How does a vitamin D deficiency manifest itself and what are the symptoms?

Vitamin D is basically produced by the body itself - namely when we feel the warm rays of the sun on our skin. 

So why are so many people talking about a vitamin D deficiency? How is it that this sunshine vitamin has attracted so much attention in recent years?

In Germany and most countries in northern and central Europe, solar radiation is significantly reduced in winter. Added to this are high sun protection factors and long office hours. Many of us only get to see the sun through a window for months on end.

The result? Almost every second German suffers from a vitamin D deficiency during the cold season!

It is now clear to researchers that vitamin D is not only of enormous importance for healthy bones or dermatological diseases.

The latest research findings show that vitamin D is active in almost all areas of the body. These include the brain, the heart, the muscles, the immune system and the skin. A lack of vitamin D is also associated with a wide range of diseases, such as cancer, autoimmunity and cardiovascular and neurological diseases.

Contents

• How is the body supplied with vitamin D?
• Why do we need vitamin D at all?
• How does a vitamin D deficiency develop?
• How do I notice a vitamin D deficiency? 8 Symptoms
• Who is affected by a vitamin D deficiency?
• How can I test for a vitamin D deficiency?
• What can I do if I have a vitamin D deficiency?
• The most important sources of vitamin D
• Osteoporosis: vitamin D strengthens bones
• Vitamin D for a healthy immune system
• Does vitamin D help with depression?
• How vitamin D inhibits inflammation
• The use of vitamin D for cancer
• What forms of vitamin D are there?

How is the body supplied with vitamin D?

Vitamin D formation in the skin 

Vitamin D is mainly produced by the skin itself through direct sunlight. The vitamin then undergoes a series of processes to make it usable for the body.

People who are regularly exposed to sunlight can cover 80 to 90 % of their vitamin D requirements themselves.  

If the skin is exposed to direct sunlight, it produces the precursor of vitamin D, provitamin D3, and sends it to the liver and kidneys. If you take appropriate vitamin D supplements oreat a vitamin D-rich diet, it is also sent from the intestine to the liver. In the liver, the vitamin is converted into a substance called 25(OH)D or 25-hydroxyvitamin D (calcidiol). This is the third conversion of vitamin D. This is the richest form of vitamin D found in the blood and is also determined in blood tests as a vitamin D value.

So when your doctor talks about your vitamin D level, he is referring to the amount of 25(OH)D in your blood. In this form, the vitamin is still not active in the body. It is a metabolic product that signals to the body that vitamin D is present.

The active form is called 1,25 hydroxyvitamin D (1,25(OH)2D). It is formed in the kidneys from 25(OH)D circulating in the blood. As soon as active vitamin D binds to a vitamin D receptor (VDR), it acts like a switch that activates several genetic processes.

Scientists have been able to identify more than 200 genes in almost all organs in which processes are triggered by active vitamin D.

Why do we need vitamin D at all?

Vitamin D, regardless of whether we absorb it through the skin or in the form of supplements, must first be converted several times in the body before it can be used.

In its activated form, vitamin D is now ready to perform its tasks. The rest of the process is a little more complicated, but you can imagine the mode of action of activated vitamin D as follows:

1. Controls calcium in your blood, bones and intestines.
2. Supports body cells in communicating within the body. 

The link between vitamin D and strong, healthy bones was established many years ago. At that time, doctors discovered that sunlight (through which the body produces vitamin D) or the intake of fish cod liver oil (contains vitamin D) could protect children from bone softening due to rickets. Nowadays, vitamin D is considered essential for good health, and not just in relation to the bones. Recent research shows that vitamin D is important for the prevention and treatment of a whole range of serious long-term conditions.

These include, among others:

• The immune system to defend against infections
• Healthy muscle function
• Cardiovascular health, i.e. the heart and blood circulation
• The respiratory system
• Development of the brain
• Anti-cancer effect

Doctors are still investigating the exact mode of action of vitamin D in the human body and its effects on general health. 

How does a vitamin D deficiency develop?

If the vitamin D level in the blood is less than 20 nanograms per milliliter (ng/ml), there is a risk of vitamin D deficiency.

A serum level of less than 12 ng/ml is referred to as a vitamin D deficiency.

This occurs when the body does not have enough vitamin D available because too little is absorbed or the body cannot metabolize the vitamin.

With severe vitamin D deficiency, children sometimes develop rickets and adults develop osteomalacia (softening of the bones). Both diseases lead to soft, thin and brittle bones.

However, vitamin D deficiency symptoms have also been linked to other diseases. These include cancer, asthma, type II diabetes, high blood pressure, depression and Alzheimer's disease as well as autoimmune diseases such as multiple sclerosis, Crohn's disease and type I diabetes.

13 Risk groups 

Here are some factors that can lead to a vitamin D deficiency - regardless of whether a person belongs to a risk group or not:

• Life at higher latitudes: The reason for this lies in the fact that ultraviolet radiation (UVB) is less pronounced at higher latitudes.
• Spending too much time indoors: people who spend little or no time outdoors so that they do not receive any sunlight.
• Living in areas with high levels of air pollution: Particles in the air absorb some of the sun's radiation, meaning that less is available for the production of vitamin D.
• Use of large amounts of sunscreen: If all sunlight is blocked by the use of sunscreen, no vitamin D can be produced. However, only very few people use such a large amount that all UV radiation is blocked.
• A darker skin color: People with darker skin need more sunlight to produce enough vitamin D.
• The ambient temperature: warm skin absorbs the sun's rays better - and therefore produces more vitamin D - than cooler skin.
• Diet: A diet low in vitamin D increases the risk of vitamin D deficiency.
• Overweight: Research suggests that being overweight is associated with low vitamin D levels. The reason for this may be that too much body fat affects the absorption of vitamin D.
• Age: The ability to absorb vitamin D decreases with increasing age.
• Intestinal health: Gastrointestinal diseases such as Crohn's disease impair the ability of the intestine to absorb vitamin D.
• Kidney and liver health: Patients suffering from kidney or liver disease tend to have lower vitamin D levels.
• Pregnancy and breastfeeding: The nutritional requirements of a fetus or infant lead to lower vitamin D levels, especially in women who already belong to a risk group.
• Infants who are fed with breast milk: Breast milk has very little vitamin D. Breastfed babies therefore need supplements, especially if they are not outdoors every day.

How do I notice a vitamin D deficiency? 8 Symptoms

You cannot cover your vitamin D requirement through food alone, as it is only present in very small quantities in food. The body mainly produces vitamin D from sunlight. You must therefore regularly "fill up" on sunlight. It is therefore somewhat more difficult to cover your individual requirements than with other vitamins and minerals. For this reason, appropriate preparations are very suitable for compensating for or preventing a vitamin D deficiency.

A vitamin D deficiency often goes unnoticed for years and as a result we suffer from inexplicable symptoms. A brief overview of the symptoms that a vitamin D deficiency can cause:

• Frequent illnesses or infections
• Permanent exhaustion and fatigue
• Bone and back pain
• Depression
• Poor wound healing
• Bone loss
• Hair loss
• Muscle pain

1. vitamin D deficiency in the case of frequent illnesses or infections

One of the most important tasks of vitamin D is to strengthen the immune system so that the body can effectively fight bacteria and viruses. It interacts directly with the cells that are responsible for fighting off infections. If you frequently catch colds or flu, a low vitamin D level could be at least one of the causes.

Several large observational studies have established a link between vitamin D deficiency and respiratory tract infections (colds, bronchitis, pneumonia). A number of studies have confirmed that taking vitamin D supplements in a dose of up to 4000 IU daily can reduce the risk of respiratory infections.

One study was dedicated to patients suffering from chronic obstructive pulmonary disease (COPD). Only those participants who also had a severe vitamin D deficiency experienced significant improvements in their symptoms after taking high doses of vitamin D for a year.

CONCLUSION: Vitamin D plays a crucial role in healthy immune function. One of the most common signs of a deficiency is an increased susceptibility to infections and other illnesses.

2. vitamin D deficiency in case of exhaustion and tiredness

Fatigue can have many causes - one of them is a vitamin D deficiency. Unfortunately, this is often overlooked as a possible cause.

Case studies show that low vitamin D levels can cause fatigue and tiredness, which have a significant impact on the quality of life of those affected.

In one case, a woman suffered from chronic daytime sleepiness; her vitamin D level was only 5.9 ng/ml, which is very low. Anything below 20 ng/ml is considered a deficiency. After taking vitamin D supplements, the level rose to 39 ng/ml and the woman's symptoms visibly improved.

But even vitamin D levels that are not extremely low can have negative effects.

A study investigated the relationship between vitamin D and fatigue in young women. The researchers found that women with a vitamin D level of less than 20 ng/ml or between 21 and 29 ng/ml complained of fatigue more frequently than those with a level higher than 30 ng/ml.

Another observational study found a strong link between low vitamin D levels and self-reported fatigue in female nurses. But worse than that, the researchers found a deficiency in 89 percent of the nurses.

CONCLUSION: Excessive fatigue and tiredness can be a sign of vitamin D deficiency. Taking appropriate supplements leads to more energy and performance.

3. bone and back pain as a result of a vitamin D deficiency

Vitamin D plays a role in many mechanisms for maintaining healthy bones, as it improves the absorption of calcium in the body.

Pain in the bones and lower back can be a sign of low vitamin D levels in the blood. Large observational studies have established a link between deficiency symptoms and chronic lower back pain.

One study looked at the link between vitamin D and back pain in more than 9,000 older women. The scientists found that those who had a vitamin D deficiency were more likely to be affected by back pain. Some participants suffered from such severe pain that it significantly restricted their daily lives.

A controlled study confirmed that patients with a vitamin D deficiency are almost twice as likely to suffer from bone pain in the legs, ribs or joints than people with a balanced vitamin D level.

CONCLUSION: Low blood levels of vitamin D can contribute to the development of bone and lower back pain.

4. depression with vitamin D deficiency

A depressed mood can also be a sign of a deficiency.

In review studies, researchers were able to link a lack of vitamin D with depression, especially in older people.

One study analyzed various observational studies. A link between low vitamin D levels and depression was found in 65 percent of the studies. However, this effect could not be confirmed in controlled test series. These are generally more meaningful for science than observational studies.

Nevertheless, the scientists noted that the vitamin D dose in these controlled studies was very low. In addition, some of these studies were not continued long enough to detect improvements in the mood of the subjects after vitamin D intake.

Nevertheless, some controlled studies have confirmed that the administration of vitamin D lifts the mood of patients with a deficiency - even in the case of seasonal depression, which occurs in colder months.

CONCLUSION: Depression is associated with low vitamin D levels. Some studies have shown that appropriate supplements have a positive effect on mood.

5. poor wound healing and vitamin D deficiency

Wounds that heal slowly after injuries or operations can indicate a vitamin D deficiency.

In test tubes, researchers found that the vitamin increases the production of important substances that are necessary for the formation of new skin as part of the wound healing process.

A series of tests on volunteers undergoing dental surgery concluded that certain aspects of wound healing are affected by a lack of vitamin D. The results also suggested that vitamin D plays a role in controlling inflammation and fighting infection. The results also suggested that the role vitamin D plays in controlling inflammation and fighting infection is also important for healthy wound healing.

One study looked at patients suffering from diabetic foot infections. It came to the conclusion that a severe vitamin D deficiency increased the risk of serious inflammation and made healing more difficult.

Unfortunately, there are currently very few studies on whether taking vitamin D supplements can improve wound healing in these patients.

However, another study was able to prove that patients with vitamin D deficiency and ulcers on their legs reduced the size of these ulcers by an average of 28 percent after taking vitamin D.

CONCLUSION: An insufficient supply of vitamin D can lead to poor wound healing as a result of surgery, injury or inflammation.

6. bone loss due to vitamin D deficiency

Vitamin D plays a decisive role in the absorption of calcium and its metabolism in the bones.

Older women who suffer from bone loss often believe that they need to take more calcium. However, they often also need more vitamin D. Bones with low mineral density show that the bone has lost calcium and other minerals. As a result, older people, especially women, have an increased risk of fractures.

A large observational study of 1100 middle-aged women (menopausal and postmenopausal) showed a strong link between low vitamin D levels and bones with low mineral density.

However, a controlled study found no improvement in mineral density after women with vitamin D deficiency took high-dose supplements, although their blood levels improved.

Regardless of this result, it is advisable to ensure a sufficient vitamin D intake in order to protect the bones from atrophy and prevent fractures.

CONCLUSION: The cause of bones with low mineral density can be a lack of vitamin D. An adequate supply of this vitamin is crucial for maintaining bones, especially with increasing age.

7. hair loss due to vitamin D deficiency

Hair loss is often associated with stress - one of the most common causes. However, severe hair loss can also be caused by illness or a lack of nutrients.

Hair loss in women has been linked to a vitamin D deficiency. However, very few studies are available to date.

Alopecia areata (circular hair loss) is an autoimmune disease characterized by severe hair loss on the head and other parts of the body. The disease is associated with rickets. This is a disease that causes bone softening in children as a result of a vitamin D deficiency. Low vitamin D levels are associated with alopecia areata and may be a risk factor for the development of this disease. Participants in a study with alopecia areata showed that low vitamin D levels caused more severe hair loss.

A case study with a boy suffering from a vitamin D receptor defect showed that applying a synthetic form of the vitamin to the scalp successfully combated his hair loss.

CONCLUSION: Hair loss can be a sign of vitamin D deficiency, especially in women or patients suffering from the autoimmune disease alopecia areata.

8. muscle pain due to vitamin D deficiency

The causes of muscle pain are often difficult to find. Some studies point to a lack of vitamin D as a possible cause of muscle pain in children and adults.

In one study, 71 percent of subjects with chronic pain showed a deficiency. Our nerve cells have a vitamin D receptor called nociceptor, which senses pain.

A study with rats showed that a deficiency led to pain and increased sensitivity as soon as the nociceptors in the muscles were stimulated.

Other studies have shown that taking a high dose of vitamin D alleviated various types of pain in deficiency patients.

In one study, the pain of 120 children was reduced by an average of 57 percent after taking a single dose.

CONCLUSION: There is a connection between chronic pain and a vitamin D deficiency. This is caused by interactions of the vitamin with pain-sensitive nerve cells.

Who is affected by a vitamin D deficiency?

It is difficult to get enough vitamin D from food alone. The consumption of vitamin D supplements together with a daily dose of sunlight ensures sufficient intake for most people. However, the following groups are always affected:

Vitamin D deficiency in breastfed infants

Der Bedarf an Vitamin D kann nicht allein über die Muttermilch gedeckt werden, die zwischen <25 IE/L bis 78 IE/L enthält. (Der Vitamin-D-Gehalt der Muttermilch ist abhängig vom Vitamin-D-Spiegel der Mutter. Stillende, die zusätzlich hohe Dosen Vitamin D einnehmen, verfügen unter Umständen über ausreichend Vitamin D in der Muttermilch.). 

The study situation

A review of reports on the incidence of nutritional rickets showed that most cases occurred in young African-Americans who were breastfed. A study conducted by Canadian pediatricians showed that rickets occurred in 2.9 out of 100,000 children. Almost all of these cases were breastfed infants.

Sunlight is generally an important source of vitamin D. However, the American Association of Pediatricians (AAP) recommends that infants should not be exposed directly to the sun and should be protected with additional UV-protective clothing or sunscreen. As noted, the AAP recommends that partially or fully breastfed infants receive an additional 400 IU of vitamin D daily, which is the recommended daily allowance for this age group.

Vitamin D deficiency in seniors

Senioren verfügen über ein erhöhtes Risiko für einen Mangel an Vitamin D. Der Alterungsprozess der Haut führt zu einer verminderten Fähigkeit das Vitamin effektiv aus Sonnenstrahlung zu bilden. Außerdem halten sich ältere Menschen häufig in Innenräumen auf und nehmen auch über die Nahrung zu wenig auf. Mehr als die Hälfte der Senioren in den USA mit Hüftfrakturen verfügt über einen 25(OH)D-Spiegel von weniger als 30 nmol/l (<12 ng/ml).

People who spend little time outdoors

People who rarely leave the house, wear long robes and headgear and those who rarely work outdoors cannot meet their personal vitamin D requirements through sun exposure. As the amount and frequency of sunscreen use is unknown, there is no reliable information on the influence of sunscreen on vitamin D synthesis in the skin. The requirement can be covered by appropriate foods or supplements.

People with dark skin

A higher proportion of the pigment melanin in the upper epidermis leads to darker skin and reduces the ability to synthesize vitamin D from sunlight. Various reports consistently confirm that people with darker skin have serum levels of less than 25(OH)D compared to fair-skinned people. It is not yet known whether the lower levels result in significant adverse effects for people with dark skin. Among African Americans, for example, bone fractures and osteoporosis occur less frequently than among Caucasians (people with fair skin). The requirement can be covered by appropriate foods or supplements.

People who suffer from inflammatory bowel disease or other fat absorption disorders

Vitamin D is fat-soluble and can only be absorbed by the body if the intestine can absorb dietary fats. Patients whose ability to absorb these dietary fats is limited may need to take vitamin D supplements. Fat absorption disorders have a variety of causes. These include some liver diseases, cystic fibrosis, coeliac disease and Crohn's disease. Fat absorption is also impaired in ulcerative colitis with inflammation in the terminal ileum. In addition, patients suffering from one or more of these diseases often consume less vitamin D-fortified dairy products.

People suffering from obesity or with gastric bypass

A body mass index over 30 is associated with low blood 25(OH)D levels. People who suffer from obesity may need to consume more vitamin D to achieve normal levels than people of normal weight. Obesity does not limit the ability to synthesize vitamin D. However, the higher proportion of subcutaneous fat tissue absorbs more vitamin D than normal, altering its release into the bloodstream. People with a gastric bypass often develop a vitamin D deficiency over time. This is because the upper small intestine - where the vitamin is absorbed - is blocked and the release from fat stores into the bloodstream is not balanced out. The requirement must then be covered by dietary supplements. 

How can I test for vitamin D deficiency?

A blood test is the only way to determine whether your vitamin D requirement is covered. This requires a test called a 25(OH)D blood test.

Your doctor can carry out this test. There may also be tests available for use at home or in a laboratory. All of these test methods provide accurate results.

The test result shows whether or not you are meeting your vitamin D requirements and whether you need to take additional vitamin D or get more sun exposure. The Vitamin D Council considers a level of 50 ng/ml to be ideal.

What can I do if I have a vitamin D deficiency?

Many patients and some doctors still think that a person's vitamin D requirement can only be met through their diet. However, this assumption is wrong. With the exception of fatty fish, the vitamin D content in most foods is negligible. 

Soak up the sun - without sun protection factor

The easiest and quickest way to stock up on vitamin D is to be exposed to the sun. Depending on the time of year, 15 minutes in the sun is enough in summer. However, at least the face, neck, décolleté, arms and legs should be exposed to the sun's rays. It is also important to note that vitamin production is best between 10 am and 2 pm. However, please avoid sun cream, as a sun protection factor of SPF20 or higher intercepts 95% of the radiation and thus completely prevents the formation of vitamin D. However, do not underestimate the length of time you spend in the sun to avoid sunburn. 

This approach is more challenging in the winter months, as the total number of hours of sunshine is reduced and the intensity of the sunlight is much lower. This is the case from around October to March. In addition, we are often dressed warmly and only our face is exposed to the sun. 

Vitamin D supplements

Supplementing with vitamin D supplements is a safe and inexpensive method of meeting the requirement. Unfortunately, a vitamin D deficiency often remains undetected and untreated for a long time. One reason for this is that the recommended age-dependent daily dose of vitamin D dates back to a time when findings from more recent studies were not yet available. Today we know that a 25(OH)D level of more than 30 ng/ml is necessary to ensure normal suppression of the hormone PTH. The current recommended daily requirement can easily be met through food or by taking a multivitamin supplement. For many people, however, this dose is not sufficient, especially not for risk groups. Unfortunately, doctors are still reluctant to prescribe higher doses, although their concerns are usually unfounded. There are some unconfirmed reports of poisoning symptoms due to too much vitamin D. However, these are in contrast to a wide range of extensive studies on vitamin D deficiency. The kidneys have a function that inhibits the production of active calcitriol. For this reason, there are few reports of symptoms of intoxication. A higher calcitriol level inhibits PTH both directly (through a molecule in the PTH gene that responds directly to vitamin D) and indirectly (through increased calcium absorption in the intestine). This suppresses calcitriol production in the kidneys. The activity of renal 24-hydroxylase further limits the availability of calcitriol by producing inactive metabolites of both calcitriol (1,24,25-trihydroxyvitamin D) and calcidiol (24,25-dihydroxyvitamin D). The 24-hydroxyglase gene is under the control of calcitriol and therefore quickly provides negative feedback in the event of a problem.

The most important sources of vitamin D

Food

Very few foods contain natural vitamin D.

Fatty fish (e.g. salmon, tuna and mackerel) and fish cod liver oil are among the best natural sources of nutrition. Unfortunately, these foods are rarely part of our diet. Small amounts of vitamin D are also found in beef liver, cheese and egg yolk. However, the amount contained in these foods is far too low to adequately cover our daily vitamin D requirements. The vitamin D in these foods is mostly present as vitamin D3 and its metabolite 25(OH)D3. Some mushrooms contain varying amounts of vitamin D2. Mushrooms with a higher vitamin D2 content are also available that have been exposed to ultraviolet light under controlled conditions.

In the USA, fortified foods provide the majority of vitamin D in the diet. For example, almost all milk is voluntarily fortified with 100 IU/250 ml. (In Canada, fortification of milk with 35-40 IU/100 ml is required by law. Similarly, margarine is fortified with ≥530 IU/100 g). In the 1930s, the milk fortification program was launched in the United States to get a grip on the rickets that was rampant at the time. Other dairy products such as cheese or ice cream are generally not fortified. Cornflakes often contain additional vitamin D, as do some types of orange juice, yogurt, margarine and other foods.

Sunlight

Most people cover at least part of their needs from the sun. Ultraviolet (UV)-B radiation with a wavelength between 290 and 320 nanometers penetrates unprotected skin and converts cutaneous 7-dehydrocholesterol into provitamin D3, which in turn becomes vitamin D3. Season, time and length of day, cloud cover, smog, the melanin content of the skin and sunscreen are among the factors that influence UV radiation exposure and vitamin D synthesis. It is perhaps a little surprising that latitude is not a reliable predictor of average 25(OH)D levels in the population. Even high up in the north, there are ample opportunities for the production (and storage in liver and body fat) of vitamin D from sunlight in the spring, summer and even fall months.

A closed cloud cover reduces UV energy by 50 percent; shade (including shade from heavy air pollution) by 60 percent. UVB rays do not penetrate glass. So if you sit by a sunny window, your skin will not produce vitamin D. Sunscreens with a sun protection factor (SPF) of eight or higher obviously block vitamin D production from UV rays. However, most people do not apply enough sunscreen or do not apply sunscreen to the entire skin or renew the protection regularly. Therefore, the skin still produces a certain amount of vitamin D, even if sunscreen has been applied.

As many different factors influence UV radiation, it is difficult to draw up general guidelines on how much sunlight we need to reliably cover our vitamin D requirements. Some scientists recommend between five and 30 minutes of sunlight between 10 am and 3 pm at least twice a week on the face, arms, legs or back without sunscreen. This should lead to sufficient vitamin D synthesis. Moderate use of sunbeds with two to six percent UVB radiation is just as effective. People who are only exposed to the sun very little or irregularly must cover their vitamin D requirements through their diet or supplements.

There is no doubt that sunlight is important for vitamin D synthesis. Nevertheless, it is essential to limit the amount of time you are exposed to sunlight or UV radiation in a solarium. UV radiation is a carcinogen and is the main cause of skin cancer and deaths from metastatic melanoma each year. Lifelong accumulation of UV damage to the skin is largely responsible for age-related skin dryness and other changes in skin appearance. The American Academy of Dermatology recommends that you always protect yourself from the sun (whenever you are outdoors), for example by using sunscreen. Due to these health concerns, sunbathing cannot be considered to meet vitamin D requirements. There are no studies to date on whether the synthesis of vitamin D through UVB is possible without an increased risk of skin cancer.

Food supplements

In food supplements and fortified foods, vitamin D is present either as vitamin D2 (ergocalciferol) or vitamin D3 (cholecalciferol). The two substances differ in terms of their side chain structure. Vitamin D2 is produced by UV irradiation of ergosterol in yeast. Vitamin D3 comes from the irradiation of 7-dehydrocholesterol from lanolin and the chemical conversion of cholesterol. Both forms are considered to be equally effective in preventing rickets. In fact, most of the metabolic processes and the mode of action are identical for both forms. Both forms (just like vitamin D from cutaneous synthesis in food) lead equally to an increase in the 25(OH)D level in the blood. No firm conclusions can be drawn about the different mode of action of these two forms. Even if both forms are equal in themselves, vitamin D2 is less effective in higher doses.

The American Association of Pediatricians (AAP) recommends a dose of 400 IU daily for fully or partially breastfed infants from birth until weaning or until infants drink at least one quart of fortified or whole milk per day. Similarly, non-breastfed infants who drink less than one liter of formula or whole milk per day should receive 400 IU of vitamin D per day. The AAP also recommends 400 IU of vitamin D per day for older children or adults who do not get this amount from fortified milk or food. However, this recommendation (November 2008) should be reconsidered as the Food and Nutrition Board now recommends 600 IU of vitamin D daily for children and adolescents. (The recommendation dates from November 2010 and was previously 200 IU/day).

Osteoporosis: vitamin D strengthens bones

More than 40 million adults suffer from osteoporosis or are considered to be at risk. Osteoporosis is a disease characterized by low bone density and structural loss of bone tissue. This leads to increased bone fragility and consequently to an increased risk of fractures. Osteoporosis is generally associated with a lack of calcium. However, an unmet vitamin D requirement contributes to reduced calcium absorption. Although rickets and osteomalacia are extreme examples of the effects of deficiency, osteoporosis is an example of the long-term consequences of calcium and vitamin D deficiency. A well replenished vitamin D store ensures strong bones and sometimes prevents osteoporosis in older adults, immobile (or exercise-restricted) patients, postmenopausal women and patients on chronic steroid therapies.

Normal bone tissue is regularly remodeled. During the menopause, the balance between these processes changes so that more bone tissue is no longer remodeled but resorbed. Hormone therapies with oestrogen and progesterone can delay the onset of osteoporosis. Various associations and medical organizations support the use of hormone replacement therapy in women with an increased risk of osteoporosis or bone fractures. Affected women should contact their doctor and/or health insurance provider.

Die meisten Versuchsreihen zu Vitamin D auf die Gesundheit des Knochenapparates beinhalten die Gabe von Calcium. Daher sind Aussagen zum Nutzen eines der beiden Nährstoffe nur bedingt möglich. Bei Frauen nach den Wechseljahren und älteren Männern resultiert die Gabe von Vitamin D und Calcium in einer geringen Zunahme der Mineraldichte der Knochen im gesamten Körper. Außerdem werden Brüche bei Bewohnern von Pflegeheimen vorgebeugt. Bei allen übrigen Personen kann dieser Effekt nur bedingt festgestellt werden. Die Einnahme von Vitamin D allein scheint keinen Einfluss auf das Risiko für Knochenbrüche zu haben. Es kann auch keine Stürze bei Senioren verhindern. Eine weitverbreitete Metaanalyse, die diesen Nutzen von Vitamin D angeblich bestätigt, wurde breit und öffentlich kritisiert. Eine großangelegte Studie begleitete Frauen ab 69 Jahren im Schnitt 4,5 Jahre. Dabei zeigte sich sowohl bei einem niedrigen 25(OH)D-Spiegel (<50 nmol/L [<20 ng/ml]) als auch bei einem hohen Spiegel (≥75 nmol/L [≥30 ng/ml]) ein erhöhtes Risiko für Gebrechlichkeit. Frauen sollten sich an ihren Arzt wenden, um ihren persönlichen Bedarf an Vitamin D (und Calcium) zur unterstützenden Vorbeugung oder Behandlung von Osteoporose zu ermitteln.

Vitamin D for a healthy immune system

Many interesting studies have been carried out on the effects of vitamin D (or calcitriol) on the body's immune system. Most of the studies were carried out using cultured cells (cells isolated from the body and grown in special nutrient solutions) and using animals - either with a severe vitamin D deficiency or with altered genes that switch off proteins that control the metabolism of vitamin D or its active processes.

These types of studies provide important proof of principle that vitamin D is extremely important for our immune system. In addition, there are the results of numerous studies that link either the estimated intake of UV light (e.g. season or latitude) or between blood 25-hydroxyvitamin D levels and certain infections or medical conditions.

Based on this research, scientists are certain that vitamin D (calcitriol) is important for strengthening our immune defenses. However, it is not yet known how much vitamin D is needed to produce enough calcitriol to strengthen the immune system. Scientists are working to find out.

Certain B and T cells have vitamin D receptors and respond to calcitriol, while some phagocytes convert 25-hydroxyvitamin D into calcitriol. This suggests that phagocytes communicate with T and B cells through calcitriol.

Studies on immune cells show that in the presence of calcitriol, it blocks certain properties of the adaptive immune system that would otherwise lead to autoimmunity. Experimental series with animals confirm that without calcitrione, immune cells attack healthy cells of the body to a greater extent (autoimmunity).

A lack of vitamin D is not the only or most important cause of an autoimmune disease. However, low vitamin D levels contribute to a weakened immune system. Unfortunately, we do not yet know how much vitamin D is needed to reduce the effects of autoimmunity on health.

As calcitriol, vitamin D influences the immune system in two ways:

• Calcitriol prevents the triggering and arming of T cells in autoimmunity. T cells play an important role in autoimmunity. Calcitriol reduces this role and blocks the increased production of the helper T cells required for the respective autoimmunity. By suppressing these cells, the ability of the T cells to recognize the native protein as a foreign body is reduced, so that fewer killer T cells are produced. In other words, adequate levels of vitamin D and calcitriol ensure that T cells do not turn against the body's own tissue.
• Calcitriol blocks chemical substances that kill natural tissue. Just as it reduces the number of T-cells, calcitriol also reduces the activity of B-cells in the production of chemical substances that destroy natural tissue. The antibody reaction against the body's own tissue is reduced and the reaction is blocked. For example, it is believed that reduced destruction of pancreatic beta cells, the cause of type 1 diabetes, occurs when sufficient amounts of vitamin D and calcitriol are present.

Does vitamin D help with depression?

Apparently there is a link between vitamin D and depression. Unfortunately, little research has been done in this area. However, Oregon State University has found a link in a study of young and otherwise healthy women. The researchers recruited 185 female college students between the ages of 18 and 25 for a study that followed them at various times during the school year. Vitamin D levels were determined by blood tests. All participants also completed a questionnaire once a week for five weeks on symptoms that indicate depression.

The scientists reported that many of the young women had vitamin D levels that were too low. It was often below the levels that are considered healthy. 61 percent of the women of color had levels that were too low and 35 percent of the white women. The levels of all participants fluctuated throughout the year and, as expected, were lowest in winter. Levels rose in the spring and fell again in the fall. More than a third of the women reported clinically relevant symptoms of depression every week.

The lower the women's vitamin D levels, the more likely they were to report clinically relevant signs of depression over the course of the five-week study - even after scientists adjusted for other factors such as the time of year, level of activity or time spent outdoors. Nevertheless, the researchers pointed out that their results should not be taken as a conclusion that low vitamin D levels cause depression. The next step would be a clinical study to determine whether the administration of vitamin D can prevent or alleviate depression.

Scientists suspect that people with too little vitamin D have a higher risk of developing depression, as the vitamin is important for healthy brain function. Nutrient deficiency may play a role in depression and other mental illnesses.

How vitamin D inhibits inflammation

Many people suffer from asthma, joint pain or other chronic inflammatory diseases. This is often caused by a lack of vitamin D. The sun is too low for us humans to be able to produce the vitamin in our skin. In addition, it is only present in very small quantities in food and normal vitamin tablets. It has long been known that vitamin D combats inflammation. A large-scale study is being planned to find out how high doses of vitamin D affect the molecular mechanisms that fight inflammation.

In our latitudes, the summer sun is our best source of vitamin D. Deficiency symptoms are becoming an ever-increasing problem that affects millions of people around the world. This is true all year round, as factors such as too little time spent outdoors and the increased use of sunscreen to prevent skin cancer further exacerbate the problem. Vitamin D is known for its important contribution to healthy bones, but it affects most cells in our body. Scientists are showing more and more interest in the molecular mechanisms involved in a number of chronic inflammatory diseases such as rheumatoid arthritis, Crohn's disease (inflammatory bowel disease), thyroid disease (Hashimoto's and Graves' disease), multiple sclerosis, isulin resistance, type II diabetes, obesity, cardiovascular disease and cancer.

The more vitamin D, the less inflammation

Scientists at National Jewish Health in Denver discovered some time ago how vitamin D influences the immune system and that it inhibits inflammatory processes through molecular mechanisms. It is extremely important that white blood cells can fight infections and repair cell damage. On the other hand, the immune system must not overreact, as chronic inflammation can sometimes cause local symptoms and tissue damage.
In addition, chronic inflammation bombards the body with extremely harmful free radicals.

In their in-vitro study, the researchers added different amounts of vitamin D to white blood cells from solutions that corresponded to a serum level of 0-50 ng/ml. The white blood cells were then exposed to a molecule called LPS (lippolysaccharide), which is found on the cell walls of bacteria and normally triggers intense inflammatory reactions.
The blood cells that received no vitamin D and only a little (so that it corresponded to a serum level of 15 ng/ml) produced many cytokines (IL-6 and TNF-alpha), which play a key role in inflammation. In contrast, the blood cells that had received enough vitamin D to correspond to a level of 30-50 ng/ml showed a significantly lower response to LPS. The response was lowest in the blood cells that had previously received the highest dose of vitamin D.

In a series of experiments, the researchers identified new sites where the cells' vitamin D receptors (VDR) react directly with cellular DNA and activate a gene (MKP-1) that switches off unwanted inflammatory processes. The study proves that vitamin D can inhibit inflammation. The extent depends on the respective serum level. The best results were achieved with levels higher than 50 ng/ml.

Several new studies confirm the effectiveness of vitamin D. It can reduce inflammation and pain because it acts at the DNA level and regulates genes that reduce inflammation. This knowledge expands our understanding of the role vitamin D plays in our body's immune response. People who suffer from various types of pain or ongoing inflammation should balance their vitamin D levels and see it as the key to alleviating or healing their conditions.

We have known for some time that vitamin D is essential for optimal immune defense - whether it's defense against pain or the flu. Vitamin D is considered to be the most important substance in our body for a process called immune system tolerance. This term refers to nothing more than the very personal threshold until the body "overheats" in response to influences. Immune system tolerance is extremely important for fighting infection ("overheated" means death or severe infection) and pain (especially from autoimmunity).

A new study examined the vitamin D status and pain levels of 2,070 adults over the age of 65. 53 percent of the participants complained of moderate to severe pain. All cases were associated with poor vitamin D status. This link remained even after other factors were taken into account.

Another study documented for the first time the exact mechanisms by which vitamin D alleviates inflammation. The scientists found a new receptor for vitamin D on DNA. As soon as vitamin D "docks" onto this receptor, a signal is sent in nuclear genes that reduces inflammation. This is a powerful anti-inflammatory mechanism of the most basic kind. With a vitamin D deficiency, this receptor may not be optimally activated, leading to a higher risk of serious inflammation - regardless of the initial problem.

This puts vitamin D on a par with DHA as effective regulators of inflammation in the human body. Both nutrients are woefully deficient in the US population, especially during the winter months. The health authorities should also be aware of this fact. Unfortunately, the FDA (US Food and Drug Administration) is at war with vitamins and rarely makes recommendations that could limit the sale of dangerous drugs with many side effects.

People who suffer from persistent pain should increase their vitamin D intake and observe whether their condition improves. The vitamin D level in the blood should be in the medium normal range or just above. A level just above the lower end of the normal range or just below is not sufficient.

The use of vitamin D for cancer

Laboratory studies, animal studies and the analysis of epidemiological data suggest that vitamin D levels may influence the risk of cancer. Strong biological and mechanistic evidence shows that vitamin D is involved in the prevention of colorectal, prostate and breast cancer. The analysis of epidemiological data shows that the effect of vitamin D is greatest in the prevention of colon cancer. In prostate and breast cancer, this effect is only visible to a limited extent; in other cancers it varies. However, this effect is not visible in all studies. For example, a study of Finnish smokers found that subjects with the highest quintile of initial vitamin D status had a threefold higher risk of developing pancreatic cancer. A recent study showed an increased risk of pancreatic cancer associated with high serum concentrations of 25(OH)D (≥ 100 nmol/l or ≥ 40 ng/ml).

Vitamin D proved to be a protective factor in a prospective cross-sectional study of 3,121 adults aged ≥50 years (96% men) who underwent colonoscopy. The study found that ten percent had at least one advanced cancer lesion. Those with the highest vitamin D intake (> 645 IU/day) had a significantly lower risk of these lesions. However, the Women's Health Initiative found no significant differences between groups in the incidence of colon cancer over a seven-year period in 36,282 post-menopausal women of different races and ethnicities who were randomly assigned to receive 400 IU of vitamin D plus 1,000 mg of calcium daily or a placebo. More recently, a clinical trial of bone health was conducted in 1,179 postmenopausal women in rural Nebraska. Subjects who took daily calcium (1,400-1,500 mg) and vitamin D3 (1,100 IU) were significantly less likely to develop cancer over the following four years compared to women who received a placebo. The small number of cancers (50) precludes generalization about a protective effect of either or both nutrients or for different cancers. This caution is supported by an analysis of 16,618 participants in NHANES III (1988-1994), in which all-cancer mortality did not correlate with baseline vitamin D status. However, the death rate from colorectal cancer was inversely related to serum 25(OH)D concentrations. A large observational study with participants from ten Western European countries also confirmed a strong inverse association between prediagnostic 25(OH)D concentrations and the risk of colon and rectal cancer.

Further research is needed to determine whether vitamin D deficiency in particular increases cancer risk, whether greater exposure to the nutrient is protective, and whether some individuals may be at increased risk of cancer due to vitamin D exposure. Taken together, the results of studies conducted to date on the intake of vitamin D with or without calcium do not suggest a reduction in cancer risk. 

What forms of vitamin D are there?

The vitamin comes in many different forms. Food supplements usually contain vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). What is the difference between these two forms and which is better?

Vitamin D3 (cholecalciferol) is the form that is normally produced in the skin through sunlight. It is also found in vitamin supplements and foods such as fortified milk, fatty fish, fish cod liver oil and egg yolk. However, the body can only use vitamin D3 after the kidneys and liver have converted it into the activated form.

However, as it is considered the natural form of vitamin D, it is often preferred to other forms in food supplements. It is obtained from the wool fat (lanolin) of sheep.

Vitamin D2 (ergocalciferol) is also present in some preparations and comes from irradiated plants and/or fungi. There is some controversy as to whether it should be included in supplements at all, as it is not the natural form of the vitamin as it is produced in the body. Studies also show that our body can store vitamin D3 better than D2 and raises vitamin D levels in the blood more quickly. Like vitamin D3, D2 must first be activated in the liver and kidneys. There is also a vegan D2 supplement on the market.

 

Sources (in English):

Bahrami, A., Mazloum, S. R., Maghsoudi, S., Soleimani, D., Khayyatzadeh, S. S., Arekhi, S. et al. (2017, July). High Dose Vitamin D Supplementation Is Associated With a Reduction in Depression Score Among Adolescent Girls: A Nine-Week Follow-Up Study. Journal of Dietary Supplements, 1-10, doi: 10.1080/19390211.2017.1334736