What is the Role of Vitamin A in Good Nutrition?



Vitamin A plays a number of important roles in the body. It is necessary for normal cell division and growth; it is involved in maintaining the mucous membranes of the respiratory, digestive and urinary tracts; it is vital to good eyesight, playing a key role in converting light into electrical signals; and it is important for normal embryonic development.

What are the Key functions of Vitamin A?

What are good Food Sources for this vatamin?

Who would benefit from using supplementation?

When to use supplementation

How much of the Vitamin is usually taken?

What are the side effects of using Vitamin A?



This supplement is a fat-soluble vitamin which is stored primarily in the liver.

This Vit-A supplement is available in two forms:

The product, Retinol, is found in animal products. It produces the pigments in the retina of the eye.

Beta carotene, which your body converts into vitamin A.

Beta-carotene is an Antioxidant protecting cells from damage caused by unstable substances called free radicals. Free radicals are believed to contribute to certain chronic diseases and play a role in the degenerative processes seen in aging.

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What are the Key Functions of Vit - A?



Vitamin A is essential for:

  • healthy skin,
  • promotes the growth of strong teeth and bones,
  • promote and helps normal eyesight,
  • growth,
  • maintain cell membranes and
  • reproduction

As a fat-soluble vitamin it has four major functions in the body:

  1. It helps cells reproduce normally—a process called differentiation. Cells that have not properly differentiated are more likely to undergo pre-cancerous changes.
  2. It is required for vision; and maintains healthy cells in various structures of the eye and is required for the transduction of light into nerve signals in the retina.
  3. It is required for normal growth and development of the embryo and fetus, influencing genes that determine the sequential development of organs in embryonic development.
  4. It may be required for normal reproductive function, with influences on the function and development of sperm, ovaries and placenta.

For some people, water-soluble forms of this vitamin supplement appear to be better absorbed than fat-soluble vit-A.

It also performs a variety of other important functions:

  • Beta carotene is a powerful antioxidant that neutralizes free radicals, molecules that damage healthy cells and increases the risk of accelerating the aging process and/or health conditions.
  • Vit-A is essential for the formation of visual purple, a pigment that allows you to see in dim light.

Retinol plays a number of important roles in the body.

It is necessary for:

  • normal cell division and growth;
  • it is involved in maintaining the mucous membranes of the respiratory, digestive and urinary tracts;
  • it is vital to good eyesight, playing a key role in converting light into electrical signals; and
  • it is important for normal embryonic development.

Vit-A deficiency causes a generalized drying up of the mucous membranes and increases the risk of infection. It also results in an inability to see in poor light - a condition known as night blindness. A continued deficiency will result in progressively worsening vision which can lead to blindness.

Although rare in developed countries, a vit-A deficiency is one of the biggest causes of preventable blindness worldwide.

Because this supplement has a specific function in the retina of the eye, it is known as retinol. It is found in foods of animal origin, such as full-fat dairy produce, eggs and liver.

The vitamin is also available, indirectly, from plant foods where it occurs as a carotenoid called beta carotene, a pigment which gives many plant foods their yellow or orange colors, and which the body converts into vit-A.

Retinol is a pale yellow solid which dissolves easily in oils and fats. It can be produced synthetically and in this form is used to enrich margarines. The richest source of retinol is liver: just l0g of fried calves' liver would meet the entire adult daily requirement.

Because the vitamin is fat-soluble and is not easily broken down by the body, excessive intakes of retinol are poisonous, and are associated with damage to the fetus during early pregnancy. This is the reason why women who are pregnant or trying to conceive are always advised to avoid liver.

Carotenoids pose no risk to health, although continued high intakes of beta carotene can lead to a condition called carotenaemia in which the skin takes on a yellow tinge, particularly on the palms of the hands and soles of the feet. This is not harmful, and the skin slowly returns to its normal color when carotenoid intake is reduced.

Six times as much beta carotene is needed to provide an equivalent amount of retinol. In most Western-style diets, some 80 per cent of vit-A is absorbed as retinol.

Vegans, who not only exclude meat and fish, but also avoid dairy produce and eggs, obtain most of their requirements in the form of beta carotene.

Carrots, red peppers, mangoes and spanspek, as well as green leafy vegetables such as spinach and kale, are all rich in this nutrient. As a rule, the more intense the color of the fruit or vegetable, the more beta-carotene it contains.

As well as supplying vitamin A to the body, beta-carotene has another important role as an Antioxidant. Scientists have observed that diets high in carotenoids are often associated with a reduced risk of certain cancers.

However, this protection seems to be afforded only if the source of beta carotene is a food: studies where high levels of beta carotene supplement have been used showed an increased risk of lung cancer among smokers.

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What are good Food Sources for Vitamin A?



Vitamin A is present in liver, cod liver oil, carrots, and sweet potatoes.

Retinol is found in meat, fish, eggs and dairy products.

However, both of these sources - except for skim milk that has been fortified with Vitamin-A - are high in saturated fat and cholesterol.

Beta carotene is present in orange and yellow fruits and vegetables and dark, leafy greens. Beta-carotene is free of fat and cholesterol.

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Who would benefit from Vitamin A supplementation?



As a parent, how do you know when someone in the family needs Vit-A Supplementation? Here follows a couple of situations which can help you decide if there is a potential deficiency in the family.

People who limit their consumption of liver, dairy foods, and beta-carotene-containing vegetables can develop a deficiency.

Extremely low birth weight babies (2.2 pounds or less) are at high risk of being born with a deficiency, and Vit-A shots given to these infants have been reported to reduce the risk of lung disease.

The earliest deficiency sign is poor night vision. Severe deficiencies causing blindness are extremely rare in Western societies.

Deficiency symptoms can also include dry skin, increased risk of infections, and metaplasia (a precancerous condition).

Less severe deficiencies are more likely to occur with a variety of conditions causing mal-absorption.

A high incidence of deficiency in people infected with HIV has also been reported.

People with hypothyroidism have an impaired ability to convert beta-carotene to vitamin A.

Very old people with Type 2 diabetes have shown a significant age-related decline in blood levels of Vit-A, irrespective of their dietary intake.

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When to use Vitamin A supplementation




Vitamin A has been used in connection with the following conditions:

Anemia (for deficiency) Childhood diseases
Cystic fibrosis Infection
Measles (for deficiency) Measles (for severe cases)
Night blindness Bronchitis
Celiac disease (for deficiency only) Leukoplakia
Lung cancer

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How much Vitamin A is usually taken?




For most people, up to 7,500 mcg of Vit-A per day is considered safe.

However, people over age 65 and those with liver disease should probably not supplement with more than 4,500 mcg per day, unless supervised by a doctor.

For women who could become pregnant, the maximum safe intake is being re-evaluated. However, less than 3,000 mcg per day is generally accepted as safe.

In the Medical community there is concern that larger intakes could cause birth defects. Pregnant women do not require increased supplementation.In fact, women should be informed of the possible risk of cranial neural crest defects and other malformations resulting from excessive use of Vit-A shortly before or during pregnancy.

The recommended daily allowance (RDA) of 800 mcg for all adult females is also appropriate for pregnant women because that meet the fetal accretion rate.

Increased requirements of Vit-A most commonly occur among sick children. In the United States, the American Academy of Pediatrics’ recommends supplementation for infants aged 6-24 months who are hospitalized with measles and for all hospitalized children older than 6 months.

The World Health Organization (WHO) and United Nations International Children's Emergency Fund (UNICEF) have issued joint statements recommending Vitamin A administration for all children, especially those younger than 2 years, who are diagnosed with measles.

DEFICIENCY in young children with measles increases the risk of death. The conclusion was that daily treatment with 200,000 IU for at least 2 days reduces mortality rates.

The Food and Nutrition Board at the Institute of Medicine recommends the following the RDAs of Vit-A for various age groups:

Infants

  • 0-6 months: 400 micro grams per day (mcg/day)
  • 7-12 months: 500 mcg/day

Children

  • 1-3 years: 300 mcg/day
  • 4-9 years: 400 mcg/day

Adolescents and Adults

  • Males age 10 and older: 900 mcg/day
  • Females age 10 and older: 800 mcg/day

Women who are pregnant or producing breast milk (lactating) need higher amounts.Always Ask your doctor what dosage is best for you.

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What are the side effects of using Vitamin A?



Excessive dietary intake of Vit-A has been associated with birth defects in humans in fewer than 20 reported cases over the past 30 years.

But it remains an unnecessary risk to take.

Presently, the level at which supplementation may cause birth defects is not known, though combined human and animal data suggest that 9,000 mcg per day should be considered safe. Women who are or who could become pregnant should consult with a doctor before supplementing with more than 3,000 mcg per day.

Vit-A supplements can both help and hurt children. Many people have heard that supplements support immune function and prevent infections. This is true only under some circumstances.

Research could not find conclusive evidence that Vitamin A provide benefits to the well-nourished kids. Therefore, it does not makes sense to give this vitamin supplement to children unless there is a special reason to do so, such as the presence of a condition causing mal-absorption (e.g., celiac disease).

In a study of people with retinitis pigmentosa (a degenerative condition of the eye), participants received 4,500 mcg of supplement per day with no signs of adverse effects or toxicity.

It was found that for some adults, intake above 7,500 mcg per day can in rare cases cause:

headaches dry skin
hair loss fatigue
bone problems liver damage

A controlled clinical trial showed that people who took 7,500 mcg of Vit-A per day had an 11% increase in triglycerides, a 3% increase in total cholesterol and a 1% decrease in HDL cholesterol compared to those who did not take the supplement.

Although the significance of these findings is not clear, people at risk for cardiovascular disease should use caution when considering long-term vitamin A supplementation.

One study found that increasing the intake of Vit-A in the diet was associated with bone loss and risk of hip fracture, possibly due to a vitamin A-induced stimulation of cells that break down bone.

Beta-carotene has not been linked to reduced bone mass. Until more is known, people concerned about osteoporosis may consider taking beta-carotene supplements rather than supplementing with Vit-A.

Taking Vit-A and iron together helps overcome iron deficiency more effectively than iron supplementation alone.

Supplementation with zinc, iron, or the combination has been found to improve Vit-A status among children at high risk for deficiency of the three nutrients.

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