That also means toxicity of water-soluble vitamins is rare. Deficiency of water-soluble vitamins is more common than fat-soluble vitamin deficiency because of this lack of storage. There is limited storage capacity in the body for water-soluble vitamins, thus making it important to consume these vitamins on a daily basis. While toxic levels are typically only achieved through vitamin supplements, if large quantities of fat-soluble vitamins are consumed, either through foods or supplements, vitamin levels can build up in the liver and fatty tissues, leading to symptoms of toxicity. On the flip side, the body’s storage capacity for fat-soluble vitamins increases the risk for toxicity. The ability to store these vitamins allows the body to draw on these stores when dietary intake is low, so deficiencies of fat-soluble vitamins may take months to develop as the body stores become depleted. The fat-soluble vitamins-vitamins A, D, E, and K-can be stored in the liver and the fatty tissues of the body. “Absorption of Fat-Soluble and Water-Soluble Vitamins.”įat-soluble and water-soluble vitamins also differ in how they are stored in the body. Because fat-soluble vitamins are absorbed along with dietary fat, if a meal is very low in fat, the absorption of the fat-soluble vitamins in that meal may be impaired.įigure 8.2. The bioavailability (i.e., the amount that gets absorbed) of these vitamins is dependent on the food composition of the diet. Fat-soluble vitamins are first incorporated into chylomicrons, along with fatty acids, and transported through the lymphatic system to the bloodstream and then on to the liver. Water-soluble vitamins are absorbed directly from the small intestine into the bloodstream. One major difference between water-soluble and fat-soluble vitamins is the way they are absorbed in the body. Classification of vitamins as water-soluble or fat-soluble. For example, water-soluble vitamins often act in the cytosol of cells (the fluid inside of cells) or in extracellular fluids such as blood, while fat-soluble vitamins play roles such as protecting cell membranes from free radical damage or acting within the cell’s nucleus to influence gene expression.įigure 8.1. Whether vitamins are water-soluble or fat-soluble can affect their functions and sites of action. Vitamins are traditionally categorized into two groups: water-soluble or fat-soluble. There is energy contained in the chemical bonds of vitamin molecules, but our bodies don’t make the enzymes to break these bonds and release their energy instead, vitamins serve other essential functions in the body. Vitamins are essential, non-caloric, organic micronutrients. Eventually, when scientists discovered that these compounds were not amines, the ‘e’ was dropped to form the term “vitamins.” 1 Classification of Vitamins He coined the term “vitamines” to describe these organic substances that were recognized as essential for life, yet unlike other organic nutrients (carbohydrates, protein, and fat), do not provide energy to the body. The name “vitamin” comes from Casimir Funk, who in 1912 thought “vital amines” (similar to amino acids) were responsible for preventing what we know now as vitamin deficiencies. After we review the classifications for vitamins and minerals, we will examine key vitamins and minerals based on their similar functions to further highlight the importance of how these micronutrients work together. These characteristics impact not only how we obtain them in our diets, but also how we absorb them and store them, as well as how we experience deficiencies or toxicities when too little or too much is consumed. And while many vitamins and minerals work together to perform various functions in the body, they are classified based on their independent characteristics. Vitamins and minerals are only needed in small quantities in the body, but their role is essential to overall health and proper functioning of all body systems.
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