3 Things Everyone Should Know About Vitamin D

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The most important reason we try to eat a balanced diet is to get the vitamins and nutrients our body needs. Essential vitamins are those that are not produced at all or in sufficient amounts by the body.

Vitamins are necessary for growth and development, as well as everyday optimal function. We can obtain most vitamins from the foods we eat or from supplements. Learning about vitamins can be as easy as A-B-C.

Vitamins A, B, C, D, E, and so on are all important to your overall health and well-being. From a young age, we hear about most of the vitamins and where to find them in food. However, we may not know much about vitamin D. Here are three important facts you need to know about vitamin D.

What Is Vitamin D

Vitamin D is one of four fat-soluble vitamins and one of two vitamins that is produced by the body. Another characteristic that differentiates vitamin D is that the body actually converts this vitamin into a hormone, which is referred to as “calcitriol.” The resulting compounds are characterized as a secosteroid.

Therefore, vitamin D can be considered a “prehormone” that is also a vitamin. A vitamin is an organic substance necessary for metabolism. A deficiency of vitamins may cause disease. (Vitamin D is not a hormone, which is defined as a substance manufactured in an organ and transported through the blood to another organ.)

Two steps are required to convert vitamin D to the active calcitriol; first, the liver converts the vitamin to calcidiol, which is the form stored in the body. Then, calcidiol is converted to calcitriol, mainly in the kidneys. Calcitriol interacts with vitamin D receptors present in almost every cell of the body.

Vitamin D (Calcitriol) and Calcium

In the human body, vitamins work synergistically. Vitamin D works with magnesium, vitamin K, and calcium. Vitamin D’s main job is to regulate calcium and it does that at three different locations in the body.

Intestines: As part of the digestive process, calcitriol boosts your body’s ability to absorb calcium from food or supplements.

Bones: Calcitriol regulates cells to build bone mass and also helps the bones absorb calcium.

Kidneys: In these filtering organs, calcium that would be excreted in urine is recycled for reabsorption by the bones.

Vitamin D and Phosphorous

Vitamin D helps the bones absorb calcium and phosphorus that are necessary for bone strength and function. Without adequate vitamin D, the bones cannot absorb calcium or phosphorous.

Why We Need Vitamin D

In addition to supporting bone health, vitamin D was discovered by researchers to help with other body functions, including:

♦ Immune system

♦ Muscle contraction

♦ Respiratory system

♦ Circulatory system

♦ Nervous system

♦ May protect against cognitive decline

♦ Heart Disease

Although a relationship has not been established between increasing intake of vitamin D with cardiovascular disease prevention, studies have shown that vitamin D deficiency is a risk factor for numerous cardiovascular diseases, including heart attacks, congestive heart failure, peripheral artery disease, and stroke, as well as hypertension and diabetes.

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Should I Take A Supplement?

Since vitamin D is fat-soluble, excess intake is not excreted in the urine. Although it is relatively rare to take too much vitamin D, excessive vitamin D can actually cause an increase in calcium levels, which, in turn, shuts off vitamin D. Excess calcium can cause problems with heart rhythm, as well as kidney stones.

How Can I Get Vitamin D?


Sources of vitamin D include sun exposure, diet, and supplements. Exposure to ultraviolet (UV) rays causes the skin to manufacture vitamin D. The amount of vitamin D varies according to climate, time of day or year, air pollution, and cloud cover. People in sunnier climates or who live closer to the equator have more exposure.


A balanced diet with a variety of foods can be a good way to get vitamin D. Here are some foods that are a good source of vitamin D.

♦ Swordfish

♦ Salmon

♦ Tuna, canned in water

♦ Milk or orange juice fortified with vitamin D

Who Is At Risk for Vitamin D Deficiency?

Certain conditions and medications may be risk factors for vitamin D deficiency. These include:

Kidney and Liver Disease: Both cause a reduction in the enzyme that changes the vitamin into the usable form calcidiol.

Cystic Fibrosis, Crohn’s Disease, Celiac Disease: These diseases prevent the intestines from absorbing vitamin D.

Gastric Bypass: This surgery removes part of the stomach and/or intestines, reducing the amount of vitamin D that is absorbed.

Obesity: There is an association between a BMI of over 30 and lower levels of vitamin D.

Age: Aging skin manufactures less vitamin D.

Medication: Certain drugs, including laxatives, steroids such as Prednisone, drugs to control cholesterol or seizures, and the weight loss drug Orlistat may lower levels of vitamin D.

The Bottom Line

Vitamin D is one of 13 vitamins essential for optimal health. The vitamin, which converts into calcitriol, has receptors in just about every cell in the body and is necessary for the absorption and balance of phosphorous and calcium, which support bone structure and strength.

Vitamin D deficiency is noted in patients with risk factors and various diseases or conditions. The vitamin is one of two that the body manufactures and is converted from UV rays by the skin.

Various foods contain vitamin D. For certain people, supplements may be advised but there is a risk of excess vitamin D, as it is fat-soluble and excess is not secreted by urine. It's best to check with a health professional.

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