1a,25-dihydroxyvitamin D has many important physiological roles beyond calcium metabolism. It modulates T and B lymphocyte functions, prevents inflammatory bowel diseases and influences myocardial contractility – among many others.

Vitamin D can be found both naturally in skin tissue exposed to UVB rays and in some foods; additionally it may also be obtained as a dietary supplement.

What Is Vitamin D?

Vitamin D, an organic prohormone derived from fatty acids, plays an essential role in bone mineralization and immune function, muscle activity and calcium absorption. Low levels can lead to rickets in children and osteomalacia in adults; optimal 25(OH)D concentrations have been linked with lower rates of fracture and improved health for older adults.

Vitamin D can be produced naturally through sun exposure or food sources; however, inadequate dietary intakes can result in deficiency. Furthermore, sunlight and food sources’ ability to increase blood levels of vitamin D decreases with age due to lower amounts of melanin producing sufficient protection from UV radiation; those who spend most of their time indoors could have deficient levels due to limited sun exposure due to location or occupation as well as those suffering from certain medical conditions like liver or kidney disease may experience lower vitamin D levels than desired.

Vitamin D inadequacy symptoms include bone pain, weakness and brittle bones. Low vitamin D concentrations may increase cardiovascular disease risk as well as diabetes risk. The Endocrine Society suggests taking 75 to 150nmol/L (37.5-60ng/mL).

Vitamin D supplements are generally safe when taken in reasonable amounts; however, excessive dosages may cause nausea and vomiting as well as increase your risk of calcium deposits in your heart (calcium myocarditis).

Some clinical trials indicate that supplementing with vitamin D could reduce muscle weakness and the rate of decline of muscle strength in frail older adults, but other studies have not discovered these benefits. It could be related to differences between studies regarding dosage or population studied or by using observational rather than randomized clinical trials for certain research projects.

How Do I Get Vitamin D?

Vitamin D can be produced naturally through sun exposure or through food and supplements; most people can meet their vitamin D needs through eating healthily and getting some sunshine, but some individuals may require taking a supplement year-round.

Fatty fish like salmon and tuna, liver, eggs, and vitamin D-fortified milk or juice are great sources of this essential nutrient; however, many children, teenagers, and adults don’t consume enough of these foods to meet the daily recommended dose of vitamin D. Therefore, food manufacturers add it into products like milk, orange juice, infant formula, yogurt margarine butter cheese breakfast cereals to fortify them with this essential nutrient; this process is called “fortifying.”

When people ingest vitamin D, their livers and kidneys convert it to its physiologically active form – 1,25-dihydroxyvitamin D [1,25(OH)2D] or calcitriol. This hormone regulates calcium levels in their blood and plays an essential role in maintaining bone health.

Most individuals can safely consume up to 4,000 International Units (IU) of vitamin D daily without risking hypercalcemia, an elevated blood calcium concentration that can damage kidneys, lungs, and heart tissue.

Vitamin D needs vary with age and are measured in micrograms or international units (IU). The Recommended Dietary Allowance (RDA) for adults 19 years or older is 600 IU daily while Tolerable Upper Intake Level is 4,000.

Too much vitamin D can lead to serious side effects, including overactive parathyroid glands that increase calcium levels in the blood, increasing osteoporosis risk and bone weakening, as well as calcium deposits building up in blood vessels and leading to hardening of arteries – an emergency situation requiring immediate medical care; often due to accidental overconsumption or prescription errors when taking supplements.

What Are the Benefits of Vitamin D?

Vitamin D is a fat-soluble secosteroid which increases intestinal absorption of calcium, magnesium, and phosphate. Additionally, vitamin D has multiple biological effects including modulating immune function and cell growth regulation. Multiple clinical trials indicate that supplementing with vitamin D could potentially improve cardiovascular disease risk factors including blood pressure reduction, cholesterol reduction and reduced heart attack or stroke risk factors.

The Institute of Medicine (IOM) advises adults ages 19 years or older to consume 600 IU of vitamin D daily; infants and children ages 1-8 years should receive 400 IU. A serum level of 25(OH)D provides the most reliable indication of vitamin D status.

Normal levels of 25(OH)D should not fall below 20 ng/mL, indicating a deficiency in this nutrient.

Lack of sun exposure, certain medications, and skin conditions may all play a part in low vitamin D levels. People with darker skin generally have lower blood vitamin D levels due to melanin being produced naturally in their skin which acts like a natural sunscreen and inhibiting production of vitamin D, while protecting from UV radiation damage.

Lack of Vitamin D can result in bone diseases such as osteomalacia and rickets. Rickets involves softened bones that easily bend. Osteomalacia occurs when bones break down faster than they can reform, leading to weak or brittleness of bones and an inability to regrow them quickly enough, creating weak or fragile bones.

Studies have demonstrated that adequate levels of vitamin D can reduce the risk of several cancers, including colorectal and breast cancers. Further study is necessary to understand whether higher vitamin D intake could prevent cancer and what other health outcomes might result from higher intakes; the US Preventive Services Task Force has determined there is not sufficient evidence for concluding whether higher than recommended dietary intakes of supplemented vitamin D will have any positive outcomes when it comes to cancer prevention or other positive health outcomes.

What Are the Risks of Vitamin D Deficiency?

People who fail to consume sufficient vitamin D through diet or sun exposure run the risk of vitamin D deficiency. Vitamin D deficiency is associated with weak bones and muscle weakness (rickets in children), increased risk for heart disease and cancer as well as impaired immune function. Vitamin D levels can be measured through blood tests known as 25(OH)D testing; its level is considered the primary indicator of status; other metabolites, like 1,25(OH)2D have shorter half lives that are tightly regulated by parathyroid hormone, calcium and phosphate making them less useful indicators [1].

In the United States, the Food and Nutrition Board of the National Academies of Sciences, Engineering, and Medicine recommends maintaining 25(OH)D concentrations between 30 nmol/L (12 ng/mL) and 50 nmol/L (20 ng/mL). Any concentration below these thresholds could indicate deficiency or inadequacy [1,2].

Age: The body’s ability to produce vitamin D decreases with age, particularly among elderly adults and infants who receive only breast milk for nutrition. Dark-skinned people generally have lower serum 25(OH)D levels compared with light skin people; whether or not this difference has major health implications remains unknown.

Fat Malabsorption: People suffering from medical conditions that restrict their gut’s ability to absorb fatty foods, including cystic fibrosis, Crohn’s disease, celiac disease and inflammatory bowel diseases, are at greater risk of vitamin D deficiency than those without these conditions. For instance, those affected may not be able to consume dairy products which provide ample vitamin D content, or may only eat small amounts due to discomfort or taste considerations.

Obesity: Individuals with higher body weight have lower serum 25(OH)D levels because more of their surface area is covered with subcutaneous fat, which absorbs vitamin D. Furthermore, people who are obese typically have higher blood pressure than people at a normal weight which further impairs bone health. Furthermore, having weight-loss surgeries which reduce stomach size or bypass parts of small intestine can make absorbing vitamins and minerals such as vitamin D more challenging.