Vitamin A (Retinol, Retinoid and Carotenoid)

Sample

1. Serum or plasma needed.
   1. A fasting sample is preferred.
2. A fasting sample is preferred.
3. The sample is stable for 4 weeks at 4 °C

Precaution

1. Avoid hemolysis.
2. Avoid sample from the light.
3. Do not ingest alcohol 24 hours prior to the blood draw.

Definition of Vitamins

1. Vitamin name was given by a Polish Chemist, Casimir Funk. in 1991.
   1. He discovered that a nutrient that was able to cure the Beri Beri in pigeons.
   2. He suggested that it is amines present in food and it prevents diseases.
   3. He named it as vitamin = vita means life so he named these substances like vitamins.
   4. Vitamins are necessary for life.
2. The deficiency of a single vitamin is usually uncommon.
3. Vitamin deficiency may be due to an inborn error of metabolism or restricted diet intake.
4. Vitamins are needed in µg or mg per day for the normal metabolic function of the body.
5. These may be water-soluble or fat-soluble.
6. Fat-soluble vitamins are:
   1. Vit. A
   2. Vit. D
   3. Vit.E
   4. Vit. K
      1. These are stored for a longer time.
      2. These vitamins don’t function as coenzymes.
7. Water-soluble vitamins are:
   1. Vit B complex
   2. Vit. C
      1. Lost for a short time.
      2. These function as coenzymes for numerous important enzymatic reactions.

Vitamin A (Retinol; Retinoic acid; Carotenoids)

1. Vitamin A is an essential nutrient.
   1. Vitamin A is found in:
      1. Diet rich in retinyl esters.
      2. Metabolism of carotenoids, provitamin A and it is primarily β-carotene.
   2. Diet sources are:
      1. Animal products.
      2. Pigmented fruits.
      3. Vegetables (carotenoids).
   3. Vitamin A is stored in the liver and in the blood circulation is bound to retinol-binding protein and transthyretin.
2. Functions: Vitamin A helps, form, and maintain healthy skin, teeth, skeletal and soft tissue, mucous membranes, and skin.
   1. It is needed for good vision.
   2. Needed for the growth of fetus and embryo (reproduction and growth).
   3. It has a role in the immune system.
   4.  It helps in wound healing.
   5. It helps in growth.
   6. It helps in the reproductive system.
3. Vit. A is sensitive to oxygen and ultraviolet light.
4. Vit. A exists in three forms:
   1. Retinol (A1) is the most important form of Vit.A.
      1. This is the transport form as the Retinol ester and also storage form.
      2. This is oxidized to aldehyde retinal which is used in visual pigments.
      3. Also oxidized to retinoic acid.
   2. Retinal.
   3. Retinoic acid.

5. Retinoids are both natural and synthetic chemicals that are structurally similar to Vit. A  but don’t have the function like vit.A.
6. These are derived from the dietary source mainly carotenoids.
7. It is insoluble in water and soluble in organic solvents and mineral oil.
8. Vit. A is sensitive to oxygen and ultraviolet light.
9. It is also known as retinol because it produces the pigments in the retina of the eye.

10. Vitamin A and provitamin A are absorbed in the presence of bile salts.
11. These are taken up by the small intestine epithelial cells.

Role of Vitamin A in the eye:

Deficiency leads:

1. To degeneration of eyes and skin.
2. There may be Vit. A deficiency night blindness (nyctalopia).
   1. When the deficiency is prolonged then the patient may have total blindness.
3. The patient may have Dry eyes (Xerophthalmia).
   1. There is dryness of the conjunctiva (xerosis conjunctivae).
   2. There are Bitot spots.
   3. There are keratomalacia and ultimately blindness.
4. Sometimes patients develop diarrhea.
5. The patient may develop skin problems.
6. There are metaplastic changes in the epithelium of the lungs (squamous metaplasia).
7. Metaplasia is the urinary tract that leads to stone formation.
8. The patient develops an immune deficiency.
   1. Common infections like measles, pneumonia, and diarrhea are very serious in these patients.
   2. Recurrent infections.
9. There is a retardation of growth.
10. There is an abnormal taste.
11. Summary of Vitamin A is essential for vision, cellular differentiation, growth, reproduction, and immune system function.
12. Deficiency of Vitamin A is caused by:
    1. Chronic fat malabsorption.
    2. Impaired liver function.
    3. Severe stress.
    4. Protein malnutrition.
    5. Premature babies are born with a deficiency of retinol and retinol-binding protein.

Dietary sources are:

1. Eggs.
2. Fish liver oil.
3. Dairy products like milk, yogurt, cheese, and butter.
4. Meat includes beef, chicken liver, and calf.
   
   1. Vit. A1 is present in the liver of mammals and saltwater fish.
   2. Vit. A2 is found in the freshwater fish oils.
5. Vegetables like carrots, squash, and spinach. Fruits and vegetables contain carotene which is the precursor of the retinol.

Overdosage side effects are:

1. This can lead to liver failure.
2. The patient may develop headaches, fatigue, and muscle joint pains.
3. The Patient skin is dry.
4. The patient may develop nausea and diarrhea.
5. There is hair loss.
6. Chronic toxicity leads to weight loss, nausea, and vomiting.

Normal

Source 1

Age	µg/dL
1 to 6 years	20 to 43
7 to 12 years	26 to 49
13 to 19 years	26 to 72
Adult	30 to 80

Other sources

1. Daily requirements are:
   1. Infants (average intake)
      1. 1 to  6 months:  400 µg per day.
      2. 7 to 12 months:  500 µg/day
   2. Children (RDA)
      1. 1 to  3 years: 300 µg/day
      2. 4  to 8 years: 400 µg/day
      3. 9  to  13 years: 600 µg/day
   3. Adolescents and Adults (RDA)
      1. Males age 14 and older: 900  µg/day
      2. Females age 14 and older: 700  µg /day
   4. Or 65 to 275 I.U / 100 ml.
   5. Or > 20 µg / 100 ml.
2. From other reference  normal values for Vitamin A (Retinol) in the serum:
   1. 1 to 6 years = 20 to 43 µg/dL.
   2. 7 to 12 years = 26 to 49  µg/dL.
   3. Adults            = 30 to 80 µg/dL.
   4. Severe deficiency = <10 µg/dL.
   5. Increased Vitamin A (hypervitaminosis) = >100 to 2000  µg/dL.
3. Another source
   1. Recommended allowance of vitamin A:
      1. Adult male = 1000 µg/say.
      2. Adult female = 800 µg/say.

Carotene

Carotene is a precursor of vitamin A.

1. 100 to 300 I.U / 100 ml or 40 to 300 µg/ 100 ml.
2. Increased Carotene (Carotonemia) = > 250  µg/dL.

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