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What is the bioavailability of any given part of your diet? How do the foods you eat interact to alter the bioavailability of any one? How does bioavailability impact the engine of your immune system – your gut microbiome? 

Bioavailability, in the context of food and diet, refers to the amount of a nutrient that your body can absorb and use from the food you eat. It is the amount of nutrient consumed that is available to your body. 

Understanding bioavailability can help you make the decision to create a more balanced diet. By eating a variety of foods and preparing them in healthy ways, you can ensure your body is getting the greatest benefit from the nutrients you ingest. 

Some nutrients are more readily absorbed by our bodies than others. Here are some of the several factors that determine bioavailability:. 

• Food type. The type of food, in part, determines bioavailability. Iron, calcium, and zinc are essential minerals. Plant-based sources of iron and calcium have a lower iron bioavailability than the iron, calcium, and zinc found in meat.  Vitamin C is highly bioavailable in most fruits and vegetables.
• Co-consumption. Certain nutrients can enhance or hinder the absorption of others. 

Vitamin C (also known as ascorbic acid) in citrus fruits enhances the absorption of iron from plant-based sources. 

If you eat a salad, with mostly spinach leaves, it is packed with vitamin A. However, for the absorption of the fat-soluble vitamin A, fat is required to reap the benefits. Without, for instance, dressing your salad with olive oil or nuts, your body will absorb less vitamin A. That is, the bioavailability of some sources of vitamin A, is dependent upon co-consumption with fat. In other vitamin A (retinol)-rich foods, such as liver, no additional fat is needed for absorption. 

Healthy fats like olive oil or avocado aid in the absorption of other fat-soluble vitamins such as D (calciferol), E (tocopherol), and K (phylloquinone).

Phytates are also known as phytic acid. Found in legumes and some grains, phytic acid can attach to minerals such as iron, zinc, calcium, and magnesium, and reduce their absorption and bioavailability. Soaking or sprouting grains reduces their binding effect and improves mineral bioavailability.

• Method of food preparation.  Some foods, when cooked, have their bioavailability increased. Others, upon cooking, have it reduced. Cooking tomatoes, for instance, releases more lycopene, an antioxidant, making them more bioavailable. Yet, overcooking many vegetables can completely destroy the bioavailability of some vitamins. Cooking by grilling or frying can decrease protein bioavailability.
• Age. As we move from our peak into older age, our digestive functions can have reduced efficacy, meaning that we have a lower rate of absorption of vitamins and minerals. That is a good reason to pay even more attention to diet and bioavailability as we age.
• Gender. Women generally have lower iron stores than men as a feature of menstruation. During pregnancy and lactation, the demands for calcium, iron, and other minerals on the reproductive body are greater.
• Medical Conditions. Some health challenges, such as digestive disorders, malabsorption syndromes, and kidney disease, can hinder mineral absorption. For example, celiac disease is an autoimmune disease that damages the small intestine, which can make it difficult to absorb nutrients from food. Other conditions that can affect nutrient absorption include Crohn’s disease, ulcerative colitis, and cystic fibrosis.
• Drugs. Some prescriptions, like antacids, antibiotics, and diuretics, can bind to minerals in the digestive tract, reducing their bioavailability. Other medications may increase mineral excretion through the urine. Antibiotics can interfere with the absorption of iron and other minerals.

How bioavailability impacts your gut microbiome

Our gut microbiome is the powerhouse of our immune system, and bioavailability impacts its effectiveness. A well-functioning gut microbiome has many helpful bacteria, and they need to be fed with a wide range of vitamins and minerals to be optimally effective. If we don’t protect our friendly protectors, many unwelcome bioavailability consequences can follow. 

Some gut bacteria can break down complex molecules in food, making them more readily absorbed by the body. 

Bacteroides and prevotella are particularly useful in breaking down complex carbohydrates, including resistant starches and fibres. Bifidobacterium, in addition to breaking down complex carbohydrates, also process proteins.

Ruminococcus have the ability to ferment dietary fibre, producing the short-chain fatty acids needed to nourish our gut lining. 

Alas, some bacteria can degrade nutrients before they are absorbed, thereby reducing their bioavailability. 

Proteolytic bacteria, for example, are essential for protein digestion by breaking down proteins into peptides and amino acids, An imbalance can lead to deficits of protein absorption.

Blue zone lessons on bioavailability

The Blue Zones are the few parts of the world where there is greater health and longevity in the local populations, because of their healthy life style and culture. 

Several elements of the blue zones diet seem to naturally enhance bioavailability. Others seem counter-intuitive. For instance, Blue Zoners have a diet rich in fruits, vegetables, legumes, and whole grains. Such foods are high in fibre, which can hinder mineral absorption. 

However, the overall abundance and variety of these foods in their diet provide a wider range of readily absorbed vitamins, antioxidants, and other beneficial nutrients.

Blue Zoners typically use cooking methods such as steaming, boiling, and light stir-frying. Such methods better preserve the nutritional value of foods, when compared to other cooking techniques.

With a greater use of whole grains, legumes, and fermented foods, the people in the Blue Zones better nourish their gut microbiome, which improves bioavailability, and strengthens their immune system. 

How can you improve bioavailability?

• Eat a varied diet. Consume a rainbow of fruits and vegetables (at least 30 different variety per week), whole grains, and lean proteins.
• Include healthy fats. These can include foods such as olive oil or avocado to further enhance the absorption of fat-soluble vitamins.
• Use healthy cooking methods. Steaming, baking, or light stir-frying.  
• Fermented foods. Include fermented foods like yoghurt or kimchi, which contain live bacteria, to boost your gut microbiome. 
• Combine foods. Consume iron-rich plant foods with vitamin c sources to enhance iron absorption.

Bioavailability plays a crucial role in our health and well-being.  By optimising nutrient absorption, you can nourish your gut microbiome and keep your immune system optimally healthy.

Table of essential vitamins

Essential minerals for human health

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