The role of vitamin D in regulating circulating levels of calcium and phosphorus to ensure normal bone mineralization is well known. Emerging evidence correlates insufficient levels of vitamin D to an increased risk of developing non-skeletal pathologies: cardiovascular diseases, hypertension, cancer, diabetes, multiple sclerosis, rheumatoid arthritis, infectious diseases.
What is vitamin D?
Vitamin D has long been recognized as an important nutrient that helps form and maintains healthy bones. Now there is a growing body of evidence showing that vitamin D is important to your overall health because it helps reduce inflammation, regulates immune system function, and helps control blood sugar (glucose) levels.
Vitamin D3 (cholecalciferol) and vitaminD2 (ergocalciferol) are the most abundant forms of vitamin D in the body. Vitamin D3 is synthesized in the skin from the sunlight. The best nutrition sources of D3 are oily fish primary salmon and mackerel. Vitamin D2’s nutrition sources are from some vegetables, yeast and fungi.
The diverse effects of vitamin D are mediated by receptors that regulate more than 200 genes. Besides the receptors present in the intestine and the bone, vitamin D receptors have been identified in brain, prostate, breast, colon, immune cells, vascular smooth muscle and cardiomyocytes.
Vitamin D is converted to 25-hydroxyvitamin D (25-OH vitamin D) in the liver. The measurement of 25-OH vitamin D concentration in the serum or plasma is the best indicator of vitamin D nutritional status.
The optimal level of 25-OH vitamin D is subject to some debate, but >30 ng/ml is accepted as sufficient for bone health. Vitamin D toxicity is a recognized problem but a rare occurrence. Instead, a recent growing public health problem is vitamin D insufficiency. Several research studies have identified widespread vitamin D insufficiency in apparent healthy populations world-wide.
What are the sources?
It can be difficult to obtain enough vitamin D from food sources alone. Most foods, with the exception of fatty fish oils, contain little vitamin D. Some foods (milk, orange juice, cereals) may be supplemented with vitamin D at very low levels. Vitamin D levels can be increased by spending time in the sun. Exposing the arms and legs to sunlight for 5 to 30 minutes between 10 AM and 3 PM twice a week is often enough. Sunscreen, which is important in protecting against skin cancer, blocks the formation of vitamin D, and winter sunlight is nowhere near as effective as summer sunlight for making vitamin D.
Who is at risk for vitamin D deficiency?
- People whose exposure to sunlight is very limited
- People who have naturally dark skin
- Adults older than 50 years of age
- Infants who are exclusively breast-fed or receiving less than about 2 cups a day of vitamin D-fortified formula or milk
- People with fat malabsorption conditions, such as pancreatitis, cystic fibrosis, celiac disease and surgical resection of the bowel
- People who have liver or kidney disease or enzyme deficiencies
- People who live in northern climates during winter
- People who are obese
What are the health risks?
- In children, vitamin D deficiency can lead to rickets, a bone disease that results in poorly developed, weak bones, delayed growth, immune deficiencies, and, when severe, seizures.
- Vitamin D deficiencycan affect bone health in adults as well.
- It may lead to osteomalacia, a condition that results in weak bones, fractures, bone pain, andweak muscles.
- Low levels of vitamin D may also play a role in the development of osteoporosis (thinning of the bones), which can lead to fractures.
Other health problems are now being linked to low (insufficient) levels of vitamin D.
- Infants and young children with insufficient vitamin D levels may for the rest of their lives be at increased risk of developing diabetes, multiple sclerosis, rheumatoid arthritis, and inflammatory bowel diseases (all conditions related to poor immune system function), as well as many common cancers.
- People with insufficient vitamin D levels may be more likely to develop and die from colon, endometrial, skin, pancreatic, or prostate cancer than those who maintain healthy levels of vitamin D.
- Vitamin D insufficiency is now linked with an increased risk for high blood pressure, heart disease, heart failure, and death due to heart attack or stroke.
How much vitamin D does a person need?
Experts believe people of all ages may need more vitamin D than the current guidelines recommend.
The following levels have been proposed as indicative of:
- Deficiency < 10 ng/ml
- Insufficiency 10-30 ng/ml
- Sufficiency 30-100 ng/ml
- Toxicity > 100 ng/ml
It has been estimated that 1 billion people worldwide do not reach the minimum optimal concentration of 30 ng/ml.
How can low levels of vitamin D be corrected?
Vitamin D deficiency or insufficiency is commonly treated by taking foods containing vitamin D or fortified foods or by vitamin D supplements or increasing your exposure to sunlight.
Ask your doctor whether he or she recommends increasing your vitamin D intake.
Maintaining a healthy level of vitamin D may play a key role in preventing certain cancers, diabetes, multiple sclerosis, cardiovascular disease, stroke, and other health problems. In addition, vitamin D may be useful in the treatment of high blood pressure.
Total Vitamin D status is assessed by measuring the serum concentration of 25-OH vitamin D.
An analysis of studies demonstrating the role of vitamin D in the prevention of several pathologies suggests that reaching and maintaining 25-OH vitamin D levels above 30 ng/ml, preferably around 35-45 ng/ml, is key to maintain good health.
Such levels include the metabolites of both forms of vitamin D: D2 and D3. Whereas vitamin D3 is produced by the skin upon exposure to sunlight, both D2 and D3 are contained in food sources.
In most countries, vitamin D supplements containing D2 or D3 are available, which can help compensate the insufficient dietary intake and sun exposure.
Accurate assessment of vitamin D status relies on the measurement of 25-OH vitamin D TOTAL levels (25-OH vitamin D2 + 25-OH vitamin D3), which can be compared with the optimal levels recommended by vitamin D experts.
Two separate values for 25-OH vitamin D2 and 25-OH vitamin D3 could lead to erroneously interpret low levels of one of the two metabolites as indicative of vitamin D insufficiency even when the sum is within the sufficiency range.
Measuring 25-OH vitamin D TOTAL levels is important to monitor treatment. Clinical cases of supplementation with vitamin D2 have been reported in which an assay that was only able to detect 25-OH vitamin D3 was used for patient follow-up. The inability to measure the increase in 25-OH vitamin D TOTAL levels upon supplementation can cause overtreatment and lead to further expensive and stressful studies.
Since 1985, DiaSorin has provided laboratories with assays that accurately measure 25-OH vitamin D total levels, thanks to antibodies that are co-specific for 25-OH vitamin D2 and 25-OH vitamin D3.
The LIAISON25 OH Vitamin D TOTAL assay is an advanced chemiluminescence (CLIA) technology with paramagnetic particles separation to achieve the best assay sensitivity and precision.
Additionally, this has been approved by the Food and Drug Administration (FDA) and has been used to define the 25-OH vitamin D reference levels.
Therefore, maintaining sufficient levels of 25-OH vitamin D (>30 ng/ml) helps preventing several pathologies and maintaining good general health.