Vitamin D ( 25OHD )


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Vitamin D is essential for bone health and many metabolic processes. The body derives it from sunlight and food sources. Many people do not get enough sunlight or do not consume enough vitamin D rich foods. This test is important to determine if you need vitamin D supplementation or if your current supplementation is effective.

Vitamin D is essential for bone health and many metabolic processes. The body derives it from sunlight and food sources. Many people do not get enough sunlight or do not consume enough vitamin D rich foods.

What is Vitamin D?

Vitamin D is essential for bone health and many metabolic processes. The body derives it from sunlight and food sources. Many people do not get enough sunlight or do not consume enough vitamin D rich foods. This test is important to determine if you need vitamin D supplementation or if your current supplementation is effective.

25-Hydroxyvitamin D (25OHD) is the major circulating form of vitamin D and the precursor of the active form (1,25-dihydroxyvitamin D). Because of its long half-life, measurements are useful for assessing vitamin D status in patients. This test measures 25OHD using liquid chromatography, the most accurate test to determine Vitamin D blood levels.

Vitamin D is the name given to a vitally important group of micro-nutrients. When activated, vitamin D becomes a potent steroid hormone, switching our genes on or off, and instructing our cells what work to do. Vitamin D's effects are varied and profound. It is structurally similar to steroids such as testosterone, cholesterol, and cortisol.

The term "vitamin D" refers to several different forms of this vitamin. Two forms are important in humans: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Vitamin D2 is synthesized by plants. Vitamin D3 is synthesized by humans in the skin when it is exposed to ultraviolet-B (UVB) rays from sunlight. Foods may be fortified with vitamin D2 or D3, although humans should not rely on synthetic food fortification as a good source of Vitamin D3 since most fortified foods do not have enough Vitamin D to meet daily requirements.

Benefits of Vitamin D:

(vitamin D3) has many health benefits when levels are kept optimal. These benefits include:

  • ·  Anti-Inflammatory- Chronic inflammation is becoming a major focus as a cause of many disease processes such as heart disease and cancer. D-3, also called “The anti-inflammatory” hormone, has been studied as an effective treatment to reduce chronic inflammation. Vitamin D deficiency is often misdiagnosed as fibromyalgia, chronic fatigue syndrome, and others. Deficiency has also been associated with multiple sclerosis, Grave’s disease, and age related muscle wasting. Degenerative arthritis also progresses more rapidly when there is a deficiency of Vitamin D.
  • ·  Blood Sugar Control- Deficiency of Vitamin D can inhibit the proper secretion of insulin and lead to increased insulin resistance. Studies show that supplementing with D3, especially during winter months, can help reduce the risks of Type II diabetes.
  • ·  Optimal Immune Function- Vitamin D helps the immune system to fight infections.
  • ·  Blood Pressure- Optimum levels of Vitamin D3 actually tend to reduce blood pressure in hypertensive people. Supplementing with Vitamin D can help reduce the risk for hypertension.
  • ·  Decreased Risk of Obesity- Deficiency of Vitamin D3 can lead to metabolic syndrome which contributes to the rapid accumulation of fat mass.

What Are Good Vitamin D levels?

Different studies suggest that higher vitamin D intakes beyond current recommendations may be associated with better health outcomes. Evidence is summarized from different studies that evaluate threshold levels for serum 25(OH)D levels in relation to bone mineral density (BMD), lower extremity function, dental health, risk of falls, admission to nursing home, fractures, cancer prevention and incident hypertension. For all endpoints, the most advantageous serum levels for 25(OH)D appeared to be at least 75 nmol/l (30 ng/ml) and for cancer risk reduction, and desirable 25(OH)D levels are between 90-120 nmol/l (36-48 ng/ml).

How Much Vitamin D Should We Take?

Vitamin D is important for skeletal and nonskeletal health. It is now well established that many people have vitamin D levels that are less than currently recommended for optimal health. Worldwide, vitamin D is predominantly obtained through exposure to UVB radiation in the form of sunlight and cutaneous vitamin D production. Latitude, cultural dress habits, season, sun avoidance, and sunscreen protection can all limit vitamin D production. Gastrointestinal, hepatic, and renal disease may be related to low vitamin D levels, but hypovitaminosis D most commonly results from inadequate intake. Hypovitaminosis D resulting from lack of UVB exposure is not easily corrected by dietary intake alone in the absence of supplementation. Food fortification with vitamin D is based on outdated recommendations for daily AI. Supplementation with 800 to 1000 IU/d of vitamin D or 50,000 IU monthly is safe for most people and can ensure levels of vitamin D within the optimal range. This intake is within the currently recommended safe upper tolerable limit for vitamin D of 2000 IU/d for those aged 1 year and older. 

An intake of no less than 1000 IU (25 mcg) of vitamin D3 (cholecalciferol) per day for all adults may bring at least 50% of the population up to 75 nmol/l. Thus, higher doses of vitamin D are needed to bring most individuals into the desired range. While estimates suggest that 2000 IU vitamin D3 per day may successfully and safely achieve this goal, the implications of 2000 IU or higher doses for the total adult population need to be addressed in future studies.

Why Get a Vitamin D Test?

Many people don’t have enough vitamin D in their bodies. Low vitamin D increases the risk of broken bones. It may also contribute to other health problems. That’s why doctors often order a blood test to measure vitamin D.

There are several factors which can increase your risk of Vitamin D deficiency. Young children andthe elderly are particularly vulnerable to complications arising from insufficient Vitamin D in their systems.

Other factors that affect Vitamin D levels are:

  • Not consuming enough food types that are rich in Vitamin This is likely if you follow a strict vegan diet, or are lactose-intolerant.
  • Not getting enough exposure to the People who are home-bound or live in northern latitudes or have a profession that keeps them from getting enough sunlight are at risk.
  • You have a darker skin tone, since greater amounts of melanin in the skin reduce the amount of sunlight the skin can absorb
  • Exclusively breast-feeding babies for prolonged time periods, which would increase their risk of developing Vitamin D deficiency
  • You have kidney issues which prevent Vitamin D being converted to its active form in your This happens mostly within older age groups
  • You’ve undergone gastric bypass surgery
  • Certain medical problems, including Crohn’s disease, cystic fibrosis, and celiac disease, can affect your intestine’s ability to absorb Vitamin D from the food you eat. Certain people with obesity can also have Vitamin D deficiency, since Vitamin D is extracted from the blood by fat cells, altering its release into the circulation.

Reference: Optimal serum 25-hydroxyvitamin D levels for multiple health outcomes. Adv Exp Med Biol. 2008;624:55-71.  


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