An inquiry into “vitamin D17” leads to an important clarification in nutritional science. The term does not represent a recognized vitamin in any official capacity. Scientific and medical literature does not contain a substance designated as vitamin D17. The term’s usage likely stems from a misunderstanding or a simple typographical error.
Clarifying the Term Vitamin D17
The name “vitamin D17” is not found in nutritional science or medical dictionaries because it does not exist as a nutrient. The most probable source of this term is a misunderstanding of chemical nomenclature, specifically related to the structure of steroid molecules. Vitamin D is a group of fat-soluble secosteroids, meaning they are derived from a steroid precursor, cholesterol. This foundational molecule has a standardized carbon-numbering system used by chemists to identify specific atoms within its structure.
Within this system, the 17th carbon atom, often written as C17, holds a specific position in the molecule’s four-ring backbone. This designation is purely for chemical identification and does not define a type of vitamin. Therefore, while C17 is part of the vitamin D molecule’s structure, it does not signify a unique form of the vitamin itself.
Another simple explanation for the appearance of “vitamin D17” is a typographical error. It is highly possible that it is a mistake for “vitamin B17,” a controversial and non-recognized term for a chemical called amygdalin. Amygdalin is a compound found in apricot pits and is incorrectly promoted as a cancer treatment.
The Recognized Forms of Vitamin D
Science recognizes two primary forms of vitamin D that are relevant to human health: vitamin D2 and vitamin D3. These forms are distinct in their origin and chemical structure.
Vitamin D2, known as ergocalciferol, is derived from plant and fungal sources. It is synthesized when ergosterol, a compound in yeast and mushrooms, is exposed to ultraviolet light. As a result, fortified foods like some cereals and plant-based milks, as well as certain mushrooms, are common dietary sources of D2. This form is often used in prescription supplements.
Vitamin D3, or cholecalciferol, is the form synthesized by the human body and found in animal products. When the skin is exposed to ultraviolet B (UVB) radiation from sunlight, a compound called 7-dehydrocholesterol is converted into vitamin D3. Dietary sources of D3 include fatty fish like salmon and mackerel, egg yolks, and liver. Many over-the-counter supplements and fortified foods, such as cow’s milk, specifically use vitamin D3 because it is the type our bodies naturally produce.
Primary Functions of Vitamin D
The main role of vitamin D in the body is the regulation of calcium and phosphorus levels in the blood. It facilitates the absorption of these minerals from the intestine, a process that is necessary for building and maintaining strong bones. Without sufficient vitamin D, the body can only absorb about 10% to 15% of dietary calcium. When vitamin D levels are adequate, this absorption rate increases to 30% to 40%, ensuring that enough calcium is available for bone mineralization.
Vitamin D sends signals that help the body form hydroxyapatite crystals, the mineral complex that gives bones their strength and rigidity. By managing calcium balance, it supports the constant process of bone renewal and maintenance. This helps protect against conditions that weaken bones over time.
Beyond its role in bone health, vitamin D contributes to other bodily systems. It supports the normal functioning of the immune system, helping to regulate immune responses. The nutrient also plays a part in muscle function, which is linked to maintaining balance and reducing the risk of falls, particularly in older adults. These functions are secondary to its primary role in mineral regulation but are an area of ongoing research.