The Importance Of Vitamin A For Immune Health
Vitamin A is a fat soluble vitamin which is important for immune system health, vision, skin and foetal development. ‘Vitamin A’ is a bit different to many other nutrients in that rather than being a singular compound, the term ‘vitamin A’ is actually used to describe a group of related compounds in the diet.
In this article we take a closer look at the different forms of vitamin A in the diet, its importance for immune health and round off with an overview of how to make sure you’re getting enough in your diet.
Different forms of vitamin A in the diet
Vitamin A is a generic term that describes a collection of related fat-soluble compounds in the diet.
These compounds can broadly be split into two categories; carotenoids which are plant forms and retinoids which are animal forms:
• Retinoids - animal forms of vitamin A
Animal products such as liver, fish oil and dairy foods contain vitamin A in the form of retinoids (retinol, retinal, retinoic acid, and related compounds). Retinal is important for vision, retinoic acid functions like a hormone and impacts over 500 different genes, and retinol is the storage form of vitamin A. Retinol and retinyl esters are often referred to as ‘preformed vitamin A’.
• Carotenoids - plant forms of vitamin A
Orange and green coloured fruits and vegetables such as carrots, spinach, pumpkin and sweet potato contain vitamin A in the form of carotenoids. Once consumed, these carotenoids must then be converted by the body into retinol and so are often referred to as ‘pro-vitamin A’ compounds. Plants make hundreds of different carotenoids but only about 10% of these (including beta carotene) can be converted into retinol.
• Genetic variant affects vitamin A conversion
It is important to note that some people carry a common genetic variant which can reduce the body’s ability to convert beta carotene into biologically active retinoids by more than 50%.
How vitamin A supports immune health:
• Supports innate & adaptive immune function
Vitamin A is involved in the development of the immune system, and several immune system functions rely on vitamin A. Deficiency is known to impair the innate ‘first line of defence’ part of the immune system. Vitamin A is important for adaptive immune function too. This is the second line of defence which takes longer to appear but is more targeted and specific, longer lasting and can generate immunologic memory which improves with every encounter. Adaptive immune responses include lymphocytes, memory cells and antibodies.
• Gene regulation
Vitamin A regulates some genes involved in immune function.
• Immune tolerance
Vitamin A has a crucial job in supporting immune tolerance across the mucosal gut barrier. In simple terms, this means vitamin A supports our ability to consume a wide range of different foods and not react adversely to them.
• Barrier function
We have many barriers in our bodies that play vital defensive roles against pathogens. For example, the gut barrier is a semi-permeable membrane which allows beneficial substances through into the systemic circulation, whilst keeping potentially harmful substances and pathogenic organisms out. Vitamin A helps to maintain and restore the integrity and function of all mucosal surfaces including the gut barrier.
Needless to say, vitamin A is a pretty crucial nutrient for all of us. It’s important therefore to ensure you are getting adequate amounts in your diet.
How to ensure you are getting enough vitamin A in your diet:
✔ Consume a mix of plant form carotenoids (carrots, squash, sweet potatoes, spinach) and animal form retinoids (liver, full fat dairy products, fish oil).
✔ The absorption of beta carotene may benefit from consuming fat at the same time as carotenoid-rich foods such as carrots and squash. And interestingly, cooked carotenoids seem to be better absorbed than their raw counterparts.
✔ Poor protein status or zinc deficiency may affect the uptake of beta-carotene and its subsequent conversion to retinol so it’s important to ensure your diet contains optimal amounts of good quality protein and zinc-rich foods.
✔ Supplements often contain vitamin A either in the form of beta carotene, retinol palmitate or a mix of both. For a shorter period of targeted immune support, vitamin A can be supplemented as either retinol palmitate or a mix of both retinol and beta-carotene. For ongoing support in a daily multi, it is best to stick to beta-carotene as your preferred source and ensure you include good sources of retinoids in your diet.
✔ If you are regularly getting good sources of beta carotene and retinoids in your diet (especially rich animal sources such as liver and organ meats) more caution is needed with vitamin A supplementation. For more individualised recommendations, it is best to check with a qualified healthcare practitioner.
Find out more here on diet and lifestyle tips to support immune health.
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