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What is vitamin D and what does it do?

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Vitamin D

Here is some valuable information about vitamin d taken from the office of dietary supplements website. The office of dietary supplements is a part of the American national institute of health. You can find the full fact sheet on vitamin d on the ODS website.

Vitamin D is a nutrient found in some foods that are needed for health and to maintain strong bones. It does so by helping the body absorb calcium (one of bone’s main building blocks) from food and supplements. People who get too little vitamin D may develop soft, thin, and brittle bones, a condition known as rickets in children and osteomalacia in adults.

Vitamin D is important to the body in many other ways as well. Muscles need it to move, for example, nerves need it to carry messages between the brain and every body part, and the immune system needs vitamin D to fight off invading bacteria and viruses. Together with calcium, vitamin D also helps protect older adults from osteoporosis. Vitamin D is found in cells throughout the body.

How much vitamin D do I need?

The amount of vitamin D you need each day depends on your age. Average daily recommended amounts from the Food and Nutrition Board (a national group of experts) for different ages are listed below in International Units (IU):

  • Birth to 12 months 400 IU
  • Children 1–13 years 600 IU
  • Teens 14–18 years 600 IU
  • Adults 19–70 years 600 IU
  • Adults 71 years and older 800 IU
  • Pregnant and breastfeeding women 600 IU

What foods provide vitamin D?

Very few foods naturally have vitamin D. Fortified foods provide most of the vitamin D in American diets.

  • Fatty fish such as salmon, tuna, and mackerel are among the best sources.
  • Beef liver, cheese, and egg yolks provide small amounts.
  • Mushrooms provide some vitamin D. In some mushrooms that are newly available in stores, the vitamin D content is being boosted by exposing these mushrooms to ultraviolet light.
  • Almost all of the U.S. milk supply is fortified with 400 IU of vitamin D per quart. But foods made from milk, like cheese and ice cream, are usually not fortified.
  • Vitamin D is added to many breakfast portions of cereal and to some brands of orange juice, yogurt, margarine, and soy beverages; check the labels.

Can I get vitamin D from the sun?

The body makes vitamin D when the skin is directly exposed to the sun, and most people meet at least some of their vitamin D needs this way. Skin exposed to sunshine indoors through a window will not produce vitamin D. Cloudy days, shade, and dark-colored skin also cut down on the amount of vitamin D the skin makes.

However, despite the importance of the sun to vitamin D synthesis, it is prudent to limit exposure of skin to sunlight in order to lower the risk of skin cancer. When out in the sun for more than a few minutes, wear protective clothing and apply sunscreen with an SPF (sun protection factor) of 8 or more. Tanning beds also cause the skin to make vitamin D but pose similar risks for skin cancer.

People who avoid the sun or who cover their bodies with sunscreen or clothing should include good sources of vitamin D in their diets or take a supplement. Recommended intakes of vitamin D are set on the assumption of little sun exposure.

What kinds of vitamin D dietary supplements are available?

Vitamin D is found in supplements (and fortified foods) in two different forms: D2 (ergocalciferol) and D3 (cholecalciferol). Both increase vitamin D in the blood.

Am I getting enough vitamin D?

Because vitamin D can come from the sun, food, and supplements, the best measure of one’s vitamin D status is blood levels of a form known as 25-hydroxyvitamin D. Levels are described in either nanomole per liter (nmol/L) or nanograms per milliliter (ng/mL), where 1 nmol/L = 0.4 ng/mL.

In general, levels below 30 nmol/L (12 ng/mL) are too low for bone or overall health, and levels above 125 nmol/L (50 ng/mL) are probably too high. Levels of 50 nmol/L or above (20 ng/mL or above) are sufficient for most people.

By these measures, some Americans are vitamin D deficient, and almost no one has levels that are too high. In general, young people have higher blood levels of 25-hydroxyvitamin D than older people and males have higher levels than females. By race, non-Hispanic blacks tend to have the lowest levels and non-Hispanic whites the highest. The majority of Americans have blood levels lower than 75 nmol/L (30 ng/mL).

Certain other groups may not get enough vitamin D:

  • Breastfed infants, since human milk is a poor source of nutrients. Breastfed infants should be given a supplement of 400 IU of vitamin D each day.
  • Older adults, since their skin, doesn’t make vitamin D when exposed to sunlight as efficiently as when they were young, and their kidneys are less able to convert vitamin D to its active form.
  • People with dark skin, because their skin has less ability to produce vitamin D from the sun.
  • People with disorders such as Crohn’s disease or celiac disease don’t handle fat properly, because vitamin D needs fat to be absorbed.
  • Obese people, because their body fat binds to some vitamin D and prevents it from getting into the blood.

What happens if I don’t get enough vitamin D?

People can become deficient in vitamin D because they don’t consume enough or absorb enough from food, their exposure to sunlight is limited, or their kidneys cannot convert vitamin D to its active form in the body. In children, vitamin D deficiency causes rickets, where the bones become soft and bend. It’s a rare disease but still occurs, especially among African American infants and children. In adults, vitamin D deficiency leads to osteomalacia, causing bone pain and muscle weakness.

What are some effects of vitamin D on health?

Vitamin D is being studied for its possible connections to several diseases and medical problems, including diabetes, hypertension, and autoimmune conditions such as multiple sclerosis. Two of them discussed below are bone disorders and some types of cancer.

Bone disorders

As they get older, millions of people (mostly women, but men too) develop, or are at risk of, osteoporosis, where bones become fragile and may fracture if one falls. It is one consequence of insufficient calcium and vitamin D over the long term. Supplements of both vitamin D3 (at 700–800 IU/day) and calcium (500–1,200 mg/day) have been shown to reduce the risk of bone loss and fractures in elderly people aged 62–85 years. Men and women should talk with their healthcare providers about their needs for vitamin D (and calcium) as part of an overall plan to prevent or treat osteoporosis.


Some studies suggest that vitamin D may protect against colon cancer and perhaps even cancers of the prostate and breast. But higher levels of vitamin D in the blood have also been linked to higher rates of pancreatic cancer. At this time, it’s too early to say whether low vitamin D status increases cancer risk and whether higher levels protect or even increase risk in some people.

Can vitamin D be harmful?

Yes, when amounts in the blood become too high. Signs of toxicity include nausea, vomiting, poor appetite, constipation, weakness, and weight loss. And by raising blood levels of calcium, too much vitamin D can cause confusion, disorientation, and problems with heart rhythm. Excess vitamin D can also damage the kidneys.

The safe upper limit for vitamin D is 1,000 to 1,500 IU/day for infants, 2,500 to 3,000 IU/day for children 1-8 years, and 4,000 IU/day for children 9 years and older, adults, and pregnant and lactating teens and women. Vitamin D toxicity almost always occurs from the overuse of supplements. Excessive sun exposure doesn’t cause vitamin D poisoning because the body limits the amount of this vitamin it produces.

Are there any interactions with vitamin D that I should know about?

Like most dietary supplements, vitamin D may interact or interfere with other medicines or supplements you might be taking. Here are several examples:

Prednisone and other corticosteroid medicines to reduce inflammation impair how the body handles vitamin D, which leads to lower calcium absorption and loss of bone over time.

Both the weight-loss drug orlistat (brand names Xenical® and Alli®) and the cholesterol-lowering drug cholestyramine (brand names Questran®, LoCholest®, and Prevalite®) can reduce the absorption of vitamin D and other fat-soluble vitamins (A, E, and K).

Both phenobarbital and phenytoin (brand name Dilantin®), are used to prevent and control epileptic seizures, increase the breakdown of vitamin D and reduce calcium absorption.

Tell your doctor, pharmacist, and other healthcare providers about any dietary supplements and medicines you take. They can tell you if those dietary supplements might interact or interfere with your prescription or over-the-counter medication, or if the medicines might interfere with how your body absorbs, uses, or breaks down nutrients.

What are the sources of Vitamin D?

Vitamin D is a naturally occurring compound but is not prevalently present in food sources. Sunlight is the most important of all sources of vitamin D. The human body gets its dose of Vitamin D through the synthesis that gets triggered by exposure to sunlight. This vitamin in its generated form is directly not of use; it needs to be broken further down and this process also takes place as a part of the sunlight synthesis. Vitamin D enhances the ability of the body to absorb calcium, thereby strengthening the bones. Apart from this, it also increases immunity against diseases and helps in cell growth.

The other sources of vitamin D include natural food varieties. The most common foods of vitamin D content are fish and fish liver extracts. All fish varieties provide the vitamin D content that is fit for consumption but Mackerels, Salmons, and Tunas have the maximum content. A single course of fish meal is enough to sustain the vitamin D requirements of the body for a day. A regular diet of foods with vitamin D content will enable the body to store this vitamin which can be accessed, whenever needed. Fish liver oil is also a prominent source of vitamin D and can be taken as a supplement.

Other sources of vitamin D include beef and the liver of animals. Beef has naturally occurring vitamin D content and can be absorbed by the human body through food. The quantity available for absorption might be lesser than fish foods with vitamin D but this is an important source for people who are allergic to seafood. The liver is the place where vitamin D synthesis happens for all animals. So, when taken as food, the liver provides good quantities of absorbable vitamin D for the body. Eggs, cheese, and milk are the other sources of vitamin D.

Since it is difficult to find foods with vitamin D content, especially for vegans, the best way to supplement the sources of vitamin D is through fortified foods. Some governments mandate certain types of food to be fortified with this vitamin, milk and ready-to-eat cereals being the most common. A typical, fortified breakfast cereal can provide enough vitamin D to last several days. Fortified foods with vitamin D include yogurt, orange juice, cheese, margarine, etc. Fortified foods are increasingly becoming the primary sources of this vitamin because of the change in diet habits of people. However, it is important to note that sunlight exposure is essential for synthesizing vitamin D, even for these supplemented food items.

The different foods with Vitamin D content

Vitamin D is a fat-soluble compound that assists the human body to improve calcium absorption. Calcium is needed for the healthy development of bones and also to prevent bone-related dilapidation. The primary source of Vitamin D for the body is sunlight. Exposure to sunlight triggers Vitamin D development in the body which in turn is synthesized in the liver and is subsequently used. Sometimes, Lack of adequate sunlight exposure or even lack of adequate sunlight might bring about a shortfall of Vitamin D in the body. Foods with vitamin D content can help people overcome this problem.

Vitamin D is not a naturally occurring substance and is not so very prevalently available in the natural world. However, there are certain types of food that have been used traditionally as supplements and the most popular one is cod liver oil. This oil is naturally equipped to provide the human body with the necessary Vitamin D, apart from other vital minerals. Cod liver oil is available in the form of capsules or syrups. The capsule form is the most popular and ingesting it does not cause any side effects. Not all manufacturers of cod liver oil have Vitamin D in them. It is advisable to check the composition of the manufacturer before buying the product.

Amongst the few naturally occurring foods with vitamin D content, Fish has the maximum percentage of this vitamin that can be absorbed by the human body. Mackerels, herrings, and other varieties of small fishes provide vitamin content to the body. A typical herring food preparation can provide the entire vitamin D requirement for one day. However, it is not necessary to ingest daily quantities of this vitamin because the human body has the capacity to store it and break it down for further use whenever required. It is important to ensure that there is an adequate amount of Vitamin D stored in the body.

What are the benefits of Vitamin D?

Vitamin D is an important ingredient that maintains the overall health and vitality of the body. The human body ideally should perform these functions: Growth, maintaining its health and strength, preventing diseases, and performing cell activities. benefits of Vitamin D the human body by aiding all these functions and therefore is vital for the wellbeing of the body. Vitamin D deficiency can lead to long-term repercussions. The vitamin D levels in the body will need to be constantly replenished to maintain body functions at an optimal level and foods with vitamin D content can help maintain this.

The growth of cells and their abilities to perform functions are directly regulated by vitamin D content in the body. Each group of cells is responsible for specific functions and vitamin D increases the ability of the cells to understand their functions and perform accordingly. Cells also need a properly regulated growth pattern. Unchecked growth in cells can lead to cancer. Lack of growth can also lead to nonperformance of functions which again is detrimental to the overall well-being. Vitamin D benefits the body by regulating this growth pattern and preventing cancer. For people afflicted with cancer, foods with vitamin D content are vital for the recovery process.

The human body needs a robust bone structure to protect itself from physical damage. Bones need calcium for their growth and also for their strength. This calcium needs to be available in an absorbable form for easy consumption. benefits of Vitamin D the body by synthesizing itself and in the process, creating enough levels of absorbable calcium for the body. Lack of vitamin D will lead to a lack of availability of calcium in the body and the end result is a weak bone structure that is prone to damage. Many bone diseases are due to the lack of bone strength and the body needs a constant supply of foods with vitamin D content to prevent this from happening.

The ability of the body to repel diseases and fight infections is called immunity. The immunity system in the body depends on vitamin D for its enhancement and sustenance. People suffering from constant bouts of flu, cold, etc. can benefit from a healthy diet that has lots of foods with vitamin D content. Vitamin D equips the immunity system in the body to fight infections. The functioning of the immune system which includes: the process of identifying infection-causing germs, isolating them, fighting and destroying them, is directly aided by vitamin D.

Three most important Vitamin D benefits

Vitamin D is a chemical substance that is essential for the well-being of the human body. This vitamin, in its broken form, is utilized by the body to perform various functions that are vital for the growth and development of the body. The most important vitamin D benefits are Bone strengthening and growth, Cell development and the development of the immune system. Calcium is the mineral that is responsible for bone growth and strength. Vitamin D triggers the process where calcium absorption is increases, thereby strengthening the bones against damage. Bone growth is also directly related to the availability of absorbable calcium and foods with vitamin D content enable the synthesis of the process through which calcium is available for usage.

Cell development and its eventual functioning are also regulated by vitamin D. Foods with vitamin D content nourish the body with a good supply of this substance that can be stored for future use. Whenever there is a need for vitamin D synthesis, the body can access it and begin the process of breakdown which in turn helps the cells not only grow and develop but also helps them to function properly. Different types of cells have different functions to perform. Vitamin D helps these cells to function as per their specialty. It also helps them from overlapping functions and intruding into the performance of other cells. This is an important function that vitamin D benefits the body with.

The other vitamin D benefits for the human body include their ability to enhance the immunity system of the body. A good immunity system is necessary to prevent the body from getting afflicted with various diseases. There are two types of functions that the immunity system does. One is the prevention of diseases and infections. Vitamin D helps the cells repel the sources of these infections, even before they start attacking the body. Lack of this vitamin reduces the capability of cells and thereby increases the risk of infection. This type of immunity is inherent in the body but needs enhancement through vitamin D. The other type is the ability to fight the disease-causing elements after they enter the body. This function enables the body to dispel diseases and also in its eventual recovery. Foods with vitamin D content replenish the body with this vitamin which in turn is synthesized for enhancing the immunity system. Amongst all the vitamin D benefits, the ones mentioned above are the most vital.

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