Vitamin A is a fat soluble vitamin and has key roles in immune function, vision and embryonic development as well as being a strong anti-inflammatory and anti-oxidant.
However, Vitamin A and vitamin D can compete for the same receptors (Retinoid X Receptors) on cells and so whilst we focus on getting our vitamin D levels into optimum range, it is important to remember that vitamins and minerals work in synergy. Inappropriate supplementation of any nutrient can have potential adverse side effects.
Vitamin A can come in two forms both of which confer different health benefits:
- Carotenoids from vegetables and other plant sources. Beta-carotene must be converted into the active form of a retinoid.
- Retinoids (retinoid acid, retinol and retinal) which comes from animal sources.
Retinol is the biologically active form of vitamin A which is needed to support eye health and healthy vision. It can be converted to retinal and subsequently to retinoic acid, which regulates other enzymes and functions within the body.
A key symptom of vitamin A deficiency is poor (or deteriorating) night vision as well as thyroid dysfunction (eg hypothyroidism) and certain skin conditions.
Who is at risk?
- Anyone following a low-fat diet may also be at risk as vitamin A is a fat soluble vitamin and found predominately in higher-fat foods.
- Anyone who is excessively supplementing with vitamin D (what is ‘excessive’ is going to be based on individual needs and other nutrient status’).
- If you have gut or gall bladder dysfunction, or had your gall bladder removed, your absorption of fat soluble vitamins may be compromised.
- A further risk for vitamin A deficiency is for certain, genetically susceptible, individuals who are following a vegan diet. There is a well-studied gene, BCO1, and for individuals who are heterozygous for this gene may have up to 50% reduced ability to convert caratonoids (the plant form) to the active form.
Food Sources: Beta-carotene is found in orange and green vegetables including carrots, pumpkins and spinach. Carriers of BCO1 gene variants, who are likely to be poor converters of beta-carotene to active vitamin A, may benefit from consuming preformed vitamin A such as that found in liver (choose organic), oily fish, eggs and dairy foods.
Solution: First assess your symptoms and your diet but, at the end of the day, if uncertain it is best to test. Both vitamin D, which is widely available via skin prick or blood draw, and vitamin A, which can be done via serum retinol. Excess vitamin A can be toxic and also inhibit vitamin K as well as requiring adequate vitamin E for recycling. So know what you are doing and why you are doing it. Remember it is all about balance and more is not always better. And of course, focus on a wide base of natural food sources to ensure as optimum an intake through food as possible.
Caution: if pregnant, supplementing with vitamin A should not be done without appropriately qualified supervision. According to the EFSA, recommended intake in pregnancy: 700 mg RE/ day. Lactation; 1300 mg (EFSA).