Vitamin D has recently received much media coverage due to studies linking its deficiency with numerous diseases.

Vitamin D levels can be elevated through diet, supplements and sunshine exposure; however, optimal levels of 25(OH)D depend on skin pigmentation, season and latitude.

What is Vitamin D?

Vitamin D is an essential nutrient for maintaining healthy bones, muscles and overall body function. The best natural source of Vitamin D is sunlight’s ultraviolet B radiation; however, food sources also contain this essential nutrient.

UVB radiation penetrates uncovered skin and converts naturally occurring 7-dehydrocholesterol cholesterol to previtamin D3, which the liver and kidneys then turn into active vitamin D. Sunscreen reduces UVB penetration, thus diminishing vitamin D production; dark-skinned people have decreased ability to synthesize vitamin D [1].

The Food and Nutrition Board of the National Academies of Sciences, Engineering, and Medicine has issued Dietary Reference Intakes (DRIs) for vitamin D that are designed to balance risks associated with excessive vitamin D toxicity with benefits gained by getting enough of this nutrient in order to avoid deficiency. In order to avoid overdoses, FNB recommends keeping serum 25(OH)D levels between 125-150nmol/L (50-60ng/mL), below 200nmol/L (80ng/mL). [1].

Most individuals obtain adequate amounts of vitamin D through a combination of sources: fortified milk or cereal, salmon, mackerel or sardines eaten as part of a balanced diet, sun exposure and skin absorption through exposure to sunlight. Note: Calcium helps the body absorb Vitamin D properly – in fact calcium helps make bones stronger!

Fat-soluble vitamins also play a significant role in many other bodily processes, including bone health, immune system function and cell signaling. Furthermore, this vitamin may protect against cancers, inflammatory conditions and neurodegeneration.

Vitamin D is a fat-soluble vitamin, meaning that it’s stored in fat-storing organs of the body and released when necessary. Because it’s fat soluble, its absorption depends on various aspects of gut health as well as other organs and systems like liver gallbladder intestines kidneys as well as cystic fibrosis Crohn’s disease celiac disease can impair absorption; people without adequate absorption due to these conditions may require supplementation with plant foods fortified with Vitamin D or supplements from supplements to achieve sufficient amounts.

How Does Vitamin D Work?

Most people associate vitamin D with keeping bones strong, but its uses go much beyond this. Vitamin D regulates various cellular functions in your body while protecting against cancer while simultaneously supporting immunity and muscle activity.

Vitamin D production begins in your skin, where sunlight converts 7-dehydrocholesterol to vitamin D3. Once produced, this precursor chemical travels to your liver and kidney for further modification and ultimately becomes 25(OH)D, binds with receptors on cells responsible for calcium metabolism and activates as 25(OH)D before finally becoming active as calcitriol – helping support bone health in its final form.

As vitamin D is fat-soluble, your body has the ability to store it for long periods of time and release it as needed when blood levels decline.

Insufficient vitamin D intake can deprive your bones of calcium, leading to osteoporosis and other bone conditions. Children suffering from vitamin D deficiency are at an increased risk for soft bones, deformities and softening while adults may be vulnerable to osteomalacia; which causes weak and fragile bones.

Food sources of Vitamin D may contain only trace amounts; researchers are studying its potential as an aid against cancer and heart disease. Although available as supplements, meat and dairy are usually the source of Vitamin D intake; instead it’s added to processed foods like cereals or ice cream for its inclusion. Researchers also test its use against cancer and heart disease symptoms through vitamin D treatments.

Vitamin D is one of the four lipid-soluble vitamins and, like its counterparts, acts like a hormone to maintain good health in even small doses. An FNB committee developed RDAs and ULs for vitamin D that would maintain adequate serum 25(OH)D concentrations in healthy individuals.

Vitamin D Deficiency

An estimated one billion people worldwide suffer from Vitamin D deficiency (VDD). This global epidemic can be largely attributed to environmental and lifestyle factors that prevent adequate sun exposure; elderly individuals, those spending less time outdoors and those limiting dietary consumption of the vitamin are particularly prone to VDD.

Vitamin D deficiency can lead to many health problems. Rickets is a condition affecting children and adolescents that occurs due to insufficient levels of this essential nutrient, often manifesting itself through bone deformities and painful, weak bones in children and adolescents. Severe cases may even require surgery as severe cases cause deformities of bones.

VDD can also have an effect on mental health and mood. A recent study demonstrated that low 25(OH)D levels are linked to depression and anxiety disorders. Researchers suggest the relationship is due to how vitamin D affects neurotransmitters in the brain.

People with darker skin are at an increased risk for vitamin D deficiency due to melanin, the natural pigment responsible for coloring skin tone. Furthermore, extra pounds may decrease production of 25(OH)D by their bodies and lead to deficiency.

Vitamin D deficiency is particularly prevalent among older individuals as their skin can’t produce vitamin D as efficiently from sunlight as younger people’s can, plus seniors often spend much of their time indoors as they age, which further decreases vitamin D production.

Other groups at risk for vitamin D deficiency include babies who are breastfed as human milk isn’t an ideal source; people living far from the equator, as their skin cannot make vitamin D from sunlight; and individuals with chronic illnesses that limit kidney or liver function or liver disease, who may have impaired ability to convert dietary vitamin D into its active form. Unfortunately, however, the committee responsible for setting vitamin D Reference Intakes (DRIs) concluded that evidence was insufficient or inconsistent enough to support any correlations between vitamin D intakes and any outcomes other than bone health outcomes.

Vitamin D Supplements

Vitamin D is often known as the “sunshine vitamin”, helping keep bones strong and healthy while also benefitting immunity and cell development. Research indicates it could even reduce depression risks.

Vitamin D, a fat-soluble vitamin found naturally in certain foods or added as dietary supplements, is converted in the body into its active form – 25(OH)D – which may contribute to various health conditions, including heart disease and cancer. Studies suggest a correlation between low vitamin D levels and certain health issues such as these.

Vitamin D is an essential nutrient and its primary source is sunlight exposure on skin. Unfortunately, prolonged sun exposure increases the risk of skin cancer and premature aging; consequently most people don’t get enough UVB rays on a regular basis to create vitamin D from sunlight [1. People with darker skin have an easier time making vitamin D from sunlight as their bodies produce more melanin which blocks some UVB rays necessary for its synthesis] while older adults may spend more time indoors thus not receiving sufficient amounts through diet alone [1.].

In November 2010, the Institute of Medicine (IOM) proposed a daily dosage of 600 International Units (IU) of Vitamin D as essential to adult health and normal calcium metabolism in healthy people. Their evidence-based recommendation stems from research showing the benefits of adequate Vitamin D consumption on bone health.

Due to variations in vitamin D intake across populations, optimal serum 25(OH)D concentrations cannot yet be identified. Although vitamin D concentrations tend to increase with increased intakes, their relationship may vary based on age, race/ethnicity, physiological measures of vitamin D status (e.g. serum 25(OH)D levels).

People with higher BMI tend to have lower vitamin D levels due to increased subcutaneous fat sequestering it from their bodies. According to IOM and other professional societies, BMI-adjusted vitamin D intakes should be used as an indicator for vitamin D deficiency; those with a higher BMI might require additional Vitamin D supplements in order to achieve an adequate serum 25(OH)D concentration level.