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Vitamin D

What is Vitamin D and why is it so important?

Vitamin D is not really a vitamin, but a hormone. It is unique because it can be made in the skin by exposure to sunlight. Life forms have been producing vitamin D for over 750 million years. Phytoplankton, zooplankton, and most animals that are exposed to sunlight have the capability to make vitamin D.  

It is important for many aspects of health, with the most widely known function being to maintain strong bones. It is critically important for the development, growth, and maintenance of a healthy body, beginning with gestation in the womb and continuing throughout the life span.  

There are two forms that are important to humans: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). It is measured in International Units (IU) and is very potent in small quantities. 

The major function of vitamin D in the body is to maintain normal blood levels of calcium and phosphorus. It aids in the absorption of calcium from the gut, helping to form and maintain strong bones.  

Vitamin D deficiency may exacerbate osteopenia, osteoporosis, muscle weakness, fractures, some cancers, autoimmune diseases, infectious diseases and cardiovascular disease. There is also some evidence that vitamin D may reduce the incidence of several types of cancer and diabetes. 

Causes of Vitamin D Deficiency

Limited Sunlight Exposure
Sunscreen/Sun-Protective Clothing
Obesity: BMI greater than 30 kg/m2
Fat Malabsorption Disorders
 – Bariatric Surgery, Cystic Fibrosis,
 – Inflammatory Bowel Disease, Crohn’s disease, radiation enteritis
Nephritic Syndrome
Certain Medications
 – Antiseizure medications, glucocorticoids, AIDs medications, antifungals, cholestryamine
Primary Hyperparathyroidism
Chronic Granuloma-forming Disorders

It is estimated that 1 billion people worldwide, across all ethnicities and age groups, have a vitamin D deficiency. People who are deficient in vitamin D may develop soft, thin, and brittle bones. This condition is known as rickets in children and osteomalacia in adults .

There are many reasons as to why so many people are vitamin D deficient. The number one reason is lack of exposure to sunlight. It has been estimated that the majority of people living in the United States, Canada, and European countries are deficient because sunlight exposure is very low, if not completely absent, during the winter months. Also, due to the fear of developing skin cancers, it is highly encouraged to wear sunscreen lotion with an SPF of 30 or higher. An SPF of 30 reduces vitamin D synthesis in the skin by greater than 95%. People with darker skin require at least three to five times the amount of sun exposure than persons with lighter skin. 

Aging may also be linked to vitamin D deficiency. As you age, the skin loses some of its ability to make vitamin D3, liver and kidney function declines, and the guts ability to absorb vitamin D from the diet is reduced.  

How do I know if my vitamin D level is appropriate?

Vitamin D screening is only recommended for patients who are believed to be at risk for vitamin D deficiency. This covers the majority of the population, however, and obtaining a blood serum level of your vitamin D is a good idea because deficiency may be present without you even knowing it.

Screening measures a form of vitamin D called: 1,25-dihydroxyvitamin D. What your results mean: 
 – Normal: greater than 30 ng/mL
 – Insufficiency: 21-29 ng/mL
 – Deficiency: lower than 20 ng/mL

The goal is to be at a level greater than 30 ng/mL. This would be considered an appropriate level.

Vitamin D Supplementation & Recommendations

Current Institute of Medicine recommends 600-800 IU of vitamin D supplementation per day. These recommendations are thought to be inadequate because the body utilizes around 3,000-5,000 IU of vitamin D per day. Recommendations for supplementation are listed in the table below.

Once the desired blood concentration is achieved (greater than 30 ng/mL),most people can maintain the level with 800-1000 IU of vitamin D daily.

Examples of some food sources with vitamin D include: salmon, mackerel, tuna, fresh and sundried shiitake mushrooms, egg yolk; fortified milk, orange juice, margarine, butter, cheeses, and cereals; and infant formulas.Food sources contain anywhere from 20 IU to 1000 IU of vitamin D. For this reason, supplementation cannot rely simply on diet. Few foods contain vitamin D, and those that do, contain too little to be of any noticeable benefit.

Vitamin D2 or D3?

Vitamin D2 (ergocalciferol) is derived from fungal sources. It is not naturally present in the human body and may have actions that differ from that received from the sun. 

Vitamin D3 (cholecalciferol) is synthesized by humans in the skin when exposed to ultraviolet B (UVB) rays from the sunlight; also found in oil-rich fish (salmon, herring, and mackerel). Vitamin D3 supplements come in two forms: oil (cod liver oil-based) which is fat-soluble and dry powder (lanolin-based) which is water soluble. Both forms are equally absorbed and metabolized by the body, and are thus equally effective.

Both vitamin D2 and vitamin D3 are used for food fortification and in vitamin D supplements. Both formulations have long been regarded as equivalent in their clinical activity. Studies indicate, however, that D2 is less potent with a shorter duration of action.  Many experts agree that vitamin D3 is the preferred form for treating vitamin D deficiency because it is the same substance as what is produced in human skin in response to sun exposure.

The Sunshine Vitamin

There are only two ways to receive enough vitamin D for proper health: UVB exposure from the sun and vitamin D supplementation. There are several factors that prevent sun-generated vitamin D including: sunscreen lotion, aging, darker skin, and residing in the northern half of the U.S. from November to February.

Vitamin D from the sun is the best source; it is superior to other forms of D. It stays in your system longer for longer-lasting benefits. This is considered the method of choice to receive vitamin D because this is how Nature intended.
The recommendation is to expose your arms, legs and face to the sun for fifteen minutes every day, during peak daylight hours. After those fifteen minutes are up, apply sunscreen to protect against skin cancer.  

Remember, if your shadow is longer than you are tall, you are not making much vitamin D.  

Vitamin D doesn’t just benefit bones…

Vitamin D has many roles in the body. It is necessary for muscles to move, nerves to carry messages between the brain and every body part, and the immune system to fight off invading bacteria and viruses. It may help with some inflammatory diseases such as rheumatoid arthritis and osteoarthritis by reducing inflammation.  

Vitamin D may also play a role in reducing risk of certain types of cancer, including:
  – Breast Cancer
  – Colorectal Cancer
  – Pancreatic Cancer
  – Prostate Cancer

It may be beneficial in the prevention and treatment of:
  – Type I and II Diabetes
  – Hypertension
  – Stroke
  – Glucose Intolerance
  – Multiple Sclerosis
  – Rheumatoid Arthritis
  – Tuberculosis
  – Alzheimer’s Disease
  – Preeclampsia
  – Seasonal flu
  – Depression
  – Schizophrenia
  – And others!

Is there such a thing as too much Vitamin D?

Vitamin D, like all things in excess, can become toxic. It is one of the safest substances known to man and vitamin D toxicity is very rare but it can still occur. Vitamin D deficiency, however, is much more likely.  

There is absolutely no risk of vitamin D toxicity due to too much sun exposure because the body makes only the vitamin D it needs. Toxicity occurs when there is too much vitamin D due to supplementation. All the cases of vitamin D toxicity published have been associated with intake of greater than 40,000 IU per day. With this in mind, the upper limit mentioned previously should not be surpassed.  

Symptoms of toxicity and overdose include: nausea, vomiting, poor appetite, constipation (possibly alternating with diarrhea),weakness, weight loss, tingling sensations in the mouth, confusion, and heart rhythm abnormalities.

Remember this is a rare condition. However, if you believe this describes you, stop supplementation and make an appointment with your physician to test your vitamin D serum levels.

© 2012 The Medicine Shoppe of Norton

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