What is Bioavailability? How it can help you get the most out of your supplements

What is Bioavailability? How it Can Help You Get the Most out of Your Supplements

What does bioavailability mean?

Bioavailability is the amount of active ingredient within a drug, food or supplement that makes it to the part of the body that needs it.  In simple terms: does the ingredient arrive where it will help you feel healthy?

It is a term that was first used in 1971 and much work has been done since to properly clarify what being bioavailable truly means.  It is fair to say though – there is still a lot of confusion and varying opinion on this topic.

For those of us who are fighting to keep our health and fitness levels at their peak, knowing if the food we eat and the supplements we take are working for us is crucial.  You will have heard claim and counter claim from companies about the capability of the products they sell to change your life.  How can we be sure that what we are taking is actually working?

What makes something more bioavailable?


So, if you have an injection at the hospital or doctors, you are receiving a drug with 100% bioavailability.  The active ingredient enters the blood stream and will travel to the parts of the body directly.

If you ingest a product, whether it be food or a supplement or a drug, the bioavailability is changed by a large number of factors – not least the ability of the active agents to be absorbed and its ability to hitch a ride into the bloodstream. 

The nutrients we take in have a rough ride through a fairly hostile environment – both our stomach and our liver would love to metabolise all they can - but it is only in the lower intestine can these nutrients be released into the blood stream.

What can reduce bioavailability?

There are many factors that limit the bioavailability of the active ingredients. For instance:

  • How long it takes for the product to dissolve
  • Where the dissolution takes place
  • How much is dissolved
  • What coating is used to help with passage to the gut
  • The presence of any inhibitors or co-factors (hinderers and helpers)
  • The interaction with any other drugs you might be taking
  • The time of day you take the product
  • The amount absorbed through the gut wall into the blood stream
  • The amount of the nutrients that are already present within your blood stream and whether your body can cope with anymore.

So, for instance, if you eat something that cannot dissolve then it will just pass straight through your system and down the toilet.  This has long been good news for small children who have attempted to eat small plastic toys.

If the ingredients dissolve too quickly they could be damaged beyond use in your stomach; if it dissolves too slowly the body will just eject it before it has chance to work. 

If you eat something that can absorb but cannot hitch a ride into the bloodstream because your body has no idea what it is you’ve just eaten: it will pass straight through to the toilet.  For instance: some minerals need to change form to get into the bloodstream – you may have heard of the term chelate.  The process occurs naturally in the lower intestine if the mineral is dissolved ready for travel.  Some supplements claim the mineral is already in chelate form and therefore should travel with ease into the bloodstream.  Please note the important use of the word “claim” – more on this later.

Then, there is the idea that some vitamins and minerals compete for the same ride.  Calcium and iron get into a bit of an argument in the lower gut.  Iron gets the ride but calcium blocks the exit.  The effect is that neither enters the bloodstream and the supplement you have taken has nil effect.  The answer is to take any iron and calcium supplements at different times of the day, but then many supplements come packaged together.

Some nutrients need the others to work best.  So, iron works much better if taken alongside vitamin C.  In fact, just stop and think about how nature works best: our gut is designed to deal with whole food.  Our body has evolved to take in nutrients together and the synergy of the vitamins and minerals makes for much better absorption rates in general. 

What does all this mean to us?


The answer is often to eat a healthy balanced diet with lots of vegetables – then your body, long evolved through time, will work as it should to get the vitamins and minerals it needs. For instance, if you eat meat, fish or poultry this gives us iron but also increases the chance of getting iron out of other foods such as spinach.

You can also choose to eat foods that are fortified with vitamins and minerals.  Vitamin B and iron is often found in breakfast cereal, for instance.  If you have a glass of orange juice with your breakfast, naturally filled with vitamin C – then, all the better for absorption rates.

But, the truth is as we get older the chances are that we are not as efficient as we used to be at taking in essential vitamins.  We produce less gastric mucosa and therefore we do not process dissolved foods as quickly through the gut as we need to.  Also, ailments common in mid-life for men, such as ulcers and IBS, can reduce our chances of taking in what we need from our food.  So, we need to look to the supplement industry for some help.

The supplement industry is worth $20 billion. This means that there is a lot of vested interest in the claims made for the bioavailability of supplements and the term has become something of a buzz word.  Each product is becoming more bioavailable than the next – with claim and counter claim.

How is bioavailability measured?

The bad news for us is that supplements are classed as food under the Dietary and Health Food Act (1994).  This means that claims made about bioavailability do not have to be tested.  Due to this, there is little agreement as to how to test bioavailability; standardised tests are an ideal the industry is still working towards.  Testing bioavailability could be as simple as testing urine and faeces and seeing how much of the active ingredient has been excreted before being used.  However, this doesn’t account for the fact that some of the product may have been destroyed before reaching the lower gut – so tracking the active agent with an element that will attach to it and following its cause through the body is what the industry is working on.  But, it is an expensive process and there is no reason in law for them to be scientifically certain that what they are claiming is true.

So currently, lots of products make claims about how good they are at getting the nutrients to the place that matters without reliable evidence to support what they say.  Saying something is 600% bioavailable is confusing on many levels.  If you are taking in 6 times the amount of calcium you need, for instance, your body with just eject all but that which it needs.  It can only store so much calcium in the blood ready for work in the bones – the rest has to go somewhere – and unfortunately, it is down the toilet.  But to take a 6th of the dose and assume that this means taking in what you need doesn’t work either – as the supplement is going to have other ingredients – no less the all-important delivery method to the gut – so this won’t work either.

We are also all individuals.  Our dietary habits, age, gender and health all impact on the bioavailability of a product.  Therefore, you and your next door neighbor might take the same product but have entirely different reactions.   For instance, there are two types of vitamin C.  One can cause irritation for some in the stomach and therefore not work.  But, for someone else, this is the perfect means of getting vitamin C into the system.


Understanding how to read the label


The way to make the best of the supplement market is to learn to read the label.  The best option is to go with products that have been FDA or GMA approved.  You then can be completely assured that someone in a lab coat has done the hard work of proving that the claims made are accurate.  You are likely to pay the price for this but then you won’t be completely wasting your money either.

If you are still keen to have some control over the choice, here are some handy tips:

  • As with food, natural tends to be better than processed. Some supplements can be made from petrochemicals, so it is always useful to look at the ingredients.  If it gives the ingredients as the vitamin, then this is likely to be synthetic.  However, if it says citrus on the side of Vitamin C or parsley on the side of Vitamin K, then you know the ingredients are likely to be natural. 
  • If the supplement is claimed to be surprisingly high in potency it is likely that it is synthetic and some natural scepticism should be applied to whether this will work as advertised. Remember that certain vitamins and minerals do not naturally store in the body.  This means if your body does not need a nutrient it will just excrete it as a waste product.  You will essentially be flushing money down the toilet.
  • The list of ingredients will seem long. On this list will a number of ingredients related to delivering the nutrient to the lower intestine, so it can then be absorbed into the blood stream.  If you value your body it would be sensible to investigate what these chemicals are and how they work.  If there are ingredients that seem to suggest the supplement won’t dissolve, then ask yourself: how will it provide the bioavailability suggested?

It is also worth checking the ingredients with your doctor.  Some supplements can actually impact the effectiveness of medications.  For instance, St Johns Wort can break down antidepressants in your system and stop them working.  Vitamins C and E can reduce the effectiveness of some cancer treatments.  Remember that even though these supplements are not considered a drug, you are expecting an impact on your health.  Therefore, seeking the advice of a medical professional is often the best route to take.


How does the FDA regulations help you use supplements safely



It is worth remembering that supplements are considered food.  This is important information for all of us, as this means that organisations such as the FDA are not allowed to test a product before it comes to market.  Even if it comes to market and is not effective, the FDA cannot remove it from sale unless the company have made a dishonest claim in the labelling.  Therefore, there is no overview of what you might think is a medical product. 

The FDA is clear in its guidance about what can be considered a dietary supplement.  A dietary supplement is a product that makes some form of health claim, or is said to be an addition to food or has an ability to reduce the risk of a condition. However, dietary supplements are not allowed to mention a set illness or complaint.  If it claims to be a certain vitamin or mineral, then it must have a relatively large amount of that nutrient within the product.  Any claims made in the literature of a dietary supplement must be submitted to the FDA for approval within 30 days of being sold.  This means you could buy the product before the FDA has had a chance to check the claims being made.

But, here is the important bit: if it has not been checked by the FDA it must have on the label a statement that informs you that the claims have not yet been checked!  It will also urge you to understand that the supplement is “not intended to diagnose, treat, cure, or prevent any disease.”

The FDA have a thorough list of vitamins, minerals and other nutrients that you can explore on the website.  They explain in some detail the health consequences of taking different supplements and stress that some can harm your health. However, since 2007 the FDA have issued GMPs (Good Manufacturing Processes) labels to those products that the FDA deem to have working practices that ensure the quality of the product and to show that nothing gets into the supplement that could be harmful.

Unfortunately, the FDA is still not able to standardise the process or the contents of the products.  There is no test used that can support the claims of bioavailability and all the FDA can do is protect against dishonest claims and poor working practices.  Still, it is better to seek out the supplements with the GMP label then it is to risk a product from somewhere that hasn’t been vetted.

Is it worth it?

At a time in our lives when we want to stay vital and maintain our energy, it is always worth investigating the many different ways to maintain our health.  There is no doubt that these nutrients are important to our well-being and whether the bioavailability is advertised or not – if they make you feel better after 30 days – then they are working for you!  Keep a sensible check on how they make you feel and if it is worth the outlay – if it is – go for it and buy a supplement from a reputable brand! We all deserve to feel better.


If you enjoyed this article, here are the rest of the articles part of the Ultimate Guide to Supplements:

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