Vitamin D has emerged as an indispensable nutrient in maintaining bone health, yet a significant proportion of people worldwide do not meet their minimum requirement for it.[1]

Early observational studies uncovered correlations between vitamin D intake and various health benefits, as demonstrated by observational studies. Later on this was corroborated by several randomized controlled trials (RCTs).

What is Vitamin D?

Vitamin D is produced when your skin is exposed to sunlight. You can also find it in certain food products like fish, dairy and fortified cereals. In the US, vitamin D measurements are measured either in micrograms (mcg) or international units (IU); where one IU equals approximately 40 mcg.

Vitamin D is a fat-soluble vitamin essential to bone health and neurologic functioning. A deficiency may result in muscle weakness, bone pain and fatigue – symptoms of which include lack of Vitamin D can also help regulate the renin-angiotensin-aldosterone system (RAAS) which plays a key role in blood pressure regulation.

Most people can obtain enough vitamin D from sunlight and some food sources; however, production decreases during winter, increasing their risk for deficiency due to limited sun exposure, skin pigmentation or anti-rejection drugs that interfere with production of vitamin D by blocking its ability.

Studies suggest that increasing vitamin D intake could decrease cancer risks; however, additional research must be completed in order to confirm these results.

The USPSTF recommends daily supplementation of most adults and children with 20 micrograms (800 international units) of vitamin D. A food or supplement considered high in nutrients when it contains 20% or more of the Daily Value for that nutrient, listed on Nutrition Facts labels of foods to help consumers evaluate the nutrient contents in relation to an overall healthy diet.

Why is it important?

Vitamin D is essential to building and maintaining strong bones, while also supporting many other vital cellular processes in the body. Calcium absorption is one of the keys to bone health; in addition, vitamin D deficiency has been linked with soft, brittle bones in children (rickets) as well as osteomalacia among adults. [1, 2]

Sun exposure remains the top source of Vitamin D for most people, yet many are falling short in meeting their minimum daily requirements. Age, skin pigmentation, sunscreen usage and cloud cover all affect how much UV radiation penetrates through to produce vitamin D; UVB radiation cannot penetrate glass windows and sun screens so therefore sun exposure under such circumstances will not result in vitamin D production.

Most people do not recognize the significance of vitamin D and do not consume sufficient amounts through their diet, particularly older adults. According to surveys conducted with those aged 51-71% years, their median daily vitamin D consumption averages 308 International Units or approximately half the Recommended Daily Allowance[3.

Vitamin D obtained either through sunlight exposure or supplements undergoes two hydroxylation reactions within the body to become active and exert its biological effects. The first occurs in the liver and forms 25-hydroxyvitamin D [25(OH)D], or calcidiol; while in kidney it transforms to 1,25-dihydroxyvitamin D or calcitriol.

Vitamin D intakes beyond the Recommended Nutrient Intake (RNI) have not been shown to cause adverse side effects in most people; however, some individuals may require supplements of Vitamin D in order to achieve an ideal serum level.

An individual who has had gastric bypass surgery often experiences difficulty digesting fat, and may require vitamin D supplements in order to achieve the necessary serum concentration levels. Furthermore, medical conditions like cystic fibrosis, Crohn’s disease, celiac disease or ulcerative colitis may interfere with fat absorption making it harder for individuals to receive enough Vitamin D.

Vitamin D deficiency has been associated with an increased rate of cancer across several sites, such as pancreas and colon, as well as higher incidences of cardiovascular events like heart attack and stroke. The VITAL clinical trial, in which 25,871 people received either 2,000 IU of Vitamin D daily for three years or placebo pills instead, revealed that those taking Vitamin D experienced reduced cancer mortality risks than their peers who received only placebo pills.

How do I get vitamin D?

Most people can obtain enough vitamin D through diet alone. Milk and cereals that contain fortified milk often include Vitamin D supplements; check nutrition labels carefully to be sure. Our bodies produce Vitamin D when exposed to ultraviolet rays from sunlight; too much exposure may lead to sunburn or skin cancer. A person suffering from deficiency often exhibit fatigue, bone pain, muscle weakness and changes in mood – if this sounds familiar speak with your GP about getting tested for vitamin D levels; they may recommend getting blood tests to measure them accurately.

Skin is an important source of vitamin D production and typically produces enough to maintain healthy levels within several months with adequate sun exposure. Unfortunately, many individuals lack sufficient exposure due to living in areas with limited sunlight during winter or spending much of their time indoors either for work or school; in addition, melanin in dark skin acts like a sunscreen, inhibiting vitamin D synthesis.

Food and Nutrition Board (FNB) experts developed Recommended Dietary Allowances (RDAs) for vitamin D to promote bone health and calcium metabolism in healthy individuals with minimal exposure to direct sunlight. The RDAs assume this daily consumption can support bone health.

Foods rich in vitamin D include liver, egg yolks, fish, fortified milk and some tropical oils. Foods with the highest amounts of vitamin D typically list their content using micrograms per daily or milliliters as measurements of how much is in each serving of their product.

Vitamin D consumption from food or supplements should generally not exceed the Tolerable Upper Intake Level (UL). Vitamin D supplementation doesn’t appear to increase kidney stone risk, however; calcium and phosphorus levels in your blood must still be closely monitored in order to detect any excess. If you are taking certain medications for kidney disease or have kidney stones, consulting your GP may advise lower doses of vitamin D so as to limit excessive absorption; they will also offer advice about adequate calcium consumption.

What is the best way to get vitamin D?

Sunlight is the primary source of vitamin D, earning it the moniker “sunshine vitamin.” UVB radiation penetrates bare skin and converts 7-dehydrocholesterol to previtamin D3 before becoming vitamin D itself. Certain food items also contain fortified versions. Since overexposure to UV radiation can damage skin cells and lead to cancer risk, experts advise people taking daily vitamin D supplements rather than spending extended time outdoors.

Vitamin D intake is typically measured using the 25-hydroxyvitamin D blood test (25(OH)D). This nutrient is thought to play an integral role in calcium absorption and bone development; without enough, calcium absorption becomes impaired and bones weaken (osteoporosis in adults, rickets in children). Furthermore, evidence indicates that vitamin D could prevent certain autoimmune diseases like type 1 diabetes and rheumatoid arthritis although further research needs to be completed on this possibility.

People with darker skin or who spend less time outdoors are at greater risk of vitamin D deficiency, but according to the National Institutes of Health’s recommendations most individuals can obtain enough Vitamin D through sunlight and food-fortified sources like fortified foods.

An effective way of meeting vitamin D requirements safely is with multivitamin and mineral supplement use; most adults and infants usually need only 10 micrograms a day of vitamin D supplementation; higher dosages may be needed if taking medications or experiencing health conditions that necessitate increased vitamin D supplementation.

Vitamin D toxicity is extremely unlikely and typically only results from taking excessively large doses of supplement vitamin D. Too much vitamin D can lead to hypercalcemia (an excessive build-up of calcium in the body) which may weaken bones and produce other serious side effects, typically when taken over an extended period without supervision from a doctor. People should not exceed taking more than 4,000 IU per day of vitamin D as this could be harmful; those with kidney issues should limit themselves to taking only 2,000 IU a day of this vitamin