Many people want to know what is vitamin? Which foods have which vitamins? What are the symptoms of vitamin deficiency? How can we effectively prevent vitamin deficiency?

So, What is vitamin exactly?

Vitamin is a large class of organic substances with different chemical structures and physiological functions. It is a rare organic substance that humans and animals must obtain from food to maintain normal physiological functions.

They have an extremely important physiological mission. They are naturally found in food. The body cannot be unable to synthesize vitamins. Although the human body needs not much, and they do not participate in forming organ tissue and do not provide energy to the human body, they each have special physiological functions. They play an important role in the growth, metabolism, and development of the human body.

What is vitamin: A, B, C, D ,E and K
What is vitamin: A, B, C, D, E and K


Usually, we divide vitamins into two categories:

Two categories of vitamins

  1. Water-soluble vitamins: vitamin C, vitamin B family.
  2. Fat-soluble vitamins: vitamins A, D, E, K and so on.

Vitamins A, B, C, D, E and other groups are divided into sub-groups like 1, 2, 3, 4, and 5. Let’s take a look at the importance of various vitamins and how to get them.


Vitamin Navigation

Vitamin A | Vitamin B (B1 B2 B3 B6 B7 B12) | Vitamin C | Vitamin D | Vitamin E | Vitamin K

Vitamin A: Good for the eyes.

Typical patients: Dry eye patients

What is vitamin A?

Vitamin A is a raw material for rhodopsin in the eye and a necessary material for skin tissue. In the absence of vitamin A, the human body will develop dry eye disease and night blindness.

The known vitamin A has two types: A1 and A2. Vitamin A1 is found in the liver, blood and the retina of the eyeball, also known as retinol. It is a fat-soluble pale yellow flaky crystal. Vitamin A2 is mainly found in the liver of freshwater fish. Vitamin A1 and vitamin A2 are usually a golden yellow oily.

The daily requirement for vitamin A in adults is about 1 mg per day.

Vitamin A deficiency symptoms:

  • Rough skin
  • Itching
  • Nails appear deep white lines
  • Dry hair
  • Memory loss
  • Restlessness and insomnia
  • Dry eye conjunctiva
  • Urinary tract stones.

Which foods contain vitamin A?

  • Beef Liver
  • Eggs
  • Red and yellow vegetables
  • Fruits
  • Cod liver oil

You may find more detail about vitamin A, intoxication, and deficiency in this article “Vitamin A: Everything You Should Know“.


Vitamin B: Promotes the metabolism of the human body.

Typical patients: Susceptible to stomatitis and dermatitis

What is vitamin B?

Vitamin B family has a large branch family. It is closely related to the cellular metabolism of the human body. Vitamin B is like a spark plug in a car. Once it is lacking, the metabolism of the human body will occur “irregularities in the oil path”, which is prone to fatigue and discomfort. Vitamin B is the most widely known vitamin, divided into more than 10 sub-types.

Vitamin B1

What is vitamin B1?

The physiological function of vitamin B1 is to increase appetite and maintain normal nerve activity. Lack of it can cause beriberi, neurodermatitis and other diseases. It is widely found in rice bran, egg yolk, milk, tomato and other foods, and can now be artificially synthesized.

The daily requirement for vitamin B1 in adults is about 2 mg per day.

Vitamin B1 deficiency symptoms:

  • Too sensitive to sound
  • Intermittent soreness in the calf
  • Suffering from beriberi
  • Neurodermatitis

Which foods contain vitamin B1?

  • Beans
  • Cereals
  • Nuts
  • Fruits
  • Milk
  • Leafy vegetables


Vitamin B2

What is vitamin B2?

Vitamin B2 is abundantly found in foods such as grains, vegetables, milk, and fish. In the absence of vitamin B2, the human body is susceptible to diseases such as stomatitis, dermatitis, and microvascular hyperplasia.

The daily requirement for vitamin B2 in adults is about 2 to 4 mg per day.

Vitamin B2 deficiency symptoms:

  • Inflammation of the mouth
  • Dermatitis
  • Scrotal inflammation
  • The limbs have a burning sensation
  • Excessively sensitive to light

Which foods contain vitamin B2?

  • Liver
  • Milk
  • Egg
  • Beans
  • Green vegetables


Vitamin B3

What is vitamin B3?

Vitamin B3, also known as niacin, is the most demanding of the B vitamins. It is not only a vitamin that maintains the health of the digestive system, but also an indispensable substance for sex hormone synthesis. For modern people who are stressed by life, it maintains the health of the nervous system and the functioning of the brain function, so it must not be ignored. People who are troubled by cholesterol can increase their intake of niacin to help alleviate the disease. When the skin is particularly sensitive to sunlight, it is often an early symptom of vitamin B3 deficiency. Vitamin B supplementation is also helpful for people who are often nervous, irritated, and even schizophrenic. Vitamin B3 is also needed for people with diabetes and hyperthyroidism.

The daily requirement for vitamin B3 in adults is about 2 to 4 mg per day.

Vitamin B3 deficiency symptoms:

  • Thick tongue coating
  • Lip swollen
  • Tongue pain
  • Lip pain
  • Increased dandruff
  • Oral mucosa dry

Which foods contain vitamin B3?

  • Cow liver
  • Meat
  • Bean
  • Mushroom


Vitamin B6

What is vitamin B6?

Vitamin B6 has functions such as inhibiting vomiting and promoting human body development. Lack of it can cause vomiting, cramps and other symptoms. B6 is generally found in foods such as yeast, liver, lean meat, cereals and cabbage.

The daily requirement for vitamin B6 in adults is about 1.5 to 2 mg per day.

Vitamin B6 deficiency:

Vitamin B6 is found in all kinds of foods, and intestinal bacteria can also synthesize vitamin B6. Therefore, people rarely have vitamin B6 deficiency.

What food contains vitamin B6?

  • Liver
  • Lean Meat
  • Cereals
  • Cabbage


Vitamin B7

What is vitamin B7?

The main role of vitamin B7 is to help human cells convert carbohydrates, fats, and proteins into usable energy. However, this is just one of its many features. Studies have shown that the role of vitamin B7 also includes helping diabetic patients control blood sugar levels and prevent nerve damage caused by diabetes.

The daily requirement for vitamin B7 in adults is about 0.01 to 0.03 mg per day.

Vitamin B7 deficiency:

Unlike most vitamins, inadequate B7 intake is not the only cause of the deficiency. Alcohol abuse can interfere with the absorption of this vitamin, and some genetic diseases may require you to increase your intake of vitamin B7.

Which foods contain vitamin B7?

Almost all foods contain at least a small amount of vitamin B7. However, some foods are more abundant.

  • Egg
  • Liver
  • Milk
  • Mushroom
  • Nuts


Vitamin B12

What is vitamin B12?

Vitamin B12 is an indispensable substance in human hematopoiesis. Lack of it can cause malignant anemia. Liver, lean meat, fish, milk, and eggs are sources of vitamin B12 for humans.

The daily requirement for vitamin B12 in adults is about 12 micrograms (1/1000 mg) per day.

Vitamin B12 deficiency:

  • Intermittent positional pain
  • Imbalance of movement
  • Fingers tingling
  • Dizziness


Which foods contain vitamin B12?

  • Liver
  • Lean Meat
  • Fish
  • Milk
  • Egg


Vitamin C: Benefits to the skin, bones, blood vessels, blood pressure.

Typical patients: various groups of people

What is vitamin C?

Vitamin C is currently the most widely marketed in vitamin health products. Like vitamin C tablets, vitamin C candy, and many skin care products all claim to contain vitamin C. The vitamin C has a strong effect on the skin, bones, blood vessels, and blood pressure. Taking vitamin C can improve your physical condition, from metabolism to disease prevention and treatment. Its function is not only to treat colds, beautify the skin, it also helps the body function and treat diseases.

The daily requirement for vitamin C in adults is about 50 to 100mg per day.


Vitamin C deficiency symptoms:

  • Easy to catch a cold, cough
  • Fatigue
  • Resistance drop to disease
  • Gingiva often bleeding
  • Difficult wound healing
  • The tongue has deep marks
  • Severe vitamin C deficiency can lead to sepsis

Which foods contain vitamin C?

Vitamin C is mainly found in fruits and vegetables.

  • kiwi
  • strawberry
  • orange
  • broccoli
  • tomato
  • green pepper
  • cucumber
  • citrus
  • grapefruit
  • red dates
  • jujube

You may find more detail about vitamin C, intoxication, and deficiency in this article “Vitamin C: Most important vitamin in the human body“.


Vitamin D: Promotes calcium absorption.

Typical patients: pregnant women, children, and adolescents especially need

What is vitamin D?

Vitamin D has the effect of regulating calcium, so it is necessary for the normal development of bones and teeth. Pregnant women, infants, and adolescents, in particular, need more vitamin D than normal adults.

The daily requirement for vitamin D in adults is about 400-800 IU(or 10-20 microgram).


Vitamin D deficiency symptoms:

If the body vitamin D is insufficient, the blood calcium and phosphorus below the normal value, and it will develop bone softens and deformity.

  • rickets (in children)
  • osteomalacia (in pregnant women)
  • Osteoporosis (in aged people)
  • Bone fracture easily
  • Bone and joint pain frequently

Vitamin D intoxication symptoms:

If excessive intake of vitamin D is harmful to the human body, it may cause the following symptoms.

  • Nausea
  • A headache
  • High blood pressure
  • Frequent urination
  • Other symptoms

Which foods contain vitamin D?

Cod liver oil
Animal liver
Sunbathing (Not food 😀 )

You may find more detail about vitamin D foods in this article “Some advice for Foods High in Vitamin D“.


Vitamin E: Anti-oxidation, softening blood vessels.

Typical patients: patients with cardiovascular disease

What is vitamin E?

Vitamin E can resist free radical damage, prevent cancer and myocardial infarction. It promotes the production of vigorous sperm in men. Vitamin E is a powerful antioxidant.

The daily requirement for vitamin E in adults is about 100mg per day. If the intake exceeds 200 mg, side effects will occur.


Vitamin E deficiency

lack of vitamin E supply can lead to various mental disorders or emotional disorders.

Which foods contain vitamin E?

  • Wheat germ
  • Cottonseed oil
  • Soybean oil
  • Sesame oil
  • Corn oil
  • Pea
  • Sweet potato
  • Egg
  • Butter


Vitamin K: Essential effective coagulation vitamin.

Typical patients: premature babies, long-term antibiotics user, easy bleeding patients

What is vitamin K?

Natural vitamin K has been found in two ways: vitamin K1 and vitamin K2. Vitamin K promotes blood clotting, so it is also called coagulation vitamins. It is also involved in bone metabolism.

The daily requirement for vitamin K

0-1 (age)
10~20 mcg per day
1-11 (age)
11~60 mcg per day
>11 (age)
50~100 mcg per day
60~80 mcg per day


Vitamin K deficiency

  • Neonatal bleeding diseases, such as vomiting blood, intestines, umbilical cord and foreskin bleeding
  • Adult abnormal blood coagulation, leading to oral gingiva bleeding, nosebleeds, blood in the urine, stomach bleeding and blood under the skin;
  • Subcutaneous bleeding because of low prothrombin disease, the symptoms are prolonged blood clotting time
  • Chronic enteritis in children
  • Tropical dysentery


Source of vitamin K

K2 is synthesized from intestinal bacteria and accounts for 50-60% of total vitamin K. Some antibiotics inhibit the growth of bacteria in the body digestive tract and affect the production of vitamin K2.

K1 is mainly taking from foods, accounting for 40-50% of total vitamin K.

Which foods contain vitamin K?

  • Green leafy vegetables
  • Milk
  • Meat
  • Cow liver
  • Cod liver oil
  • Cheese
  • Seaweed
  • Spinach



To answer the question “what is vitamin“, We’ve summarized the vitamin definition,  benefits of vitamins, the symptoms of vitamin deficiency, and the types of vitamin supplement foods. Vitamins are essential micronutrients in the body. So, If you find that you or your family have these symptoms, we suggest going to the hospital to check for vitamin deficiency.


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