Vit D can be hard to come by, and sunlight is the ultimate source. Working together, calcium and vitamin D work wonders on strengthening bone tissue.

Lack of this “sunshine vitamin” has been linked with numerous health conditions, including multiple sclerosis and type 1 diabetes. Here’s how it works: 1. UVB rays from the sun initiate production of vitamin D3. 2. Once this process begins, any further exposure leads to further vitamin production by means of increased metabolism in cells which produce it 3.

Vitamin D Production

Vitamin D is essential to the absorption of calcium, essential for strong bones and teeth. Our bodies produce vitamin D from UV radiation exposure but it can also be obtained through food. Adults and children aged 1-year can consume 10 micrograms (mcg) daily of vitamin D; for younger children (aged 1-1) it’s 7mcg per day.

Vitamin D exists in two forms, known as D3 (cholecalciferol) and D2 (ergocalciferol). UVB rays from sunlight penetrate skin to convert 7-dehydrocholesterol to previtamin D3, which in turn is converted to 1,25 dihydroxyvitamin D by enzymes 25-hydroxylase, CYP2R1, and CYP27B1 to become 1,25(OH)2D; which acts by binding to vitamin D receptors on DNA at specific locations on DNA to regulate genes associated with bone, cell, and tissue growth and development.

People with darker skin have difficulty synthesizing vitamin D from sun exposure due to melanin pigment in their skin, although sunscreen usage and some occupational activities that limit sun exposure may help increase levels of Vitamin D production. Our kidneys convert the inactive form of Vitamin D into its active hormone form; however as we age this becomes less effective; while certain medical issues, such as Crohn’s disease or cystic fibrosis may inhibit how our bodies absorb Vitamin D through diet alone.

Most people can meet their vitamin D requirements from natural sunlight alone, provided they spend at least an hour outside and unclothed during midday when UV rays are strongest. In addition, certain food items – including fish, beef liver oil, egg yolks and fortified dairy and grain products – contain small amounts of vitamin D.

The Food and Nutrition Board (FNB) established RDAs for vitamin D to establish daily intakes sufficient to preserve bone health and normal calcium metabolism in healthy individuals while decreasing osteoporosis risk and fracture risk. They are expressed both in micrograms and international units; with one microgram equivalent to 40 international units. They noted that signs and symptoms of toxicity are unlikely at intakes below 250 micrograms/day but their optimal intakes remains uncertain, as lower doses could increase cardiovascular disease risks as well as decreasing bone mineral density and muscle strength.

Vitamin D Absorption

Vitamin D, commonly referred to as the “sunshine vitamin,” is essential for healthy bones and teeth. It plays an integral part in calcium absorption as well as regulating calcium metabolism and bone remodeling processes (the process by which old bone is broken down to make way for new ones). Vitamin D also has important immune system regulating properties.

Vitamin D can be found naturally in some food products, fortified foods and available as dietary supplements. There are two forms of vitamin D – D2 (“ergocalciferol” or pre-vitamin D) and D3 (“cholecalciferol”). Both forms are fat-soluble so can be stored by your body or absorbed through UVB light exposure to be synthesized by skin absorption to produce vitamin D synthesis.

Vitamin D production depends on factors like skin pigmentation and age; darker skin produces less, while using sunscreen reduces vitamin D synthesis. Some populations are at increased risk for low vitamin D levels due to living in northern latitudes, working shifts indoors or being homebound; older adults also face greater exposure risks as their ability to produce vitamin D decreases with age and reduced sun exposure.

After being synthesized or taken orally, vitamin D enters circulation and is converted to its biologically active form in both liver and kidney. First hydroxylation takes place in liver to create 25-hydroxyvitamin D or calcidiol; this form is then utilized throughout the body; second hydroxylation occurs in kidney to create 1,25-dihydroxyvitamin D or calcitriol for additional body use.

Deficient levels of active vitamin D can lead to bone diseases in adults such as osteomalacia and in children such as rickets. Furthermore, secondary hyperparathyroidism occurs, in which parathyroid glands overexpress calcium levels in blood to accelerate bone demineralization that causes bowed or bent bones.

Vitamin D Deficiency

Vitamin D is a fat-soluble vitamin that works to maintain normal calcium and phosphate levels in the blood, supporting bone health. Additionally, Vitamin D serves numerous other purposes, such as reduced inflammation, cell growth modulation, neuromuscular immune functions as well as glucose metabolism.

Human skin has the capacity to produce vitamin D with moderate sunlight exposure; however, the exact amount needed can depend on factors like season and time of day, skin pigmentation and disease such as celiac disease and Crohn’s disease that restrict fat absorption limiting vitamin D production.

Vitamin D deficiency is most often experienced among older adults due to inadequate sun exposure. People with dark complexions need longer exposure than people with lighter skin to create enough vitamin D; additionally, sunscreen use inhibits vitamin D synthesis.

Vitamin D deficiency symptoms include muscle and joint pain, weakness and fatigue. One study showed that 93% of patients referred for evaluation of chronic musculoskeletal pain had serum 25-hydroxyvitamin D concentrations below 20 ng/mL (50nmol/L), an indication of vitamin D deficiency.

Vitamin D deficiency can result in various medical issues for children and the elderly alike. For children, this can manifest itself in the form of rickets – caused by insufficiently mineralized bone tissue resulting in soft bones with deformities – while adults suffer osteomalacia which weakens bones with increased fracture risk as well as symptoms including fatigue, irritability, weakness and fasciculations (fasciculations).

Chronic vitamin D deficiency increases your risk of osteoporosis, according to research conducted on a large global scale. Researchers found that higher intakes of vitamin D were linked with reduced risks of osteoporosis among both women and men of all ages. Furthermore, vitamin D deficiency can lead to secondary hyperparathyroidism which accelerates bone demineralization resulting in osteoporosis as well as increased fracture risks among elderly persons. Furthermore, deficient levels may also result in muscle atrophy as well as reduced resistance against infections compared with their counterparts.

Vitamin D Supplements

There is ample evidence that diets rich in vitamin D can help prevent bone issues. Vitamin D also plays a crucial role in helping strengthen immunity, lower inflammation and conditions such as rheumatoid arthritis. Unfortunately, not everyone can produce enough of their own vitamin D through food alone; to make sure you receive sufficient amounts, supplements are usually the way to go.

Vitamin D supplements can be purchased over-the-counter in both capsule and tablet form, with Vitamin D3 (cholecalciferol) proving more effective than its cousin D2 (ergocalciferol). Vitamin D belongs to a class of fat-soluble secosteroids that promote intestinal absorption of calcium, magnesium, phosphate as well as have other biological impacts.

Studies indicate that vitamin D deficiency is linked with higher rates of cancer at various locations, cardiovascular disease, rheumatoid and type 1 diabetes as well as depression and other mental health disorders and bone health problems such as osteoporosis. Furthermore, studies indicate it could play a part in preventing influenza and coronavirus (COVID-19).

People with dark skin may not produce enough vitamin D from sunlight alone and should take supplements year-round to achieve the recommended daily allowance of vitamin D.

Review of clinical trials has demonstrated that most people with low serum 25(OH)D levels who took vitamin D supplements saw their rates of cancer and other diseases decrease, particularly among those diagnosed with depressive disorders or mild depression. This finding was particularly true among people who had previously been prescribed anti-depressant medication.

The Endocrine Society has issued recommendations that daily vitamin D intake not exceed 250 mcg (10.000 IU). While this does not indicate potential toxicity risks, excess intake could have adverse health implications over time. Notably, 1,25(OH)2D is the active form of vitamin D with a shorter half-life than 25(OH)D that is tightly regulated by parathyroid hormone levels, calcium-phosphorus metabolism and glucose metabolism [1]. 1.25(OH)2D directly regulates genes related to cell growth and differentiation, neuromuscular function and immunity [2]. A blood test designed to measure vitamin D can measure its level in your body in either nanomoles per liter (nmol/L) or nanograms per milliliter (ng/mL).