Toddler, Child
5th Aug 2020

As a parent, you know the importance of vitamins and minerals for supporting your little one’s health and wellbeing. After all, it’s part of the reason you persist in trying to persuade them to eat their greens at dinner!

But did you know that not all nutrients are created equal?

While some are readily absorbed and quickly put to work in the body, others may be a little slower on the uptake.

This is known as bioavailability, which refers to the percentage of a nutrient that the body can use and absorb.

What Is Nutrient Bioavailability?

When we consume a vitamin or mineral, its bioavailability refers to the amount of the nutrient that has an active effect within our bodies.

Put simply, the higher a nutrient’s bioavailability is, the more of it that will get sent to the parts of the body that need it.

For example, if your child consumes a highly bioavailable form of calcium, more calcium will enter their circulation and be sent to the parts of the body where it’s needed most: like their bones.

Why Is Nutrient Bioavailability Important?

Vitamins and minerals each play specific roles within your little one’s body to help maintain their optimal health and support important bodily functions.

But, these nutrients can only do their job if they’re effectively absorbed by the body.

It’s the idea of strength in numbers: the more of a nutrient that’s absorbed by the body, the greater effect it may have.

So, by including bioavailable forms of vitamins and minerals in your child’s healthy diet or dietary supplement, their body reaps more of the rewards.

However, it’s important to remember that even if a dietary supplement is highly bioavailable, it can only be of assistance if your child’s dietary intake is inadequate.

Are Some Nutrients More Bioavailable Than Others?

Of course, different forms of nutrients are more easily absorbed (or more bioavailable) than others.


In our diets, there are two different types of iron, known as haem and non-haem iron.

Haem iron may be found in animal products (like red meat, poultry and seafood) and is absorbed much more efficiently than non-haem iron, which may be found in plant-based foods (like vegetables, wholegrains, legumes, nuts and seeds) (1).

In fact, the bioavailability of haem iron is 15-35% while the bioavailability of non-haem iron is just 2-20% (2).

If you’d like to learn more about iron, you can discover the signs and symptoms of low iron levels in children here.


The forms of nutrients in different dietary supplements also have varying bioavailability.

For example, two forms of zinc that are commonly found in dietary supplements are zinc gluconate and zinc glycinate. A study comparing these two different forms found that zinc glycinate was significantly more bioavailable than zinc gluconate.

In fact, zinc glycinate was found to increase zinc bioavailability by 43% (3)!

This was confirmed by a subsequent study, which concluded that zinc glycinate increased zinc levels in the body more effectively than zinc gluconate (4).

If you’re interested in learning more about zinc, you can discover why zinc is an important nutrient for babies and children here.


Calcium phosphate, calcium citrate and calcium lactate are three different forms of calcium that are often used in dietary supplements.

A study that compared the bioavailability of these different forms found that calcium phosphate was the most bioavailable (5).

You can explore the importance of calcium for supporting your child’s bones here.

How Is Nutrient Bioavailability Measured?

Nutrients come in lots of different forms.

So, when it comes to developing dietary supplements, it’s important to measure and compare their bioavailability to ensure they’re easily absorbed by the body.

To do this, extensive clinical testing is used. Usually, researchers conduct several tests in the lab before enlisting the help of human volunteers for more in-depth testing.

The volunteers ingest nutrients from different sources (like foods or supplements) and the amount of that particular nutrient present in their bloodstream is measured before and after consumption. This allows the researchers to see how much of the nutrient was absorbed and made its way into the body’s circulation.

What Factors Affect Nutrient Bioavailability?

Of course, every vitamin and mineral is unique. So, the factors that might positively or negatively affect bioavailability varies from nutrient to nutrient.

Bioavailability also fluctuates from person to person, depending on a range of different influences, like good digestion (which begins with properly chewing your food).

The bioavailability of a vitamin or mineral may also be influenced by external factors such as the food combination in a meal or nutrient combination in a supplement.

Vitamin C And Iron

The effect of vitamin C on iron absorption is an example of a positive effect on nutrient bioavailability.

In the gut, vitamin C coverts non-haem iron (the less easily absorbed form of iron) into a more bioavailable form that the body prefers, which helps absorption.

Top tip: Giving your child food sources of vitamin C at the same time as high-iron foods may help to increase the amount of iron their body absorbs from that meal.

If you’re interested in learning more about vitamin C, you can find more information about its benefits for children here.

Vitamin D And Calcium

Another example of nutrients working together to increase bioavailability is vitamin D and calcium.

Vitamin D aids the absorption and use of calcium in the body.

So, by choosing a calcium supplement with added vitamin D for your child, their body may absorb more calcium.

If you’d like to learn more about vitamin D, you can discover more information here.

Fat Soluble Vitamins And Fat

Vitamins A, D, E and K are all known as fat soluble vitamins because they are stored in the body within fat cells.

Fat soluble vitamins are more easily absorbed by the body in the presence of fat. For this reason, ‘healthy’ fats such as the monounsaturated kind found in avocados may help to aid the absorption of vitamins A, D, E and K.

If you’d like to learn more about the difference between fat and water soluble vitamins, click here

As with most health concerns, there are a variety of factors to consider when it comes to your little one’s nutrition. If you have any concerns or questions about their diet, talk to your friendly health professional.

Vitamin and minerals can only be of assistance when dietary intake is inadequate.

This information provided in reference to ingredients is general in nature and provided as information only. Any product specific therapeutic claims for an ingredient are linked to specific dosage requirements based on evidence of traditional or scientific nature.

What's Next?


  1. Whitney, E, Rolfes, S, Crowe, T, Cameron-Smith, D, Walsh, A. (2014). Understanding Nutrition: Australian & New Zealand Edition. 2. Melbourne; Victoria.
  2. Schonfeldt, H & Hall, N. (2011). Determining iron bio-availability with a constant heme iron value. Journal of Food Composition and Analysis, 24 (4). 738-740.
  3. Gandia et. Al. A Bioavailability Study Comparing Two Oral Formulations Containing Zinc (Zn Bis-Glycinate vs. Zn Gluconate) After a Single Administration to Twelve Healthy Female Volunteers. International Journal for Vitamin and Nutrition Research (2007), 77, pp. 243-248.
  4. Disilvestro, R, Koch, E & Rakes, L. (2015). Moderately High Dose Zinc Gluconate or Zinc Glycinate: Effects on Plasma Zinc and Erythrocyte Superoxide Dismutase Activities in Young Adult Women. Biological Trace Element Research, 168 (1), 11-14.
  5. Patwardhan, UN, Pahuja, D & Samuel, A. (2001). Calcium bioavailability: an in vivo assessment. Nutrition Research, 21 (4), 667-675.
  6. Lynch, S & Stoltzfus, R. (2003). Iron and Ascorbic Acid: Proposed Fortification Levels and Recommended Iron Compounds. The Journal of Nutrition, 133 (9). 2978S-2984S.
  7. Saunders, A, Craig, W, Baines, S, et al. (2013). Iron and vegetarian diets. Medical Journal of Australia, 199 (4). doi: 10.5694/mja11.11494.
  8. Hambidge, K. (2010). Micronutrient bioavailability: Dietary Reference Intakes and a future perspective. The American Journal of Clinical Nutrition, 91 (5). 1430S-1432S.