Vitamin A

Vitamin A is a fat-soluble vitamin essential to the body for vision and growth of bones and teeth. It helps with reproduction and the development of tissues that become an integral part of the brain, muscles, lungs, blood and other specialized tissues. Vitamin A additionally helps boost the body’s immunity by promoting the synthesis of white blood cells that destroy disease causing bacteria and viruses.

Vitamin A is also responsible for the maintenance of integrity of the surface linings such as the skin and mucous membranes. These linings protect the eyes, and respiratory and urinary tracts. External application of Vitamin A is effective to treat acne, boils, carbuncles, and open ulcers.

Some studies have shown that pro-vitamin A found in fresh fruits and vegetables contain anti-oxidants that may help scavenge free radicals. Free radicals are potentially dangerous elements that can damage the cells and promote development of chronic illness. B carotene a form of Vitamin A is viewed as a weapon to fight the harmful effects from these free radicals.

Forms of Vitamin A: Vitamin A is available in two forms.

1. Pre-formed Vitamin A: can be readily absorbed. Retinol is the most active form. The others are retinal or retinoic acid. Sources are animal foods such as milk and milk products, eggs, etc.
2. Pro-Vitamin A is carotenoids which can be converted to retinol in the liver. Sources are dark greens, coloured vegetables and fruits.

Pro vitamin A also includes a group of compounds- alpha and beta carotenoids, beta crytoxanthin of which beta carotene is the most efficient. The availability of Vitamin A from is ½ to 1/3 from carotenoids. The Institute of Medicine (IOM) recommends a daily high intake of carotenoid rich foods for their health benefits.

 

RDA of vitamin A & Beta carotene.

(Vit A as micrograms (mcg or μg) of Retinol Activity Equivalents (RAE).

Infants - Age (months) Males and females (mcg RAE) US Males and females (mcg RAE) Indians 0 - 6 400 350 7 - 12 500 350

(Based on the information from adequately breastfed infants)

Children - Age (years) Males and females (mcg RAE) US Males and females (mcg RAE) Indians 1 - 3 300 400 4 - 8 400 400 9 - 13 600 600

 

Age (years) Males (mcg RAE) US IND Females (mcg RAE) US IND Pregnancy (mcg RAE) US IND Lactation (mcg RAE) US IND US IND US IND 14 - 18 900 600 700 600 750 600 1,200/950 19+ 900 600 700 600 770 600 1,300/950

National Institute of Nutrition (NIN) recommends 600 - 950 micrograms (μg) of Vitamin A (Retinol) for adults per day - 600 μg for males and pregnant as well as non-pregnant females, and 950 μg during lactation. Thus, mother's intake of VA should be higher during breastfeeding as breast milk is the source of Vitamin A for the baby.

There is no RDA for beta-carotene or other provitamin A - carotenoids. According to IOM consuming around 3 - 6 mg of beta-carotene daily (833 IU - 1,667 IU vitamin A) will maintain blood levels required to reduce risk of chronic diseases. Everybody and especially vegetarians who do not consume eggs or dairy will require a minimum of 5-6 or more servings of fruits and vegetables per day, including dark green and leafy vegetables and deep yellow or orange fruits to provide sufficient beta-carotene and other carotenoids.

For the lower economic strata, at least 1 tablespoon of cooked green leafy vegetable per day for a young child, 2 tablespoons of cooked green leafy vegetable per day for pregnant woman and 3 tablespoons of green leafy vegetable per day for a lactating mother will provide the required amount for good health.

According to American dietary guidelines “Nutrient needs should be met primarily through consuming foods. Foods provide an array of nutrients and other compounds that may have beneficial effects on health. In certain cases, fortified foods and dietary supplements may be useful sources of one or more nutrients that otherwise might be consumed in less than recommended amounts. However, dietary supplements, while recommended in some cases, cannot replace a healthful diet”

Food sources: of Vitamin A

Our body cannot make Vitamin A but it can convert Beta Carotene to Vitamin A in the liver and any dietary excess can be stored and made available in time of need.

For infants and young children, the best source of Vitamin A is breast milk including colostrums (yellow milk secreted for the first 5 days). For young children, pregnant and lactating women, there are two other Vitamin A rich dietary sources - plant and animal foods.

Animal Sources of Vitamin A mainly as retinol, and is converted into retinal and retinoic acid. Some important sources include livers of all animals, beef, chicken, eggs, fish, cheese and seafoods.

Plant Sources of Vitamin A: are found as provitamin A carotenoids in green leafy vegetables and yellow/orange vegetables such as carrot, pumpkin, broccoli, peas, spinach, sweet potato, turnip, tomatoes, wheat germ, escarole, collards, dandelion green, mustard green, aloe vera etc, and fruits such as papaya, apricot, cantaloupe, mango, orange, apple, watermelon, plum, blackberry, peach and kiwi etc

Ghee/oil/butter should be added to these vegetables for better conversion of β-Carotene to VA.

Vitamin - A Deficiency.

According to WHO/IVACG, if in any area, 1% of children suffer from night blindness or 0.5% children have visible signs of Vitamin A deficiency (VAD) such as Bitot's spot or 5/% pregnant women suffer from night blindness, then VAD is defined as a public health problem in that area.

WHO guidelines for community health, suggests that Under 5 Mortality Rate (U5MR) of 70 or more could be taken as an indicator of likely Vitamin A deficiency problem.

Vitamin A and vision:

Globally around 250,000-500,000 of malnourished children become blind due to vitamin A deficiency. Zinc required for the synthesis of RBP (retinal binding protein) is yet another nutrient which is deficient in malnourished individuals. Deficient RBP will hinder or limit transport of Vitamin A to liver stores or from stores to body tissue.

Vitamin A & night vision

The 1st signs of Vitamin A deficiency can be seen by the onset of Night blindness. It begins with dryness of the corneal tissue. With severity it results in Bitot's spots, Corneal Xerosis/ ulceration, Keratomalacia and Corneal scar and finally blindness due to complete damage to the retina and cornea.

How can Vitamin A Deficiency in Children* be prevented?

Vitamin A deficiency is the leading cause of preventable blindness in children.

• Early initiation of breast feeding i.e. breast feeding within an hour of delivery and continued feeding of colostrums,
• Exclusive breast feeding for the first 6 months,
• Introducing Vitamin A rich, complementary foods to 6 month old children.
• Continued breast feeding till the child is 2 years old, and
• If needed providing children in the age group of 9-36 months with Vitamin A supplementation at 6 monthly intervals. ( In consultation with the doctors or as a community based program)
• Preventing illnesses such as diarrhoea, measles and ARI; and round worm infestation. Ensuring proper management of illness in case of an infant or young child suffering from these.

Vitamin A and infections

Skin integrity and the ability to fight infections are compromised in Vitamin A deficiency. Along with improper immunisations millions of children die each year due to complications of infectious diseases such as measles and respiratory infections leading to pneumonia. Thus there is an increased risk of disease and death from severe infections such as measles and diarrhoea. The World health Organisation (WHO) and United Nations Children’s Fund (UNICEF) recommend supplementation/administration of Vitamin A for all children detected with measles in communities where vitamin A deficiency is a major problem and also where death from measles is greater than 1%.

Most malnourished children (PEM or protein energy malnourishment) with accompanying Vitamin A deficiency succumb also to diarrheal infections. Added to it there would be iron deficient anemia leading to poor recovery and sometimes even fatal.

Vitamin A and alcohol abuse.

Excess alcohol consumption depletes vitamin A stores. It is therefore vital to provide good amounts of Vitamin A by diet everyday.

Vitamin A, Beta carotene, and Health Cancer

Many studies have shown a co relation between diets rich in beta-carotene and vitamin A and lowered risk of many types of cancer. High intake of green and yellow vegetables or other food sources of beta carotene and/or vitamin A (and not as supplements*) has shown a decrease in the risk of lung cancer. IOM categorically states that that "beta-carotene supplements are not advisable for the general population," but it also states that "does not pertain to the possible use of supplemental beta-carotene as a provitamin A source for the prevention of vitamin A deficiency in populations with inadequate vitamin A"

*(In the Alpha-­Tocopherol Beta-­Carotene (ATBC) Cancer Prevention Study, where more than 29,000 men who regularly smoked cigarettes, were randomly given 20 mg beta-­ carotene alone, 50 mg alpha-­tocopherol alone, supplements of both, or only a placebo for 5 to 8 years. Incidence of lung cancer was 18% higher among men who took just the beta-­ carotene supplement. Similar results were seen in the Carotene and Retinol Efficacy Trial (CARET), a lung cancer chemoprevention study that provided subjects with supplements of 30 mg beta-­carotene and 25,000 IU retinyl palmitate (a form of vitamin A) or a placebo. This study was stopped after researchers discovered that subjects receiving beta-­carotene had a 46% higher risk of dying from lung cancer

Osteoporosis - is a disorder characterized by weak and porous or brittle bones or just decreased bone density (osteopenia) afflicts millions of people especially women, globally. Contributory factors are inactivity, advanced age and genetic predisposition. Insufficient calcium intake, excessive smoking or alcohol consumption increase the risk. Research has shown that an abnormally high intake of Vitamin A or decreased Vitamin D also high risk factors for osteoporosis. A dietary intake of over 1500 mcg/day of dietary retinal decreased mineral density and increased risk for hip fractures.

Hypervitaminosis A - Excessive stores of vitamin A in the liver can lead to toxicity. The 4 well known adverse effects of hypervitaminosis A are - birth defects, liver abnormalities, reduced bone mineral density that will eventually result in osteoporosis (see the previous section), and disorders of central nervous system(CNS).

Acute toxicity such as when a person consumes polar bear liver or over supplementation etc can include nausea and vomiting, headache, dizziness, blurred vision, and lack of muscular co-ordination

Sources:

1. http://ods.od.nih.gov/factsheets/vitamina.asp
2. *http://hetv.org/resources/vitamin-a/faq.htm