What Is Bioavailability? How to ensure you're absorbing your supplements!

What Is Bioavailability? How to ensure you're absorbing your supplements!

15 Jun 2022

What is bioavailability?


We often hear this term thrown around when it comes to bio-hacking and supplementation, but what on earth does it mean and why does it matter? Well, in plain English, bioavailability refers to the fraction of a nutrient or medicine that can be absorbed into the body to be used, for example in the chemical activities of the body’s cells, or in structures such as muscles and bones.

Why is this important?

When you swallow a supplement, drink a herbal tonic or rub on a herbal cream, active components such as vitamins or herbal constituents need to be absorbed into your body before they can work. If they can’t be absorbed they have little effect.

How are foods, vitamins and medicines absorbed?

When you take medicines orally, the substances are moved by the contracting of the muscles in your digestive tract (this is known as peristalsis) from the mouth and throat into the gastrointestinal tract. In the stomach and small intestine, digestive acids and enzymes break the compounds of the medicine or vitamin down into smaller fragments.

Of these, water-soluble compounds such as vitamin C are taken up by the intestinal cells and then released into the bloodstream. Fat-soluble compounds such as Omega-3 fatty acids are taken up by lymph nodes, which carry lipids into the lymphatic circulation. The amount or proportion of these unique compounds absorbed is referred to as bioavailability.

Water-soluble particles are easily absorbed while the lymphatic system easily deals with fat-soluble lipids. Ingredients that are poorly soluble (don't break down in fat or water) in both, are very poorly absorbed. To sum it up, some components are far more easily absorbed than others, making them more bioavailable.

The journey of a nutrient in your body

Once a nutrient or medicine is taken into the body, cells may break it down, pump it straight back into the digestive tract, or release it into the bloodstream. From there it is carried directly to the liver, where it may be metabolised (broken down), activated, or inactivated by the liver cells (hepatocytes). This is known as first-pass metabolism. And finally, the liver may simply eliminate the compound by secreting it into the bile, which then carries it back to the intestine for excretion. All these factors affect bioavailability. Thus it is clear that to be highly bioavailable, an ingredient needs to be efficiently absorbed and remain in the body in an active form long enough to have an effect.

Here are some examples:
• Iodine is an essential nutrient. This trace mineral is very water-soluble. It is easily dissolved in and almost 100% is absorbed. This is a highly bioavailable nutrient.
• Magnesium, also an essential element, is absorbed from food at a rate of 30-40%.   In supplements, magnesium oxide is poorly soluble and bioavailability is only 15%. In contrast, taking magnesium as the citrate raises serum magnesium more effectively than the oxide by 7.5%. Small studies have found that magnesium in the aspartate, citrate, lactate and chloride forms is absorbed more completely and is more bioavailable than magnesium oxide and magnesium sulphate.
Does this mean bioavailability is improved? Yes, it does.

What reduces bioavailability?

Now as important as improving bioavailability is, it is also important to understand what can inhibit bioavailability. Strap in as we're going even deeper on the science!

Insoluble compounds. For example, magnesium citrate is water-soluble and magnesium oxide is much less so. The insoluble oxide form reduces absorption.  Soluble minerals should be preferred in dietary supplements.
Large molecules. Polyphenols, for example, are the most abundant bioactive phytochemicals in the human diet (think berries, coffee and cocoa), but their bioavailability is extremely low: only 1-10% due to their relatively large molecular size.
Food binders. Phytic acid in legumes, grains and rice binds to essential minerals and reduces their absorption.
Poor digestion. Recent studies of bioavailability have started to show that there are many factors that drive the efficiency of the digestion and absorption processes. These include a person's unique metabolism and characteristics of the food bring digested. In essence, poor digestion drives poor bioavailability.
• Gastrointestinal dysbiosis, or an overgrowth of nasty gut bugs. For example, healthy microbiota (healthy gut bugs) produce the enzyme phytase which releases essential minerals from phytate in the food. Without a healthy microbiome, this will not occur and you will not be able to release nutrients from certain foods.
Tea and coffee. These beverages contain polyphenols which markedly reduce the absorption of plant-based iron.
• Fibre supplements. Large doses of fibre supplements can reduce the absorption of calcium, magnesium, zinc, vitamin B12 and potentially other nutrients if taken at the same time. The fibre should be taken at least half an hour before a meal or by consuming supplements so that it doesn't impact absorption.
Alcohol. Excessive alcohol consumption reduces the bioavailability of many nutrients including biotin, folate, other B vitamins, vitamin A, lutein, and zeaxanthin. This can be due to reduced absorption, poor digestive function, increased urination, increased bowel movements, or all of these. When this is the case, additional supplementation is recommended. Excessive alcohol consumption may also unfavourably alter the microbiome of the digestive tract. This is where replacement probiotic supplements can support a healthy microbiome.

How to improve your absorption of nutrients

There are several methods that increase the bioavailability of nutrients in your body. Here are some top suggestions:

  • Focus on your gut health: Healthy digestive structures and functions are needed to enjoy optimum bioavailability and value of foods, medicines and supplements. A varied, balanced and whole food diet is essential. Effective digestion requires a healthy microbiome, which needs regular consumption of prebiotic foods such as soluble fibre, dairy foods and fermented foods as well as probiotic bacteria, eg in yoghurt.
  • Fibre is best as food. Where fibre supplements are necessary supplements should be soluble, fermentable fibre, rather than insoluble. Sources of soluble fibre include oat bran and psyllium. Fibre supplements should be taken at least half an hour before meals or other supplements and medicines, to avoid interfering with absorption.
  • Take your supplements with food. Nutritional supplements are best taken with food as the digestive system is active, increasing the digestion and absorption of nutrients.
  • Spice up your meals. Meals should include spices especially pepper and ginger, to enhance the bioavailability of all nutrients.
  • Ease up on the liquid pleasures. Moderation in the consumption of tea, coffee and alcohol is recommended as it can impact the absorption of vital nutrients.

Vitable offers subscription vitamins where you can mix and match nutrients to address your health needs and goals. Another great thing about Vitable is its vitamin delivery service that ensures you receive your personalised vitamins on time.  If you need custom vitamin packs in Australia, consider Vitable.

*Always read the label and follow directions for use. If you experience any symptoms or if symptoms persist, talk to your health professional. Vitamin and/or mineral supplements should not replace a balanced diet.

References

[1]Schonfeldt B et al, Bioavailability of Nutrients. Chapter in Encyclopedia of Food and Health, 2016, 401-406, Elsevier, 2016.

[2]Srinavasan V, Bioavailability of Nutrients and Other Bioactive Components from Dietary Supplements. J. Nutr. 131: 1349S–1350S, 2001.

[3]Augusti P et al, Bioactivity, bioavailability, and gut microbiota transformations of dietary phenolic compounds: implications for COVID-19.  Journal of Nutritional Biochemistry 97, 2021.

[4]Higdon J, An Evidence-Based Approach to Vitamins and Minerals. Thieme, 2003.

[5] Kass L et al, Effect of transdermal magnesium cream on serum and urinary magnesium levels in humans: A pilot study. PLoS ONE 12(4): e0174817.

[6] Dietary reference intakes for vitamin A, vitamin K, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc : a report of the Panel on Micronutrients ... [et al.], Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board, Institute of Medicine., 2001.

[7]Higdon J, An Evidence-Based Approach to Vitamins and Minerals. Thieme, 2003.

[8]Office of Dietary Supplements. Magnesium fact sheet for health professionals. National Institutes of Health, updated 2022.

[9]Dei Cas M et al. Dietary Curcumin: Correlation between Bioavailability and Health Potential . Nutrients 2019, 11, 2147.

[10]Shoba G et al, Influence of piperine on the pharmacokinetics of curcumin in animals and human volunteers. Planta Medica 64 (1998) 353-356.

[11] Hadadi N et al, Intestinal microbiota as a route for micronutrient bioavailability. Current Opinion in Endocrine and Metabolic Research 2021, 20:100285

[12] Chopra H et al, Curcumin Nanoparticles as Promising Therapeutic Agents for Drug Targets . Molecules 2021,26,4998.

[13]Chen Y et al, Nano Encapsulated Curcumin: And Its Potential for Biomedical Applications. International Journal of Nanomedicine 2020:15 3099–3120

[14] Chopra H et al, Curcumin Nanoparticles as Promising Therapeutic Agents for Drug Targets . Molecules 2021,26,4998.

[15]Office of Dietary Supplements. Magnesium fact sheet for health professionals. National Institutes of Health, updated 2022.

[16] Agusti P et al. Bioactivity, bioavailability, and gut microbiota transformations of dietary phenolic compounds: implications for COVID-19. Journal of Nutritional Biochemistry 97 (2021) 108787.

[17]Higdon J, An Evidence-Based Approach to Vitamins and Minerals. Thieme, 2003.

[18]Viera I et al. Bioaccessibility of marine carotenoids. Mar. Drugs 2018, 16, 397.

[19]Mattioli R. et al. Anthocyanins: A Comprehensive Review of Their Chemical Properties and Health Effects on Cardiovascular and Neurodegenerative Diseases. Molecules 2020, 25, 3809.

[20] Hadadi N et al, Intestinal microbiota as a route for micronutrient bioavailability. Current Opinion in Endocrine and Metabolic Research 2021, 20:100285

[21]Higdon J, An Evidence-Based Approach to Vitamins and Minerals. Thieme, 2003.

[22]Higdon J, An Evidence-Based Approach to Vitamins and Minerals. Thieme, 2003.

[23] Braun L et al. Herbs & Natural Supplements. An evidence-based guide. 4th edition, volume 2. © 2015 Elsevier Australia.

[24] Braun L et al. Herbs & Natural Supplements. An evidence-based guide. 4th edition, volume 2. © 2015 Elsevier Australia.

[25]Coates P et al. Encyclopedia of Dietary Supplements. Second Edition. Informa Healthcare, 2010.