What Is Bioavailability & Why Does It Matter?

Jun 01, 2022 | BY First & Foremost Clinical Team

What Is Bioavailability & Why Does It Matter?
By Adam Felman


Bioavailability is the degree to which your body absorbs food, vitamins and nutrients, which can be impacted by several factors. Below, the science, facts, and tips to make nutrient absorption work for you.

Staying conscious about healthy food choices is central to a stable, energized, and balanced level of well being. But you might be missing out on important nutritional benefits if you consume them in a way that your body can’t process.

It can be frustrating when you follow all the best nutrition advice only to find that you’re still not seeing the positive health outcomes you’d expect. However, taking bioavailability into account may improve the health outcomes of your diet.

Below, we’ll define bioavailability, explain how to improve it, provide some examples of bioavailability, and explore why a nutrition plan and supplement regimen based on high nutrient absorption is essential for your health.

What is bioavailability?

Bioavailability describes the body’s ability to absorb or store food, vitamins, and nutrients. Many scientists define bioavailability as the amount of a consumed nutrient that the body then makes available. 

The term “bioavailability” concerns how the body processes nutrients. Dietitians are often concerned about the nutrient absorption of supplements. For example, if a nutrient or drug is “orally bioavailable,” it means your body can absorb and use the substance when you consume it by mouth.

People also regularly use the term bioavailability when talking about prescription drugs, but for the purposes of this article, we’re focused on nutrition.


How does bioavailability work?

Bioavailability is driven by several key factors including the timing of taking a nutrient, whether the nutrient is taken with food or without, and the pairing of nutrients with others.

Complementary nutrients may improve absorption, while conflicting nutrients may interfere with it. The solvent in which the nutrient dissolves also makes a difference. For instance, some nutrients may block or speed absorption of others, and some substances may help a nutrient dissolve, while others may not.

Nutrient interactions: Certain nutrients can interact in ways that affect each others’ bioavailability. For instance, including a large number of high-zinc foods like oysters, meat, avocados, and blackberries in your diet might reduce how much copper you can absorb.

Food bioavailability: Fruits, vegetables, and dairy products, in particular, have shown that they provide health benefits based on a complex interaction of different nutrients rather than any single beneficial compound. However, some foods can actually block absorption, such as the phytates in whole grains that block iron absorption.

Vitamin absorption: Some vitamins are inherently more bioavailable than others. Some research estimates that vitamin A is only 15% bioavailable, meaning that the body doesn’t absorb 85% of the vitamin A you consume. This makes a varied diet crucial, as fats improve the body’s ability to absorb vitamin A. Iodine, on the other hand, has high bioavailability at 90%, so your body can use much more of the iodine you ingest.

The notion of bioavailability makes a wide-ranging, nutrient-dense diet key to getting the most from your food. It also highlights the benefits of choosing bioavailable nutritional supplements that can help the other nutrients in your diet work more efficiently.

Complementary nutrients help each other become more bioavailable.

Complementary nutrients are those vitamins and minerals that work together to make it easier for your body to absorb, use, and store. People with a deficiency of a particular nutrient can make adjustments to their diet to improve bioavailability.

For example, one type of iron present in grain-based meals — non-heme iron — is harder for the body to absorb than iron present in animal products, called heme iron. According to a 2021 review, consuming grain-based meals along with foods rich in vitamin C may boost the nutrient absorption of non-heme iron.

To make the most of these beneficial interactions and to mitigate any hindrances to absorption, F&F offers a three-occasion-per-day program that pairs complementary nutrients and separates antagonistic ones at the most bioavailable time of day.

How Complementary Bioavailability Works

In one example of complementary bioavailability, vitamin D interacts with the parathyroid hormone to balance calcium levels in the body. Vitamin D is also a key player in making calcium easier to absorb through the intestinal tract. Both of these interactions help you improve and maintain the integrity of your bones.

By boosting calcium absorption, vitamin D helps maintain high enough concentrations of calcium and phosphate to support how your body makes bone. It also helps you avoid the effects of calcium deficiency.

Solubility in fat or water affects how your body uses a nutrient.

Your body’s ability to use a nutrient also depends on the fluid that allows it to dissolve. After taking in food, either the fats or water in your body absorb its nutrients. Different nutrients dissolve in each substance. Solubility dictates whether the body puts nutrients to work immediately or keeps them in reserve for later use.

Fat Soluble Vitamins

Some nutrients, like vitamins A, D, E, and K, dissolve in fat, making them easier for your body to store and use over time. These are known as fat-soluble vitamins.

Eating the right foods with these types of nutrients, like oily fish, eggs, or avocados, can help your body absorb and make better use of them.

Water-soluble vitamins

Water-soluble vitamins dissolve in your body’s water supply the moment they enter your digestive system, so they can’t be stored for later use. Nine vitamins are water-soluble, including several B-vitamins, thiamine, and folate.

Conflicting nutrients can work against each other to reduce bioavailability.

Some vitamins and minerals can reduce the bioavailability of others. As with medications, nutrients start working when your digestive system breaks down your food. While many nutrients are vital for your health, some can interfere with your digestive system’s ability to absorb others.

For example, a high calcium intake through foods like leafy green vegetables and dairy products can reduce how much iron your body can absorb. 

Bioavailability Example

In a key example of bioavailability, the calcium absorbed by the small intestine gains a boost from phosphorus, improving absorption into the bone and encouraging your kidneys to reabsorb calcium from the body’s waste.

This is one example of nutrients improving bioavailability. A whole range of vitamins and minerals interact in a complex network of chemical reactions, affecting nutrient absorption. A varied diet can resolve many imbalances due to nutrient absorption, but taking supplements to strategically boost your intake of certain nutrients can help you stay on top of gaining maximum benefit from what you eat.

Why bioavailability matters

Bioavailability provides an important link between the nutritional content of your food and how it provides health benefits, reduces disease risk, and keeps basic bodily functions running smoothly.

Some food sources are more bioavailable

Whether you’re simply trying to maintain a balance of nutrients or managing a deficiency, it’s important to consider the source of the nutrient as well as its quantity.

For example, you may prefer eating green, leafy vegetables to eating fruits. If you wanted to boost your intake of vitamin A, you might turn to spinach or kale, because they provide a lot of beta-carotene for the body to convert to vitamin A (335 micrograms per 100 g). However, even though fruits provide less vitamin A, fruits like mangoes (26 micrograms per 100 g) store their beta-carotene in cells that are easier for humans to digest. That makes them a more bioavailable source.

If you include less bioavailable nutrients, food sources, or supplements in your diet, you might need more of them to prevent a hidden imbalance — even though you’re technically eating your recommended daily intake of nutrients. Another example involves people who follow a plant-based diet: they can find plenty of iron in leafy greens, seitan, and pulses, but it’s a less bioavailable form than the iron in animal-sourced products.

You can offset these shortfalls in nutrition by taking supplements engineered to increase nutrient absorption.

What are the health consequences of not fully absorbing nutrients?

If your small intestine can’t absorb as many nutrients as you need from food, it could lead to malabsorption syndromes. Your ability to absorb nutrients can become less effective during infections of the digestive system, after surgery on the intestines, and while living with chronic disorders that affect digestion like Crohn’s disease. These conditions increase your risk of a nutrient deficiency. 

While symptoms might differ depending on the nutrient that’s lacking, some common effects include:

  • Developmental delays or skeletal deformities (in children)
  • Diarrhea
  • Steatorrhea, which is an increase in the amount of fat your body gets rid of in your stool
  • The visible effects of anemia, including pale skin, breathlessness, and fatigue
  • Unintentional weight loss

Taking nutrient absorption into account is especially important for those addressing a nutrient deficiency.

How to increase bioavailability

Some foods offer more efficient nutrient absorption than others. It’s best to combine your recommended intake of each vitamin and mineral with complementary nutrients that boost their absorption.

There are a few potential ways to boost the bioavailability of vitamins and minerals:

Take a course of strategic daily supplements

Given the complexity of balancing the various chemical reactions involved in nutrient absorption, you may benefit from a simple, effective supplement regimen. The research-backed supplements you’ll find at F&F provide three scheduled daily doses of vital nutrients like magnesium, zinc, vitamin K, potassium, and iron at the most nutritionally impactful times.

This uniquely-timed delivery and separation of “antagonistic” nutrients maintains optimal levels of these essential micronutrients. It can also increase the bioavailability of vitamins and minerals in your food through complementary reactions.

Eat a nutrient-dense, varied diet

Another way to increase bioavailability in food is to eat as many different nutrient-dense whole foods as possible. 

A diet that incorporates the following food groups should provide a wide range of high-bioavailability nutrients:

  • vegetables
  • fruits
  • whole grains
  • beans
  • nuts
  • seeds
  • lean meat
  • seafood
  • eggs
  • milk
  • yogurt
  • cheese

The bioavailability of popular supplements

Taking bioavailable vitamins and minerals in supplement form is a simple but effective way to manage nutrient absorption.

How do bioavailable supplements work?

Certain nutrients have higher bioavailability than others. Bioavailable supplements work by giving you as much of each nutrient as you need while also taking into account the nutritional absorption of the vitamin or mineral.

However, you can take extra steps to increase the bioavailability of supplements. For example, taking fat-soluble supplements with food is often the best way to ensure better absorption of fat-soluble vitamin supplements like vitamins A and K.

Following a scheduled regimen like F&F’s supplement plan can help ensure that some of your most crucial nutrients are taken care of, leaving more flexibility in your diet and providing increased energy in your lifestyle.

How to ensure maximum nutrient absorption for supplements in F&F’s daily regimen

Here’s how to make sure your supplements are working for you — morning, noon, and night. Getting nutrients from a nutrient-rich diet alone is a completely healthy way to approach nutrition. But extra processing at the pill manufacturing stage can make the nutrients more bioavailable. 

Taking a specially tailored supplement made with bioavailability in mind can make keeping on top of nutrient absorption in nutrition a simple part of your daily routine. A balanced, holistic approach to supplemental nutrition can help you get the most out of your diet.

The morning pill


This metal supports a range of processes across the body like nerve function, DNA synthesis, protein and bone production, and blood sugar control. 

Some studies have shown that calcium, iron, and zinc — all available in the daily F&F supplement regimen alongside magnesium — can bind to magnesium and make it more bioavailable. Casein and whey peptides may also have the same effect.

If you take magnesium supplements, it might be best to avoid vegetables rich in oxalate like spinach, which forms an acid that can reduce magnesium’s bioavailability. High-fiber foods might have a similar effect, but more research is needed to explore these interactions.


Zinc helps your body build DNA, facilitates your sense of taste and smell, and helps you develop fully as a child. It also supports your immune system in protecting you from disease.

Phytate is a plant compound that can significantly reduce zinc absorption. People pursuing a plant-based lifestyle might find that they need to supplement zinc to absorb the same amount as those who eat a mixed diet.

The midday pill


Iron helps your blood transport oxygen throughout the body and is essential for survival. Animal sources of iron provide easily digestible heme iron, but the non-heme iron in plants isn’t as bioavailable.

You may have read that taking vitamin C along with iron can help your intestine absorb more iron, which is good because Iron deficiency anemia is one of the most common nutrient deficiencies in the world. Vitamin C's role in enhancing iron's absorption is that it reduces ferric iron to the ferrous state. F&F provides our iron as Iron Bisglycinate Chelate, which is already in the ferrous state and thus easily absorbed — so vitamin C is not needed to increase bioavailability here. 

READ: 10 iron-safe snacks

Vitamin K

Vitamin K is more bioavailable in supplement form than in plant foods. That’s because the molecules cling tightly to the plant cells. According to the Office of Dietary Supplements, you can only absorb 4-17% as much vitamin K from spinach as you can from a supplement.

In a 2016 study, a group of people aged 45-65 years ate either vitamin K2 capsules or a yogurt fortified with K2 along with magnesium, vitamin D3, and vitamin C, as well as polyunsaturated fatty acids. The researcher found that the K2 levels in the blood of the participants who ate the yogurt were significantly higher than the control group. 

Taking vitamin K in addition to these nutrients may increase its bioavailability as part of a controlled, science-supported regimen. While fermentation may have boosted the nutrient absorption of the vitamin, it’s not clear whether eating fermented foods along with vitamin K supplement pills would have a similar effect.

The evening pill

Calcium is a mineral that’s vital for bone strength and reducing fat stores in the body. A few factors can make calcium more bioavailable:

  • Consuming calcium alongside vitamin D increases how much of the mineral the body can absorb in low-to-moderate amounts (hence the importance of getting 15 minutes of sun exposure, which generates vitamin D).
  • Casein (a milk protein), whey proteins, and amino acids bind to calcium and help it digest in the stomach. Taking these nutrients at the same time can boost absorption.
  • The lactose in dairy products makes calcium more bioavailable by allowing the linings of cells to have wider gaps. This helps calcium molecules pass into the body more easily.


Potassium is an electrolyte that the body uses to balance blood pressure. Researchers don’t know much about the factors that improve potassium’s bioavailability. Humans can absorb a high percentage of the potassium they consume from dietary sources.

In the U.S. and countries where populations follow a Western diet, many people don’t consume enough potassium every day. Supplemental potassium is easily absorbed and can help you keep your levels optimized.


Bioavailability is the amount of a nutrient or drug your body can absorb. Some vitamins and minerals are more bioavailable than others. Some can interact with each other in ways that can either enhance or reduce their nutrient absorption.

While bioavailability may seem to complicate everyday nutrition, there are easy steps you can take to improve the bioavailability of what you eat.

Following F&F’s daily supplement program guarantees a boost in the essential vitamins your body can absorb from food. F&F combines the bioavailability-boosting effects of strategically scheduled nutrients with the extra solubility that lab processing provides — all in three simple capsules.

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