The main difference between fat-soluble and water-soluble vitamins is that fat-soluble vitamins dissolve only in fat, whereas water-soluble vitamins dissolve only in water.
Fat-soluble and water-soluble vitamins are two vitamin types that occur in the body. They differ in their dissolving properties.
Key Areas Covered
1. What are Fat Soluble Vitamins
– Definition, Structure, Types
2. What are Water Soluble Vitamins
– Definition, Structure, Types
3. Similarities Between Fat Soluble and Water Soluble Vitamins
– Outline of Common Features
4. Difference Between Fat Soluble and Water Soluble Vitamins
– Comparison of Key Differences
Fat Soluble Vitamins, Vitamin A, Vitamin B, Vitamin C, Vitamin D, Vitamin E, Vitamin K, Water Soluble Vitamins
What are Fat Soluble Vitamins
Fat-soluble vitamins are a type of vitamins that are only soluble in organic solvents. They include vitamins A, D, E, and K.
Vitamin A (retinol) is a lipid-soluble vitamin primarily found in animal sources that contain fat. Significantly, the body requires vitamin A for better eyesight, fresh skin, and healthy teeth. It is also important for lung health, bone strength, and immune strength. The liver and fat tissue store vitamin A for longer times. The liver releases vitamin A in the presence of zinc.
Vitamin D is a micronutrient essential for the body’s absorption of calcium, magnesium, and phosphate. Our body naturally produces this vitamin with exposure to the UV rays from the sunlight. It also enters the body through food and supplements. Vitamin D plays multiple roles in the body, as listed below.
- Maintenance of bones and teeth
- Supporting the immune system, brain, and the nervous system
- Helping the management of diabetes by regulating insulin levels
- Supporting the functioning of lungs and heart
- Regulating the expression of genes involved in the formation of cancers
Vitamin E, or α-tocopherol, is a fat-soluble vitamin in egg yolk and leafy vegetables. It also includes four tocopherols and four tocotrienols. However, vitamin E deficiency is not prominent as vitamin E readily occurs in dietary fat. But it causes nerve problems. Moreover, vitamin E scavenges hydroperoxyl radicals in lipids. Subsequently, this protects red cell membranes and nervous tissues.
Vitamin K is a group of vitamins that play a critical role in blood clotting. The three vitamin K forms are K1, K2, and K3. All of them comprise a similar structure and are fat-soluble. However, the two main forms of vitamin K are vitamin K1 (phylloquinone) and K2 (menaquinone). Importantly, the predominant form of vitamin K in the diet is vitamin K1, which plants produce. Some rich sources of vitamin K1 include leafy green vegetables such as kale, collard greens, spinach, turnip greens, broccoli, and Brussels sprouts. The main difference between vitamin K1 and K2 is the amount of absorption; the body can absorb less than 10% of the K1.
What are Water Soluble Vitamins
Water soluble vitamins are the vitamins that are washed away from the body. Therefore, the body does not easily store water-soluble vitamins. Also, the two types of water-soluble vitamins are vitamin B and vitamin C.
Vitamin B is a complex vitamin that is essential to the body as a cofactor. It is important for the growth and development, maintenance of healthy skin, proper function of nerves and the heart, and the formation of red blood cells. Moreover, the types of vitamin B include vitamin B1 or thiamin, vitamin B2 or riboflavin, vitamin B3, niacin or nicotinic acid, vitamin B5 or pantothenic acid, vitamin B6, pyridoxine, pyridoxal or pyridoxamine, vitamin B7 or biotin, vitamin B9 or folic acid, and vitamin B12 or various cobalamins.
Vitamin C, or ascorbic acid, is a water-soluble vitamin found in citrus fruits and vegetables. It is an important vitamin for tissue repair that prevents scurvy. Most animals synthesize their vitamin C, but humans do not. Hence, it is also a dietary supplement. Besides, α-ketoglutarate-dependent dioxygenases are the enzymes that use vitamin C as a cofactor. For instance, prolyl hydroxylases are one of those enzymes involved in collagen biosynthesis. The enzyme down-regulates hypoxia-inducible factor (HIF)-1 in regulating genes responsible for energy metabolism, tumor growth, neutrophil function, and apoptosis.
Similarities Between Fat-Soluble and Water-Soluble Vitamins
- Fat-soluble and water-soluble vitamins are the two types of vitamins that occur in the body.
- Their function is to be involved in metabolic reactions.
Difference Between Fat Soluble and Water Soluble Vitamins
Fat-soluble vitamins are soluble in organic solvents and are absorbed and transported in a manner similar to that of fats. In contrast, water-soluble vitamins refer to a group of vitamins that can dissolve in water.
Also, fat-soluble vitamins dissolve in fat, while water-soluble vitamins dissolve in water.
Additionally, fat-soluble vitamins require fat or bile salts for absorption, while water-soluble vitamins are easily absorbed.
Excretion in Urine
The excretion of fat-soluble vitamins does not occur, while the excretion of excess water-soluble vitamins occurs in urine.
The liver does not store fat-soluble vitamins, while the body does not store water-soluble vitamins.
Action as Coenzymes
Fat-soluble vitamins do not act as coenzymes, while water-soluble vitamins act as coenzymes.
Fat-soluble vitamins include vitamins A, D, E, and K, while water-soluble vitamins include vitamins B and C.
In brief, fat-soluble and water-soluble vitamins are the two vitamin types that occur in the body. Fat-soluble vitamins are only soluble in fat. Therefore, they require fat or bile salts for absorption. They are not secreted in urine. But they are stored in the liver. Also, they do not act as coenzymes. Importantly, fat-soluble vitamins include vitamins A, D, E, and K. In comparison, water-soluble vitamins only dissolve in water. Also, they are easily absorbed and excreted in urine. However, they are not stored in the body. But they act as coenzymes. Examples of water-soluble vitamins include vitamins B and C. Hence, the main difference between fat-soluble and water-soluble vitamins is their dissolving.
- National Research Council (US) Committee on Diet and Health. Diet and Health: Implications for Reducing Chronic Disease Risk. Washington (DC): National Academies Press (US); 1989. 11, Fat-Soluble Vitamins.
- Lykstad J, Sharma S. Biochemistry, Water Soluble Vitamins. [Updated 2023 Mar 6]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.