The Importance of Vitamin APLEASE NOTE: The Carrot Museum does not recommend self diagnosis or self medication. The information contained in this web site has not been verified for correctness. Some of the information contained herein is hearsay and may not be correct. Use the information from this page only at your own risk! If in doubt consult a doctor.
Carrots are a super source of beta carotene which is converted to Vitamin A in the body as needed This page gives much more detail on the health benefits of Vitamin A. Click on a subject which interests you.
What is Vitamin
Deficiency Overdose Therapeutic Uses Your Needs
History of Vitamin
For thousands of years, liver has been used as a cure for night blindness but it was only in the early part of the 20th century that researchers discovered that it is a rich source of vitamin A, which is essential for healthy eyes. The value of certain foods in maintaining health was recognised long before the first vitamins were actually identified. In the 18th century, for example, it had been demonstrated that the addition of citrus fruits to the diet would prevent the development of scurvy. In the 19th century it was shown that substituting unpolished for polished rice in a rice-based diet would prevent the development of beriberi.
In 1906 the British biochemist Frederick Hopkins demonstrated that foods contained necessary "accessory factors" in addition to proteins, carbohydrates, fats, minerals, and water. In 1911 the Polish chemist Casimir Funk discovered that the anti-beriberi substance in unpolished rice was an amine (a type of nitrogen-containing compound), so Funk proposed that it be named vitamine for "vital amine." This term soon came to be applied to the accessory factors in general. It was later discovered that many vitamins do not contain amines at all. Because of its widespread use, Funk's term continued to be applied, but the final letter e was dropped.
In 1912 Hopkins and Funk advanced the vitamin hypothesis of deficiency, a theory that postulates that the absence of sufficient amounts of a particular vitamin in a system may lead to certain diseases. During the early 1900s, through experiments in which animals were deprived of certain types of foods, scientists succeeded in isolating and identifying the various vitamins recognised today.
Elmer V. McCollum and M. 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 1947.
In 1912 E V McCollum from Wisconsin University developed an approach which opened the way to the discovery of all nutrients - the use of rats, because they were easy to maintain, inexpensive and could give quick results. Rats fed butter were healthier than those fed lard; butter contains more vitamin A.
Using rats he discovered the first vitamin
- A it was first called "fat soluble A".
In 1930 the structure of vitamin A was determined, and five years later it was found to be necessary for normal vision. In the years that followed, researchers started to study the vital role vitamin A plays in growth, development and reproduction.
Read more about the history of Vitamins here.
So what is VITAMIN A- it is a pale yellow primary alcohol derived from carotene. It affects the formation and maintenance of skin, mucous membranes, bones, and teeth, vision and reproduction. In addition dietary Vitamin A, in the form of beta carotene, an antioxidant, may help reduce the risk of certain cancers. Read more about antioxidants here. Like all the other vitamins which are necessary for normal growth and maintenance of a healthy body, vitamin A must be included in small amounts in the diet. Man and all animals cannot make their own vitamin A, and so must receive the necessary quota from an external source.
We can get all our vitamin A ultimately from plants, which contain not vitamin A as such but vitamin A precursor substances, called carotenes.
Once the fruit or vegetable has been eaten and digested, a simple chemical reaction converts the carotenes into vitamin A proper. This chemical conversion takes place either in the intestinal wall or within the liver, which also acts as a store for about 90 per cent of the total vitamin A in the body. Man therefore gets his vitamin A by eating plants which are rich in carotenes or by eating those parts of domestic animals which are rich in the vitamin itself: liver, butter and cream from milk; egg yolk; and cod-liver oil.
It is highly recommended that vitamin A
be consumed from the diet rather than from supplements (particularly in the
case of beta carotene). Because vitamin A obtained from a varied diet offers
the maximal potential of health benefits that supplements cannot. The richest
sources of preformed vitamin A are liver, fish liver oils, milk, milk products,
butter, and eggs. Liver is an especially rich source because vitamin A is
primarily stored in the liver of animals and humans.
Vitamin A is also found in a variety of dark green and deep orange fruits and vegetables, such as carrots, sweet potatoes, pumpkin, spinach, butternut squash, turnip greens, bok choy, mustard greens, and romaine lettuce. Beta carotene is the most active carotenoid (the red, orange, and yellow pigments) form of vitamin A, but it is inefficiently absorbed and converted to retinol in comparison to vitamin A from animal sources.
As you can see Vitamin A intake is essential
to human health. If you do not get enough then you could become A-deficient,
this is known as Hypovitaminosis A. One of the first evidences of vitamin
A deficiency may be noted in the difficulty of adjusting your sight in a
dim light, as in entering a dark room, or theatre, from a brightly lit hall.
A more serious symptom is the inability to regain focus of the road after
the glare of passing car headlights. This sight defect is known as "night
blindness" or "glare-blindness" and has been the cause of many serious accidents.
A diet rich in fat, working at the computer or under artificial light, pollution, cigarette smoke and other factors contribute in provoking an increased need of Vitamin A - Betacarotene. The same goes for people who spend a lot of time in front of the tv. Vitamin A helps counteract the toxic effects of radiation from home appliances.
Vitamin A deficiency is the cause of xerophthalmia which can result in night blindness (difficulty in adapting to darkness), if this is not treated with Vitamin A it becomes irreversible. Other symptoms are excessive skin dryness; lack of mucous membrane secretion, causing susceptibility to bacterial invasion; and dryness of the eyes due to a malfunctioning of the tear glands, a major cause of blindness in children in developing countries. It maintains healthy body tissues and normal glandular functions. Vitamin A is necessary in the diet of expectant mothers to build up and maintain the health of both mother and the developing child. Carrots improve a variety of digestive disorders such as upset stomach, peptic ulcers, gastritis, Crohn's disease and celiac disease which is a defective digestion disorder found in children.
Vitamin A deficiency is quite rare in the western world. Who is likely to deficient? Those individuals who limit their consumption of liver, dairy foods and beta carotene containing vegetables. This map shows where the main areas of the world suffer from Vitamin A deficiency (source FAO/WHO full paper here) Also WHO Vitamin A deficiency page here.
According to the World Health Organization (WHO), "vitamin A deficiency (VAD) is the leading cause of preventable blindness in children." In fact, WHO estimates that 250 million young children, and an unknown but substantial number of pregnant women, are vitamin A deficient worldwide.
Vitamin A is essential in keeping the mucous membranes which line all the cavities of the body in a healthy condition. The mucous membrane may be described as consisting of two layers. The top layer, known as epithelium is composed of billions of cells. Close under the epithelium lies the mucous membrane, a thin layer of involuntary muscle fibres, which are extremely pliable and elastic. The vitality of this lining depends upon an adequate supply of vitamin A. When a deficiency of vitamin A exists the cells harden and degenerate into a horny rough surface, obstructing the normal function of the secretion of the disinfectant mucous. Infections resulting from vitamin A deficiency may affect the bladder or kidneys, the alimentary tract, the mouth, tonsils, sinuses, the tongue, ear canal, eyes or tear ducts.
In addition to those already mentioned, some of the symptoms which have been traced to vitamin A deficiency are: dry, scaly and rough skin, especially on the arms and legs; intestinal disorders and diarrhoea; poor appetite; retarded growth; lack of vigour; loss in weight and physical weakness; atrophy of the glands; poor development of teeth through defective formation of enamel and dentine and poor gum structure, and may also be a causative factor in cases of sterility; nerve degeneration and stones in the kidney and bladder. The vitamin can also ease alcohol withdrawal symptoms, fight bronchitis, reduce the risk of high blood pressure and reduce acne. Its antioxidant properties make it valuable in counteracting the onset of old age.
Vitamin A is soluble in fat but not in water. Consequently, surplus vitamin A is not lost in the body fluids, such as urine, perspiration, etc., but is stored for future use. Approximately 95% of all such surplus vitamin A is stored in the liver, with small amounts in the kidneys, lungs and under the skin. As a matter of interest ancient Chinese and Indian writings indicate eye disease was treated by squeezing the juice of liver on to the eye. Although not known at the time enough vitamin A (stored in liver) got into the eye to cure the disease.
The liver is capable of storing large quantities of vitamin A over a period of years to be called upon when needed. In order to keep this surplus at an adequate point, an ample daily intake should be provided. For example, an 8-ounce glass of fresh carrot juice will provide an average of 50,000 or more units of vitamin A. In this form the daily requirements are easily satisfied and any surplus is accumulated in the system to meet any emergency.
Absorption of vitamin A is dependent on fat from food sources and bile (cholesterol substance produced by your liver and stored by your gall bladder and used to break down fats, seeds and skins). Your body can store about a year's worth of Vitamin A in your liver. If you don't eat enough Vitamin A, it can cause blindness or in milder cases, your ability to see or drive at night. But it does need topping up.
The amount of carotene (which is converted
to vitamin A in the liver) contained in carrots is indicated by the depth
of the colouring matter. The large, firm, dark-yellow carrots, therefore,
should be selected for juicing, rather than the light-yellow ones, because
of their greater carotene content. You get approximately 10mg of Vitamin
from 20 average carrots.
Another vitamin contained in carrot juice is vitamin E. This vitamin appears in three forms, known chemically as alpha-, beta-, and gamma-tocopherol, and commonly known as the vitamin E complex. In animal experimentation, vitamin E has been found to affect reproduction. When foods bearing this vitamin were fed to animals which had failed to reproduce, their sterility was overcome.
Tests have shown that three percent of the total beta-carotene content is released from raw carrots when consumed in raw pieces. When homogenized (pulped) 21% was released. Cooking the pulp increased the accessibility to 27%. Addition of cooking oil to the cooked pulp further increased the released amount to 39%. (European Journal of Clinical Nutrition (2002) 56, 425–430- Estimation of carotenoid accessibility from carrots determined by an in vitro digestion method, Hedren et al)
Vitamin A and skin health - website which explains the efficacy of the topical application of Beta Carotene. Here
Sources of Vitamin A
Vitamin A can be found in animal livers, fish liver oils, and green and yellow fruits and vegetables. Foods that contain significant amounts include apricots, asparagus, beet greens, broccoli, cantaloupe, carrots, collards/kale, dandelion greens, dulse (a high fibre snack made from seaweed), fish liver and fish liver oil, garlic, mustard greens, papayas, peaches, pumpkin, red peppers, spirulina (a microalgae 60% all vegetable protein), spinach, sweet potatoes, Swiss chard, turnip greens, watercress, and yellow squash.
Vitamin A is also present in the following herbs: alfalfa, borage leaves, burdock root, cayenne (capsicum), chickweed, eyebright, fennel seed, hops, horsetail, kelp, lemongrass, mullein, nettle, oat straw, paprika, parsley, peppermint, plantain, raspberry leaf, red clover, rose hips, sage ,uva ursi, violet leaves, watercress, and yellow dock.
During the first five months of storage, carrots will actually increase their vitamin A content; and, if protected from heat or light, can hold their nutrient content for another two or three months. Since carrots are rich in beta carotene, steaming them makes this nutrient more readily availability to the body as heat breaks down the tough cellular walls that encase the nutrient. The crisp texture of carrots is the result of the cell walls being stiffened with the indigestible food fibers cellulose, hemicellulose, and lignin.
Pre-formed vitamin A occurs in foods of animal origin such as cod liver oil, beef liver, some seafood, butter, whole milk and egg yolks. It is sometimes added to milk. Main sources are:
Liver, fried 100g 10729 mcg RE
Cod liver oil 1 tbsp 4080 mcg RE
Liverwurst 28g 2353 mcg RE
Carrot, raw, peeled ˝ cup, slices 1715 mcg RE
Squash 1 cup 1435 mcg RE
Kale, boiled 1 cup 962 mcg RE
Mangoes, raw, peeled 1 fruit 805 mcg RE
Vegetable soup, canned 1 cup 588 mcg RE
Cantaloupe melon, raw, peeled 1 cup, diced 502 mcg RE
Apricots, canned in syrup 1 cup 412 mcg RE
Mixed vegetables, frozen, boiled ˝ cup 389 mcg RE
Canned vegetable juice 1 cup 283 mcg RE
Sardines 1 can 259 mcg RE Tomato sauce, canned 1 cup 240 mcg RE
All Bran ˝ cup 225 mcg RE
Apricot juice drink, canned 1 cup 145 mcg RE
Milk, vitamin A-fortified 1 cup 139 mcg RE
Pumpkin, peeled, boiled ˝ cup, mashed 132 mcg RE
Paté 1 tbsp 130 mcg RE
Kidney, lamb, simmered 85g 116 mcg RE
Margarine 1 tbsp 112 mcg RE
Broccoli ˝ cup 108 mcg RE
Butter 1 tbsp 107 mcg RE
Sweet potatoes, peeled, boiled ˝ cup, mashed 96 mcg RE
Green peppers, raw 1 cup 93 mcg RE
Apricots 1 fruit 91 mcg RE
Egg, boiled 1 large 84 mcg RE
Cheeseburger 1 serve 79 mcg RE
Milk 1 cup 75 mcg RE Cream cheese 1 tbsp 55 mcg RE
How does the body take in Vitamin A?
The body obtains vitamin A in two ways. One is by manufacturing it from carotene, a vitamin precursor found in such vegetables as carrots, broccoli, squash, spinach, kale, and sweet potatoes. The other is by absorbing ready-made vitamin A from plant-eating organisms. In animal form, vitamin A is found in milk, butter, cheese, egg yolk, liver, and fish-liver oil. Although one-third of American children are believed to consume less than the recommended allowance of vitamin A, sufficient amounts can be obtained in a normally balanced diet rather than through supplements. Excess vitamin A obtained through supplements can be toxic and can interfere with growth, stop menstruation, damage red blood corpuscles, and cause skin rashes, headaches, nausea, and jaundice.
In the body, proteins, carbohydrates, and
fats combine with other substances to yield energy and build tissues. These chemical reactions
are catalyzed, or accelerated, by enzymes produced from specific vitamins,
and they take place in specific parts of the body. The vitamins needed by
humans are divided into two categories: water-soluble vitamins (the B vitamins
and vitamin C) and fat-soluble vitamins (A, D, E, and K).
The water-soluble vitamins are absorbed by the intestine and carried by the circulatory system to the specific tissues where they will be put into use. The B vitamins act as coenzymes, compounds that unite with a protein component called an apoenzyme to form an active enzyme. The enzyme then acts as a catalyst in the chemical reactions that transfer energy from the basic food elements to the body. It is not known whether vitamin C acts as a coenzyme. When a person takes in more water-soluble vitamins than are needed, small amounts are stored in body tissue, but most of the excess is excreted in urine. Because water-soluble vitamins are not stored in the body in appreciable amounts, a daily supply is essential to prevent depletion.
Fat-soluble vitamins seem to have highly specialized functions. The intestine absorbs fat-soluble vitamins, and the lymph system carries these vitamins to the different parts of the body. Fat-soluble vitamins are involved in maintaining the structure of cell membranes. It is also believed that fat-soluble vitamins are responsible for the synthesis of certain enzymes. The body can store larger amounts of fat-soluble vitamins than of water-soluble vitamins. The liver provides the chief storage tissue for vitamins A and D, while vitamin E is stored in body fat and to a lesser extent in reproductive organs. Relatively little vitamin K is stored. Excessive intake of fat-soluble vitamins, particularly vitamins A and D, can lead to toxic levels in the body. Many vitamins work together to regulate several processes within the body. A lack of vitamins or a diet that does not provide adequate amounts of certain vitamins can upset the body's internal balance or block one or more metabolic reactions.
Vitamin A is the name given to a group of compounds which have certain actions in the body. One of these compounds is called retinol and it is used as a standard against which the activity of other compounds can be measured. While the vitamin A we obtain from food comes in many different forms, these can be divided into two main types - pre-formed vitamin A and provitamin A.
Pre-formed vitamin A which is often in the form of retinol or retinal, is found in foods of animal origin such as liver and butter. Provitamin A is the name given to around 50 compounds in a group of plant pigments known as carotenes (or carotenoids), with beta carotene being the best known of these. This is because these compounds can be turned into vitamin A in the body.
Both pre-formed vitamin A and provitamin A are fat soluble. Vitamin A is essential to the human body, either directly or indirectly, for the function of all the organs in your body and is particularly important for growth and development. Despite the fact that vitamin A was the first vitamin to be discovered, its actions in the cells of our bodies are not well understood at a chemical level.
Key Functions of Vitamin A
Maintenance of normal vision - Our eyes need vitamin A to function effectively as vitamin A is involved in the production of a chemical called visual purple, which helps us to see in dim light. Growth, repair and cell differentiation Vitamin A is necessary for the growth and repair of many body cells including those of bones, teeth, collagen and cartilage. It is also essential for a process known as cell differentiation in which unspecialised cells are modified so that they can perform specific functions. Thus vitamin A plays a central role in tissue development and maintenance.
Health of epithelial cells - Vitamin A is vital for the formation of healthy epithelial cells. These cells cover the internal and external surfaces of the body and are found in the skin, lungs, developing teeth, inner ear, cornea of the eye, sex organs, glands and their ducts, gums, nose, cervix and other areas. Many epithelial cells produce mucus which is necessary to lubricate body surfaces and protect against invading micro-organisms. For example, the good health of the digestive tract lining is important in protecting against ulcers, and maintenance of the lining of the vagina and uterus is important in fertility.
Pregnancy and fetal development - Because of its vital role in cell development and differentiation, adequate vitamin A helps to ensure that the changes which occur in the cells and tissues during fetal development take place normally. It may be involved in cell to cell communication.
Protection against infection - Known as 'the anti-infective vitamin', vitamin A plays an essential role in protecting your body from infection. It keeps body surfaces healthy so they can act as barriers to invading micro-organisms. Vitamin A stimulates and enhances many immune functions including antibody response and the activity of various white blood cells such as T helper cells and phagocytes. This immune-enhancing function promotes healing of infected tissues and increases resistance to infection.
Other actions - Laboratory experiments have shown vitamin A to have antiviral activity. Vitamin A also has antioxidant activity and has a role in protecting against free radical damage which contributes to many common diseases. Vitamin A is involved in iron metabolism and storage. Read more about antioxidants here.
Absorption and metabolism - The presence of fat and bile in the intestines is necessary for vitamin A absorption. Around 80 to 90 per cent of vitamin A in the diet is absorbed, although this is reduced in older people and those who have trouble absorbing fat, such as pancreatitis, celiac disease and cystic fibrosis sufferers, who may run the risk of vitamin A deficiency. Vitamin A is joined to fatty acids in the intestinal lining, combined with other substances and transported to the liver, which stores 90 per cent of the body's vitamin A.
The World Health Organization estimates that as many as 250 million children worldwide are threatened by vitamin A deficiency. However, it is relatively rare in developed countries and is usually limited to those who have absorption difficulties, liver disease or who drink a lot of alcohol. Vitamin A deficiency is common in alcoholics and contributes to some of the disorders of alcoholism such as night blindness, skin problems, cirrhosis of the liver and susceptibility to infections.
Aspects of deficiency.
Eyes - One of the first symptoms of deficiency is night blindness due to lack of visual purple. Prolonged deficiency leads to xerophthalmia, a condition in which eyes become dry, ulcers appear on the cornea, the eyelids become swollen and sticky, and which eventually leads to blindness. Vitamin A deficiency is the leading preventable cause of blindness in developing countries.
Skin - Prolonged deficiency leads to thickened dry skin which is prone to infections. Small hardened bumps of a protein known as keratin may develop around the hair follicles.
Growth - Deficiency causes growth retardation; weight loss; diarrhoea, thickening of bone shafts; congenital malformations; impaired hearing, taste and smell; wasting of testicles; and reduced sperm count. Inadequate vitamin A intake can lead to improper tooth formation in children and to gum disease.
Immune system - Epithelial surfaces are adversely affected by vitamin A deficiency, causing increased susceptibility to skin and respiratory infections. Immune cells and antibody functions are also affected which may lead to an increase in pre-cancerous cells in the epithelial tissues of the mouth, throat and lungs. Many studies have shown that vitamin A deficiency is associated with increased risk of infection in developing countries. This may also be the case in developed countries. A 1992 study involving 20 children with measles in Long Beach, California found that half of them were vitamin A deficient.
HIV - Vitamin A deficiency is often seen in HIV-positive people and this may be due to metabolic changes associated with HIV infection. A 1995 study done on HIV-infected drug users in the US found that there was a higher risk of death in those with vitamin A deficiency. Vitamin A deficiency is often seen in HIV-positive pregnant women and severe deficiency increases infant mortality and the risk of mother-to-child transmission of HIV.
Thyroid gland - A deficiency of vitamin A can contribute to lower levels of active thyroid hormone with symptoms of low body temperature, depression, difficulty with weight loss, headaches and lethargy.
Cancer - Many studies suggest that high blood levels of vitamin A can help prevent certain forms of cancer, particularly cancers of epithelial tissue. This may be due to the importance of vitamin A in maintaining healthy epithelial cells, strengthening the immune system and stimulating the response to abnormal cells. Several population studies suggest links between low vitamin A intakes and various types of cancer, particularly those of the lungs, head and neck. Vitamin A deficiency may also increase the risk of breast cancer. In a study published in 1997, researchers at Harvard School of Public Health compared the concentrations of various forms of vitamin A in the breast fat tissue from 46 cancer patients and 63 women with benign breast l