Bioavailability 101

Learn why bioavailability is important when buying vitamins, nutrients and supplements.

Many commercially available supplements use vitamins and minerals with very low bioavailability. If you don't really know what to look for when buying supplements, you're literally flushing money down the drain, because your body can't absorb the nutrients if they don't contain adequate bioavailability.

Before you start taking supplements, you should become familiar with the facts. We've put together a guide to the bioavailability of vitamins and minerals so you can reap all the benefits of taking supplements. For more tips and tricks, check out the NOUMEN Supplements 101 Guide.

What is bioavailability?

In nutrition science and medicine, the term bioavailability traditionally used to refer to how fast a specific vitamin, mineral, or other nutrient is absorbed into the bloodstream

In studies of vitamin D and magnesium intake, blood tests are usually conducted to assess how much of either nutrient is in a blood sample. However, this value is not always sufficiently conclusive, because just because a nutrient has been absorbed into the bloodstream does not necessarily mean that it is being used effectively. This may explain why there are so many conflicting studies on certain nutrients. For example, for vitamin D, there are many very strong studies and also health claims in the EU, such as "Vitamin D contributes to normal immune system function." However, not all studies on vitamins and minerals are conclusive enough and some are even contradictory. Researchers suspect that while many supplements increase blood levels of the vitamin, they are not really absorbed and used efficiently. This is where the term bioavailability comes into play.

How well can your body absorb and metabolize a supplement?

The University of British Columbia, divides the traditional definition of bioavailability into two different terms: 

  • Bioaccessibility 
  • Bioavailability

Bioavailability indicates 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. This is the traditional notion of bioavailability that we touched on at the beginning of this article. 

However, according to British Columbia University studies and modern definitions, bioavailability is the rate and extent to which the therapeutic portion is absorbed and available at the organ site. In simpler terms, it means how well the body absorbs and metabolizes a particular nutrient at the right place and time.

Let's take magnesium as an example. Many supplements use beneficial forms of the nutrient, such as magnesium oxide or magnesium sulfate. However, these types of magnesium are not as readily absorbed by the body as magnesium citrate or magnesium aspartate.

NOUMEN Nahrungsergänzungsmittel mit hoher Bioverfügbarkeit für Männer

3 questions about bioavailability you should ask yourself before every purchase

The next time you buy supplements, don't just look at the dosage or milligrams of the nutrient, but take a closer look at the actual ingredients on the label.

🧬 Question 1: Does the supplement use the most absorbable form of the vitamin, mineral or nutrient?

Just because a supplement contains a high dose of a nutrient doesn't mean your body can actually absorb and metabolize it. In fact, with some commonly used ingredients, your body has such a hard time absorbing them that the supplement can be almost worthless! 

Vitamin B12 (cobalamin), for example, has two bioactive forms: Methylcobalamin and Adenosylcobalamin. The synthetically produced form - cyanocobalamin, on the other hand, is not very bioactive and cannot be digested by the body. This form is often included in B12 preparations because it is very inexpensive. Because of its low bioactivity, however, it is worthwhile to use the two forms adenosyl- and methylcobalamin for vitamin B12. This applies to a wide range of vitamins.

  • Vitamin D: ✅ Vitamin D3 ⛔ Vitamin D2
  • Vitamin B12: ✅ methylcobalamin ⛔ cyanocobalamin
  • Vitamin B9: ✅ 5-MTHF ⛔ folic acid
  • Zink: ✅ zinc bisglycinate ⛔ zinc oxide
  • Vitamin A: ✅ retinyl palmitate ⛔ beta-carotene
  • Vitamin B6: ✅ P5P ⛔ pyridoxine 

🧪 Question 2: Does the dietary supplement use the purest form of the ingredient?

Researchers warn that many food supplements contain vitamins, minerals, and other ingredients that have been contaminated with potentially toxic substances. And in some cases, the supplements contained little of what they promised to contain. DNA tests of store-brand products often detected fillers, including wheat and legumes, which can pose a risk to people with intolerances or allergies. 

You should therefore avoid manufacturers that use fillers. They are often used for products that contain only a few active ingredients, otherwise the capsule would look empty. Many manufacturers also use magnesium stearate, a plasticizer used to make it cheaper to squeeze ingredients into a capsule.

♻️ Question 3: How do the ingredients interact?

Some nutrients increase the bioavailability of other nutrients. Commonly combined combinations that increase the effectiveness of each nutrient include:

✅ Iron and vitamin C 

✅ Vitamin B12 and folic acid

✅ Zinc and copper

✅ Calcium and vitamin D

Equally important, the opposite can also be true - some nutrients limit the bioavailability of another nutrient. Some vitamins you should never take on an empty stomach, but with a meal. In particular, the fat-soluble vitamins A, D, K and E should always be taken with a meal, otherwise they cannot be absorbed by the body. The mineral calcium should also be taken with a meal, as its absorption depends on sufficient gastric acid.

NOUMEN Supplements is designed with the highest bioavailabilities in mind.

Let's recap the most important things you should ensure when buying: 

  • Use the most absorbable form of a given nutrient 
  • Buy supplements with the purest ingredients possible
  • Make sure it doesn't contain fillers and magnesium stearate
  • And, that no ingredients negatively impact the bioavailability of others

NOUMEN supplements are designed with the highest bioavailabilities in mind. Only ingredients that enhance your well-being and help you achieve maximum performance are used. To learn more about our supplements and how to take them properly, subscribe to our newsletter or contact us at

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