Vitamin D is one of the most important nutrients for our bodies. Despite its important role in maintaining health, many people do not realize how crucial it is to our daily functioning.
What is vitamin D?
Definition and history of discovery
Vitamin D is a group of fat-soluble prohormones that play a key role in regulating the body's calcium metabolism. It was first discovered in the early 20th century, when it was noted that a diet rich in cod liver oil helped treat rickets in children. This led to the discovery of vitamin D as an essential nutrient.
Forms of vitamin D
Vitamin D comes in two main forms:
- Vitamin D2 (ergocalciferol): Derived mainly from plants and fungi. It is often used in dietary supplements.
- Vitamin D3 (cholecalciferol): Is produced in the skin of humans and animals when exposed to UVB radiation. It can also be found in animal products such as fatty fish and egg yolks.
Vitamin D3 is more effective in raising vitamin D levels in the body than D2.
How is vitamin D synthesized in the body?
The process of synthesis
Vitamin D is unique in that our body can synthesize it on its own when exposed to UVB radiation. This process takes place in the skin, where 7-dehydrocholesterol (a precursor to vitamin D) is converted into previtamin D3 and then into vitamin D3.
Factors affecting vitamin D synthesis
Vitamin D synthesis depends on many factors, including:
- Time spent in the sun: Shorter winter days and longer summer nights affect the amount of UVB radiation reaching our skin.
- Season: Vitamin D synthesis is reduced during the winter months, especially at higher latitudes.
- Skin pigmentation: People with darker skin have more melanin, which can reduce the efficiency of vitamin D synthesis.
- Sunscreen use: UV filters can block UVB radiation and thus reduce vitamin D synthesis.
Functions of vitamin D in the body
Effects on bone health
Vitamin D plays a key role in the metabolism of calcium and phosphorus, which are essential for bone health. It helps absorb calcium from the gut and maintains adequate levels of this mineral in the blood, which is important for bone mineralization.
Supporting the immune system
Vitamin D influences the function of the immune system, helping to fight infections. Studies have shown that people with adequate levels of vitamin D have a lower risk of respiratory infections such as the flu and colds.
Role in cardiovascular health
A growing body of evidence suggests that vitamin D may have a positive effect on heart health. It helps regulate blood pressure, and a deficiency may be associated with a higher risk of cardiovascular disease.
Effects on mental health
Vitamin D is also important for mental health. Studies indicate that its deficiency may be associated with a higher risk of depression and other mood disorders.
Effects on metabolism
Vitamin D affects metabolic processes, which may be important for weight control. It supports insulin action, which is important for people with type 2 diabetes.
Sources of vitamin D
Natural dietary sources
Although skin synthesis is the main source of vitamin D, there are also natural food sources that can help maintain adequate levels:
- Oily fish: Such as salmon, mackerel, sardines or tuna.
- Trane: Is one of the richest sources of vitamin D.
- Egg yolks: They contain small amounts of vitamin D.
- Beef liver: Contains both vitamin D and other essential nutrients.
- Mushrooms: Some species, especially those exposed to UV light, are sources of vitamin D2.
Dietary supplements
For many people, vitamin D supplementation is essential, especially during winter or for those with limited sun exposure. Both vitamin D2 and D3 supplements are available, with D3 being more recommended due to its better bioavailability.
Enriched foods
Some foods are fortified with vitamin D, which is especially popular in countries with low sunlight:
- Milk and dairy products: Often fortified with vitamin D, which helps with its consumption in the daily diet.
- Fruit juices: Some orange juices are fortified with vitamin D.
- Breakfast cereals: Many brands enrich their products with vitamin D.
Vitamin D deficiency
Causes of deficiency
Vitamin D deficiency is a common problem worldwide, and the causes can be varied:
- Limited sun exposure: Particularly in countries with low sunlight.
- Improper diet: Lack of intake of vitamin D-rich foods.
- Absorption problems: Some diseases, such as celiac disease and Crohn's disease, can affect vitamin D absorption.
- Aging: As we age, the skin loses its ability to efficiently synthesize vitamin D.
Symptoms of deficiency
Vitamin D deficiency can lead to a number of symptoms, including:
- Muscle weakness: Vitamin D deficiency can lead to muscle weakness and muscle pain.
- Mood disorders: Deficiency is often associated with depression and anxiety.
- Increased risk of infection: Vitamin D deficiency can weaken the immune system.
- Bone problems: It can lead to osteomalacia in adults and rickets in children.
Deficiency diagnosis
Diagnosis of vitamin D deficiency is based mainly on blood tests that measure 25-hydroxyvitamin D levels. A level below 20 ng/ml is considered deficiency.
Treatment and prevention
Treatment of vitamin D deficiency usually consists of supplementation and increased intake of vitamin D-rich foods. Regular exposure to the sun is also important.
Vitamin D excess
Causes of excess
Excess vitamin D, known as hypervitaminosis D, is rare, but can occur as a result of over-supplementation.
Symptoms of excess
Symptoms of vitamin D excess may include:
- Hypercalcemia: Too high a concentration of calcium in the blood, which can lead to nausea, vomiting and weakness.
- Kidney problems: Excess calcium can lead to kidney stones and kidney damage.
- Heart problems: High levels of calcium can affect heart rhythm.
Treatment of excess
Treatment of vitamin D excess involves stopping supplementation and limiting calcium intake. In more severe cases, hospitalization may be required.
Vitamin D and different age groups
Children
Vitamin D is crucial for normal bone growth and development in children. Vitamin D deficiency in childhood can lead to rickets, a disease characterized by softened and deformed bones. Therefore, pediatricians often recommend vitamin D supplementation for infants and children, especially during winter or for breastfed children who may not be getting enough of the vitamin from breast milk.
Adults
For adults, vitamin D is important not only for bone health, but also for maintaining adequate energy levels and well-being. Adults who don't spend enough time in the sun may be at risk of vitamin D deficiency, which can lead to weakened muscles and reduced bone density, increasing the risk of fractures.
Elderly people
The elderly are particularly vulnerable to vitamin D deficiency due to their skin's reduced ability to synthesize the vitamin and more frequent avoidance of sun exposure. Vitamin D deficiency in the elderly has been linked to osteoporosis, increased risk of fractures, and muscle weakness, which can lead to falls.
Vitamin D and chronic diseases
Osteoporosis
Osteoporosis is a disease characterized by reduced bone density, which increases the risk of fractures. Vitamin D plays a key role in preventing osteoporosis by promoting the absorption of calcium and phosphorus, which are essential for maintaining healthy bones.
Diabetes
Research suggests that vitamin D may affect insulin sensitivity and glucose metabolism, which is important in the prevention and treatment of type 2 diabetes. People with vitamin D deficiency may be at greater risk of developing the disease.
Cardiovascular diseases
Vitamin D deficiency is associated with a higher risk of cardiovascular diseases, such as hypertension, atherosclerosis, and heart attack. Vitamin D can affect heart health by regulating blood pressure and reducing inflammation.
Cancers
Some studies indicate that adequate vitamin D levels may have a protective effect against certain types of cancer, such as colon, prostate, and breast cancer. The mechanisms may include regulating cell growth and reducing inflammation.
How to maintain adequate vitamin D levels?
Recommended dosages
Recommended vitamin D dosages vary depending on age, gender and health status. General guidelines suggest:
- Infants (0-12 months): 400-600 IU per day
- Children (1-18 years): 600-1000 IU per day
- Adults (18-70 years): 600-2000 IU per day
- Elderly (over 70 years): 800-2000 IU per day
Ways to increase vitamin D levels
To maintain adequate vitamin D levels, it's a good idea:
- Expose yourself to the sun regularly: About 15-30 minutes of sun exposure per day is recommended, depending on the season and latitude.
- Consume foods rich in vitamin D: Incorporating oily fish, eggs and fortified products into your diet can help increase your vitamin D intake.
- Supplement vitamin D: Especially during the winter months or for those with limited sun exposure.
Lifestyle tips
In addition to diet and supplementation, there are other ways to increase vitamin D levels:
- Outdoor activity: Regular walks outdoors can increase sun exposure.
- Healthy lifestyle: Avoiding smoking and excessive alcohol consumption, which can affect vitamin D metabolism.
Vitamin D is an essential nutrient that plays a key role in maintaining bone health, supporting the immune system and regulating metabolism. Despite its importance, many people are deficient in this vitamin, which can lead to serious health problems. Understanding how vitamin D works in the body, what its sources are and how to maintain adequate levels is crucial for a healthy life.
Sources:
- Sources of vitamin D / Deficiency / Excess / Recommended doses / Increasing levels: https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
- Age groups: https://nutritionsource.hsph.harvard.edu/vitamin-d/
- Vitamin D and the Immune System
- Vitamin D: An overview of vitamin D status and intake in Europe
- Clinical characteristics and outcomes of pediatric patients with desmoplastic small round cell tumor
- Inhibition of Contraction-Stimulated AMP-Activated Protein Kinase Inhibits Contraction Stimulated Increases in PAS-TBC1D1 and Glucose Transport Without Altering PAS-AS160 in Rat Skeletal Muscle