Nobody absorbs 100% of all nutrients consumed Bioavailability of Nutrients - The Nutrition of Micronutrients

Bioavailability of Nutrients - The Nutrition of Micronutrients

Nobody absorbs 100% of all nutrients consumed

Nobody absorbs 100% of all nutrients consumed, due to bioavailability issues. Foods, nor supplements, are never completely digested to the point of releasing all of their nutrient and toxin content to the human body. The mere fact that everyone should have several bowel movements a day indicates that our bodies do not utilize much of what we eat.

Trying to calculate quantitatively how much of each known nutrient you are getting out of your diet is both a waste of time and impossible to do. It is recommended that you do not try to quantify your intake of specific Micronutrients from your diet.

Highlights of Bioavailability of Nutrients - The Nutrition of Micronutrients:

  • Good nutrition from eating a healthy diet is the foundation of the biomedical model of natural health.
  • Any change in your diet, however small, that improves your natural health is a step in the right direction.
  • Micronutrients include vitamins, minerals, phytochemicals, and water.
  • Micronutrients do not provide any energy to the body.
  • You improve your nutrition and natural health by choosing to eat healthier foods than you are currently eating.

Micronutrients include vitamins, minerals, phytochemicals, and water. Macronutrients are carbohydrates, proteins, fats and individual fatty acids. Micronutrients do not provide any energy to the body, while macronutrients primarily provide the body with energy.

Toxins contained in food are a pretty open ended concept. You should think of toxins as being any possible food negative. Certainly, a toxin would include heavy metals like aluminum, arsenic, mercury, and lead. Food negatives and toxins include other things like goitrogens, oxolates, and even Maillard reactions introduced by browning foods during the cooking process.

The Importance of Bioavailability

You may be tempted to look up your diet in a food database, or with a computerized diet program. Analyzing your diet is appropriate for macronutrients, but would be largely inaccurate for your micronutrients. You could indeed spend a considerable amount of time generating numbers regarding how much of each nutrient you are currently getting from your diet.

However, what would your numbers really mean? Not very much, in the opinion of the Natural Health Perspective.

Before you could be accurate, you would need to know not only the nutrient composition of foods, but also all sources of potential losses to those nutrients.

"Nutrients ingested but not released during the digestive process for absorption are of no nutritional value."[1] "An assessment of the adequacy of dietary intakes of nutrients requires not only knowledge of the nutrient content of the foods ingested but also the extent to which the nutrient present in the diet is available for absorption and utilization."[1] Bioavailability is the technical term used to convey the fact that you do not absorb 100% of all nutrients and toxins consumed no matter if you take them in the form of nutritional supplements or as food. In fact, you may absorb from food, close to none of some nutrients and toxins.

"The term 'bioavailability' attempts to include in a single concept the effect of a sequence of metabolic events, i.e., digestibility, solubilization, absorption, organ uptake and release, enzymatic transformation, secretion and excretion."[2]

A number of factors affect bioavailability: factors contained in the food itself, factors of human physiology, factors specific to your health status, and factors related to the food processing.

Food Related Factors -- "The bioavailability of a nutrient can, in some cases, be significantly influenced by the chemical form in which it appears in the diet and by the presence of other factors in food that may enhance or depress mineral absorption and utilization."[4]

"While most vitamins are very well absorbed [from food], most essential minerals are not. Usual absorption of minerals ranges from less than 1% to over 90%. The bioavailability of dietary minerals must be considered when determining whether the diet contains enough, too little, or too much."[3]

Human Physiology Related Factors -- "Various nutrients and dietary components interfere with the bioavailability of vitamins. Hence, requirements for vitamins cannot be considered independently, but must be evaluated in relationship to other nutrients and compounds consumed by an individual."[1]

Nutrients compete with other nutrients for absorption. Some nutrients will either enhance or reduce the amounts of other nutrients being absorbed by your body. This is especially true for all the oil-soluble nutrients. The relatively tiny distal ileum or the very end of the small intestine, where it turns into the large intestine, is where most of the oil soluble nutrients are absorbed by the human body. When the ileum absorbs retinol, for example, it effectively blocks vitamin D from being absorbed.

Health Status Related Factors -- Good digestion is a requirement for natural health to work. Probiotics can be used to improve your intestinal tract health in order to enhance the bioavailability of some nutrients.[5] You may also have a genetic defect that adversely affects the absorption of specific nutrients.

Negative Toxin Related Factors -- What is true for the good stuff is likewise true for all negative factors contained in your food. Just because fish is reported to contain mercury does not mean that your body will absorb most, or even any of it, any more than all the calcium content would be absorbed.

Food Processing Related Factors -- There is no best way to prepare food. Boiling food, for example, depletes more of its iodine content than baking does. Consuming fruits and vegetables raw enhances the absorption of some nutrients, whereas soaking and fermentation will increase the absorption of minerals in legumes and grains to the detriment of the water-soluble nutrients. Cooking by breaking down fiber generally increases digestibility of many nutrients, while all the oil soluble nutrients require the presence of fat for best absorption.


In conclusion: Trying to calculate quantitatively how much of each known nutrient you are getting out of your diet is both a waste of time and impossible to do There are simply too many factors evolved. Thus, it is recommended that you do not try to quantify your intake of specific Micronutrients from your diet.

"It will therefore require major research programs before the term 'bioavailability' of a nutrient can become a quantitative concept useful for clinical, nutritional or managerial evaluation and counseling."[2]

The best approach to optimizing your diet is to follow the simple dietary rules of thumb provided elsewhere on this Web site.

Return to Eating Healthy Whole Foods

Additional information on this Web site on Nutrition is located at:

  1. The Nutrition of a Varied Diet
  2. The Nutrition of a Balanced Diet
  3. The Nutrition of Macronutrients

Bioavailability of Nutrients - The Nutrition of Micronutrients Comments:


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  2. Bronner F. Nutrient bioavailability, with special reference to calcium. J Nutr. 1993 May;123(5):797-802. Review. PMID: 8487089
  3. Turnlund JR. Bioavailability of dietary minerals to humans: the stable isotope approach. Crit Rev Food Sci Nutr. 1991;30(4):387-96. Review. PMID: 1910521
  4. Dreosti IE. Recommended dietary intakes of iron, zinc, and other inorganic nutrients and their chemical form and bioavailability. Nutrition. 1993 Nov-Dec;9(6):542-5. Review. PMID: 8111146
  5. Kopp-Hoolihan L. Prophylactic and therapeutic uses of probiotics: a review. J Am Diet Assoc. 2001 Feb;101(2):229-38; quiz 239-41. Review. PMID: 11271697
  6. McKee LH, Latner TA. Underutilized sources of dietary fiber: a review. Plant Foods Hum Nutr. 2000;55(4):285-304. Review. MID: 11086873
  7. Gascon-Vila P, Ribas L, Garcia-Closas R. [Dietary sources of vitamin A, C, E and beta-carotene in a adult Mediterranean population] Gac Sanit. 1999 Jan-Feb;13(1):22-9. Spanish. PMID: 10217703
  8. Slavin JL, Jacobs D, Marquart L. The role of whole grains in disease prevention. J Am Diet Assoc. 2001 Jul;101(7):780-5. Review. PMID: 11478475
  9. Pennington JA, Schoen SA. Contributions of food groups to estimated intakes of nutritional elements: results from the FDA total diet studies, 1982-1991. Int J Vitam Nutr Res. 1996;66(4):342-9. PMID: 8979163
  10. Pennington JA, Young BE. Total diet study nutritional elements, 1982-1989. J Am Diet Assoc. 1991 Feb;91(2):179-83. PMID: 1991931
  11. Love JA, Prusa KJ. Nutrient composition and sensory attributes of cooked ground beef: effects of fat content, cooking method, and water rinsing. J Am Diet Assoc. 1992 Nov;92(11):1367-71. PMID: 1430722
  12. Ackman RG. Nutritional composition of fats in seafoods. Prog Food Nutr Sci. 1989;13(3-4):161-289. Review. PMID: 2699043
  13. Smit E, Nieto FJ, Crespo CJ. Estimates of animal and plant protein intake in US adults: results from the Third National Health and Nutrition Examination Survey, 1988-1991. J Am Diet Assoc. 1999 Jul;99(7):813-20. PMID: 10405679
  14. Tovar J. Bioavailability of carbohydrates in legumes: digestible and indigestible fractions. Arch Latinoam Nutr. 1996 Dec;44(4 Suppl 1):36S-40S. PMID: 9137637
  15. Micozzi, M.S. et al. (1990) Carotenoid analyses of selected raw and cooked foods associated with a lower risk for cancer. Journal of the National Cancer Institute 82:282-285. PMID: 2299676
  16. Kris-Etherton PM, Yu-Poth S, Sabate J. Nuts and their bioactive constituents: effects on serum lipids and other factors that affect disease risk. Am J Clin Nutr. 1999 Sep;70(3 Suppl):504S-511S. Review. PMID: 10479223
  17. Fraser GE. Nut consumption, lipids, and risk of a coronary event. Clin Cardiol. 1999 Jul;22(7 Suppl):III11-5. Review. PMID: 10410300
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  19. The Natural Health Perspective™ Health Program Principle 2: The Fundamental Principle of natural health and fitness is Moderation and Balance in all things.
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