The role of vitamin D
A well-known and proven function of vitamin D in our body is to ensure the health of bone tissue.
It also participates in the absorption of calcium and phosphorus from the intestines, thereby ensuring the maintenance of optimal concentrations of these elements in the blood, normal bone mineralization, and protection of the body from the various consequences of calcium deficiency.
Main source of vitamin D
The method by which the body produces the main amount of vitamin D it needs is unique: it is produced by exposing bare skin to the sun's ultraviolet rays.
Jeremy Scott Fitness on Apple Podcasts npp steroid dose Could one of these seven new fitness classes be your summer fling this year?This process is accompanied by many interfering factors. In particular, vitamin D synthesis is inhibited by:
- Dark skin
- increasing age
- Use of sunscreens
- Clouds and fog
In addition, the production of vitamin D is critically dependent on geographical location, time of day, and time of year; for example, in winter, production is minimal or may cease altogether. It is also noteworthy that the ultraviolet rays involved in its synthesis do not penetrate through windows.
Other Facts About vitamin D synthesis
- Vitamin synthesis from exposure to sunlight is maximal in spring, summer, and fall between 10 a.m. and 15 p.m.
- Exposure to sunlight for a period of time that results in mild redness after 24 hours produces approximately the amount of vitamin D equivalent to a dose of 10000 to 25000 units of the drug.
- Vitamin D obtained from the sun stays in the body twice as long as that absorbed from the intestines.
- Prolonged exposure to sunlight does not cause vitamin A deficiency.
Other sources of vitamin D
Additional sources of vitamin D include: food, food supplements, and medications.
Very few foods naturally contain this vitamin. The highest amounts are found in fatty fish.
There is much less vitamin D in beef liver, egg yolks, cheese, and mushrooms.
In some countries, vitamin D may be artificially added to various ready-made products, such as milk, breakfast cereals, juices, and yogurt.
Because vitamin D is fat-soluble, it is better absorbed when taken with foods containing a certain amount of fat.
Daily dose of vitamin D
Age is the main determinant of the body's daily requirement for vitamin D. The amount of vitamin D needed per day to maintain bone health is:
- From birth to 12 months: 400 IU
- Ages 1 to 70: 600 IU
- From 71 years: 800 IU
- Pregnant and breastfeeding women: 600 IU
The only way to check whether we are getting enough vitamin D is to measure the amount of its so-called reserve form – 25(OH)D – in the blood. The results are interpreted as follows:
- More than 30 ng/ml – sufficient amount
- 21-29 ng/ml – indicates vitamin D deficiency
- Less than 20 ng/ml – indicates vitamin D deficiency
- Less than 12 ng/mL – a severe deficiency and can cause serious damage to bone and general health.
Vitamin D deficiency
Over the past decades, technological developments have significantly changed our lifestyles. In the modern world, people spend less time outdoors, which results in less exposure to sunlight, and vitamin D deficiency has become more prevalent and common than ever before.
However, the risks of developing vitamin D deficiency are not equal and it is more likely to occur in these population groups:
- In children who are on natural feeding.
- In the elderly: As we age, the skin's ability to produce vitamin D from sunlight decreases, and its absorption from the intestine may also become more difficult.
- In people who rarely go out in the sun or who frequently use sunscreen.
- With darker skin tones: The more pigmented the skin, the less vitamin it produces.
- In gastrointestinal diseases that reduce fat absorption, because vitamin D is a fat-soluble vitamin and is absorbed with fat.
- People with a history of obesity and bariatric surgery: They may need more vitamin D than usual.
Consequences of vitamin D deficiency
In conditions of vitamin D deficiency, bones become thin, brittle, misshapen, and easily broken.
As a result, children develop Rickets, which leads to deformed, painful, weak bones.
In adults it happens Osteomalacia The cause is bone pain and muscle weakness.
As for the impact of vitamin D deficiency on general health, this is still a subject of research and leads to conflicting opinions among specialists.
Receptors through which vitamin D exerts its effects have been found in many different organs, which has led to interest in the impact its deficiency may have on non-bone tissues and other vital processes.
It is considered that:
- It is needed by muscles to move the body.
- It is needed by nervous tissue to transmit signals between the brain and other parts of the body.
- It is needed by the immune system to effectively fight viruses and bacteria that invade the body.
- Studies also show that vitamin D plays an active role in the development of the fetus's brain, lungs, and bones.
Epidemiological and clinical case studies have shown that vitamin D deficiency is associated with an increased risk of developing diseases such as cancer, diabetes, insulin resistance, hypertension, heart disease, multiple sclerosis, and depression. However, randomized trials have not yet sufficiently proven the positive effect of vitamin D supplementation on reducing the risk of these diseases.
Therefore, additional studies are needed to provide more clarity. One thing is clear: when a vitamin deficiency is detected, it should be supplemented with medication to ensure bone health.
Symptoms of vitamin D deficiency
Vitamin D deficiency is often clinically hidden in its early stages. Its eventual manifestation is as follows:
- The children are just starting to walk and prefer to sit for long periods of time. On examination, their feet are deformed.
- Adults may experience chronic muscle pain and bone pain, which can be felt by pressing on the chest or shin bones.
Who should undergo a preventive vitamin D test?
According to current international guidelines, preventive laboratory testing is recommended only for individuals at high risk of deficiency. These include:
- People with osteoporosis
- People with malabsorption syndrome
- People of color
- During obesity – when the body mass index is more than 30
- In diseases that affect vitamin D metabolism, such as chronic kidney disease.
Vitamin D and obesity
It was found that the amount of vitamin D in the body is inversely related to obesity, more specifically, the amount of adipose tissue.
Possible reasons for this are considered to be:
- Fatty tissue reduces the absorption of ultraviolet rays
- In the same tissue, vitamin D, as a fat-soluble vitamin, may be degraded and broken down, making it unusable by the body.
- Obesity generally contributes to immobilization and reduced exposure to the sun.
If vitamin D replacement therapy is required for an obese person, the dose may need to be two to three times higher than usual to achieve the target level.
Vitamin D excess
We should not forget that not only a deficiency, but also an excess of vitamin D can cause various pathologies. Overdose is mainly associated with taking more than 4 units of the drug per day for a long period of time.
Signs of vitamin D excess include weakness, dry mouth, nausea, vomiting. Also, increased calcium levels in the blood, muscle weakness, confusion, dehydration, frequent urination, and kidney stones.
Use of Vitamin D during COVID-19
There is a suggestion that low vitamin D levels are associated with a relatively increased risk of infection with Covid-19, but this link has not been proven.
There is also no proven benefit in the prevention or treatment of COVID-19 from vitamin D. Giving it in large doses to both outpatients and inpatients does not provide symptom relief and/or prolong life.
Evidence-based medicine approach
So, what we know today is that laboratory analysis of vitamin D is recommended not for everyone, but only for people in risk groups. In case of a deficient indicator, we should try to raise it and then maintain it above the normal level, primarily to maintain bone health.
Author: Elga Giorgadze (Endocrinologist)
