für Vitamin- und Ernährungsforschung. Supplement. 30. (1989): 103–8. Web. 24 Aug. 2016.
- Nieper HA. Recalcification of bone metastases by calcium diorotate. Agressologie. 1970;11(6):495-502. Available as article #CA21 from the A. Keith Brewer International Science Library at (608) 647-6513 or on the Internet.
- Rosenfeldt FL. Metabolic supplementation with orotic acid and magnesium orotate. Cardiovasc Drugs Ther. 1998;12(Suppl 2):147-52.
- Disler, P B et al. “The Effect of Tea on Iron Absorption.” Gut 16.3 (1975): 193–200. Print.