| Vitamin A | |||||
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- Why vitamin A is good for you
- Important vitamin A facts
- Groups at risk of vitamin A deficiency
- Symptoms of vitamin A deficiency
- Vitamin A and health
- Vitamin A in foods
- Vitamin A recommended daily intake (RDI)
- Vitamin A works best with
- Overdosage, toxicity and cautions for vitamin A
Vitamin A is essential for healthy eyes as it helps the eyes to function properly in all conditions, even the dark and it prevents a leading case of blindness in the elderly called age-related macular degeneration (ARMD).
Vitamin A helps the immune system fight infection and illness by helping the epithelial tissues (the cells that make up the skin, line the mouth, nose, eyes, throat, lungs, digestive and urinary tracts and which keep out infective agents) grow and repair themselves. Without enough vitamin A, these cells become stiff, dry and much more likely to let their guard down and when that happens, germs can easily pass through them and into the body.
All humans (especially children and teenagers) need vitamin A for a wide range of body functions, including to help the body cells repair, grow properly and to keep bones and teeth strong.
- Vitamin A can be found preformed in animal foods such as egg yolks, meat and fish
- There are three forms of preformed vitamin A:
- retinol
- retinaldehyde and
- retinoic acid
- The highest source of vitamin A is the polar bear liver, which has 13,000IU-18,000IU per gram of liver!! More than enough to give vitamin A poisoning, even if only a tiny bit was eaten
- Retinol is destroyed by light, high temperatures as well as when using copper or iron cooking utensils
Groups at risk of vitamin A deficiency
- People with certain illness - such as liver disease, cystic fibrosis or chronic diarrhoea - may have low levels of vitamin A in their body
- Smokers - usually have low vitamin A levels and may need supplementation
- Users of birth control pills - have high levels of vitamin A in their blood, but low levels stored in the liver (the pill does not have this effect on Vitamin A)
- People with chronic infections - illness or chronic infection produces free radicals, which lower vitamin A levels
- Stress – physical or physiological stress, such as overwork, fatigue, not eating enough/properly and exercising too much all create free radicals which lower vitamin A levels
- People taking certain drugs - there are many drugs which reduce the absorption of vitamin A. NEVER mix supplements with drugs without consulting a medical practitioner for professional advice
Talk to a medical professional about vitamin A supplements BEFORE taking them.
Symptoms of vitamin A deficiency
A deficiency of vitamin A may lead to eye problems with dryness of the conjunctiva and cornea, dry skin and hair, night blindness as well as poor growth. Dry itchy eyes that tire easily are normally a warning of too little vitamin A. If the deficiency becomes severe, the cornea can ulcerate and permanent blindness can follow. The hair and scalp can also become dry with a deficiency, especially if protein is also lacking. Insomnia, fatigue and reproductive difficulties may also be indicative of vitamin A is in short supply.
Major symptoms of deficiency are :
- abscesses forming in the ear
- sinusitis
- frequent cold and respiratory infections, such as asthma, allergic rhinitis (hay fever), bronchitis
- skin disorders, such as acne, eczema, boils and a bumpy skin
- Preventing night blindness - vitamin A helps you see better in the dark, because it tops up all the Vitamin A in your retina
- Preventing cataracts - vitamin A (and betacarotene) help mop up the free radicals which damage the lens of the eye and cause cataracts
- Preserving eyesight - vitamin A helps prevent age-related macular degeneration (ARMD) which causes blindness
- Preventing heart attacks and heart disease - people who eat foods high in Vitamin A (and betacarotene) have fewer heart attacks and strokes
- Boosting the immune system - vitamin A has an enhancing effect on the immune system due to its powerful antioxidant properties
| FOOD | AMOUNT |
Vitamin A (IU) |
|---|---|---|
Beef liver |
85g |
9,000 |
Chicken liver |
100g |
4,913 |
Skim milk |
1 cup |
149 |
Ice-cream, vanilla |
1 cup |
133 |
Egg |
1 large |
97 |
Cheddar cheese |
28g |
86 |
>
Swiss cheese |
85g |
72 |
Chicken drumstick, with skin |
1 piece |
45 |
>
Yoghurt, low fat |
230g |
36 |
Butter |
1 Tsp |
35 |
>
Swordfish |
85g |
35 |
Salmon |
85g |
11 |
>
vitamin A recommended daily intake (RDI)
| RDA | lifestage | age | Amount |
|---|---|---|---|
| INFANTS | 0-6mths 7-12mths |
400mcg 500mcg |
|
| CHILDREN | 1-3yrs 4-8yrs |
300mcg 400mcg |
|
| CHILDREN | 9-13yrs male: 14-18yrs female: 14-18yrs |
600mcg 900mcg 700mcg |
|
| ADULTS | male: 19-50yrs female: 19-50yrs |
900mcg 700mcg |
|
| SENIORS | male: 51+yrs female: 51+yrs |
900mcg 700mcg |
|
| PREGNANT | <18yrs 19-50yrs |
750mcg 770mcg |
|
| LACTATING | <18yrs 19-50yrs |
1200mcg 1300mcg |
|
| TOLERABLE UPPER LIMIT | lifestage | age | Amount |
| INFANTS | 0-12mths | 600mcg | |
| CHILDREN | 1-3yrs 4-8yrs |
600mcg 900mcg |
|
| CHILDREN | 9-13yrs 14-18yrs |
1700mcg 2800mcg |
|
| ADULTS | 19-50yrs | 3000mcg | |
| SENIORS | 51+yrs |
3000mcg | |
| PREGNANT | <18yrs 19-50yrs |
2800mcg 2000mcg |
|
| LACTATING | <18yrs 19-50yrs |
2800mcg 3000mcg |
|
| TOXIC LEVELS | >25,000IU per day >8,000IU per day for females of child bearing age |
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The tolerable upper limits should only be taken for short periods and only under medical supervision.
Retinol Equivalents (IU and mcg)
The above recommended dietary allowances of Vitamin A are given in Retinol Equivalents (RE) of vitamin A (in mcg).
The following shows the International Unit (IU) equivalents of Vitamin A:
One Retinol Equivalent (RE) of Vitamin A (in mcg) =
6 International Units (IU) from beta-carotene
10 IU from other carotenoid-rich plant foods
4.10 IU from milk and yogurt
3.33 IU from animal sources and fortified foods
- Vitamin B1
- Vitamin B2
- Vitamin B3
- Vitamin B5
- Vitamin B6
- Vitamin B12
- Vitamin C
- Vitamin D
- Vitamin E
- Choline
- Essential Fatty Acids
- Calcium
- Phosphorus
- Zinc
Overdosage, toxicity and cautions for vitamin A
NOTE: High intake of vitamin A during pregnancy is NOT recommended as it may cause birth defects. Women of child-bearing age should not take more than 8,000IU of vitamin A per day for this very reason.
Vitamin A is toxic in large doses and should not be taken. To avoid vitamin A toxicity, take Betacarotene instead.
People who are alcoholics are advised not to take high levels of Vitamin A because their liver may be too sensitive from the alcohol abuse and therefore more susceptible to liver toxicity of vitamin A.
Symptoms of overdosage in children are:
- bone pain
- fontanelle bulging (the soft spot on an infant’s skull)
- irritability
- lethargy
- loss of appetite
- stunted growth
Symptoms of overdosage in adults are:
- blurry vision and headache
- diarrhoea and vomiting
- drowsiness and loss of appetite
- hair loss
- irritability
- lethargy
- skin irritation
references
- Ambalavanan N, Tyson JE, Kennedy KA, et al. Vitamin A supplementation for extremely low birth weight infants: outcome at 18 to 22 months. Pediatrics 2005;115(3):e249-e254
- Barker ME, Blumsohn A. Is vitamin A consumption a risk factor for osteoporotic fracture?. Proc Nutr Soc. 2003;62:845-850
- Bates CJ. Vitamin A. Lancet. Jan 7 1995;345(8941):31-5
- Chang L-C, et al. Retinoic acid induced glandular differentiation of the oesophagus. Gut, Dec 2006 doi:10.1136/gut.2006.097915
- Cox SE, Arthur P, Kirkwood BR, et al. Vitamin A supplementation increases ratios of proinflammatory to anti-inflammatory cytokine responses in pregnancy and lactation. Clin Exp Immunol. 2006 Jun;144(3):392-400
- Fletcher AE, Breeze E, Shetty PS. Antioxidant vitamins and mortality in older persons: findings from the nutrition add-on study to the Medical Research Council Trial of Assessment and Management of Older People in the Community. AJCN, 2003; Vol 78(5): 999-1010
- Genaro Pde S, Martini LA. Vitamin A supplementation and risk of skeletal fracture. Nutr Rev. Feb 2004;62(2):65-7
- Hathcock JN, Hattan DG, Jenkins MY, et al. Evaluation of vitamin A toxicity. Am J Clin Nutr. Aug 1990;52(2):183-202
- Office of Dietary Supplements USA - has the official USA RDI for all vitamins (these are also adopted by Australia), accessed 9 August 2005
- Osiecki, Henry, The Nutrient Bible 2002, BioConcepts Publishing
- Wolbach SB, How PR. Tissue Changes Following Deprivation of Fat-Soluble A Vitamin. The Journal of Experimental Medicine 1925, Vol 42, 753-777
