Vitamin A : Sources,daily requirement,deficiency

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In this blog, we learn about Vitamin A.This is very important and interesting topic. We need it for good immunity, normal vision, and cell growth. First, I will discuss some basic information, so it will be better to understand.

chemical structure of retinol

There are two types of vitamin : 
Fat soluble vitamin – vitamin A,D,E,K
Water soluble vitamin – vitamin B,C

So, vitamin A is fat soluble vitamin.It means that it can be stored in body fat eg. liver. Due to that deficiency of vitamin A can not happen overnight.If you are not taking food which contain vitamin A for long time than & than deficiency occur.

SOURCES OF VITAMIN A

We can get vit. A from two sources.
One is animal source by which we get vitamin A in preformed retinols form.
Second one is plant source by which we get vit. A in carotene form.

Animal sources

  • Milk & milk products
  • liver
  • fish liver oils
  • egg yolk

Plant sources

  • Carrots
  • potato
  • spinach
  • mango
  • papaya
  • apricoat

REFERENCE NUTRIENT INTAKE (RNI)

If we not take particular nutrition properly than we suffer from deficiency. If we take more than required than also we may suffer from toxicity. So, to take nutrition within range is important for our health.

For men900 mcg per day

For female700 mcg per day

Above range is recommended daily allowance, that should we take daily.If we take slightly more than that body will tolerate it. 

But after certain dosage, body can not tolerate and give response to that.It is called upper tolerable limit.UTL is 3000mcg (10,000 IU). Above that body can not tolerate & it causes acute toxicity.

Mostly we get sufficient vitamin A from our diet.I am giving example of few sources, so you can calculate daily required dose.

Sources  Retinol activity equivalences mcg/100gm. percentage of adult male RDA per 100g
Ghee 3069  344%
Sweet Potato 961 107%
Carrot 835   93%
Egg 140 16%
Spinach 469 52%
Tomatoes 42 5%
Milk  28 3%
Cod Liver Oil  30000  3333%
Liver Chicken 3296  366%
Papaya 55 6%

SIGN & SYMPTOMS DUE TO DEFICIENCY

If we not take vitamin A in daily required dosage for long time than deficiency of vit. A occurs.It is common  in undeveloped countries , especially amongs children and women of reproductive age. In developed countries cases of vit. A deficiency is rarest.

EYE PROBLEMS

Eyes are organs of visual system. For healthier eye, we need sufficient vit. A level.Once deficiency of this nutrition occur, eyes start to damage. Problems occur as below mention. Early diagnosis will save patient’s eye.

Night blindness

It is the first sign of vitamin A deficiency.Patient can not see object in dim light or at night time.This is important point where we can doubt that patient may having this nutrition deficiency.

Hamarolopia

Inability to see bright light.

Xerophthalmia 

It means “dry eye” is a medical condition in which the eye fails to produce tears.Eye becomes dry, thick and wrinkled. If this is not treated timely, than patient may suffer from corneal ulceration and finally blindness as a result of corneal damage.

Bitot’s spot

Forming greyish-white triangular plaques on conjunctival surface lateral to the cornea. It is alarming sign, doctor can detect early and give supplement to correct deficiency.

TEETH

Impaired enamel formation

SKIN

Skin becomes dry and rough. Colour of skin changed, it becomes brown to dark brown. 

In severe deficiency cases the follicular papules develop in entire upper and lower extremities, shoulder, abdomen, buttocks, face and back of neck.

ACUTE TOXICITY OF VITAMIN A (massive single dose)

It is temporary, symptoms goes with time.

  • Abdominal pain
  • Nausea
  • Vomiting
  • Headache
  • Dizziness
  • Generalised skin peeling

CHRONIC POISONING OF VITAMIN A

If someone take nutrition more than required for long period than they may suffer from chronic poisoning.

  • Bone and joint pain
  • Loss of hair
  • Fissuring of lips
  • Loss of appetite
  • Weight loss
  • Hepatomegaly
  • Benign intracranial hypertension

HOW DEFICIENCY OCCURS

Vitamin A deficiency occurs either due to primary or secondary causes.

Primary deficiency

It occurs to them who do not take adequate intake of provitamin A caratenoids from fruits and vegetables or preformed vitamin A from animal or dairy products. Early weaning of breast feeding also increase chances of vitamin A deficiency.

Secondary deficiency

Patient is taking food in proper quantity but due to digestion problem, patient is suffering from vit. A deficiency.

Problem like chronic malabsorption of lipid and impaired bile production and release may cause this.It is also caused by chronic exposure to oxidants like cigarette or alcohol.If patient have zinc deficiency, it also causes impair absorption, transport and metabolism of vitamin A.