Vitamin D represents a group of five vitamers, or sub-types, which are organic compounds that share similar and related functions, but have different molecular structures. Vitamin D3 is the most physiologically important sub-type, which is readily synthesized in the skin when exposed to sunlight. Lack of appropriate sun exposure eventually leads to vitamin D deficiency symptoms, which are related to bones, muscles, mood and immunity. Vitamin D3 is also found in some foods, such as meats and fortified products, and is available as a supplement.
Vitamin D3
Vitamin D3, or cholecalciferol, is a hormone-like substance that is required for healthy bones, strong immunity and regulated moods. Vitamin D3 is produced within the skin when 7-dehydrocholesterol reacts to UV-B radiation at frequencies between 270 and 300 nm. All forms of vitamin D are fat-soluble, which means they are stored within the body when in excess and used when needed. The National Institutes of Health indicates that 400 IU per day of vitamin D is adequate for infants, whereas most adults require 600 to 700 IU, depending on age.
Causes of Deficiency
The most common cause of vitamin D deficiency is lack of appropriate sun exposure, according to "Human Biochemistry and Disease." The different forms of vitamin D are not widely found in foods; therefore, dietary consumption without supplementing usually cannot overcome a lack of sun exposure. Indoor life-styles, fear of skin cancer and use of sun-blocks are common reasons why people do not get enough UV-B exposure. Sun blocks prevent UV-B from penetrating the skin deep enough to produce D3. According to "Contemporary Nutrition," vitamin D deficiency in the United States is at epidemic proportions--with up to 80 percent of some ethnic groups, such as African Americans, being affected. Americans with darker skin have higher rates of deficiency, because their skin contains more melanin, which reduces D3 production.
Geography and Deficiency
Although tropical climates closer to the equator receive the specific UV-B frequencies from the sun daily, many locations in the United States only receive them during spring and summer months at specific times of the day. As such, people living in northern U.S. cities, especially Anchorage, have the highest incidence of vitamin D deficiency. Pollution, elevation and cloud cover also affect UV-B penetration. In ideal conditions, lighter skinned people can produce thousands of IU of D3 per hour when fully exposed to midday summer sunshine, according to "Nutritional Sciences." Thus, getting enough daily D3 may only require a few minutes of sun exposure, but this depends on time of year, time of day, amount of skin exposed and melanin content of the skin.
Symptoms of Deficiency
According to "Vitamins: Fundamental Aspects in Nutrition and Health," serum concentration of calcidiol is the best measure of vitamin D status, and levels below 37.5 nanomoles per liter are considered deficient. The initial symptoms of D3 deficiency may take many months to develop, but often include profuse sweating, anxiety, fatigue not resolved by sleep, disrupted sleep cycles, reduced appetite, mild depression, achy or cramping muscles and sore joints. More advanced symptoms include insomnia, moderate depression, reduced cognition, muscle weakness, bone pain, compromised immunity and bone malformation. Bone malformations from lack of D3 occur due to "softness" and are characterized by bowed legs and curved spinal deformities similar to scoliosis. This deficiency disease is referred to as rickets in children and osteomalacia in adults.
References
- National Institutes of Health: Office of Dietary Supplements: Vitamin D Fact Sheet
- "Human Biochemistry and Disease"; Gerald Litwack; 2008
- "Contemporary Nutrition"; Gordon M. Wardlaw; 2010
- "Nutritional Sciences"; Michelle McGuire; 2007
- "Vitamins: Fundamental Aspects in Nutrition and Health"; G. Combs; 2008
Member Comments