vitamin D

Examples of vitamin D in the following topics:

• Metabolic Functions

  • Vitamin D refers to a group of fat-soluble steroids responsible for increasing intestinal absorption of calcium, iron, magnesium, phosphate, and zinc.
  • Vitamin D deficiency is associated with impaired bone development in children, which leads to the development of rickets and a softening of bones in adults.
  • Deficiency in vitamin D has been termed a modern disorder associated with both a poorer diet and reduced time spent outside.
  • Vitamin D is produced in the two innermost strata of the epidermis, the stratum basale and stratum spinosum.
  • Vitamin D from the diet or that is synthesized by the body is biologically inactive; activation requires enzymatic conversion in the liver and kidney.

• Osteomalacia and Rickets

  • Women who avoid sun exposure have very low levels of vitamin D.
  • Women who wear a burqa can have undetectable levels of vitamin D despite living in a sunny region.
  • The predominant cause is a vitamin D deficiency.
  • Vitamin D is required for proper calcium absorption from the gut.
  • Treatment involves increasing dietary intake of calcium, phosphates, and vitamin D.

• Lipid Soluble Vitamins

  • Vitamin D 5 to 10 μg ( upper limit ca. 2000 μg)
  • From this data it is clear that vitamins A and D, while essential to good health in proper amounts, can be very toxic.
  • Vitamin D, for example, is used as a rat poison, and in equal weight is more than 100 times as poisonous as sodium cyanide.
  • The structure of vitamin D can be described as a steroid in which ring B is cut open and the remaining three rings remain unchanged.
  • The precursors of vitamins A and D have been identified as the tetraterpene beta-carotene and the steroid ergosterol, respectively.

• Onset, Duration, and Half-Life of Hormone Activity

  • Vitamin D is a hormone that has a half-life of one to two months.
  • If one obtains vitamin D solely through sun (UVB) exposure during the summer months, serum vitamin D levels will be critically low by late winter.
  • This is one reason why current recommendations are to take vitamin D supplements in order to maintain serum vitamin D levels throughout the year.

• Bone and Calcium Homeostasis

  • Supplementation with vitamin D and calcium slightly improves bone mineral density.
  • Vitamin D is converted to calcidiol in the liver.
  • Part of the calcidiol is converted by the kidneys to calcitriol, the biologically active form of vitamin D.

• Introducing the Topic, Thesis, and Main Points

  • Vitamin D deficiency may be the hottest topic in nutrition today.
  • No one is disputing its importance: vitamin D helps with calcium absorption, promotes bone health, boosts immunity, and reduces inflammation.
  • That is why recent studies estimating that 10 to 75 percent of Americans are deficient in vitamin D are so scary.
  • I have prepared a chronological overview and analysis of methodologies for measuring vitamin D levels in the U.S. population, beginning with a study conducted at this university.
  • The opening of this speech names a topic (vitamin D deficiency), explains its importance, explains its relevance to the audience, and then states the purpose of the presentation—to investigate the improbably wide range of deficiency-rate estimates from different studies—and outlines the main points.

• Calcium and Phosphate Balance Regulation

  • In the typical Australian diet, there is about 1200 mg/d of calcium.
  • In addition, absorption is regulated by active vitamin D and increased amounts of this increase Ca++ absorption.
  • Absorption is controlled by vitamin D while excretion is controlled by parathyroid hormones.
  • However, the distribution from bone to plasma is controlled by both the parathyroid hormones and vitamin D.
  • This increases ionized calcium levels by increasing bone re-absorption, decreasing renal excretion and acting on the kidney to increase the rate of formation of active Vitamin D, thereby increasing gut absorption of calcium.

• Food Requirements and Essential Nutrients

  • Each vitamin has its own special role to play.
  • For example, vitamin D (added to whole milk or naturally-occurring in sardines), helps make bones strong, while vitamin A (found in carrots) helps with night vision.
  • Some fat-soluble vitamins include vitamin A, vitamin K, vitamin D, and vitamin E.
  • Unlike the other fat-soluble vitamins, vitamin D is difficult to obtain in adequate quantities in a normal diet; therefore, supplementation may be necessary.
  • Some water-soluble vitamins include vitamin B6, vitamin B12, vitamin C, biotin, folic acid, niacin, and riboflavin.

• Anticoagulants

  • However, they are also the main dietary source of vitamin K, which is necessary for blood clotting to occur.
  • However, if you are taking warfarin to prevent heart attacks, then it is necessary to control intake of leafy green vegetables since warfarin is an antagonist to vitamin K and could work improperly if the diet is high in vitamin K.
  • Coumadins such as warfarin are oral anticoagulant pharmaceuticals that antagonize the effects of vitamin K1.
  • Depletion of vitamin K by coumadin therapy increases risk of arterial calcification and heart valve calcification, especially if too much vitamin D is present.

• Absorption of Monosaccharides, Amino Acids, Dipeptides, Tripeptides, Lipids, Electrolytes, Vitamins, and Water

  • Glucose, amino acids, fats, and vitamins are absorbed in the small intestine via the action of hormones and electrolytes.
  • The fat soluble vitamins A, D, and E are absorbed in the upper small intestine.
  • The factors that cause malabsorption of fat can also affect absorption of these vitamins.
  • If intrinsic factor is missing, then Vitamin B12 is not absorbed and pernicious anemia results.
  • Of the water soluble vitamins, transport of Folate and B12 across the apical membrane are Na+ independent, but the other water soluble vitamins are absorbed by Na+ co-transporters.