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Related Concept Videos

Role of Skin in Vitamin D Synthesis01:23

Role of Skin in Vitamin D Synthesis

The skin plays a crucial role in the synthesis of vitamin D, a vital nutrient for various physiological processes in the body. Vitamin D is unique because it can be synthesized in the skin through a series of chemical reactions triggered by exposure to ultraviolet B (UVB) radiation from sunlight.
The solar UV B rays (290-315 nm) are absorbed by the skin, and 7-dehydrocholesterol (provitamin D3) photolyzes it to previtamin D3, which undergoes a rapid transformation to vitamin D3(cholecalciferol).
Role of Vitamins in Maintaining Bone Health01:25

Role of Vitamins in Maintaining Bone Health

The growth and maintenance of bone are regulated by a combination of nutritional factors, including vitamins, such as vitamin A, B12, C, D, and K.
Vitamin A
Vitamin A is involved in the process of bone remodeling. Retinoic acid, the active metabolite of Vitamin A, has nuclear receptors in osteoblasts and osteoclasts, which are involved in bone remodeling.
Vitamin B12
Vitamin B12 acts as a cofactor during the formation of osteoblast-related proteins, such as osteocalcin. Vitamin B12 plays a role...
Connective Tissue Cell Types01:22

Connective Tissue Cell Types

Connective tissue develops from the mesoderm of a developing embryo and consists of cells, fibers, and ground substance: a gel-like material containing large complexes of carbohydrates and proteins. Connective tissue was first identified as a separate tissue family in the 18th century, and Johannes Peter Muller coined the term connective tissue.
Fat cells (adipocytes), smooth muscle cells (myoblasts), and bone cells (osteoblasts) are some connective tissue cell types. Some immune system cells...
Vitamins01:30

Vitamins

Vitamins, derived from the Latin word for life, are essential organic substances required in small quantities for optimal growth and overall well-being. Unlike other organic nutrients, vitamins don't act as sources of energy or building materials but rather facilitate these nutrients' utilization by the body. Vitamins are predominantly coenzymes, assisting enzymes in specific chemical actions, like the oxidation of glucose for energy involving B vitamins. Most vitamins are not produced in our...
Decreased Body Temperature01:29

Decreased Body Temperature

A decreased body temperature can occur in patients with hypothermia and frostbite. Heat loss with extended cold exposure overpowers the body's ability to create heat, resulting in hypothermia. Core temperature readings help classify hypothermia. Mild hypothermia is temperatures between 32 °C (89.6 °F) and 35°C (95 °F) and is caused by impaired thermoregulation. Moderate hypothermia is temperatures between 28 C (82.4 °F) and 32 °C (89.6 °F) caused by sustained extreme cold exposure, and severe...

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Vitamin D supplementation during Antarctic winter.

Scott M Smith1, Keri K Gardner, James Locke

  • 1Space Life Sciences Directorate, NASA Johnson Space Center, Houston, TX 77058, USA. scott.m.smith@nasa.gov

The American Journal of Clinical Nutrition
|February 20, 2009
PubMed
Summary

This study found that daily vitamin D supplementation of 2000 IU effectively raised vitamin D levels in individuals with limited sun exposure. These findings support recommendations for space travelers and others needing adequate vitamin D.

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Area of Science:

  • Human Physiology
  • Nutritional Science
  • Space Medicine

Background:

  • Limited ultraviolet B (UVB) light exposure, common in space travel, can lead to insufficient vitamin D levels.
  • Optimal serum 25-hydroxyvitamin D [25(OH)D] concentrations are considered to be greater than or equal to 80 nmol/L.

Purpose of the Study:

  • To assess the efficacy of three distinct vitamin D dosages in achieving and maintaining serum 25(OH)D levels above 80 nmol/L.
  • To provide evidence-based vitamin D supplementation guidelines for individuals with restricted UVB exposure.

Main Methods:

  • A 5-month prospective, randomized, double-blind study was conducted during Antarctic winter with zero UVB radiation.
  • 55 participants were randomized into three groups receiving 2000 IU/d, 1000 IU/d, or 400 IU/d of vitamin D.
  • Blood samples were collected approximately every two months to monitor 25(OH)D levels.

Main Results:

  • After 5 months, the 2000 IU/d group achieved an average 25(OH)D level of 71 ± 23 nmol/L.
  • The 1000 IU/d and 400 IU/d groups reached average levels of 63 ± 25 nmol/L and 57 ± 15 nmol/L, respectively.
  • A control group not taking supplements showed a decrease in 25(OH)D to 34 ± 12 nmol/L.

Conclusions:

  • Daily vitamin D supplementation, particularly at 2000 IU, can significantly increase serum 25(OH)D levels in individuals with limited UVB exposure.
  • Findings support the development of evidence-based vitamin D recommendations for space crews.
  • The study's implications extend to polar workers, the elderly, and others with reduced sun exposure.