Vitamin D (cholecalciferol) is an essential nutrient for bone health. Sunlight with UVB wavelength can penetrate exposed skin to produce vitamin D; additionally, foods and supplements provide additional sources of this essential nutrient.

Early research indicated that vitamin D could prevent rickets and possibly reduce risks related to influenza, respiratory infections, cancer, autoimmune diseases and other chronic conditions. More recent studies also suggest it can improve sleep and mood.

Sunlight

Sunlight is an important source of vitamin D, often known as “sunshine” vitamin. This fat-soluble nutrient plays a crucial role in strengthening bones, supporting cell growth and regulation and increasing immunity; helping absorb calcium and phosphorus essential for bone health as well as modulating over 1000 genes within our bodies.

At times, sunlight exposure triggers photosynthesis reactions in our bodies to produce vitamin D on its own, providing our bodies with enough of this essential nutrient for normal function. How much vitamin D we make depends on factors like season, latitude and skin pigmentation: light-skinned people can produce the recommended daily intake (25(OH)D) with half an hour of uninterrupted sun in summer at noon provided no sunburn occurs, while darker-skinned individuals require two hours. Both methods produce an equivalent level of 25(OHD). These amounts correspond with what would be produced from taking an oral 10 mg dose.

Evidence indicates that low serum 25(OH)D levels are linked with disease and mortality, including cardiovascular disease and cancer; studies also demonstrate a correlation between serum 25(OH)D levels and cardiovascular disease as a risk factor, and deficiency being an additional risk factor for these diseases.

Vitamin D stimulates production of cathelicidin, an antimicrobial polypeptide produced by our bodies that effectively fights viral and bacterial infections. Cathelicidin plays an integral part of our immune defense system’s arsenal against infection; lower vitamin D levels may explain an increase in respiratory infections like influenza or bronchitis during winter when 25(OH)D levels drop.

Although many populations receive adequate sources of vitamin D through diet alone, those who have limited exposure to sunlight could be vulnerable. This includes homebound people; women wearing religious head coverings for religious reasons; and people who regularly apply sunscreen, which has been shown to decrease vitamin D synthesis by up to 90 percent.

Food

Vitamin D is an essential fatty-soluble vitamin needed by your body to absorb calcium and phosphorus for strong bones, muscle function, immune health support and glucose metabolism.

Food sources of vitamin D include fatty fish (e.g. salmon, tuna and mackerel), beef liver and egg yolks; it can also be produced when exposed to sunlight; the Food and Nutrition Board of the Institute of Medicine recommends that people get most of their vitamin D through food sources in the US.

FNB’s 2011-2014 data indicates that most adults age one year and over in the United States were receiving adequate vitamin D levels based on serum 25(OH)D levels; however, 18% were at risk for inadequacy compared with FNB thresholds; proportions at risk differed depending on race/ethnicity with Blacks having the highest rate of inadequacy, followed by Hispanics and Whites.

This pilot study will use stable isotopically labeled vitamin D3 and cutting-edge mass spectrometric methodology to examine the dynamics of circulating 25(OH)D levels during gestation and its relationship to body fatness, vitamin D binding protein genotype/concentration genotype/concentration genotype and concentration in order to provide invaluable insight into how vitamin D is absorbed, utilized, and eliminated from our bodies.

Supplements

People can get vitamin D through food and supplements as well as sunlight exposure. Salmon, mackerel, trout, tuna and egg yolks all contain some form of vitamin D; also fortified products like yogurt cereal margarine fruit juices plant-based milk are often fortified with it too; fruit juices and some plant-based milks have added amounts of it too; capsules softgels gummies drops and drops are all forms of supplements available as capsules, softgels softgels or drops can contain higher doses such as 10,000 to 10,000 IU per day; doctors typically prescribe higher dosages than what FDA advises due to overdose symptoms including nausea vomiting diarrhea [2].

Vitamin D comes in two primary forms, D2 (ergocalciferol) and D3 (cholecalciferol). Both forms are easily absorbed from food or supplements in the small intestine through passive diffusion, without needing fat for absorption. Furthermore, intestinal fat increases vitamin D absorption without impacting conversion to 1,25(OH)2D production.

Vitamin D plays a central role in helping calcium ions move freely into and out of extracellular fluid, acting as a part of a regulatory system to balance calcium intake with mandatory excretory losses as well as parathyroid hormone-mediated calcification and bone mineralization processes.

Studies involving both healthy populations and those suffering from chronic illnesses have demonstrated the importance of adequate levels of vitamin D to bone formation and maintenance, but it remains unknown if higher 25(OH)D blood levels could help prevent or treat disease.

Vitamin D not only supports bone health but is also being studied to decrease cancer risks. Early research results indicate that vitamin D supplementation could potentially lower risks of colorectal, esophageal, and endometrial cancers.

Vitamin D requirements depend on factors like age, race and gender. Sunlight is one source of vitamin D production but sunscreen blocks it so achieving adequate amounts can be difficult for many. A federally funded food nutrition board committee in the US set Recommended Dietary Allowances (RDAs) based on an assumption that people do not spend excessive time outdoors while also receiving sufficient sources from diet.

Other Sources

Food provides numerous sources of vitamin D. Fatty fish such as salmon, tuna and mackerel are excellent sources; egg yolks and beef liver also contain some. Vitamin D can also be found in mushrooms, fortified dairy products (such as fortified milk and breakfast cereals) as well as some orange juices; unlike fatty fish these sources provide D2 (ergocalciferol) rather than D3 (cholecalciferol).

Sunlight is the main natural source of vitamin D; UVB radiation penetrates skin, where UVA energy converts 7-dehydrocholesterol to previtamin D3, which in turn forms 25(OH)D as an active hormone. Season, time of day, cloud cover, smog levels and melanin content of skin all influence its production; elderly individuals are at particular risk as their ability to make vitamin D diminishes with age; those who spend most of their lives indoors for religious or personal reasons such as homebound elderly or those wearing long robes won’t get enough sunlight to meet their vitamin D needs through sun exposure alone.

People with darker skin may have lower blood levels of vitamin D due to melanin’s role as a filter that reduces their ability to absorb UVB radiation and produce vitamin D. While evidence for any health implications from differences in serum 25(OH)D levels between ethnicities remains inconclusive, many experts advise maintaining adequate serum 25(OH)D levels regardless of skin tone; NHANES 2011-2014 data indicate that most Americans get enough Vitamin D intake.