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What Is The Function Of Vitamin D

When Should I Pay Extra Attention To A Vitamin D Deficiency

FIVE Functions of Vitamin D

Our bodies make vitamin D when our skin is directly exposed to the sun, which is why people with low sun exposure are more prone to having lower levels of this vitamin. This can include people who live in countries with long periods of low sun exposure or people who regularly fully cover their bodies with clothing .

People with darker skin also need to keep their vitamin D levels in mind, because the skin pigment melanin reduces the production of vitamin D.

With age, our bodies have less capacity to make vitamin D and were also more likely to stay indoors, which reduces our sun exposure. Particularly, the elderly need to keep good intakes of vitamin D, as it helps to increase the calcium absorption from foods and to face health problems such as osteoporosis.

Physiological Functions Of Vitamin D: What We Have Learned From Global And Conditional Vdr Knockout Mouse Studies

The physiological role of vitamin D depends on calcium supply and calcium balance.

When the calcium balance is normal, the major target of vitamin D is intestine.

Vitamin D stimulates mainly active intestinal calcium transport mechanism.

During a negative calcium balance, bone effects of vitamin D become dominant.

The role of vitamin D in maintaining normocalcemia has priority over skeletal integrity.

The physiological role of vitamin D depends on calcium supply and calcium balance. When the calcium balance is normal, the major target of vitamin D is intestine. Vitamin D stimulates mainly active intestinal calcium transport mechanism. During a negative calcium balance, bone effects of vitamin D become dominant. Thus, the role of vitamin D in maintaining normocalcemia appears to have priority over skeletal integrity in these situations.

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Good Sources Of Vitamin D

From about late March/early April to the end of September, most people should be able to make all the vitamin D they need from sunlight.

The body creates vitamin D from direct sunlight on the skin when outdoors.

But between October and early March we do not make enough vitamin D from sunlight. Read more about vitamin D and sunlight.

Vitamin D is also found in a small number of foods.

  • fortified foods such as some fat spreads and breakfast cereals

Another source of vitamin D is dietary supplements.

In the UK, cows’ milk is generally not a good source of vitamin D because it is not fortified, as it is in some other countries.

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Vitamin D Is A Secosteroid

All forms of vitamin D belong to a family of lipids called secosteroids. Secosteroids are very similar in structure to steroids except that two of the B-ring carbon atoms of the typical four steroid rings are not joined, whereas in steroids they are.

The levels of each of the vitamin D metabolites are affected by a complex network of feedback mechanisms involving multiple enzymes and receptors, indicating vitamin D is regulated more like a steroid than a nutrient.

In the published literature, researchers sometimes distinguish between steroid and secosteroid, but not always.1)2)

Functions Of Vitamin D Unrelated To Calcium

Vitamin D Function and Deficiency

One of the most important findings after discovery of the receptor was that the receptor appeared not only in the target cells of enterocytes, osteoblasts, and distal renal tubule cells but also in parathyroid gland cells, skin keratinocytes, promyelocytes, lymphocytes, colon cells, pituitary gland cells, and ovarian cells . The expression of VDRs in these cells and not in skeletal muscle, heart muscle, and liver suggests that they must serve a function there . Although VDRs have been reported in liver, heart, and skeletal muscle , we and other groups failed to confirm those reports, with the use of specific monoclonal antibodies and other methods . This led to the investigation and discovery of functions of vitamin D not previously appreciated, which takes the vitamin D system beyond bone.

An important discovery was made by Suda et al , who demonstrated that the vitamin D hormone plays an important role in the terminal differentiation of promyelocytes to monocytes, which are precursors of the giant osteoclasts. Those authors also found that, when the cells differentiated into a functional cell line, growth ceased. This function did not involve calcium and phosphorus and was later shown to be fundamental to vitamin D-induced production of osteoclasts through the RANKL system .

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Vitamin D Plays A Role In Cell Proliferation Differentiation And Apoptosis

When we obtain vitamin D from food or synthesis in the skin, this compound then undergoes two conversions within the body.

First of all, the liver converts cholecalciferol into a compound called calcidiol. After this, calcidiol undergoes further conversion to calcitriol in the kidney .

Calcitriol is the active metabolite of vitamin D, and it binds to vitamin D receptors in the body.

These VDRs are present in almost all cells and tissues, and here, vitamin D acts as a steroid hormone and influences various genes. The vitamin can modify the expression ofor activate or inactivatethese different genes .

Among the different processes vitamin D can influence, it can modulate cell proliferation, differentiation, and apoptosis .

In simple English, this means that vitamin D helps to control the lifecycle of a cell, and it can promote cell death . Cell death refers to the destruction of cells that we no longer require or that threaten to become harmful .

Since vitamin D plays such an important role in these processes, it is thought that maintaining adequate vitamin D levels may hold importance for reducing cancer risk .

Key Point:

Vitamin D: Functions Health Benefits And Research

Last Updated on December 16, 2020 by Michael Joseph

Vitamin D is a hormone that is essential for human health.

This critical nutrient has many vital roles within the body, and we can obtain it from either sunlight, food, or supplements.

In this article, we examine the various functions and benefits of vitamin D, how much we require, and the best ways to get it.

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Vitamin D: Synthesis And Functions

Vitamin D is a fat-soluble vitamin that occurs in 2 main forms: ergocalciferol produced by plants and cholecalciferol derived from animal-based foods. The major source of vitamin D in humans is the cutaneous synthesis in the presence of sunlight. The exposure of 7-dehydrocholesterol to ultraviolet radiation B of wavelength 290-315 nm results in the formation of previtamin D in the skin, which is thermally isomerized to the stabler vitamin D . The vitamin D, whether synthesized in the skin or obtained from diet, undergoes 2 hydroxylation reactions: first in the liver by vitamin D 25-hydroxylase enzyme to form 25-hydroxyvitamin D, 25D, also known as calcidiol and then in the kidney by 1-hydroxylase to form an active metabolite, 1,25-dihydroxyvitamin D, 1,252D, also known as calcitriol. Both 25D and 1,252D may be metabolically inactivated through hydroxylation by 24-hydroxylase . The levels of vitamin D in serum are tightly regulated by a feedback mechanism of calcium, phosphorus, parathyroid hormone, fibroblast growth factor and vitamin D itself . The vitamin D status is evaluated by measuring the serum 25D level, which is its major circulating form. According to the US Endocrine Society guidelines, vitamin D deficiency is defined as a serum level of 25D below 20 ng/mL and vitamin D insufficiency as a serum 25D level between 21 and 29 ng/mL .

How Can I Help Prevent Vitamin D Deficiency

VITAMIN D: Its Role, Function, and Levels

The goals of treating and preventing the lack of vitamin D of treatment and prevention are the sameto reach and keep an adequate level of vitamin D in the body. Your healthcare provider will let you know if you need to take or keep taking vitamin D supplements. If so, they will also let you know how much you should take. You might also want to consider:

Eating more foods that contain vitamin D: See the vitamin D food sources table included in this article. Keep in mind that foods alone usually don’t meet the daily recommended levels of vitamin D.

Getting some exposure to sunshinebut not too much: Exactly how much sun exposure is needed isnt clear. 10 to 15 minutes of sun exposure two to three times a week to the face, arms, legs or back may be all that is needed to absorb a suitable amount of vitamin D. You might need more sun exposure if:

  • You are older.
  • You have a darker skin color.
  • You live in northern climates.

The use of sunscreen, and standing behind a window, prevents vitamin D from being produced in the skin. However, you should remember that too much sunshine increases the risk of skin cancer and ages the skin. That is why taking an appropriately dosed D supplement is far safer than intentionally getting routine sun exposure.

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Summary Of The Rnis For Vitamin D Byage Group

Table 21

RNIs for vitamin D according to age groups

Age group

Lactating women

5aUnits: for vitamin D, 1 IU = 25 ng, 40 IU = 1µg, 200 IU = 5 µg, 400 IU = 10 µg,600 IU = 15 µg, 800 IU = 20 µg for 25-OH-D, 1 ng/ml= 2.5 nmol/l,10 ng/ml = 25 nmol/l, 11 ng/ml = 28.5 nmol/l ,30 ng/ml = 75 nmol/l , 60 ng/ml = 150 nmol/l .

Skin Synthesis And Sunlight

This is the source that provides your body with the most vitamin D. Solar ultraviolet radiation stimulates vitamin D3 production in the epidermis.

According to current scientific studies, five to 15 minutes of direct sun exposure on the face and arms is enough to prevent vitamin D deficiency.

However, some factors can hinder this synthesis:

  • As we get older, we lose the ability to synthesize vitamin D.
  • The darker your skin, the more you need to expose yourself to the sun.
  • Sun protection factors greater than eight make it difficult for the suns rays to penetrate the skin.
  • The intensity of sunlight: It isnt the same during the winter as it is during the summer, nor in all regions.

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Getting Vitamin D From Food

Most foods dont contain much vitamin D so its hard to get enough vitamin D from food alone.

Foods which contain vitamin D include:

  • oily fish such as salmon, sardines, mackerel, trout
  • red meat
  • liver and fish liver oil
  • egg
  • foods with vitamin D added such as most fat spreads, some breakfast cereals and some plant-based alternatives to milk. Check the labels.
  • infant formula which has vitamin D added to make sure babies get enough.

As most of these foods are animal products, its harder to get vitamin D from food if you are vegan or vegetarian. Plant-based sources of vitamin D include sun-exposed mushrooms and fortified foods such as vegetable spreads, breakfast cereals and plant based dairy alternatives.

In the UK, cows’ milk is generally not a good source of vitamin D because it isn’t fortified, as it is in some other countries. There are some yoghurts which have been fortified, but check the label as they can also be high in saturated fat and so should be avoided.

Understanding Vitamin D Metabolism & Function

Vitamin D Function / Figure 1 from Vitamin D and immune ...

Vitamin D is a steroid hormone involved in the intestinal absorption of calcium and the regulation of calcium homeostasis, bone differentiation and immune response. The term vitamin D refers to several different forms of this vitamin.

There are two major types of vitamin D:

  • Vitamin D2 which is synthesized by plants and is not produced by the human body.
  • Vitamin D3 which is made in large quantities in the skin when sunlight strikes bare skin. It can also be ingested from animal sources.
  • The storage type of vitamin D, namely 25- hydroxy vitamin D, is formed in the liver. The hormone 1,25-dihydroxy vitamin D is formed in a second hydroxylation step in the kidney. The responsible enzyme, the kidney 1 -hydroxylase, is subjected to a rigid control through hormones and its activity is influenced by the serum concentrations of calcium and phosphate.

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    What Is Cystic Fibrosis

    Cystic fibrosis is a genetic disease that causes sticky, thick mucus to build up in organs, including your lungs and pancreas.

    If you dont have CF, the mucus that lines organs and body cavities, such as your lungs and nose, is slippery and watery. If you do have CF, thick mucus clogs the airways and makes it difficult to breathe.

    Mucus also blocks the ducts in the pancreas, causing problems with digesting food. Babies and children who have CF might not be able to absorb enough nutrients from food. CF, which is chronic and progressive , also affects your liver, sinus, intestines and sex organs.

    Theres also a form of disease called atypical cystic fibrosis. Its different from classic CF because its a milder form and may only affect one organ. The other atypical thing about it is that it usually comes on much later in life. Typical or classic CF generally shows up in the first few years of a childs life.

    Vitamin D Boosts Weight Loss

    Consider adding vitamin D supplements to your diet if youre trying to lose weight or prevent heart disease. You can find a great selection of vitamin D supplements on .

    In one study, people taking a daily calcium and vitamin D supplement were able to lose more weight than subjects taking a placebo supplement. The scientists said the extra calcium and vitamin D had an appetite-suppressing effect.

    In another study, overweight people who took a daily vitamin D supplement improved their heart disease risk markers.

    Many factors can affect your ability to get sufficient amounts of vitamin D through the sun alone. These factors include:

    • Being in an area with high pollution
    • Using sunscreen
    • Spending more time indoors
    • Living in big cities where buildings block sunlight
    • Having darker skin.

    These factors contribute to vitamin D deficiency in an increasing number of people. Thats why its important to get some of your vitamin D from sources besides sunlight.

    The symptoms of a vitamin D deficiency in adults include:

    • severe bone or muscle pain or weakness that may cause difficulty climbing stairs or getting up from the floor or a low chair, or cause you to walk with a waddling gait
    • stress fractures, especially in your legs, pelvis, and hips

    Doctors can diagnose a vitamin D deficiency by performing a simple blood test. If you have a deficiency, your doctor may order X-rays to check the strength of your bones.

    • salmon

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    The Functions Of Vitamin D And Its Role In Health

    According to information published in the International Journal for Vitamin and Nutrition Research, the most important functions of vitamin D are the following. Overall, this vitamin:

    • Helps maintain calcium and phosphorus balance.
    • Increases calcium absorption from the intestine.
    • Plays a role in cell development.
    • Is a powerful modulator of the immune system.
    • Plays a role in the transmission of nerve impulses to the muscle.

    Theres a clear relationship between the functions of vitamin D and bone health. A severe deficiency can manifest itself as rickets in children or osteomalacia in adults.

    Although these conditions arent common nowadays, osteoporosis is increasingly prevalent. Normal vitamin D levels can prevent the development of this disease that weakens bones and increases the risk of fractures.

    However, in recent years, researchers have studied its role in other health aspects.

    More and more is known about its possible role in the development of autoimmune diseases , high blood pressure, cardiovascular diseases, and some types of cancer. A study published in the journal Portuguese Medical Act stated this.

    What Are The Functions Of Vitamin D

    Vitamin D – Metabolism, Function, and Deficiency


    . Also asked, what is the function of vitamin D in the body?

    Your body must have vitamin D to absorb calcium and promote bone growth. Too little vitamin D results in soft bones in children and fragile, misshapen bones in adults . You also need vitamin D for other important body functions.

    Subsequently, question is, what happens when your vitamin D is low? Symptoms of bone pain and muscle weakness can mean you have a vitamin D deficiency. Yet, even without symptoms, too little vitamin D can pose health risks. Low blood levels of the vitamin have been associated with the following: Increased risk of death from cardiovascular disease.

    Herein, what is are the main functions of vitamin D quizlet?

    To maintain the normal range of calcium and phosphorus in the blood. inadequate calcium intake, inefficient calcium absorption in the intestine, or poor conservation of calcium by the kidneys.

    What is the difference between vitamin D and d3?

    Vitamin D3 Comes from Animals, Vitamin D2 from PlantsThe two forms of vitamin D differ depending on their food sources. Vitamin D3 is only found in animal-sourced foods, whereas D2 mainly comes from plant sources and fortified foods. Since vitamin D2 is cheaper to produce, it’s the most common form in fortified foods.

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    How Much Vitamin D Is Enough

    Adults and children over the age of one need 10mcg of vitamin D per day. This is the same for everyone, including people at risk of vitamin D deficiency and women who are pregnant or breastfeeding.

    Babies up to one year old need 8.5-10mcg of vitamin D per day. Find out more about how you can reach this from the NHS.

    Molecular Mechanisms Of Vitamin D Actions

    The vitamin D hormone functions through a single vitamin D receptor , which has been cloned for several species including humans, rats, and chickens. It is a member of the class II steroid hormones, being closely related to the retinoic acid receptor and the thyroid hormone receptor . It, like other receptors, has a DNA-binding domain called the C-domain, a ligand-binding domain called the E-domain, and an F-domain, which is one of the activating domains. Despite many statements to the contrary in the literature, a single receptor appears to mediate all of the functions of vitamin D, which complicates the preparation of analogs for one specific function rather than another. The human receptor is a 427-amino acid peptide, whereas the rat receptor contains 423 amino acids and the chicken receptor contains 451 amino acids. This receptor acts through vitamin D-responsive elements , which are usually found within 1 kilobase of the start site of the target gene. The VDREs, which are shown in , are repeat sequences of 6 nucleotides separated by 3 nonspecified bases. It is now clear that the 5 arm of this sequence binds the retinoic acid X receptor and the 3 arm binds the VDR. Of all of the genes identified to date, the most powerfully regulated is the CYP24 or 24-hydroxylase enzyme, which is responsible for the degradation of vitamin D . The programming of its own destruction is thus an important aspect of this endocrine system, which uses one of the most potent ligands known.

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