What are the functions of vitamins?
Vitamins and Minerals

What are the functions of vitamins?

Written by

Lauren Dobischok
12 April, 2023

Medically checked article All HOMED-IQ content is reviewed by medical specialists

Vitamins are organic compounds that are only needed by the body in small quantities, but perform very important functions in the body. The word vitamins is derived from the Latin word “vita”, which means life and highlights their importance for our health. There are 13 essential vitamins that your body needs to function. Since most vitamins do not naturally occur in our bodies, they must be obtained through the food we eat. Only vitamin D, also known as the sunshine vitamin, can be synthesized by humans themselves with the help of the sun’s UVB rays

A shortage of essential vitamins in the body is known as a deficiency and can cause health problems and unpleasant symptoms. Vitamin deficiency is most often caused by a diet lacking in certain nutrients or problems with the absorption of vitamins from food. Read on to learn more about the different types of vitamins, their role in the body, and foods that can help you get your daily intake. 

What are the essential vitamins? 

The 13 essential vitamins can be divided into fat-soluble and water-soluble vitamins. Fat-soluble vitamins are absorbed along with fat in the diet and can be stored to a limited extent in fatty tissue or in the liver (NCI). Fat-soluble vitamins can be stored in the body for long periods of time, where the body can access them as needed.

Fat-soluble vitamins include:

  • Vitamin A
  • Vitamin D
  • Vitamin E 
  • Vitamin K 

Water-soluble vitamins are absorbed through the intestinal wall and thus enter the blood directly. With the exception of vitamin B12, water-soluble vitamins are not stored in the body, meaning they must be taken in through diet daily (NCI). 

Water-soluble vitamins include:

  • Vitamin B1
  • Vitamin B2
  • Vitamin B3
  • Vitamin B5 
  • Vitamin B6
  • Vitamin B7
  • Vitamin B12
  • Vitamin B9 
  • Vitamin C

What is the function of vitamins?

Vitamins are essential for the maintenance of many bodily processes, such as wound healing, nerve function, and maintaining the immune system (Calderón-Ospina & Nava-Mesa, 2020; CDC, 2022). The following tables summarize each essential vitamin with their functions in the body and in which foods they are most commonly found.

Fat-soluble vitamins

Vitamin A  • Strengthens the body’s immune system
• Supports vision, especially in low light conditions
• Strengthens the development and maintenance of tissue
structures in the body (such as mucous membranes)
Beef liver
Sweet potato
Milk products 
Vitamin D • Helps maintain strong bones and teeth
• Supports muscle function and the immune system
• Is important for the absorption of calcium from food  
Oily fish
Milk products
Fortified soy products
Vitamin E • Is an antioxidant and protects sensitive cellular components
• Supports the immune system
Wheat germ oil
Sunflower seeds/oil
Vitamin K • Assists in blood clotting
• Helps heal wounds 
Green cabbage

Source: Amboss, 2022; NIH,2020

Water-soluble vitamins

 Vitamin C • Supports the production of collagen and the maintenance of healthy skin, bones, and blood vessels 
• Aids iron absorption in the intestine
• Supports wound healing 
Red bell pepper
Citrus (orange, kiwi lemon, grapefruit)
Thiamine (B1) • Favors the conversion of carbohydrates into energy 
• Supports the transmission of nerve signals
• Important for growth, development and function of cells
Fortified breakfast cereals
Riboflavin (B2) 
• Helps the body obtain energy from food
• Strengthens the skin
Fortified breakfast cereals
Milk, cheese
  Niacin (B3) • Assists the body in obtaining energy from food
• Supports the nervous system
• Strengthens the skin
Beef liver
Brown rice
Pantothenic Acid (B5) • Assists the body in obtaining energy from food and storing it
• Supports the formation of hemoglobin
Organ meats (liver, kidney)
Shiitake mushrooms
Nuts and seeds
 Vitamin B6 • Supports metabolism
• Promotes brain development
• Improves immune function
Beef Liver
Chicken Salmon
 Biotin (B8) • Supports skin and hair growth
• Promotes nervous system function
• Assists the body in obtaining energy from food
Organ meat
Sweet potatoes
 Folic Acid (B11)
• Supports the formation of red blood cells 
• Needed for brain function and the production of DNA/RNA
• Essential during pregnancy to prevent neural tube defects 
Dark leafy green vegetables such as spinach, asparagus, and broccoli
Whole grains
 Vitamin B12 • Production of red blood cells and DNA
• Supports the function of the nervous system  
Milk, yogurt, cheese
Fortified breakfast cereals

 (Amboss, 2022; NIH,2020)

How much of each vitamin do you need per day?

An individual’s daily vitamin requirements depend on his or her age, level of physical activity, and other environmental or lifestyle factors. In most cases, a person’s essential vitamin requirements can be obtained by a balanced and varied diet. There are also certain factors that increase vitamin requirements, such as during pregnancy and breastfeeding (NHS, 2020). Vitamin requirements can also increase due to nicotine and/or alcohol consumption, as well as when taking certain medications (UC San Diego, 2023; MSD, 2023).

Get tested for a vitamin deficiency

With a balanced diet, most people get adequate amounts of all essential vitamins. However, vitamin deficiencies can arise due to certain diets, medical conditions, or malnutrition. Problems with absorption of vitamins in the intestine or chronic diseases can also be a cause of a vitamin deficiency. An untreated vitamin deficiency may not initially cause any symptoms, but over time can cause a range of health problems. The symptoms of a vitamin deficiency are often very non-specific (such as fatigue or difficulty concentrating), which can make it difficult to detect. Blood tests can measure specific vitamin levels and provide clear insight into whether a deficiency exists or not.

If you have non-specific symptoms that could indicate a vitamin deficiency or are concerned that you might have a deficiency due to your diet, you should have your vitamin levels tested. This can be done with your GP or using a home test. Homed-IQ’s Vitamin Deficiency Test checks for three of the most common vitamin deficiencies; Vitamin D, Vitamin B12, and Folic Acid. This blood test can be taken from home before being sent to a certified laboratory for analysis. 

Are vitamin supplements necessary?

If you follow a balanced diet, it is generally not necessary to take vitamin supplements, as you obtain adequate amounts of essential vitamins through food. Vitamin supplements may be needed if your vitamin needs are increased, if you are unable to obtain enough vitamins through your diet, or if a medical condition causes a deficiency. If you have been diagnosed with a vitamin deficiency, you should consult your doctor before taking vitamin supplements, as excessive vitamin consumption can also negatively impact your health (NHS, 2022).

In summary, vitamins are essential to our health and help regulate many important functions in our bodies. Consuming a balanced and varied diet usually can meet essential vitamin requirements, but certain individuals may have increased needs that require vitamin supplementation. As a vitamin deficiency can have non-specific symptoms, testing vitamin levels provides clarity on whether a deficiency exists or not. 


AMBOSS. (2022). Vitamine – Wissen. https://www.amboss.com/de/wissen/Vitamine

Calderón-Ospina, C. A., & Nava-Mesa, M. O. (2020). B Vitamins in the nervous system: Current knowledge of the biochemical modes of action and synergies of thiamine, pyridoxine, and cobalamin. CNS Neuroscience & Therapeutics, 26(1), 5–13. https://doi.org/10.1111/cns.13207

Centers for Disease Control and Prevention. (2022, May 9). Critical Vitamins and Minerals. https://www.cdc.gov/nutrition/micronutrient-malnutrition/about-micronutrients/why-it-matters.html

MSD Manuals. (2023). Some Drugs That Cause Vitamin Deficiency. MSD Manual Consumer Version. https://www.msdmanuals.com/home/multimedia/table/some-drugs-that-cause-vitamin-deficiency

National Cancer Institute. (n.d.-a). NCI Dictionary of Cancer Terms. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/fat-soluble-vitamin

National Cancer Institute. (n.d.-b). NCI Dictionary of Cancer Terms. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/water-soluble-vitamin

National Institutes of Health. (2020). Dietary Supplement Fact Sheets. Dietary Supplement Fact Sheets. https://ods.od.nih.gov/factsheets/list-all/#V

NHS. (2020, February 14). Vitamins, supplements and nutrition in pregnancy. nhs.uk. https://www.nhs.uk/pregnancy/keeping-well/vitamins-supplements-and-nutrition/

NHS. (2020, August 3). Vitamins and minerals. nhs.uk. https://www.nhs.uk/conditions/vitamins-and-minerals/

UC San Diego. (2023). How Alcohol Affects You. https://studenthealth.ucsd.edu/resources/health-topics/alcohol-drugs/nutrition-endurance.html#:~:text=Alcohol%20use%20inhibits%20absorption%20of,%2C%20folic%20acid%2C%20and%20zinc.

About the author

Lauren Dobischok

Lauren is a health scientist and science communicator currently living in the Netherlands. Originally from Canada, she completed a Research Master’s in Health Sciences at the Netherlands Institute of Health Sciences at Erasmus University Rotterdam (NIHES) with a specialisation in epidemiology. Prior to her master’s degree, she completed a Bachelor’s degree in Health Sciences at Simon Fraser University. With a background in public health, her goal is to create accurate scientific content that is easy to understand and empowers people to make informed decisions. Within Homed-IQ, Lauren works as a Product Developer and Content Lead, working closely with physicians and scientists on medical devices for Homed-IQ’s new products and written communications.