A D E K: The vital vitamins

A certified nutritionist explains how the fat soluble vitamins (A, D, E and K) play key role in our daily functions

Young Woman Buying Vegetables at Local Market \ A D E K vitamins
Evidence-based | Written by an expert

It’s funny how sometimes we know so little about the things that are most important to us. Take vitamins for instance.

Sure, we all learnt about them in school, but forgot about them just as quickly with the passing years, even though they are important for almost every process and function of our body. But it’s never too late to start to learn good things. So let’s begin with the basics.

Vitamins are of two types: fat soluble [vitamins A, D, E, K] and water soluble [B-complex and vitamin C]. In this article, I will discuss the importance of A D E K vitamins to our health. Also read about the water soluble vitamins: Vitamin B-Complex and Vitamin C.

Why we need A D E K

A D E K are the fat soluble vitamins. In other words, they are insoluble in water and therefore are carried in the body through fats. One of the factors that make these group of vitamins handy is that cooking does not make them less potent.

Fat soluble vitamins are important for our body for general good health, daily repair of the body cells and functioning of the organs. These vitamins also play an important role in Protein-Energy Malnutrition [PEM]. The level of vitamin A and E decreases in these children and thus supplementation becomes a priority for all the PEM cases.

It is important to get the dosage of A D E K right—less leads to toxicity, excess leads to toxicity.

In general, fat soluble vitamins are stored in the body in sufficient reserves so that daily intake is not required. But, deficiencies could set in due to long-standing illnesses like Crohn’s disease or cystic fibrosis [there is impaired digestion and fat malabsorption in both these cases], low-fat diets or certain drugs that interfere with fat absorption.

Vitamin A

Vitamin A, also known as retinol, plays an important role in our body. It is available in its active form, retinol [which is readily available for use in the body after digestion] and a precursor form, beta carotene [raw form, which gets converted to retinol for absorption].


The primary function of vitamin A is maintaining good night vision. This is done by maintaining the cornea and epithelial cells of the eyes. For instance, when you go from a well lit room to a dark room, vitamin A helps you to adjust to the darkness.

The secondary function is bone growth, reproduction and health of the skin and mucous membrane. It is also a good source of antioxidants; protecting the body from harmful free radicals, which in turn may help to reduce the risk of certain cancers.

Deficiency symptoms

Deficiency usually starts with malnutrition or fat malabsorption. They may sometimes be accompanied by protein and zinc deficiencies. Usually our body has the ability to store a year’s supply in it. Therefore, the deficiency symptoms do not start immediately after the losses begin.

Firstly the skin and the mucous membrane functioning starts getting affected, leading to dried and flaky skin. The cornea starts hardening and vision gets disturbed leading to a condition called xerophthalmia. In children, growth may get affected and wounds healing may take longer to heal. The most common deficiency symptom is night blindness.

Daily requirement

Vitamin A is measured in micrograms [µg]. Recommended Dietary Allowance [RDA] for vitamin A [retinol] is 1000µg for males and 800µg for females.

Sources of Vitamin A

Foods like sweet potato, red pepper, watermelon, eggs, chicken liver, carrots, spinach, papaya, apricot, mango, peas and oatmeal are rich sources of retinol. The precursor form maybe needed through supplements, if required.


Additional supplementation maybe required in extreme cases as per the doctors’ advice. If you are pregnant or plan to get pregnant, do not start with vitamin A supplements until prescribed by the doctor.


Excessive intake of vitamin A during pregnancy could lead to foetal abnormalities; in normal adults the problems could vary from mild dermatitis to haemorrhage or liver damage.

Vitamin D

Vitamin D, also known as calciferol, is required for the absorption of calcium and phosphorous and helps avoid osteoporosis and rickets. Vitamin D also helps the neuromuscular system, the immune system, and reduces inflammation.


The main function is formation of healthy bones, teeth and cartilage. Vitamin D along with correct doses of calcium, helps in preventing osteoporosis [brittle and porous bones].

Deficiency symptoms

Vitamin D deficiencies are similar to calcium deficiencies. The bones become brittle and bend with body weight, if the person is overweight or obese. Also in some cases, deformities of the spine, thorax or the pelvic muscle may set in. Lack of vitamin D can also damage the muscular and the nervous system.

Daily requirement

Vitamin D is also measured in micrograms [µg]. If you see it labelled in IU then one µg = 40 IUs. RDA is 5-10 µg/day as per the age.


The best source of vitamin D is sunlight. One should make it a point to sit in the morning sun for 10 minutes for better vitamin D absorption every day. Some foods rich in vitamin D are cod liver fish, halibut [type of flatfish], salmon, sardine, egg yolk, and also some fortified products like vitamin D fortified milk, cereals, and juices.


Those who are unable absorb sunlight because of sickness or climatic conditions should start supplementation. Vitamin D supplements are available readily through chemists/medical stores. They should also be taken during pregnancy and menopause to avoid osteoporosis or rickets. They are usually available through doctor’s prescription.


Hypercalcaemia [high levels of calcium and vitamin D] is common with higher doses of vitamin D. It could lead to stone formation in the kidney or demineralisation of the bones.

Vitamin E

kiwi fruitAlso known as tocopherol, vitamin E is a good source of antioxidants and helps with the immune system and the repair of our DNAs.


Its antioxidant properties prevent the body against free radicals. Vitamin C also helps make red blood cells, stabilise the cell membrane and regulate oxidation reactions.

Deficiency symptoms

Vitamin E deficiency is rare, however, lesser levels of vitamin E in the blood could lead to erythrocyte haemolysis [destroying red blood cells] and breakdown of the red blood cells. In some cases, problems related to the nervous system could arise and/or cause anaemia [in premature infants].

Daily requirement

Vitamin E is measured in milligram [mg]. The RDA for males is 10mg and females are 8mg.


Vitamin E gets readily destroyed by heat and therefore it is better available through natural sources. Its common food sources are vegetable oils like soy bean and wheat germ, nuts, kiwi, broccoli, green leafy vegetables and certain fortified cereals.


It may be required during pregnancy, lactation and for menopausal women and the requirement could differ from person to person.


Problems due to excessive intake of this vitamin are rare, compared to vitamin A and D. But in some cases excess intake could lead to blurred vision, headache, gastrointestinal distress, fatigue, weakness.

Vitamin K

This vitamin is the most important of all the fat soluble vitamins. The name K comes from a German word, koauglation. They are synthesised by the bacteria in our gut/throat.


The most important function of this vitamin in our body is to clot blood. It also helps in maintaining bone health to reduce the risk of osteoporosis and also in kidney metabolism.

Deficiency symptoms

If vitamin K is missing, blood cannot clot, which could lead to hemorrhagic disorders or a deficiency known as coagulopathy. This is a rare deficiency, however, it may be seen in babies, as the bacteria required for synthesis are absent in the digestive tract. The reason for deficiency in adults could be due to obstruction, malabsorption or certain liver diseases. People with vitamin K deficiency should avoid getting bruised or should consult the doctor before undergoing any surgery or dental work.

Daily requirement

The research is still on for the actual requirements, but on an average, 1µg [microgram] for every kilogram of weight/ day is recommended for normal blood clotting.


Vitamin K is found in green leafy vegetables like spinach, turnips, broccoli, brussels sprouts, cauliflower, soy beans, and some percentage through milk. Our body is the best source to produce this vitamin through the gut bacteria, but most of the times it gets partially stored in the liver and partially absorbed. Thus, it is important to take it through food and supplements.

In newborns, the first breast feed [colostrum], which is rich in vitamin K, helps in increasing the infant’s immunity levels and helps to build in the gut bacteria.


In cases of deficiency, supplementation is extremely important under medical supervision. Vitamin K injections are administered in extreme cases.


Chances of toxicity are rare in the case of this vitamin, however in some cases, it may occur on account of taking water-soluble substitutes for vitamin K. Symptoms could be red cell haemolysis, jaundice or in extreme cases brain damage.

Finally, all vitamins and minerals if taken in the correct amounts, are beneficial to our body. The correct dosage can be determined by your doctor/ dietician depending on the need. Do make it a point to supplement your diet with all the good sources of A D E K vitamins.

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  1. Here we get to know about A D E K: the vital vitamins information in detail. It helps us to decide that which one is best among its types. I enjoyed reading this article and would suggest others it as well. Thank you for this article! This is really very informative for us.

  2. i want to buy a retinol cream or products. but i don’t know from where i purchase these please mail me the name & address of shop close to defence (lahore)

  3. As I have been suffering from malabsorption
    of fat for three years now, my doctor gave me a
    prescription of ADEK (Vitamine A D E and K),
    water soluble.
    1) Where can I get this and is this one formula,
    or separate vitamins?
    2) Should I leave out vitamine A and K, because
    of possible oxicity?


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