Vitamin D deficiency has been identified as a common metabolic/endocrine abnormality. Despite the known dietary sources of vitamin D and the role of sunlight in its production, much of the population may have inadequate serum 25-hydroxyvitamin D levels.
Vitamin D deficiency can be caused by a variety of conditions that we will discuss below.
There are varying definitions of vitamin D deficiency, based on different thresholds for serum 25-hydroxyvitamin D. During the last decade, there has been exceptional interest from all sectors in relation to the role of vitamin D in human health and diseaseand in the possibility that improving the state of the Vitamin D would bring benefits not only in relation to the skeleton, but also in non-skeletal tissues.
Over the same time period, there have been differences of opinion, and in some cases heated debates, regarding the strength of the evidence to support a role for vitamin D in non-skeletal health outcomes in particular and also in the serum 25-hydroxyvitamin D, which is the most appropriate indicator of vitamin D status.
What is vitamin D
Vitamin D is a fat-soluble vitamin that plays an important role in calcium homeostasis and bone metabolism. Vitamin D deficiency can cause osteomalacia and rickets in children and osteomalacia in adults.
The fortification of milk with vitamin D in the 1930s was effective in eradicating rickets in the world. Nevertheless, subclinical vitamin D deficiency remains very common in both developed and developing countries, with a global prevalence of up to 1 billion.
This subclinical vitamin D deficiency is associated with osteoporosis, increased risk of falls, and fragility fractures. Many conflicting recent studies now show an association between vitamin D deficiency and cancer, cardiovascular disease, diabetes, and autoimmune disease.
What does it mean to be deficient in vitamin D?
Vitamin D deficiency/deficiency is a clear global pandemic. It is described that 88% of the population has a plasma concentration of 25-hydroxyvitamin D less than 30 ng/ml, 37% less than 20 ng/ml and a mean level of 7% less than 10 ng/ml.
In Spain, the situation is very similar. In people older than 65 years concentrations of 25-hydroxyvitamin D have been described less than 20 ng/mL in 80-100% of the populationand in populations under 65 there is a deficit of up to 40% of the Hispanic population.
Causes of vitamin D deficiency
Inadequate exposure to sunlight, improper food sources, and malabsorption are common causes of deficient 25-hydroxyvitamin D.
Geographic location and sun exposure
A person’s exposure to UV-B rays varies by time of day, season, latitude, altitude, clothing, use of sunscreen, skin pigmentation, and age.
People living at latitudes above 37 degrees do not get enough UV-B rays to make vitamin D during the winter months. Age further complicates adequate exposure to sunlight.
An adult over the age of 70 needs about 3 times more exposure to sunlight to produce the same amount of vitamin D as a child. Even a diet high in foods rich in vitamin D can cause a deficiency. Babies are at risk of vitamin D deficiency only if they are breastfed.
Vitamin D malabsorption
Vitamin D malabsorption can be caused by disorders that affect the gastrointestinal tract, including Crohn’s disease, celiac disease, chronic hepatitis, chronic kidney disease (CKD) with or without dialysis, inflammation, chronic pancreatitis, or primary liver cirrhosis .
Vitamin D catabolism
Liver disease, chronic kidney disease, and alcohol abuse are most common causes of increased catabolism of Vitamin D. Certain medicationssuch as anticonvulsants, glucocorticoids, antifungals such as ketoconazole, and highly potent antiretroviral therapy, can increase the catabolism of vitamin D.
Sequestration of Vitamin D
Vitamin D is fat-soluble and there is evidence of its sequestration by adipose tissue. The researchers measured serum 25-hydroxyvitamin D in 3,890 elderly participants in the Framingham Heart Study without cardiovascular disease or diabetes, found a decrease in 25-hydroxyvitamin D levels with higher BMI that could not be explained by changes in physical activity or diet.
On the other hand, they also found an inverse relationship between 25-hydroxyvitamin D and subcutaneous and visceral fat even in lean individuals. Still, this area needs further study to elucidate the relationship and mechanism.
How we solve this problem
Before trying to take a solution ourselves, this should be consulted with a doctor who is up to date on the subject, since consuming vitamin D without any supervision can cause other problems.
The Institute of Medicine recommends 600 IU of vitamin D per day to meet the needs of most people ages 1 to 70. People older than 70 years may need 800 IU per day, with minimal sun exposure. The Endocrine Society recommends 1,500 to 2,000 IU per day for adults and 1,000 IU per day for children. In addition, vitamin D should be given with calcium to maintain bone health in people with deficiency.
Currently, there is no consensus on which form of vitamin D supplementation is best. However, a randomized, double-blind, placebo-controlled study looked at vitamin D2 and vitamin D3 supplementation in 85 healthy people for 25 weeks beginning in late summer. The researchers found that vitamin D3 was more effective than vitamin D2 in maintaining serum levels of 25-hydroxyvitamin D during the fall and winter months. They also found relatively low serum levels of 25-hydroxyvitamin D in the vitamin D2 supplementation group. A single 50,000 IU dose of D2 or D3 produces a similar increase in total 25-hydroxyvitamin D, but D3 has a longer half-life.
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