What is vitamin D?
Vitamin D is a fat-soluble vitamin (which dissolves in lipids), whose main function is to maintain normal values of calcium and phosphorus in the blood. This vitamin is necessary for bone growth and remodeling. Its deficiency can cause bone changes, such as osteomalacia in adults and rickets in children.
How is vitamin D produced?
Vitamin D is produced in the body through sun exposure (ultraviolet-UVB rays), and is particularly relevant in childhood and the elderly.
Are there different forms of vitamin D?
The main forms are known as vitamin D2 (ergocalciferol: plant-based) and vitamin D3 (cholecalciferol: animal-based).
Vitamin D3 is produced in the body through exposure to sunlight, and vitamin D2 is the form present in most supplements.
There is also calcidiol, the way vitamin D is stored in our body, and calcitriol, the active form of vitamin D.
Is the sun the only source of vitamin D?
Nope. Vitamin D can be acquired through diet and supplementation. However, there are few foods naturally rich in this vitamin, so you should prioritize the consumption of:
- Fatty fish such as:
- salmon
- tuna
- herring
- sardine
- mackerel
- eel
- cod liver oil
- egg yolk
- some mushrooms
There are also other sources of vitamin D: dairy products, cereals fortified with vitamin D, vegetable spreads with vitamin D.
Vitamin D supplements are found in the form of tablets, capsules or liquid/drops, and are generally indicated at certain stages of life, for people with a low intake of foods rich in this nutrient, little exposure to the sun or health problems that decrease the absorption of this vitamin, such as some medications (anticonvulsants, antiretrovirals, glucocorticoids), diseases associated with malabsorption, such as celiac disease.
Supplementation should be indicated by a healthcare professional.
What is the function of vitamin D in our body?
Its main function is to intervene in the processes that lead to an adequate mineralization of the bones, but also to favor:
- intestinal absorption of calcium and phosphorus
- Maintenance of normal immune system function
- Normal growth and development of bones and teeth
Vitamin D also has a protective effect on some diseases:
- infectious
- Autoimmune
- Cardiovascular
- Oncology
What are the symptoms of vitamin D deficiency?
The manifestations of a lack of vitamin D in our body depend on the amount lacking and its duration.
Most patients have a mild to moderate deficit and therefore have no symptoms. In cases where symptoms arise, they include pain and weakness in the muscles and tiredness.
Should we have tests to assess vitamin D levels?
Nope. In general, it is not recommended that a healthy person undergo tests to find out if they have a lack of vitamin D.
What factors reduce vitamin D production?
The situations that favor vitamin D deficiency are:
- lack of sun exposure in a healthy and adequate way
- greater skin pigmentation, as dark skin produces less vitamin D
- low intake of vitamin D-rich foods
- Living in places (countries or regions) with little sun
- diseases that prevent the proper absorption or utilization of vitamin D
Who is most likely to need supplementation?
It is estimated that a considerable number of people have low levels of vitamin D, especially in children and the elderly.
Therefore, vitamin D supplementation is indicated in children up to 12 months and may be indicated in risk groups such as people with chronic diseases, the elderly, pregnant women, patients with chronic medication that decreases vitamin D absorption.
Why is vitamin D especially important in children?
Vitamin D is very important for children as it is essential for bone health. Its severe deficiency leads to alteration in bone growth (rickets).
How much vitamin D is recommended for children?
In Portugal, it is recommended:
- during the first year of the child's life: oral supplementation with 400IU of vitamin D per day, regardless of the type of diet you are eating, since direct sun exposure is not recommended until 6 months of age, and after this age it should be limited by the use of protective clothing and sunscreen
- From the first year of age there is no recommendation to maintain supplementation, but you should ensure that the child has:
- consumption of foods rich in calcium and vitamin D: such as dairy products, fish, eggs, among others
- Outdoor physical activity, with adequate sun exposure, for 10 to 15 minutes a day