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How does vitamin A affect the immune system?

Vitamin A is also referred to as retinol. It is a fat-soluble vitamin that comes in a number of different forms including retinoids and carotenoids. Both function in the body through the most active form, retinoic acid. It helps to maintain and is involved in immune function, vision, cellular communication, growth and development, and male and female reproduction. Vitamin A is essential in ensuring the normal formation of vital organs including the eyes, lungs and heart.


Variety of carrots, rich in vitamin a to support immune health
Vitamin A Sources: Photo by Gabriel Gurrola on Unsplash

Mucous Membrane Integrity

In developing countries, approximately 250 million preschool children have an increased susceptibility to infection due to vitamin A deficiency. Vitamin A plays a crucial role in the formation of the mucous membranes. The mucous membranes can be found in the lining of the inside of your nose, mouth, lungs and intestine. It forms a protective barrier against pathogen invasion and is often referred to as our first line of defence. Vitamin A is what glues the mucous membranes together, it increases the integrity and also maintains the defence of the oral mucosa. A diet rich in sources of vitamin A can improve the innate immune function of the mucosal cells and prevent respiratory tract infections, diarrhoea and other diseases from developing.


Foods High in Vitamin A

Dietary vitamin A can be found in either pre-formed sources such as retinol or provitamin A carotenoids such as beta-carotene which is a precursor to vitamin A. Preformed vitamin A is found in animal products including dairy, eggs, fish and organ meats. Whereas, carotenoids and most commonly beta-carotene are found in plant pigments such as dark leafy greens, orange and yellow vegetables, tomato products and fruits. Retinol is highly absorbed between 75-100%, whereas beta-carotene sources when eaten raw are between 10-30%, but have an increased bioavailability when heated such as sweet potato, pumpkin and carrots. Beta-carotene is converted into retinol (vitamin A) in the intestine and stored in the liver.


How much Vitamin A do I need?

In Australia, the recommended daily intake of Vitamin A is approximately 700 mcg for women and 900 mcg for men as retinol equivalents (RE). So what does that look like on a plate?


Provitamin A sources that are rich in beta-carotene include:

  • 1 whole baked sweet potato includes 1,403 mcg of RE

  • ½ cup of raw carrots includes 459 mcg of RE

  • ½ cup of boiled broccoli includes 60 mcg of RE


Pre-formed sources of vitamin A such as retinol include:

  • ⅓ cup of beef liver includes 6,582 mcg of RE (liver is nutrient-rich but unfortunately not everyone’s cup of tea)

  • ⅓ cup of herring includes 219 mcg of RE

  • 1 hard-boiled egg includes 75 mcg of RE


Of course, Vitamin A is not the only essential vitamin we need from the diet. So the key is to include a variety of fruits and vegetables, picture the rainbow on your plate. Aim for ½ a plate of fruits or vegetables with each main meal.


If you’ve been experiencing frequent colds and flu, or just feeling generally run down.

Book a naturopath appointment today to discover a tailored approach to improve your general well-being.

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