Vitamin D, also known as calciferol, is an essential nutrient for the human body. It is classified as a fat-soluble vitamin, meaning it dissolves in fats and oils and can be stored in the body's fatty tissues. There are two main forms of vitamin D: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). The first is found in some plant foods and fungi, while the second is obtained mainly through exposure to sunlight and in foods of animal origin.
The importance of vitamin D lies in its crucial role in regulating calcium and phosphorus in the body, which is essential for maintaining bone health. Additionally, recent research has linked vitamin D to a variety of additional biological functions and health benefits, including modulating the immune system and reducing the risk of certain chronic diseases.
Sources of Vitamin D
Solar exposition
The main source of vitamin D for most people is exposure to sunlight. When the skin is exposed to the sun's ultraviolet B (UVB) rays, 7-dehydrocholesterol in the skin is converted to previtamin D3, which in turn is converted to active vitamin D3. The amount of vitamin D a person can synthesize depends on several factors, including geographic latitude, season of year, time of day, skin color, and sunscreen use.
Food Sources
Although few food sources contain significant amounts of vitamin D naturally, some foods are fortified with this vitamin. Major dietary sources of vitamin D include:
Fatty fish: such as salmon, tuna and mackerel.
Cow liver.
Cheese.
Egg yolks.
Fortified foods: such as milk, cereals and orange juices.
Supplements
In many cases, especially in regions with little sun exposure or for people with specific dietary needs, vitamin D supplements are an important source. These supplements are available in two forms: vitamin D2 and vitamin D3. Vitamin D3 is generally preferred due to its greater effectiveness in increasing vitamin D levels in the body.
Absorption and Metabolism
Once ingested or produced in the skin, vitamin D3 is transported to the liver, where it is converted to 25-hydroxyvitamin D [25(OH)D], also known as calcidiol. This is the main circulating form of vitamin D and the one measured in blood to assess a person's vitamin D status. Then, in the kidneys, calcidiol is converted to its active form, 1,25-dihydroxyvitamin D [1,25(OH)2D], or calcitriol.
Calcitriol acts as a hormone, regulating various biological processes. Its best-known function is the regulation of calcium and phosphorus in the blood, promoting the intestinal absorption of these minerals and facilitating their deposit in the bones.
Features and Benefits
Bone Health
The most recognized function of vitamin D is its role in bone health. Calcitriol increases the intestinal absorption of calcium and phosphorus, two essential minerals for the formation and maintenance of strong bones. Without adequate levels of vitamin D, bones can become thin, brittle, or misshapen. In children, vitamin D deficiency causes rickets, a disease characterized by poor growth and skeletal deformities. In adults, vitamin D deficiency can lead to osteomalacia, which results in weak bones and an increased risk of fractures.
Immune system
Vitamin D also plays a crucial role in the functioning of the immune system. Calcitriol can modulate the immune response, helping to fight infections and reduce inflammation. Studies have shown that vitamin D can influence the activity of immune cells such as macrophages and lymphocytes, improving the body's ability to fight pathogens. Additionally, adequate levels of vitamin D have been associated with a lower incidence of autoimmune diseases, such as multiple sclerosis and rheumatoid arthritis.
Cardiovascular health
Recent research has suggested a relationship between vitamin D levels and cardiovascular health. Vitamin D may have beneficial effects on blood pressure and endothelial function, which is essential for maintaining blood vessel health. Some studies have found that low levels of vitamin D are associated with an increased risk of hypertension, heart disease, and stroke.
Mental and Cognitive Health
Vitamin D may also play a role in mental and cognitive health. Vitamin D deficiency has been found to be linked to an increased risk of mood disorders, such as depression, as well as cognitive decline in older adults. Although the exact mechanisms are not completely clear, vitamin D is thought to influence neurotransmitter synthesis and protect neurons from damage.
Vitamin D deficiency
Causes of Deficiency
Vitamin D deficiency can result from a variety of factors:
Insufficient sun exposure: due to spending a lot of time indoors, living in high latitudes, using sunscreen or clothing that covers most of the body.
Diet low in vitamin D: especially in people who follow strict vegetarian or vegan diets.
Absorption problems : Diseases that affect fat absorption, such as Crohn's disease or cystic fibrosis.
Impaired kidney or liver function: as these organs are crucial for the conversion of vitamin D to its active forms.
Older age: The skin's ability to produce vitamin D decreases with age.
Deficiency Symptoms
Symptoms of vitamin D deficiency can range from mild to severe and include:
Bone pain and muscle weakness.
Increased risk of infections.
Fatigue and general weakness.
Depression and mood swings.
In severe cases, rickets in children and osteomalacia in adults.
Supplementation and Dosage
General recommendations
Vitamin D needs vary depending on age, sex, and other individual factors. The general daily intake recommendations are:
Infants (0-12 months): 400 IU (10 mcg).
Children and adolescents (1-18 years): 600 IU (15 mcg).
Adults (19-70 years): 600-800 IU (15-20 mcg).
Older adults (>70 years): 800 IU (20 mcg).
Pregnant and lactating women: 600-800 IU (15-20 mcg).
Vitamin D supplementation may be necessary in certain population groups, such as people with limited sun exposure, diets poor in vitamin D, or medical conditions that affect the absorption or metabolism of the vitamin. It is important that supplementation be supervised by a health professional, since both deficiency and excess of vitamin D can have adverse effects.
Risks of Excess Vitamin D
Although rare, it is possible to have vitamin D toxicity, usually due to excessive supplement intake. Symptoms of vitamin D toxicity include:
Hypercalcemia (high levels of calcium in the blood).
Nausea, vomiting and weakness.
Bone pain.
Kidney problems, such as kidney stones.
Vitamin D and Chronic Diseases
Osteoporosis
Osteoporosis is a disease characterized by a decrease in bone density and an increased risk of fractures. Vitamin D is crucial in the prevention and management of osteoporosis, as it improves the absorption of calcium and phosphorus, necessary for the formation and maintenance of strong bones. Vitamin D supplements, often combined with calcium, are commonly recommended for people at risk of osteoporosis.
Diabetes
Some studies suggest that vitamin D may play a role in regulating insulin and glucose, which could have implications for the prevention and management of type 2 diabetes. However, the evidence is inconclusive and more research is needed. to confirm these effects.
Cancer
Research on the relationship between vitamin D and cancer has shown promising but not definitive results. Some studies have found that adequate levels of vitamin D may be associated with a lower risk of certain types of cancer, such as colon, prostate, and breast cancer. Vitamin D could influence cell proliferation and apoptosis, processes that are key in preventing the development and progression of cancer.
Vitamin D, or calciferol, is an essential nutrient with multiple functions in the human body. Its role in bone health is well known, but it also has important effects on the immune system, cardiovascular health, and possibly mental health and chronic disease prevention. Vitamin D deficiency is common and can have significant health consequences, underscoring the importance of maintaining adequate levels through sun exposure, diet, and, if necessary, supplementation.