History of Vitamin A
Vitamin A was the first vitamin ever discovered so it was named
after the first letter of the alphabet. Elmer V. McCollum and
marguerite Davis discovered vitamin A during 1912–1914. In
1913, Yale researchers, Thomas Osborne and Lafayette Mendel
discovered that butter contained a fat soluble nutrient soon
known as vitamin A. Vitamin A was first synthesized in a
laboratory in 1947 where it could be used in supplement form .
There has been much earlier references to vitamin A dating back to 400 B.C where biblical writing describes how the squeezing of liver juice into the eyes was used as treatment for eye disease. Of course we know now the cause of this eye disease was due to vitamin A deficiency. This deficiency was restored by the high amounts of vitamin A present in liver.
Most people have heard their mum say “eat your carrots they’ll
make you see in the dark!” well there is actually logic behind that
statement, read on to find out why.
What is vitamin A
- Vitamin A is an essential vitamin that we can not produce
- It’s fat soluble so needs dietary fat with it to be absorbed
- It’s divided into 2 forms, preformed vitamin A retinol made of fat soluble retinoids from animal sources and provitamin A carotene made of carotenoids from plant sources (retinol and beta-carotene being the most common)
- Provitamin A (basically meaning before vitamin A) beta carotene needs to be converted into one of its active forms retinal and retinoic acid before we can use it
- Preformed vitamin A retinol from animal products is already in a bioactive form and most likely already converted by an animal that once consumed provitamin A
- Vitamin A beta carotene is also a powerful antioxidant
Vitamin A along with other fat soluble vitamins are stored in the liver and in the fat cells so providing adequate vitamin A intake is met, reserves can build up and stores can last months so it doesn’t necessarily need to be consumed everyday providing a reasonable amount is eaten at each time.
What does vitamin A do?
- Vitamin A makes our eyes, skin, lining of the nose and immune system healthy and functioning properly.
- Our eyes need vitamin A retinol to produce pigments in the eyes retina that allow the conversion of light energy into electrical impulses allowing for low light and colour vision (scoptopic vision).
- Pro vitamin A beta carotene is an antioxidant that stops harmful unpaired electrons known as free radicals causing damage in the body destroying healthy cells.
Historical uses for vitamin A
- Useful in preventing eye disorders prevent cataracts and is used to improve eyesight and night vision
- Improves recovery from laser eye surgery when combined with vitamin E
- Reduces complications from serious diseases such as HIV, malaria, measles and diarrhoea in children with vitamin a deficiency
- May help to fight bronchitis
- Can reduce the risk of high blood pressure
- Reduces health issues in malnourished women during and after pregnancy
- Raises men’s sperm count
- Useful for skin conditions such as acne, eczema, psoriasis, cold sores, wounds, burns and sunburn
- It can also be applied to the skin to reduce wrinkles, improve wound healing and to protect the skin from UV rays
- Effective at treating gastrointestinal ulcers, Crohn’s disease, gum disease, diabetes, Hurler syndrome, sinus infections, hay fever, and urinary tract infections
- May help to prevent cancer, protecting the heart and cardiovascular system, slowing the aging process, and boosting the immune system due to its antioxidant properties
- Vitamin A may also ease alcohol withdrawal symptoms
Vitamin A deficiencies
Common deficiency symptoms:
- Reduced night vision or night blindness
- Reduced day light/colour vision
- Dry and/or sore, inflamed eyes
- Rough and/or dry skin
- Dry hair
- Yellow/orange colouring of the skin
- Reduced appetite
- Broken/ridged nails
Hypovitaminosis A is a condition caused by vitamin A deficiency. It can lead to mild conditions such as night blindness to more severe problems like cataracts and full on blindness. If your diet is low in a variety of fresh fruit and vegetables then it may lead to health problems over time that may be reflected by some mild symptoms such as inability to see in low light conditions.
Pregnant women tend to be vitamin A deficient and more so during the last trimester as the fetal demand is at its highest.
Between 100 and 140 million children are vitamin A deficient, 250,000-500,000 of these children become blind every year and half of these die within 12 months of losing their sight. This deficiency is leading cause of preventable blindness in children. Unfortunately not every child has access to a healthy diet like we have the privilege of having. Many children in developing countries every day fall victim to hypovitaminosis outside of their control. One more reason to make the most of the healthy foods we have the privilege of having because having vegetables in the diet for some can mean the difference between life and death
There are two types of vitamin A deficiency, primary and secondary:
- Primary deficiency is caused by a direct prolonged deficiency of vitamin A which is usually the case in developing countries and countries where rice is a staple food, as rice contains no beta carotene or retinol. This type of deficiency in many cases can be alleviated in time by consuming adequate vitamin A through meat, dairy and vegetables.
- Secondary deficiency is caused by an inability to convert carotene into vitamin A and can be also be attributed to conditions where improper absorption of nutrients are concerned. People suffering with coeliacs, cystic fibrosis, pancreatic and liver disease are all at risk of secondary vitamin A deficiency. Alcoholism is also another cause of secondary deficiency.
Vitamin A over dose
Common overdosing symptoms include:
- Loss of appetite
- Peeling skin
- Hair loss
- Menstrual irregularity
- Enlarged liver
- Enlarged spleen
- Skin discolouration (orange tint)
- Birth defects
- Reduced bone density
Hypervitaminosis A, which is toxicity from consuming excessive amounts of vitamin A is more likely to occur from retinol the animal source. Vitamin A retinol from animal sources can become toxic in consistently high doses due to the accumulation of it in the fat and liver stores where it is stored. Therefore excessive doses of retinol long term should not be consumed.
It has been documented that vitamin A retinol toxicity has been responsible for a number of deaths. Certain animal livers will contain such tremendously high amounts of vitamin A that it will kill you if you consumed. For older children and adults, you need more than 100,000 IU per day for months before you start to accumulate any serious toxicity. To give you an example of the scale of this, 200g of beef liver would give you 110,000iu of vitamin A retinol, which if consumed everyday would result in toxic illness and liver problems. Whereas 200g of polar bear liver would give you 4,800,000iu! So literally one bite would be enough to make you seriously ill, very quickly. In 1913 two Antarctic explorers Douglas Mawson and Xavier Mertz were both poisoned (and Mertz died) from eating the livers of their sled dogs. In 1974 a British man called Basil Brown who was a well known scientist and “heath food addict” who consumed 10 gallons of carrot juice which is 10,000 times the amount of RDA in 10 days, unfortunately those were his last 10 ten days as his skin turned bright yellow he died of severe liver damage.
Despite these cases, its very unlikely for anyone to consume that amount (150,000IU) or for anyone here to eat the livers of exotic animals that contain such toxic amounts of vitamin A retinol everyday. Lower but still excessive doses around 4,500IU of daily vitamin A consumption (which is more then 6x the RDA) is likely to leach your bones of minerals reducing bone density putting you at risk for osteoporosis as you age. The key is dont consume any more than couple carrots each week, some sweet potatoes each week, liver once a month and you’ll be healthy.
Measurements are in IU which means international units, mcg which means micrograms and mg for milligrams, different measurements are usually used for different foods and brands so I have included all 3 to make things easier for you)
RNI (Reference Nutrient Intake, gender and age specific nutrient requirements) of vitamin A intake
0 to 12 months: 350mcg/0.35mg day (1166IU)
children 1 to 3 years: 400mcg/0.4mg day (1333IU)
children 4 to 10 years: 500mcg/0.5mg day (1666IU)
children 11 to 14 years: 600mcg/0.6mg day (2000IU)
males 15 years and older: 700mcg/0.7mg day (2333IU)
females 15 years and older: 600mcg/0.6mg day (2000IU)
Pregnant women: 700mcg/0.7mg day (2333IU)
Breastfeeding women: 950mcg/0.95mg day (3166IU)
Over 65 years: 600mcg/0.6mg day (2000IU)
Top sources of vitamin A carotene
Carrots, sweet potato, pumpkins, kale, spinach, collards, turnip greens, winter squash, mango, tomato
Top sources of vitamin A retinol
Liver, salmon, sardines, mackerel, trout, tuna, beef, milk, skimmed milk powder, butter, margarine, cheese, eggs and cod liver oil
Foods that provide around 100% of RNI of vitamin A for adults
150g sweet potato (600mg), 100g carrot (800mcg), 1.5ltr whole milk (690mcg), 10g beef liver (600mcg), 100g mango (694mcg)