CLINICAL KNOWLEDGE MAGAZINE
3 min read
Vitamins: Categorization, Sources, and Functions
Wojciech Wiśniewski
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Diets Premium Medical Expert • 23.03.2026
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Scientifically reviewed by a clinical dietitian:
This article has been peer-reviewed for adherence to IŻŻ, WHO, and PTGiP clinical nutritional standards.
| CLINICAL KNOWLEDGE MAGAZINE CLINICAL KNOWLEDGE MAGAZINE | min read 3 min |
| Diets Premium Medical Expert Wojciech Wiśniewski | Scientifically reviewed by a clinical dietitian 23.03.2026 |
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Key Takeaways
Vitamins are an indispensable component for the human body, influencing its growth, development, and well-being. In most cases, they are compounds of external origin that must be supplied through appropriate foods. Vitamin deficiencies, known as avitaminoses, cause a multitude of diseases resulting from disruptions of the body's internal processes. Is it possible to provide the necessary amounts of vitamins through a balanced diet? Against which factors do they specifically provide protection? In which products can the various types of vitamins be found?
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Categorization of vitamins
Vitamins are classified based on their physical properties, such as solubility, which include: – water-soluble vitamins: B1 (tiamin), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B12 (cyanocobalamin), C (ascorbic acid), biotin, folic acid; – fat-soluble vitamins: A (retinol and its derivatives), D (cholecalciferol), E (tocopherol), K (phyloquinone). It is assumed that the human body is capable of storing fat-soluble vitamins primarily in the liver. If the intake is too high, it can lead to hypervitaminosis with toxic effects on the body. On the other hand, excess water-soluble vitamins are excreted in urine, so an adequate intake from the diet must be ensured. Vitamins can also be arranged according to their structure. All B-group vitamins contain a nitrogen molecule and are therefore classified as nitrogenous compounds, while all other vitamins are considered to be nitrogen-free.
Tasks that vitamins carry out
The term 'vitamin' was introduced by Kazimierz Funk, a Polish scientist, in 1911. The name is derived from the combination of the two words vita (life) and amina (a substance of basic nature). This Polish scientist discovered and named vitamin B1, which is invaluable in the fight against beri-beri disease, a condition that results from disorders in carbohydrate metabolism and affects nerve and muscle tissue damage. This demonstrates how indispensable vitamins are for life and health. Fat-soluble vitamins are hydrophobic and polar molecules, whose structure and properties influence the functions they perform in the body, including the regulation of calcium-phosphorus metabolism and the blood clotting process. They are indispensable in the visual process and the growth of epithelial tissue. Water-soluble vitamins, on the other hand, are coenzymes or cofactors in many metabolic processes and participate in protein, fat, carbohydrate, and mineral metabolism.
The sources of nutrients
Nutrients are present in both plant and animal products. Seafood is rich in vitamins A and D, while walnuts and vegetable oils are a valuable source of vitamin E. Vitamin K can be found in leafy green vegetables and egg yolks. Full-grain products, liver, and yeast contain high amounts of vitamin B. Vitamin C, which possesses antioxidant properties, can be found in citrus fruits, red peppers, and wild rice. A diverse and colorful diet, based on fresh products, can provide the body with all the necessary nutrients.
Necessity of the body for vitamins
The necessity of the body for vitamins is highly variable and depends on its physiological condition, age, sex, and physical involvement. As previously mentioned, vitamins are substances that must be supplied from external sources. However, under specific physiological conditions, the human body is capable of synthesizing several of them from provitamins. These include vitamin A, synthesized from carotenoids, vitamin D3, formed from 7-dehydrocholesterol, and vitamin PP, as a derivative of tryptophan. The bacterial flora residing in the digestive tract is capable of synthesizing some vitamins from the B group and vitamin K.
Compilation of data on vitamins – table
Table 2. Vitamin requirements, functions of vitamins in the body Original compilation based on: Dietary norms for the population of Poland, ed. Jarosza M., Warsaw 2017. Although vitamins are not a source of energy for the body and are not a building material, they are indispensable for proper functioning. A one-sided diet, stress, and excessive physical activity can lead to a weakening of the body due to a deficiency in the required amounts of vitamins. It is crucial to incorporate as many foods as possible into the diet that contain individual vitamins. This way, one can enjoy good health and vitality for many years.
Wojciech Wiśniewski
Diets Premium Medical Expert
Member of the Diets Premium clinical editorial board. Specializes in medical diet therapy, metabolic health, and nutritional planning.
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