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Vitamin Functions, Deficiency Symptoms, and Natural Sources

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Here is an overview of the functions of vitamins, symptoms of vitamin deficiency, and natural sources.

Here is an overview of the functions of vitamins, symptoms of vitamin deficiency, and natural sources.

Vitamins and Their Functions

A vitamin is an organic compound found in food and other natural sources that our body needs for basic function and health. Many vitamins are available to us via food.

For example, citrus fruits are an abundant source of vitamin C. We get vitamin D by eating fish, eggs, and mushrooms. Exposure to sunlight is an important source of Vitamin D as well.

There are 13 essential vitamins:

  1. Vitamin A
  2. Vitamin B1 (thiamine)
  3. Vitamin B2 (riboflavin)
  4. Vitamin B3 (niacin)
  5. Pantothenic acid (B5)
  6. Vitamin B6
  7. Biotin (B7)
  8. Folate (folic acid and B9)
  9. Vitamin B12 (cyanocobalamin)
  10. Vitamin C
  11. Vitamin D
  12. Vitamin E
  13. Vitamin K

Below is a brief overview of the roles that these vitamins play in our health, how we know when we are deficient, and where vitamins can be found in food.

Essential Vitamin Functions and Sources



1. Vitamin A

Form and maintain teeth, bones, tissue, and skin.

Ripe yellow fruits, carrots, oranges, paprika, squash, red peppers, leafy green vegetables, cayenne, pumpkin, chili powder, spinach, soy milk, and sweet potatoes.

2. Vitamin B1 (thiamine)

Essential to help cells turn carbohydrates into energy.

Whole grains, enriched cereals, brown rice, sesame seeds, sunflower seeds, dried herbs and spices, pine nuts, pistachios, macadamia nuts, pecans, legumes, wheat germ, bran, brewer’s yeast, and blackstrap molasses.

3. Vitamin B2 (riboflavin)

Maintains red blood cells and body growth.

Bananas, dried herbs, asparagus, almonds, wheat bran, dried spices, green beans, sesame seeds, dried roasted soybeans, sun-dried tomatoes, dried peppers, and popcorn.

4. Vitamin B3 (niacin)

Maintains healthy skin and nerves.

Rice bran, wheat bran, paprika, peanuts, sun-dried tomatoes, mushrooms, and tree nuts.

5. Pantothenic acid (B5)

Essential for metabolism of food.

Broccoli, wheat bran, avocado, rice bran, sunflower seeds, whey powder, mushrooms, cheese, corn, broccoli, caviar, sun-dried tomatoes, squash, and fish.

6. Vitamin B6

Form and maintain red blood cells and brain function.

Tree nuts, dried spices, wheat bran, sesame seeds, bananas, rice bran, dried herbs, pistachios, raw garlic, sunflower seeds, molasses, sorghum syrup, filberts, and hazelnuts.

7. Biotin (B7)

Essential for metabolism of protein and carbohydrates.

Oil-roasted peanuts, oil-roasted sunflower seeds, soy beans, dried yeast, oatmeal, walnuts, baker’s yeast, mustard powder, salted peanut, salted sunflower seeds, salted hazelnuts, dried peanuts, instant coffee, oil-roasted hazel nuts, and green laver.

8. Folate (folic acid or B9)

Forms red blood cells and essential to production of DNA.

Leafy green vegetables, pasta, bread, cereal, spinach, dark leafy greens, asparagus, turnip, beets, mustard greens, Brussels sprouts, lima beans, soybeans, brewer’s yeast, root vegetables, whole grains, wheat germ, bulgur wheat, kidney beans, white beans, mung beans, orange juice, and avocado.

9. Vitamin B12 (cyanocobalamin)

Forms red blood cells and maintains central nervous system.

Clams, oysters, mussels, liver, caviar, octopus, fish, crab, lobster, beef, beef, mutton (especially shoulder), cheese (especially Swiss), and eggs.

10. Vitamin C

An antioxidant that promotes healthy teeth and gums.

Red chili peppers, guava, green chili peppers, bell peppers, fresh herbs (thyme and parsley), dark leafy greens (garden cress, kale, and mustard), broccoli, cauliflower, Brussels sprouts, kiwi, papaya, strawberries, oranges, and clementines.

11. Vitamin D

Essential for development of healthy teeth and bones.

Fish, eggs, liver, mushrooms, and sunshine.

12. Vitamin E

Helps form red blood cells and process Vitamin K.

Corn oil, sunflower seeds, paprika, soybean oil, margarine, safflower oil, wheat germ oil, sunflower oil, red chili powder, cooked taro root, almonds, pine nuts, peanuts, dried herbs (basil and oregano), dried apricots, pickled green olives, and cooked spinach.

13. Vitamin K

Essential for blood coagulation and bone health.

Dried herbs, prunes, pickled cucumber, dark leafy herbs, spring onion, Brussels sprouts, broccoli, chili powder, curry, paprika, cayenne, asparagus, and cabbage.

Vitamin A Deficiency

  • Vitamin A deficiency causes impaired vision, particularly in reduced light. This condition is commonly known as night blindness.
  • Deficiency can also lead to hyperkeratosis, which is a thickening of the stratum corneum, or the outermost layer of skin. This appears as white lumps at the hair follicles.
  • Deficiency of vitamin A also causes keratomalacia, an eye disorder.

Vitamin B1 Deficiency

  • Vitamin B1 deficiency can cause beriberi, a potentially life-threatening condition. Symptoms include constant fatigue, numbness in the hands or feet, shortness of breath, increased heart rate, and general malaise. This condition is rare in developed countries.
  • A severe B1, or thiamine, deficiency can also lead to Wernicke-Korsakoff syndrome, which manifests as vision disturbances, mental confusion, and loss of muscle coordination.
  • Increased risk of heart failure
  • Excessive consumption of alcohol can lead to a B1 deficiency.
Some vitamin deficiencies can cause skin rashes or inflammation.

Some vitamin deficiencies can cause skin rashes or inflammation.

Signs of Vitamin B2 Deficiency

  • Skin rashes and moist, scaly skin inflammation
  • Vision problems due to the formation of blood vessels in the clear covering of the eye
  • Sore throat
  • Inflammation of the lips and fissures in the mouth

Vitamin B3 Deficiency

A severe deficiency can result in a condition called pellagra: Symptoms include diarrhea, dermatitis, dementia, aggression, red skin lesions, insomnia, weakness, and confusion.

Vitamin B5 Deficiency

A deficiency in vitamin B5 is extremely rare and has only been found in cases of severe malnutrition.

The most common symptom is paresthesia, or “pins and needles.”

Broccoli is an excellent natural source of Vitamin B5.

Broccoli is an excellent natural source of Vitamin B5.

Vitamin B6 Deficiency

This is another deficiency that is uncommon. However, alcoholics may be most at risk due to low dietary intake and impaired metabolism of the vitamin.

Low levels may lead to anemia and peripheral neuropathy. Symptoms may include inflammation of the skin, a sore tongue, depression, cognitive issues, and convulsions.

Raw garlic is an excellent source of Vitamin B6.

Raw garlic is an excellent source of Vitamin B6.

Signs of Vitamin B7 Deficiency

  • Dermatitis
  • Enteritis (inflammation of the intestine)
  • Hair loss
  • A scaly red rash in the face and genital area
  • Depression

Signs of a Folate, or Vitamin B9, Deficiency

  • Megaloblastic anemia
  • Fatigue
  • Weakness
  • Shortness of breath

During pregnancy, a vitamin B9 deficiency can affect the fetus's nervous system, so it's recommended that pregnant people take folic acid.

Vitamin B12 Deficiency Symptoms

  • Weakness and fatigue
  • Breathlessness
  • Light-headedness
  • Rapid heartbeat
  • Pale skin
  • Sore tongue
  • Weight loss due to decreased appetite
  • Diarrhea or nausea

Vitamin C Deficiency

A vitamin C deficiency is rare in developed countries and can be easily fixed with a daily supplement. However, children and older people are most at risk because of having a more limited diet.

Symptoms include the following:

  • Fatigue
  • Joint pain and swelling
  • Bruising or bleeding easily
  • Hair or tooth loss
Oranges are an abundant source of Vitamin C.

Oranges are an abundant source of Vitamin C.

Vitamin D Deficiency

The following groups of individuals are more at risk for this deficiency:

  • Infants who are exclusively breastfed and aren't given a supplement (especially if the mother has low vitamin D)
  • The elderly
  • Individuals with dark-colored skin, especially those who live far away from the equator

Vitamin D deficiency causes rickets and osteomalacia. Adults may have bone pain or softer bone as well as muscle pain or weakness.

Sunlight is an excellent source of Vitamin D.

Sunlight is an excellent source of Vitamin D.

Vitamin E Deficiency

Vitamin E deficiency is very rare. Children who develop a severe deficiency may have neurological problems. Neurological symptoms can also be found in adults who are severely lacking.

Almonds are an abundant source of Vitamin E.

Almonds are an abundant source of Vitamin E.

Vitamin K Deficiency

Vitamin K deficiency is rare in healthy adults since the vitamin can be found in a wide variety of foods. However, individuals who take anticoagulant medications or have significant liver disease or damage are more at risk.

Symptoms include easy bruising or bleeding and tarry black stools.

Brussels sprouts are rich in Vitamin K.

Brussels sprouts are rich in Vitamin K.

Vitamin Facts

  • Vitamins are organic compounds.
  • An otherwise healthy person usually can get all the vitamins they need from a healthy diet.
  • There is debate about whether supplements are beneficial. Some supplements can lead to complications when combined with certain medications or when taken before surgery. It's always best to consult with your doctor before adding any vitamins or supplements.
  • Some vitamins are water-soluble while others are fat-soluble.
  • Dark, leafy, green vegetables are excellent sources of many vitamins, including A, C, E, and K.
  • Sunlight is an excellent source of Vitamin D.

Daily vitamin requirement chart.

VitaminDaily requirement

Vitamin A

600 µg

Vitamin B1

Men: 1.2 mg; Women: 1 mg

Vitamin B2

1.6 mg

Vitamin B3

18 mg

Vitamin B5

6 mg

Vitamin B6

2 mg

Vitamin B7

7 µg

Vitamin B9

400 µg

Vitamin B12

6 µg

Vitamin C

75 mg

Vitamin D

5 µg

Vitamin E

10 mg

Vitamin K

80 µg


This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

Questions & Answers

Question: Which vitamin gives more strength?

Answer: Vitamin B and Vitamin D are strong, but we need all of them.

Question: Why there a need of vitamins in our daily life?

Answer: Because they are essential nutrients.

Question: Why isn't there vitamin B8 on this list?

Answer: Well, it is a nonessential nutrient.

Question: What are vitamins?

Answer: Vitamins are organic molecules.

Question: Why isn't there vitamin B10 on this list?

Answer: It is a chemical component of the folate molecule produced by plants and bacteria.

Question: Which vitamin promotes health?

Answer: Vitamin C

Question: Which vitamin is the least essential?

Answer: Vitamin D and biotin are (relatively) inessential.

Question: Why is there no vitamin B4 on this list?

Answer: One substance was known as vitamin B4, but later experts decided that it should not be a vitamin.

Question: Why do we need to know about vitamins?

Answer: Because awareness is a key to good health.

Question: What is the ATC code name for vitamin B6?

Answer: Its ATC code is A11HA02.

Question: Can you tell me briefly about minerals?

Answer: Minerals are essential nutrients. They are needed in fairly substantial amounts for proper health.

Question: Which vitamin increases height?

Answer: Vitamin B1

Question: Why vitamins are important?

Answer: They are essential nutrients. We need them for good health.

Question: What does osteomalacia mean?

Answer: Softening of the bones, typically through a deficiency of vitamin D or calcium.

Question: Which vitamin is helpful for eyesight?

Answer: Vitamin A is good for the eyes.

Question: What are vitamins useful for?

Answer: Vitamins are essential nutrients. They perform hundreds of roles in your body. They heal wounds, bolster your immune system, convert food into energy and repair cellular damage.

Question: Are taking too many vitamins dangerous?

Answer: Vitamin overdose can be harmful. For instance, too much vitamin C could cause nausea, diarrhea, and stomach cramps.

Question: Are vitamins more important than minerals?

Answer: Well, I'd say that both are important for wellness.

Question: Is there a vitamin that acts as an enzyme?

Answer: Members of the vitamin B complex serve as coenzymes that assist every cell in the human body.

Question: Since there is no yoghurt in this list, does that mean its not healthy?

Answer: No. Yogurt is generally good for health.

Question: Which vitamins take care of sickle cell patients and stop them from having pain?

Answer: Vitamin B6 and vitamin B12.

Question: Why are there so many vitamin Bs?

Answer: Even though symptoms of deficiency of each vitamin B are similar, each and every B vitamin is a unique chemical. Different B vitamins perform different functions in the body.

Question: Which vitamins contain sulfur?

Answer: Thiamine, lipoic acid, and biotin.

Question: How do vitamins work?

Answer: Vitamins are chemical compounds. They react with various chemical compounds in the body, thereby performing various vital functions.

© 2013 Srikanth R


Srikanth R (author) on March 26, 2019:


Billo swag on March 26, 2019:

Thank you sir

Srikanth R (author) on January 31, 2019:


Rizwan on January 31, 2019:

Thanks This is very helpful

Srikanth R (author) on December 03, 2018:

Thank you.

Adanech on December 03, 2018:

it's nice and information

Srikanth R (author) on September 25, 2018:


Jyotirmoy on September 24, 2018:

Very helpful thanku

Srikanth R (author) on September 15, 2018:


J.A.mujahid on September 15, 2018:

helpful thank you

Srikanth R (author) on August 30, 2018:

Thank you.

Aryan on August 30, 2018:

Amazing work thank you

Srikanth R (author) on August 27, 2018:

Thank you.

Vaibhav jadhav on August 27, 2018:


Srikanth R (author) on July 14, 2018:

Thank you.

Japhet Chawang on July 13, 2018:

Very informative. Good effort sirji, u deserve applause. Looking forward for more updates.

Srikanth R (author) on June 26, 2018:

Thank you.

Ashish on June 26, 2018:

Very informative

Srikanth R (author) on June 23, 2018:

No. I am not.

prity on June 23, 2018:

are u a doctor?

Srikanth R (author) on June 23, 2018:

Thank you.

prity on June 22, 2018:

it's nice and informative

Srikanth R (author) on June 17, 2018:


Ashutosh on June 16, 2018:

Thanks my holiday homework is done

Srikanth R (author) on June 10, 2018:

Even though I have a thorough understanding of nutrition, currently I am not practicing. You need to consult a practicing nutritionist.

Stacy the grt on June 10, 2018:

R u a nutritionist?? If yes, then can I ask u about a problem???

Srikanth R (author) on May 26, 2018:

Thank you.

Angela on May 26, 2018:

I want more functions of all the vitamins,as well as their deficiency, but ur note is very simple and understandable

Srikanth R (author) on April 06, 2018:

Thank you.

Google user on April 06, 2018:

Quite helpful !

Covered almost all the stuff i needed !

Thanks !

Srikanth R (author) on March 30, 2018:


Maaz Al Razy on March 29, 2018:

Thank you for sharing us :-)

Srikanth R (author) on March 23, 2018:


ompraksh paswan on March 22, 2018:

Thank u for helping us

lihlizulu ntini on March 22, 2018:

very educational indeed. I enjoyed learning so much. shout out to LAVENY!!!

#@CJR primary in Gweru and it rocks!!


Srikanth R (author) on February 08, 2018:

Thank you Harsh.

Harsh on February 08, 2018:

Excellent job srikanth sir. I liked ur article and I expect more articles for other matters too so I can search fornur website .well done!

Srikanth R (author) on January 09, 2018:

Thank you.

Jaideep sharma on January 09, 2018:

NYC SIR simple and Clear topic on Vitamins

Srikanth R (author) on October 24, 2017:


Rushikesh Sathe on October 24, 2017:

Thanx SIR

Srikanth R (author) on October 23, 2017:


Prerna on October 23, 2017:

Thxx alot Sir it really helped me with my projects such a simple n easy language

Srikanth R (author) on July 04, 2017:

Thank you.

Rudra Teja Reddy on July 04, 2017:

This is such a simple way to know vitamins and their function. It is easy to know thank you for this information. Done a great job.

Srikanth R (author) on May 22, 2017:


Genesis Johnson on May 22, 2017:

Nice Work and very imformative


Srikanth R (author) on September 01, 2016:


PHANI KUMAR M V on September 01, 2016:

SIMPLY SUPERB. Covered most of the information a layman needs. Thank you.

Srikanth R (author) on August 17, 2016:


Brian Koome on August 17, 2016:

The article is quite informative. I have now known some things I didn't know.

Thank you much.

ahmed abdelgaid from egypt on December 15, 2014:

I absolutely will have to after reading this.

Srikanth R (author) on August 26, 2013:

Thank you!

LAKSHMI.S on August 24, 2013:


Srikanth R (author) on July 27, 2013:

Ok. :-)

David from Birmingham, UK on July 25, 2013:

No; sorry srirad. I meant your question at the top which says 'How do you get your vitamins? through natural sources because that is the right way, or I take vitamin supplements'. Presumably that is talking about all vitamins? And my answer to that is 'both'. :)

Srikanth R (author) on July 25, 2013:

I am glad you liked the article. Thank you.

Srikanth R (author) on July 25, 2013:

Well... That question and options were created keeping the importance of sunlight as a source of vitamin D in mind.

David from Birmingham, UK on July 24, 2013:

An excellent and very comprehensive hub on vitamins. Vitamin D can also be obtained from some food sources such as oily fish and eggs. And I couldn't do your quiz at the top because my answer is both :)