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Bioavailability 101: what it is, and why it matters

The definition of bioavailability. Learn why bioavailability matters when buying vitamins, nutrients, and supplements.

June 22, 2021
6 min read

When it comes to bioavailability, most vitamins, minerals and other health supplements leave a lot to be desired. Unless you know what to look for when you’re buying supplements, you’re probably flushing a lot of hard-earned money down the drain. Literally.

Let’s break down what bioavailability is, why bioavailability matters, and key questions to ask when to ensure you’re reaping all the benefits of your supplements.

What is bioavailability?

In the world of medicine and nutrition, the term “bioavailability” has traditionally referred to how quickly a certain vitamin, mineral, or other nutrient entered your bloodstream. 

For example, studies on magnesium and on vitamin D supplementation typically use blood tests to identify how much of either nutrient is in a blood sample after someone has taken a magnesium or vitamin D pill.

But that doesn’t always tell you the whole story. Just because a nutrient has entered your bloodstream doesn’t mean it’s getting to where it needs to go, or even being used effectively. 

This may explain why there are so many conflicting studies on certain nutrients. Using vitamin D as an example again, researchers know vitamin D has its benefits, but the research results on vitamin D supplements are often inconclusive

Could this be because certain vitamin D supplements may elevate your blood levels of the vitamin, but are not actually being absorbed and used efficiently? And how can you, as a savvy supplement shopper who wants your supplements to actually do their job, ensure your body is truly getting the nutritional support it needs? 

This has led to a newer take on the definition of bioavailability.

True bioavailability = how well your body absorbs and uses a supplement

Dr. David Kitts, an experimental medicine scientist at the University of British Columbia, breaks down the traditional definition of bioavailability into two separate terms: 

  • Bioaccessibility 

  • Bioavailability

Bioaccessibility is how quickly a supplement is broken down by your digestive system, and the specific vitamin, mineral or other nutrient is made available to your body. Think of that as the “old” idea of bioavailability. 

Meanwhile, Dr. Kitts says that true bioavailability is the "rate and extent to which the therapeutic moiety is absorbed and becomes available at the organ site."

To put it into everyday language, this new-and-improved understanding of bioavailability refers to how well your body absorbs and uses a specific nutrient in the right place, at the right time.

“Take magnesium as an example,” we noted in a previous Heights article on using our best-selling Smart Supplement as a replacement for other supplements. “Many cheaper supplements use magnesium oxide or magnesium sulfate, but these types of magnesium aren't as easily absorbed by your body as magnesium citrate or magnesium aspartate.”

So, how can you make sure that you’re buying supplements that have high bioavailability?

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3 bioavailability questions to ask to ensure your supplements actually work

The next time you’re buying supplements, don’t just pay attention to the milligrams on the label or the promises made by the manufacturer. Take a peek at the actual ingredients and consider the following questions.

1. Does the supplement use the most absorbable form of the vitamin, mineral or nutrient?

Just because a supplement has a high dose of a nutrient doesn’t mean your body can actually absorb and use it. In fact, when it comes to some commonly used ingredients, your body has such a hard time absorbing them that the supplement might almost be worthless!

Take an omega 3 supplement, for instance. The most absorbable and effective types of omega 3 are EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). However, many omega 3 pills contain a form of omega 3 known as alpha-linolenic acid. 

Researchers have found that in some people, your body converts as little as 0.3% of ALA into EPA (the conversion success rate to DHA is a bit better at 4%). 

In other words, when you take an omega 3 supplement made with ALA, 99% of it is basically ineffective. 

2. Does the supplement use the purest form of the ingredient?

Researchers warn that many supplements contain vitamins, minerals, and other ingredients that have been tainted with potentially toxic substances. And in some cases, the supplements contained little of what they promised to contain.

“DNA testing of store-brand products often detected fillers—including wheat and legumes, possible risks for people with intolerances or allergies,” warns the School of Nutrition Science and Policy at Tufts University.

“For example, pills sold as ginkgo biloba, a Chinese plant touted for memory benefits, actually contained powdered radish, houseplants and wheat. Ginseng pills, which promise to boost ‘physical endurance and vitality,’ were found to be nothing more than powdered rice and garlic.”

Even beyond such alarming mislabeling, many manufacturers also use ingredients that are not the purest, most concentrated form of the actual nutrient you want. 

Let’s use medium-chain triglyceride (MCT) supplements as an example. Many people take MCT supplements for cardiovascular benefits and other health reasons. 

Some brands may contain pure MCT oil, where the coconut oil has been put through a process known as fractionation to isolate the MCTs themselves. Other supplements may just use pure coconut oil, which is made up of only an estimated 55% MCTs. Pure MCT oil is also more rapidly absorbed by your body than pure coconut oil.

3. Do the ingredients interact with each other (or with other supplements you’re taking)?

Some nutrients boost the bioavailability of other nutrients. Some commonly combined pairings that make each individual nutrient more effective include:

  • vitamin D and calcium

  • vitamin B12 and folate

  • zinc and copper

  • iron and vitamin C 

Likewise, taking a fat-soluble vitamin (e.g., vitamin A, vitamin E, etc.) with a meal containing fat helps your body to better absorb and use the vitamin. 

The opposite can also happen, where some nutrients limit the bioavailability of another nutrient. For example, high doses of vitamin C may reduce the effectiveness of several B vitamins. 

The Smart Supplement was designed with bioavailability in mind

In conclusion, ensure all of your supplements:

  • use the most absorbable form of a specific nutrient

  • contain the purest ingredients

  • do not contain ingredients that negatively affect the bioavailability of other nutrients

While many of our readers may be exploring the importance of bioavailability for the first time, the effectiveness and absorption of specific nutrients have always been front and centre for us at Heights. 

That’s why we only use the purest ingredients that have been vetted by third-party reviewers, and we always select the best forms of each vitamin or mineral to ensure maximum bioavailability.

Similarly, every ingredient in the Smart Supplement has gone through rigorous research under the supervision of Chief Science Officer Dr. Tara Swart, and Sophie Medlin, our Head of Nutritional Research.

Learn more about the exceptional bioavailability of our Smart Supplement and why Heights only offers the highest quality nutrients for better brain health and improved mental well-being.

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