The Complete Guide to Vitamin D: Benefits, Deficiency, Dosage and More
Effect, deficiency, dosage, side effects, overdose
D
Dr. Truls Marius Aarra
Mar 25, 2022
Reading time: 11 minutes11 minutes
Vitamin D ensures healthy bones and is involved in a variety of metabolic processes in the human body. In contrast to all other vitamins, the need can't be met through nutrition alone; and a lack of the vitamin can cause serious illnesses. An adequate supply of vitamin D is therefore important.
Vitamin D is not only involved in bone metabolism and bone mineralization, as it promotes the absorption of calcium into the bones, among other things. It is also a component of several other important processes in the human body.
Unlike all other vitamins, your body has to produce vitamin D itself, but it needs sufficient sunlight to do so. You cannot provide your body with it exclusively through your diet, as very few foods contain sufficient amounts of the vitamin. This can lead to a vitamin D deficiency, especially in the months with little sunlight, which in the worst case can result in serious illnesses.
Symptoms of Vitamin D Deficiency
You can determine whether you are suffering from a vitamin D deficiency by symptoms such as
increased hair loss,
susceptibility to infections, or
soft and deformed bones due to poor bone mineralization.
That is why an adequate supply of vitamin D is extremely important. The best way to achieve this is by taking high-quality dietary supplements, such as the vitamin D supplements from Vitaminexpress.
Vitamin D levels: How much vitamin D does the human body need?
The German Nutrition Society (DGE) recommends that adolescents and adults aged 15 to 65 consume 800 international units (IU) of vitamin D per day if their bodies are unable to produce vitamin D themselves. This corresponds to around 20 micrograms of the vitamin.
However, according to various vitamin D experts, this dose is only sufficient to cover the minimum requirement and protect against vitamin deficiency diseases. In order to keep vitamin D levels constant at the required level, experts therefore recommend a daily dose of 5,000 IU on average for adults weighing 70 kilograms.
Recommended dosage of vitamin D
The correct dosage of vitamin D depends on age, weight, skin color, location, and health status.
DGE recommendation: 800 IU of vitamin D per day for adults (20 µg) if the body is unable to produce it itself.
Expert opinion: For stable, optimal levels, 2,000–5,000 IU of vitamin D per day is often recommended (depending on weight).
Children: Often 400–1,000 IU of vitamin D per day, depending on age.
Children: 1,000–2,000 IU of vitamin D per day, depending on age
Important: The exact requirement can only be determined by a blood test (25-OH vitamin D level). Optimal values are 40–60 ng/ml (100–150 nmol/l).
Your body needs vitamin D for these important processes
Contrary to what its name suggests, vitamin D is not actually a vitamin, but a hormone that the body can produce itself with the help of sunlight. It is particularly important for the development of bones, teeth, and joints.
Vitamin D contributes to, among other things:
maintaining normal calcium levels in the blood,
normal muscle function,
normal teeth,
normal immune system function, and
normal cell division.
Effects of vitamin D
Vitamin D not only affects bones and calcium metabolism, but also has a much broader range of functions in the body:
Bones and teeth: Promotes the storage of calcium and phosphate in the bones, making them stable.
Immune system: Supports the activity of immune cells (T cells, macrophages) and has an immunomodulatory effect.
Muscles: Regulates muscle strength and coordination, which reduces the risk of falls, especially in older people.
Hormonal balance: Influences the regulation of insulin, testosterone, and estrogen.
Nervous system and psyche: Plays a role in signal transmission in the brain, has a mood-lifting effect, and may counteract depression.
Cell protection: Has antioxidant properties that protect cells from damage caused by free radicals.
Cancer prevention (under discussion): Studies suggest a possible protective effect against certain types of cancer, but this has not yet been confirmed.
Vitamin D and the immune system
Vitamin D is a real power vitamin. Our immune system in particular can only benefit from an optimal supply of the “sun vitamin.”
It already plays a crucial role in the so-called innate immune system, while the acquired immune system, which develops during the first years of a child's life through contact with as many pathogens as possible, benefits primarily from the antioxidant properties attributed to vitamin D.
What role does vitamin D play in preventing disease?
Scientific studies suggest that vitamin D also plays a role in the prevention of a variety of diseases.
These include:
Autoimmune diseases
Colds
Osteoporosis and other bone diseases (including rickets and osteomalacia)
Many people have a higher need for vitamin D, e.g., the elderly, children, or people who spend little time outdoors, have dark skin, or wear veils. In these cases, health experts recommend taking vitamin D as a dietary supplement.
Since the global outbreak of coronavirus, doctors and virologists have also been recommending vitamin D supplements, as these could have a positive effect on the course of the disease.
How is vitamin D absorbed by your body?
According to the German Nutrition Society (DGE), adolescents and adults in Germany only consume 10 to 20 percent of their daily requirement through food – the majority of the vitamin is produced by the body in the skin with the help of sunlight.
In summer, just 15 minutes of sunlight a day is enough for the body to produce its daily requirement of the vitamin. Even on cloudy days, UV radiation is usually sufficient to ensure adequate production.
Nevertheless, studies have shown that around one billion people worldwide have insufficient vitamin D levels.
There are many reasons for this, which are related to lifestyle (spending little time outdoors), living environment (in regions with little sunlight, e.g., Iceland) or the aforementioned underlying conditions that can impair vitamin D absorption.
How can a vitamin D deficiency develop in the body?
Vitamin D deficiency is particularly common in Northern Europe during the winter months.
The reasons for this are:
less time spent outdoors than in the warmer months
the low position of the sun between October and March (north of the 40th parallel, i.e., north of Rome) – as a result, not enough UV rays reach the skin
Although it is advisable to replenish vitamin D stores during the summer months by spending time outdoors, vitamin D levels drop dramatically after just a few weeks without sufficient vitamin intake.
Vitamin D deficiency
A deficiency is mainly caused by:
Lack of sunlight
Inadequate nutrition
Diseases that block absorption/utilization
Typical symptoms of a deficiency:
Fatigue, exhaustion, low mood
Muscle weakness, muscle pain
Bone pain, increased bone fragility
Hair loss
Increased susceptibility to infections
Difficulty concentrating
Consequential diseases in cases of prolonged deficiency:
Rickets (in children: soft, deformed bones, changes to the skull and spine)
Osteomalacia (in adults: soft bones, bone pain, muscle weakness)
Osteoporosis (reduced bone density → increased risk of fractures)
Possible associations with diabetes, cardiovascular disease, depression, autoimmune diseases
In these cases, supplementation with vitamin D preparations is advisable
It is difficult to maintain a consistently high level of vitamin D, not only during the winter months due to the low amount of sunlight typical at this time of year.
In addition, the following underlying diseases can also prevent you from filling your vitamin D stores sufficiently:
chronic gastrointestinal diseases
liver diseases, and
kidney diseases
Certain medications, such as
cytostatics (medications for tumor treatment) or
antiepileptics
can also negatively influence the metabolism of vitamin D.
If you are diagnosed with vitamin D deficiency due to the reasons mentioned above, supplementation with the sun vitamin is absolutely advisable in order to prevent the above-mentioned secondary diseases.
You can recognize vitamin D deficiency by the following symptoms
Low vitamin D levels initially manifest themselves through atypical symptoms such as
As the condition progresses, there may be an increase in
respiratory tract infections,
increased susceptibility to allergies, and/or
pain in the musculoskeletal system.
If vitamin D deficiency persists over a longer period of time, it can lead to insufficient calcium storage in the bones, causing them to become soft and flexible. This can lead, for example, to
rickets (in children), which is a deformation of the bones, especially the skull and spine,
osteomalacia (soft bones in adults) or
a decrease in bone density due to calcium deficiency, which promotes the development of osteoporosis.
Side effects of vitamin D
There are virtually no side effects at normal doses. Problems only arise in the event of overdose or incorrect intake.
Possible side effects of vitamin D in case of excessive intake:
Nausea, vomiting
Loss of appetite
Abdominal pain
Headaches
Muscle weakness
Increased urination and thirst (due to disturbed calcium metabolism)
Can vitamin D overdose occur?
Yes, vitamin D overdose is possible – but only if extremely high amounts are taken over a long period of time.
While a dosage of around 5,000 IU of vitamin D per day is considered normal and safe, an overdose usually only occurs when 10,000 IU or more is taken daily for at least three months. In some cases, values of up to 40,000 IU per day have even been observed.
Symptoms of an overdose
Excessive intake of vitamin D can disrupt calcium metabolism and cause the following symptoms:
Nausea and vomiting
Loss of appetite
Abdominal pain
Headaches
Muscle weakness
Increased thirst and frequent urination
Minimizing risk
To avoid these risks, your individual vitamin D requirements should always be determined by a doctor – preferably via a blood test (25-OH vitamin D level).
How to determine your individual vitamin D requirements
Babies, children, pregnant women, and people with various medical conditions have different vitamin D requirements.
In addition, many other factors play a role in vitamin D absorption. These include
age,
body weight,
skin color,
intensity of sunlight exposure,
lifestyle, and
vitamin D absorption and metabolism.
The recommended guidelines for calculating the optimal vitamin D dosage therefore only provide a rough guide. A blood test is essential to find out what your vitamin D level is.
Capsules, tablets, or drops: Which dosage form is best for vitamin D supplements?
Vitamin D supplements are available from Vitaminexpress in various dosage forms. Each has its own individual advantages:
Capsules
High bioavailability
Suitable for allergy sufferers
Tablets
Long shelf life
Lozenges Very easy to take, especially for children
Drops/liquid content
Ideal for on the go
Easy to take if you have difficulty swallowing
Can be diluted if necessary
Fish, eggs, and dairy products: foods with a high vitamin D content
A vitamin D-rich diet is not easy to achieve. This makes it all the more important to know exactly which foods actually contain large amounts of vitamin D. These should be included in your diet more often, especially during the dark winter months.
The following foods, for example, are particularly rich in vitamin D:
Fish
Eggs
Oysters
Dairy products
Mushrooms
COVID-19 and vitamin D
Vitamin D is an important component of our immune system – it controls important antibodies and messenger substances, which are key factors in protecting against viruses.
It therefore makes sense to investigate the influence of vitamin D on COVID-19.
The assumptions were confirmed in studies conducted by the University of Heidelberg: healthy vitamin D levels can reduce the risk in several ways. On the one hand, the risk of infection is lower, and on the other hand, the risk of severe disease progression is reduced.
Even in people who are already ill, the course of the disease is mitigated, according to a study by the University of Cordoba.
It is not surprising that a group of researchers and doctors are currently forming an international alliance. An alliance that calls on all national governments to increase the recommended intake of vitamin D to 4,000 IU per day during the pandemic.
Researchers in the UK came to this conclusion based on their study, which showed that vitamin D deficiency leads to significantly more severe disease progression in the event of COVID-19 infection.
Vitamin D and the treatment of COVID-19
In February 2021, the Spanish Society of Geriatrics and Gerontology recommended in a statement that the treatment of COVID-19 in elderly hospitalized patients should include vitamin D supplementation as standard.
Patients who were given vitamin D had a lower mortality rate. This was the result of a meta-analysis.
Although it is not possible to derive a specific dosage of vitamin D for the treatment of COVID-19 in elderly patients, standardization of its use in clinical practice is necessary.
The suspected positive effect of vitamin D supplementation on COVID-19 patients may be due to a restoration of immune balance.
In any case, the connection between vitamin D levels and the severity of the disease is clear.
However, the statement also warned of the dangers of vitamin D overdose:
Nausea, vomiting
Depression
Hypercalcemia
Kidney stones
Irreversible cardiovascular damage, etc.
Frequently asked questions about vitamin D
Many doctors are cautious about vitamin D because the amount needed depends greatly on individual lifestyle, skin type, and sun exposure. In addition, too high a dose can actually be harmful (e.g., kidney problems). That's why many recommend a blood test before simply supplementing.
Different organizations recommend varying doses of vitamin D. For example, in cases where vitamin D formation through sunlight is deficient, the DGE currently recommends a dose of 400 IU for infants up to 1 year of age and 800 IU for children, adolescents, adults, seniors, and pregnant and nursing women.
According to vitamin D experts this recommendation is too low and only represents the minimum daily intake required to stave off rickets.
Recent studies clearly demonstrate that vitamin D3 and vitamin K2 are essential to good health. Deficiencies in both these vitamins are extremely common, which is why more and more people are taking vitamins D3 and K2 as a daily dietary supplement.
It's very important to know that if you take vitamin D3 regularly over a long period, you definitely need to take vitamin K2 as well. This raises the question of how these two key vitamins should best be combined in order to promote health and vitality.
You can measure your vitamin D levels by using a blood test to determine if you have enough vitamin D in your body. In fact, not the active form of vitamin D is measured, but the concentration of 25(OH)D (25-hydroxyvitamin D) in the blood.
The 25 (OH)D value is a precursor of vitamin D, in which form is is transported in the blood. If necessary, this form is converted into the active form of vitamin D (calcitriol).
The 25 (OH)D value shows how much vitamin D you got through nutrition or produced during sun exposure. But this value does not tell you anything about your vitamin D levels throughout the year, which will vary depending on the sun exposure and vitamin D uptake from food.
The half-life of 25(OH) Vitamin D is 2 month. This means, that the vitamin D level will fall to half of its value, provided that you no longer get any vitamin D at all.
