What is vitamin D?

The "sunshine" vitamin is a hot topic. You may have recently found out that you are deficient or know someone who is. It's shocking for most people when they have never had a problem before and believe nothing has changed to make it a problem now. The truth is that a lot has changed, and vitamin D deficiency and insufficiency is now a global public health problem affecting an estimated 1 billion people worldwide.

Vitamins are considered essential nutrients because either your body cannot make them or they are made in inadequate amounts to prevent negative health consequences or diseases. So it's essential that you provide vitamins for your body by food and/or supplements. Vitamin D was discovered to be essential when it was found to be needed for the treatment of rickets. Vitamin D is one of the four fat-soluble vitamins (A, D, E, and K). There are two forms of vitamin D: D2 and D3. Vitamin D2, also known as ergocalciferol, comes from fortified foods, plant foods, and over-the-counter supplements. Vitamin D3, also known as cholecalciferol, comes from fortified foods, animal foods (fatty fish, cod liver oil, eggs, and liver), supplements, and can be made internally when your skin is exposed to ultraviolet (UV) radiation from the sun. Structurally, these two are not the same. Many believe that vitamin D should be classified as a hormone, with some calling it the forgotten neurosteroid. The health consequences of being deficient go far beyond rickets and what occurs with any other vitamin. And unlike other vitamins, it can be made by your body when exposed to sun and the active form in your body, called calcitrol, has similarities to other hormones (estrogen, cortisol, and testosterone).

The real dangers of excess exposure to the sun and skin cancer have been greatly publicized and resulted in people covering up and using sunscreen when in the sun. We have also had a shift in spending less time outdoors because of increased work hours and more sedentary lives. As a result, vitamin D levels began dropping without most health care professionals realizing it. Researchers have been focusing on the consequences of vitamin D deficiency and have found an alarming number of health issues outside of its role with rickets. These include skeletal diseases like osteoporosis, certain cancers, cardiovascular disease, autoimmune diseases, infections, inflammatory bowel diseases, psychological disorders, cognitive disorders, obesity, and or mortality. Correcting vitamin D deficiency is not as simple as taking a pill or getting more sun. This article will teach you all that you need to know about the benefits of achieving and maintaining optimal vitamin D levels and how you can do it.

Only 20% of our vitamin D is meant to come from our diet with the remaining 80% provided by our skin from UV-B exposure to the sun. There are currently two sets of guidelines for vitamin D intake. Typically, vitamin guidelines are established by the Institute of Medicine (IOM) in the form of Recommended Dietary Allowances (RDA) or adequate intakes (AI). The RDA is the average daily intake sufficient to meet the nutrient requirements of nearly all (97.5%) healthy individuals. These guidelines were set on a population model to prevent vitamin D deficiency based on bone health (osteomalacia, rickets, bone mineral density, and calcium absorption) for the general population. The Endocrine Society put together a task force to review the research and came up with a set of guidelines based on a medical model for those at risk for a deficiency. The two recommendations are as follows:

These amounts are based on what is needed to maintain the blood levels that each guideline committee has established as ideal. The higher the blood level that you need to maintain, the more vitamin D you will need to maintain that level. If your blood level is deficient, these are not the guidelines for you to follow. You will first need to get your levels up by taking vitamin D above these amounts and then you will follow these levels once you have reached your adequate level. Your health care provider can provide recommendations for a safe way to do this.

By the turn of the 20th century, 90% of the children living in New York, Boston, and Leyden in the Netherlands were afflicted with rickets, a bone-deforming disease. The first observation of this disease was in the mid-1600s by Whistler and Glissen, who reported that children living in industrialized cities in Great Britain had short stature and deformities of the skeleton, especially of the lower legs. It wasn't until 1889 that the discovery that "sunbathing" was important for preventing rickets came about.

Since then, many other health benefits of vitamin D and risks associated with deficiency have been reported. These include the following:

Autoimmune disease

• Type 1 diabetes (T1DM): Research has shown that children with type 1 diabetes have a higher chance of having a vitamin D deficiency compared with the general population. In Finland, the recommendation for daily vitamin D supplementation was gradually reduced from 4,000-5,000 IU/day in 1964 to 400 IU/day in 1992. During this period, T1DM increased by 350% in those 1-4 years of age, 100% in those 5-9 years of age, and 50% in those 10-14 years of age. In 2006, authorities required that all dietary milk be fortified with vitamin D2, and the incidence of T1DM plateaued and began to decrease.
• Multiple sclerosis (MS): Current evidence supports that vitamin D deficiency increases the risk of developing MS and alters the disease activity in people with MS. Numerous studies have linked the occurrence of MS with birth month. There is also a higher prevalence of MS in geographic areas farther from the equator, where people are exposed to less sunlight. The lack of sunlight exposure appears to be a significant predictor, and research is ongoing in this area. A large review of studies shows that with adequate vitamin D levels in people with MS there are fewer relapses, lower risk of development of new lesions in the brain, less disability and disease severity, and better nonverbal long-term memory performance. Studies now need to be done to confirm if this is directly due to vitamin D levels.
• Lupus: People with lupus are often photosensitive, causing rashes and possible disease flares when exposed to sunlight. The resulting lack of exposure to sunlight puts them at high risk for vitamin D deficiency. Evidence has shown that a deficiency can affect disease activity and damage along with contributing to the morbidity and mortality in people with systemic lupus erythematosus (SLE).
• Rheumatoid arthritis (RA): A review of research found that people with the highest vitamin D levels had a 24.2% lower risk of developing RA compared to those with the lowest levels. They also found that there was a higher rate of vitamin D deficiency among people with RA than with the general population, and the activity of RA got worse as the level decreased.
• Autoimmune thyroid disease (AITD) (Graves' disease and Hashimoto thyroiditis): In a review of 20 studies, they found that AITD patients has lower levels and were more likely to have vitamin D deficiency compared with controls. In a review of 26 studies of Graves' disease, they concluded that low vitamin D status may increase the risk of Graves' disease.