Vitamin D is special because it can be made in the skin from exposure to sunlight (Nair & Maseeh, 2012). It is classified as a conditional vitamin (Beauchesne, 2018). What makes it an essential vitamin is that people’s dress, work, and geography get in the way of attaining enough Vitamin D from sunlight (Nair & Maseeh, 2012). The purpose of Vitamin D is to control calcium absorption in the small intestine; it works with the parathyroid hormone to facilitate skeletal mineralization and sustain calcium homeostasis in the bloodstream” (Kulie et al., 2009).
Vitamin D exists in two forms: Vitamin D2 and Vitamin D3. Vitamin D2 or ergocalciferol is seen in plants and some fish (Nair & Maseeh, 2012). Vitamin D3 or cholecalciferol is synthesised in the skin when it is exposed to natural light (Kulie et al., 2009). One way to get vitamin D is through a small number of dietary sources (Brickley et al., 2014). Human beings can not make vitamin D2, but it can be found in food sources such as fatty fishes like sardines or salmon, cod liver oil, fortified dairy, and a little from eggs, butter, and liver (Nair & Maseeh, 2012). People can reach their vitamin D requirements by either ingesting vitamin D or receiving sunlight for enough time to create sufficient amounts (Kulie et al., 2009).
The focus of Vitamin D intake is largely on Vitamin D3 because Vitamin D3 can be created in the skin by ultraviolet B rays (Kulie et al., 2009). It begins with a compound called 7-dehydrocholesterol and the sunlight changes this to cholecalciferol (Kulie et al., 2009). This Vitamin D3 comes into the bloodstream and it is transformed into the active form calcitriol by the liver and kidneys (Kulie et al., 2009). The time needed to produce an acceptable level of vitamin D from the skin depends on the strength of the UVB rays from geographical location, the length of time spent in the sun, and the amount of pigment in the skin (Kulie et al., 2009). The exposure time required is generally low; experts estimate 5–10 minutes, two to three times per week, with limited skin exposure is sufficient (Brickley et al., 2014).
Prevalence of Vitamin D Deficiency
Even though it seems that people all over the world can have enough Vitamin D because it is so easily absorbed into the skin from sunlight, Vitamin D insufficiency impacts almost 50% of the population worldwide (Nair & Maseeh, 2012). There is an estimated 1 billion people worldwide, across all ethnicities and age groups, have a vitamin D deficiency (VDD) (Nair & Maseeh, 2012). This pandemic can mainly be credited to lifestyle and environmental factors that reduce exposure to sunlight (Nair & Maseeh, 2012).
Vitamin D deficiency has been defined by the Institute of Medicine as a 25(OH)D (Calcifediol hormone) of 21–29 ng/mL (Nair & Maseeh, 2012). Children and adults are at equally high risk for Vitamin D deficiency and insufficiency worldwide (Nair & Maseeh, 2012). Vitamin D deficiency is very common in the Western world, particularly in northern latitude (Nair & Maseeh, 2012). Figuring of Vitamin D needs is an area of significant scientific research and uncertainty. It depends on exposure to sunlight, but also we do not know what is ideal. Experts on this topic say that anything greater than 30 ng/ml is good, but many people have levels below 20 ng/ml in North America and Europe (Nair & Maseeh, 2012).
Factors Associated with Vitamin D Deficiency
Poor Intake
There are multiple reasons for vitamin D deficiency. An important reason for vitamin D deficiency can be insufficient intake of dietary vitamin D. There are not many foods that naturally contain vitamin D; Oily fish like salmon, mackerel, and sardines are some foods that are rich in vitamin D (Haroon & Fitzgerald, 2012). Only a few number of foods are secured with vitamin D such as milk, orange juice ,and some bread and cereals (Haroon & Fitzgerald, 2012). This defense against deficiency is used in many developed countries.
The average rise in serum 25(OH) D concentrations has been estimated at 1–2 nmol/L for every 40 IU of vitamin D3 contingent on baseline 25(OH)D concentrations (Haroon & Fitzgerald, 2012). Normally, the two forms of vitamin D are considered equal. In actuality, vitamin D3 is the more potent form of vitamin D compared to vitamin D2 when looking at 25(OH) D objectiviely (Haroon & Fitzgerald, 2012). This is why vitamin D2 should not be used for fortification; Vitamin D3 from sunlight should be weighed more when combating VDD (Brickley et al., 2014).
Season and Latitude
Seasonal and latitudinal variations of 25(OH)D levels are crucial factors of determining Vitamin D deficiency (Haroon & Fitzgerald, 2012). These variations of sunlight report that sun exposure has the greatest levels during the summer and reduced levels in late winter season (Haroon & Fitzgerald, 2012). The scientific reasoning for this is that more UVB photons are absorbed by the ozone layer during the winter because the sun rays come through a more oblique angle (Haroon & Fitzgerald, 2012). Little vitamin D3 is created in the skin during the winter months due to a decreased number of UVB photons reaching the earth surface (Holick & Chen, 2008).
Even in the sunniest areas of the world, vitamin D deficiency is very common issue in both children and adults (Holick & Chen, 2008). The angle at which the sun reaches the earth has a significant impact on the number of UVB photons that reach the earth’s surface (Holick & Chen, 2008). Clothing is a factor that limits the sun exposure to people in good latitudes for Vitamin D. An example of this is the practice of purdah (Holick & Chen, 2008). This is cultural custon where all of the skin covered (Holick & Chen, 2008). The people who practice this custom are at high risk of vitamin D deficiency. The location you live in always keep you at risk from vitamin D deficiency. About 30 – 50% of people living in the United States, Europe, Middle East, India, Australia, and Asia are all at risk for vitamin D deficiency (Holick & Chen, 2008).
Skin Exposure to Sunlight
The major source of vitamin D for people is sunlight exposure (Haroon & Fitzgerald, 2012). About 90% of our vitamin D requirements come from sunlight exposure (Haroon & Fitzgerald, 2012). Melanin is tremendously effective for absorbing UVB radiation; this is because the increased skin pigmentation distinctly diminishes vitamin D3 synthesis (Holick & Chen, 2008). African Americans at risk for Vitamin D deficiency because the ability to make vitamin D in their skin is decreased by as much as 99% (Holick & Chen, 2008). Black people absorb more UVB in the melanin of their skin than do white people; as a result, they need more sun exposure in order to generate the same amount of vitamin D (Nair & Maseeh, 2012). Most African Americans who live in a temperate climate are vitamin D deficient (Holick & Chen, 2008). Africans that reside near the equator at not deficient because vitamin D3 synthesis is more effective from the higher flux of UVB photons (Holick & Chen, 2008).
Infancy
All these factors can be prevented in early stages of development. There is a compelling correlation between maternal circulating serum 25 (OH) D levels and infant vitamin D levels (Brickley et al., 2014). Breast fed infants are one of the general groups that are considered to be at a higher risk of acquiring vitamin D deficiency (Nair & Maseeh, 2012). Breast milk is still important for health because it has compounds for growth, maturation and immunity to local pathogen (Beauchesne, 2018). Human milk usually provides <25 IU/L to 78 IU/L, but this is not sufficient to meet vitamin D requirements (Nair & Maseeh, 2012). There has been evidence that Vitamin D content of breast milk is related to mother’s vitamin D status (Nair & Maseeh, 2012). The conclusion of this correlation is that vitamin D deficiency in a pregnant woman causes deficiency in the fetus (Nair & Maseeh, 2012). This can greatly influence the baby’s health, not only during their early stages of life but also adulthood (Brickley et al., 2014).
Consequences of Vitamin D Deficiency
Vitamin D deficiency ensues irregularities in calcium, phosphorus, and bone metabolism (Nair & Maseeh, 2012). VDD creates a decrease in the absorption of dietary calcium and phosphorus, resulting in an increase in PTH levels (Nair & Maseeh, 2012). This increase causes an rise in osteoclastic activity and the location of bone weakness; the result is a widespread decrease in bone mineral density (Nair & Maseeh, 2012). In time, this can become serious issues such as osteopenia and osteoporosis (Nair & Maseeh, 2012). A mineralization defect in the skeleton comes from deficiency as well (Nair & Maseeh, 2012). Young children already have little mineral in their skeleton, so this defect can be even worse for them (Nair & Maseeh, 2012). A major skeletal deformity is known as rickets (Nair & Maseeh, 2012).
Rickets
The effect of breast feeding on the occurrence of vitamin D deficiency and rickets in infants is a possibility that has been discussed (Brickley et al., 2014). In the USA, there have reports of cases of nutritional rickets from at least 17 states between 1986 and 2003 (Papandreou et al., 2009). A high prevalence of vitamin D deficiency has also been reported in infants, children, and adolescents from diverse countries around the world, including the UK, France, Greece, etc (Papandreou et al., 2009).
Research studies that have been done in China show that 18% of total 42 healthy infants were found with rickets and not all infants with rickets in this study had low 25(OH)D concentrations (Papandreou et al., 2009). This creates two different possibilities: (1) rickets is not necessarily linked to vitamin D deficiency, or (2) serum 25(OH)D concentrations are not the greatest marker of vitamin D status (Papandreou et al., 2009). More research among infants and adolescence shows that prevalence rates of vitamin D deficiency have secondary variations due to season, latitude, and race/ethnicity (Papandreou et al., 2009). Another report from Canada has shown that 94% of infants detected with rickets had been breast fed (Nair & Maseeh, 2012). The American Association of Pediatrics recommends for infants who are breastfed to be supplemented with 400 IU of vitamin D per day to combat Vitamin D defiency (Nair & Maseeh, 2012).
Solutions for Preventing Vitamin D Deficiency Early
Breast milk is an ideal mode of nourishment for a newborn (Kulie et al., 2009). Research has shown that only breast milk is not adequate to maintain newborn vitamin D levels within a normal range (Kulie et al., 2009). Newborns are not exposed to enough sunlight. Many nursing mothers or their infants need vitamin D supplementation for optimal health (Kulie et al., 2009).
The American Academy of Pediatrics recommends that 200 IU of vitamin D be used as supplementation during the first 2 months after birth for infants (Kulie et al., 2009). In 2008, the recommendation intensified to a minimum of 400 IU daily during the first days of life to inhibit vitamin D deficiency that may lead to rickets (Kulie et al., 2009).
Other Treatments for Children
The public health measures to prevent Vitamin D deficiency is important. As children grow older, sun exposure is more recommended. Sunlight exposure to the arms and legs for 5 to 30 minutes in the late morning or early afternoon twice a week can be acceptable to prevent vitamin D deficiency (Kulie et al., 2009).
Vitamin D intake through diet is another important natural source that should be used instead of supplementation (Kulie et al., 2009). If serum 25(OH)D testing in infancy shows that a child is Vitamin D deficient, then it is still necessary (Kulie et al., 2009). If possible, the best way to get essential vitamins and minerals is through food (Beauchesne, 2018). The American diet are so deficient in different nutrients that supplements are needed to make up for it (Beauchesne, 2018). Dietary sources of vitamin D contain salmon, sardines, mackerel, tuna, cod liver oil, and egg yolk (Kulie et al., 2009). Examples of fortified foods are milk, orange juice, yogurts, butter, etc. (Kulie et al., 2009). Those people with risk factors of melanin, latitude, and sun exposure should be using the recommended daily vitamin D for prevention of deficiency.
Future Implications
Vitamin D deficiency is an important public health issue because it is an independent risk factor for mortality in the general population (Nair & Maseeh, 2012). New research shows the possible role of vitamin D against cancer, heart disease, fractures and falls, autoimmune diseases, influenza, type-2 diabetes, etc. (Nair & Maseeh, 2012). This is why many health care providers up their recommendations for vitamin D supplementation to at least 1000 IU (Nair & Maseeh, 2012). It is certain that various cancers, infections, and hip fractures will still happen under conditions of optimal vitamin D status (Heaney, 2008). It is just with sufficient Vitamin D, there is less risk (Heaney, 2008).
Conclusion
Vitamin D is an important hormone as the numbers of people with Vitamin D deficiency is increasing. Vitamin D deficiency is common amongst all ages, but can be preventative in the early stages of infancy and adolescence. There are few foods contain vitamin D and breastmilk is not enough Vitamin D. Also, the change in latitude, season, or skin exposure from the sun significantly influences the skin’s production of vitamin D3. The guidelines recommend supplementation of vitamin D at acceptable UL levels. There has been an increase of rickets situation worldwide. The paper examines maternal vitamin D deficiency as well as infant deficiency and how proper infant and child feeding along with supplementation can combat it. To fight future Vitamin D problems, having a standardization of vitamin D deficiency and repletion protocols is necessary to better shape future studies of vitamin D supplementation.