The sunshine vitamin
Vitamin D is THE mood enhancer amongst vitamins. It not only is a present from the sun and freely available for anyone, but also fuels our body cells due to its functions as a vitamin and hormone. It contributes to key functions of the body and thus becomes increasingly popular in scientific studies. Also in family practices and private households it gains more and more recognition. Many already refer to it as ‘the wonder vitamin’ due to its healing effects. In spite of its publicity and vital use to the body, only few people manage to fulfill the recommendations. According to the German Robert-Koch-Institute, 60 % of the population have too low vitamin-D levels.  Sufficient supply of vitamin D, however, is an important preventive health measure as the consequences of vitamin D-deficiency can be severe. Therefore, you should already correct a possible undersupply at an early stage.
In the following you will learn more about how to optimize your vitamin D supply
What is vitamin D
Vitamin D belongs to the group of fat-soluble vitamins, strictly speaking to the seco-steroids. Due to its hormone-like effect, it can also be referred to as a hormone. By definition, vitamin D is not a vitamin as it is produced by the skin with sun exposure. Its key functions are the participation in bone and muscle metabolism, the promotion of the immune system and the protection of the blood vessels. The two most important forms of vitamin D are vitamin D2 (ergocalciferol) in plant foods and vitamin D3 (cholecalciferol). The latter is the most important form and can only be found in animal-derived foods. It is also called 25 (OH) D. 
The role of vitamin D in the body
- participation in bone health through bone mineralisation
- promotes muscle development and muscle power
- promotes absorption of calcium and phosphate
- regulates more than 200 genes
- supports the normal function of the immune system
- positively influences the heart muscle’s function
- promotes the elasticity of the vascular walls and decreases their inclination to inflammation
- antihypertensive effect
- plays a key role in the growth of the skeleton of children
Due to its unique double effect as a vitamin and hormone it participates in numerous bodily processes.  The positive effect caused by an optimized vitamin D supply confirms its key importance. In addition to calcium it not only participates in bone metabolism but also in many other central metabolic processes.
The 25 (OH) D plays a leading role in skeletal and cardiovascular disorders, cancer, diseases of the central nervous system, infections and autoimmune diseases. 
Conclusion: Vitamin D is participating in central processes of our body. Due to its versatile functions it thus plays a key role for our health. Due to its unique double effect as a vitamin and hormone, it is a relevant factor beginning from maintenance of bone health up to reduction of inflammations.
How does the body absorb vitamin D?
Vitamin D production with sun exposure
Vitamin D3 is made in the skin from its precursor 7-dehydrocholesterol when exposed to sunlight. This precursor is produced in the liver and intestinal mucosa using cholesterol and is then transported back to the skin. The pre-vitamin D3 is converted to the active vitamin D3 under the effect of warmth and then further converted to 25-Hydroxy-Cholecalciferol (25 OH D) - the storage form of vitamin D. 
Vitamin D production from food and tablets
80 % of the vitamin D supplied through food or tablets is absorbed by an healthy small intestine. The vitamin D3 is transported in form of fat-soluble substances from the bowel wall to the liver. By a chemical reaction, the so-called hydroxylation, the intermediate product 25-Hydroxy-Cholecalciferol (25 OH D) - the storage form - is produced.
How much vitamin D should you have a day?
The vitamin D requirement depends on individual lifestyle factors. This means how often and, above all, how long the person is exposed to sunlight. But it also matters how old you are, what’s the strength of solar irradiation, and what skin type category you belong to. So far, no exact value for a general optimal vitamin D supply can be provided. 
Opinions concerning the vitamin D requirements diverge. The recommended values vary worldwide, and also in Germany the organizations, physicians and scientists disagree on this value.
RDA1 in IE/day
tolerable upper intake level (UL2) in IE/day
from the age of 18
no data available
from the age of 18
no data available
from the age of 18
1 Recommended Daily Allowances = the estimated amount of a nutrient per day considered necessary for the maintenance of good health by the Food and Nutrition Board of the National Research Council/ National Academy of Sciences
2 tolerable upper intake level = the highest level of nutrient intake that is likely to pose no risk of adverse health effects for almost all individuals in the general population. As intake increases above the UL, the risk of adverse effects increases.
Vitamin D is measured in micrograms (µg) or international units (IE).
1 µg = 40 IE bzw. 1 IE = 0,025 µg. 
What established expert associations say
In case of missing sun exposure, the German Nutrition Society (DGE) recommends a value of 20 µg per day, which corresponds to 800 international units (IE). This estimated value is valid for all ages after the first year of age.  According to current studies, this value seems to be far too low.
The European Food Safety Authority (EFSA) defines a daily maximum intake level of 4,000 IE for adults from the age of 18, which may also be taken up through food. This value defines the highest level of nutrient supply that is likely to pose no risk of adverse health effects in case of long-term and regular supply. 
The Journal of Clinical Endocrinology and Metabolism emphasizes in a report from 2011 by the Institute of Medicine (IOM) that adults aged between 19 and 50 years need minimum 600 IE vitamin D per day to maximize bone health and muscle function. In order to keep the blood level of 25 (OH) D within an optimal range (> 30 ng/ml), at least 1,500 to 2,000 IE per day are necessary. In order to correct a vitamin deficiency, higher values of up to 10,000 IE per day may be necessary for a defined period and for people from 19 years of age. In this case, the vitamin D-dosage depends on the severity of the vitamin D-deficiency.  Please read here how you can treat your vitamin D-deficiency.
Summary: The correct determination of the vitamin D-requirement for a person is still the subject of current research. This is further complicated by individual needs of men and different life circumstances. The fact that there is disagreement on the values of vitamin D levels having a positive impact on the body’s functioning, casts doubts on the present recommendations of the expert associations.
Which foods contain vitamin D?
Natural vitamin D-containing foods are limited. The most important form, the vitamin D, can only be found in foods of animal origin. In high concentrations, vitamin D can be found in the liver of oily fish (herring, kipper). Herring can contain up to 30 µg Vitamin D3 per 100 g fish. Other fish species contain much less vitamin D3.
Further good sources are margarine, butter, egg yolk and milk. [2, 5]
Compared to other vitamins, vitamin D can only be found in very few foods. The sun is the decisive factor for our vitamin D-level.
How much vitamin D can be taken up from food?The German National Food Consumption Study II (Nationale Verzehrsstudie, NVS) shows that Germans only take up 2-4 µg vitamin D per day. In case of a requirement of 20 µg/day, the exclusive coverage through food is far lower. The balance must be satisfied by the body’s own production and/or by intake of vitamin D-supplements. [2, 8]
Edible mushrooms contain substantial quantities of vitamin D3, which can, however, be absorbed less good due to its bioactive type. [2, 5] Generally speaking: through food preparation, approximately 10 % of the vitamin D3 get lost.  Please note: eating vitamin D-containing foods is not sufficient to cover the daily vitamin D requirement.  Here is a small sample calculation: in order to take up 5 µg vitamin D, you must consume the following foods: 600 grams mushrooms, 1 kilogram bovine liver, 1 kilogram butter or 20 eggs. 
Only 10 to 20 % of the vitamin D-demand can be covered from food.
Conclusion: Our vitamin D-requirement can not be covered from food as the vitamin D-content is too low. For the coverage, the sun is necessary as well as the intake of vitamin D-supplements. Please read here, how you can guarantee an optimal vitamin D-dosage.
It is estimated that about 1 billion people worldwide are affected by vitamin D-deficiency (blood level of 25-hydroxy vitamin D in serum (25OHD) below 30 ng/ml). [9, 10] Also the World Health Organization emphasizes that vitamin D-deficiency is a widespread health problem. The essential role of 25 (OH) D in bone metabolism and muscle function is comprehensively documented. [10-12] In recent years, scientific attention concentrated, in addition, on the non-skeletal effects of 25 (OH) D. [12, 13] Evidence from numerous studies indicates the correlation between vitamin D-deficiency and several chronic diseases like diabetes mellitus, cancer, depression, cardiovascular diseases and immune malfunction [14–17] as well as increased total mortality risk. 
Vitamin D-deficiency has also been linked to unspecific symptoms such as muscle weakness, fatigue, musculo-skeletal complaints. 
In the light of the health-promoting functions of vitamin D, an early treatment of a vitamin D-deficiency can considerably contribute to health prevention.
Read on to learn more about who’s at risk for developing a vitamin D-deficiency and how you can take counteraction.
Risk groups for vitamin D-deficiency - Do some people have a higher risk to develop vitamin D-deficiency?
Who is at risk for vitamin D-deficiency?
There are certain groups of people who are at risk to develop vitamin D-deficiency. This means that a regular analysis of their vitamin D-levels is of crucial importance:
- people, who are scarcely or never outdoors
- pregnant women due to their higher requirement
- people who are covering their bodies (e.g. for cultural or religious reasons)
- people with dark skin, as they produce less vitamin D from the same UV radiation than fair-skinned people
- older people as the vitamin D-production decreases with age and as they spend less or no time outdoors for reasons of mobility
- infants, as the vitamin D-content of mother’s milk is very low and as infants should, in general, not be exposed to direct sunlight
- people who are taking medication for a long period 
The German Federal Institute for risk assessment (BfR) states: ‘It is sensible for risk groups to take vitamin D-supplements.’ 
Conclusion: In the light of the causes of a vitamin D-deficiency and the risk groups stated above, it can be said in general that vitamin D is needed nationwide. The overview of the people especially at risk shows that most people belong to one of the risk groups.
As Central and northern Europe belongs, due to its geographic location, to the vitamin D-deficiency-areas emphasizes the importance of a regular vitamin D-analysis for its population.
How to test for vitamin D-deficiency?
In spite of the health advantages of vitamin D, the awareness for the risks of vitamin D-deficiency is lacking. All the more serious is the fact that people with a vitamin D-deficiency have no obvious symptoms. The symptoms are often vague and develop gradually until they are so serious that diseases like e.g. osteomalacia (bone softening) have developed. 
Symptoms may be: 
unspecific symptoms such as fatigue, exhaustion
poor skin condition
muscle weakness, difficulty in muscle building
susceptibility for infections
In case of serious vitamin D-deficiency (25-OH-D below 25 nmol/l) there is an increased risk for: 
- osteomalacia and osteoporosis
- rachitis in children
- bone pain and bone weakness (osteoarthritis)
- (bone) fractures > 65 years
According to recent scientific studies, vitamin D-deficiency is also associated with: [20, 21]
- heart diseases
- high blood pressure
- diabetes mellitus
- certain cancers
- severe infections such as tuberculosis, chronic kidney diseases
- hair loss
Vitamin D - the deficiency hormone in old age
The importance of vitamin D in old age is an aspect which is still not enough attention paid to. A vitamin D-deficiency can generally be found in all age groups. But especially with increasing age, there are further factors that complicate the utilization of vitamin D in the body. Causes are the aging processes and not the lack of sun exposure. Quite the contrary: A slight suntan reduces the remaining own production of vitamin D even more. 
A demography study, KORA-Age from 2017, shows that one in two test persons older than 65 years has a vitamin D-deficiency. Thus, more than 50 % out of 1,079 men and women have a value below the limit of 20 ng/ml. 
Did you know that older people produce four times less dermatological vitamin D than younger people? Especially the age group ‘65 years and older’ are affected. 
Tips for vitamin D in old age:
- at the latest at the age of 60, the vitamin D blood levels should be checked regularly,
- following advice such as ‘daily sunbathing for about 15 minutes’ is not sufficient in case of too low blood levels,
- a fixed dose of 800 IE vitamin D per day is by far insufficient,
- an individual dose should be determined by blood analysis before and during intake. 
Examination of 686 people aged 60 to 89 years revealed that the vitamin D-status was by far insufficient which had significant impact on life quality and negative effects on health. 
The significance of common deficiency in old age is stressed by the positive effects of vitamin D on the body. Studies confirm the following positive effects:
- prevention of bone fractures 
- promotion of heart and cardiovascular health 
- reduction of cancer risk, e.g. colon cancer [22, 28]
- reduction of age-related chronic diseases [22, 28]
- improved sense of balance [22, 28]
- support of muscle power in old age 
Vitamin D-deficiency - Test
The health benefits and thus the risks in case of too low vitamin D-levels are enormous. How can you find out if your vitamin D-level is too low? Or rather, how can you take preventive action and test your current vitamin D-status? Here you can get more details on how to determine your vitamin D-level and what you should pay attention to.
Vitamin D-testing explained
Vitamin D-levels can be determined exclusively by means of blood tests. Expert associations recommend to analyse the 25 (OH) D-level in serum. Only the 25 (OH) D-level provides a clear statement on the vitamin D-storage levels. The often discussed 1,25 (OH) D is not relevant in this respect to depict a deficiency.
For people belonging to one of the risk groups, the blood test is necessary as a prompt reaction to the improvement of the vitamin D-levels can be expected. 
Vitamin D - Test-execution
Nowadays, a vitamin D-test can be executed by means of a small quantity of blood in serum. It is important that the laboratory is working as per the gold standard to guarantee diagnosis according to scientific standards. You can enquire whether the laboratory is a gold standard laboratory or find out here. 
The 25 (OH) D-value is measured in ng/ml or nmol/l (1 ng/ml corresponds to 2.5 nmol/l). 
Where to test your vitamin D-levels
You can have your vitamin D-level analysed at your family doctor’s or alternative practitioner. However, your health insurance only reimburses the cost if your doctor deems it necessary. Alternatively, you can test your vitamin D-status easily at home. The cerascreen® Vitamin D-Test comprises a free analysis as well as a comprehensive result report.
What can cause vitamin D-deficiency?
Due to changes in lifestyle, increased urbanization and long working hours in mainly closed rooms we don’t get enough sun. This involves the risk to develop vitamin D-deficiency even in summer.
The causes for vitamin D-deficiency can be summarized in a simple equation:
‘Lack of skin sun exposure = decrease of vitamin D-blood levels’
Lacking sun exposure of the skin is the main factor for vitamin D-deficiency.
The reason for this is that the ultraviolet sunlight (UVB) is the main source of 25 (OH) D for the endogenous production from natural sunlight. 
But the causes are not that easy after all. The body’s own production of vitamin D in the skin also depends from the following geographic, climatic and cultural factors: 
- time of year and time of day
- weather conditions
- time spent outdoors
- skin type
- use of sunscreens
- age of the person, > 65 years of age the body’s synthesis capacity decreases
What can disturb the absorption of vitamin D?
Moreover, the intestinal vitamin D-absorption can be disturbed by impaired fat digestion or fat absorption in case of the following diseases: celiac disease, bile acid deficiency or excretory pancreas insufficiency.
Besides, certain medications can induce a vitamin D-deficiency. These are, amongst others: antihypertensive drugs, antiestrogens, anticonvulsants and herbal medicines. They can inactivate vitamin D or increase demand by stimulating metabolism. 
In return, sufficient supplies of vitamin D can improve the effect of drugs like e.g. antihypertensive drugs and reduce side effects of medicines, like e.g. anti-cancer drugs. 
Good to know:
The use of sunscreen with factor 30 reduces the vitamin D-synthesis in the skin by more than 95%. 
How much vitamin D can I get from the sun?
An example: in order to produce 400 IE vitamin D, a person with fair to medium skin type (tans slowly and rarely sunburns) living on the 42°N degree latitude (e.g. southern France) has to expose one fourth of his / her skin (e.g. arms, face, décolleté) for 3-8 minutes to sunlight at noontime and during the months April to October. 
Summary: Whatever affects the transmission of UVB rays to the earth’s surface (e.g. latitude) or the penetration of the UVB rays into the skin (e.g. degree of pigmentation, sunscreen) influences the skin’s production of 25 (OH) D. [32, 4] Thus, the body’s synthesis is impaired and the vitamin D-stores in the body cannot be sufficiently replenished. This results in vitamin D-deficiency. A main reason for this is the changed lifestyle. As the main time is spent indoors and life in cities makes it impossible to cover our vitamin D-demand only from the sun. From evolutionary perspective, our ancestors had an advantage in this respect.
Vitamin D-deficiency - therapy:
How to optimize my vitamin D-levels
When to supplement vitamin D?
According to studies, you can stabilize your vitamin D-level by taking in 2,000 IE vitamin D per day - in case there is no deficiency. Risks and side effects are not to be expected for this dosage.
During winter, orthomolecular physicians recommend up to 5,000 IE per day. However, this dosage is mostly not sufficient to correct a too low vitamin D-level. The vitamin stores have to be replenished at first. 
To keep vitamin D-levels stable, you need to take 2,000 IE vitamin D per day! 
Summary: If there is no deficiency, you can take 2,000 IE vitamin D per day in order to stabilize your blood level. In case of a deficiency, 2,000 IE are not sufficient to increase your vitamin D-levels.
Please note: 2,000 IE per day do not necessarily lead to the same stable levels for everybody. Factors such as competitive sports, serious illnesses and certain medicines can influence the personal requirements. 
How do I treat vitamin D-deficiency?
From a medical perspective, vitamin D-supplementation is required if the vitamin D-levels are below 20 ng/ml. Some bodily functions are impaired at blood levels below 31 ng/ml. At a level of less than of 11 ng/ml, severe illnesses such as e.g. bone softening, are to be expected. According to orthomolecular medicine, a vitamin D-level of 40-90 ng/ml is considered adequate for healthy people. In order not to act when necessary and when the risk for disease development rises substantially, the target value of vitamin D-levels should be 40-90 ng/ml. Only within this range we are taking preventive action and can eliminate the risk of vitamin D-deficiency. [33, 34]
Table of vitamin D-concentration :
The duration and intensity of the therapy depend on the severity of the vitamin D-deficiency
Optimizing vitamin D-levels
A balanced diet, i.e. a vitamin D-rich diet, is not sufficient to raise vitamin D-levels. It only makes sense in combination with other therapies. 
The most natural way is making use of the synthesis in your skin. This means especially whole body sun exposure in the warm months.  In this context, less is more! With regard to skin cancer prevention, you should take into account your skin type and the duration. During sunbathing, the body can replenish its vitamin D-stores. Even if the stores are full, they are mostly not sufficient to bridge the winter months. Due to this, the exclusive sunbathing could lead to vitamin D-deficiency latest in winter. 
From vitamin D-supplements
The most effective way to treat vitamin D-deficiency is to use vitamin D-supplements. In accordance with the 25 (OH) D levels you can customize the dosage and duration. 
Tips how to correct vitamin D-deficiency
- eat sea fish twice a week (herring, mackerel, salmon)
- regularly eat mushrooms
- regular spend time outdoors with sun exposition
- in winter: intake of 5,000 IE daily to maintain blood levels
- in summer: intake of 2,000 IE daily to maintain blood levels
- check the vitamin D-levels regularly
- risk groups: use vitamin D-supplements according to the severity of the deficiency
How to calculate your personal vitamin D-dosage
Below, we are demonstrating to you by means of an exemplary calculation how to calculate the vitamin D loading dosage in order to reach a good vitamin D-supply.
Formula: 10.000 IU x (60 - measured blood level) x (weight / 70)
Example: Per 70 kg body weight, further 10.000 IU are necessary to increase the level by 1 ng/ml.
We assume an initial value of 20 ng/ml and a target serum level of 60 ng/ml (lower limit of a good vitamin D level). Thus, we want to increase the level by 40 ng/ml.
For a person weighing 70 kg, this is calculated as follows:
10.000 IU (per kilogram 142,9 IE) x 40 ng/nl = 400.000 IU vitamin D
By means of these 400.000 IU that are taken in over a period of several weeks (in addition to the daily maintenance dosage of 2.000 IU), the target vitamin D serum level of 60 ng/ml can be reached as follows:
daily intake of 5.000 IU vitamin D in the form of a balanced diet or
in the form of an otc product with e.g. 1.000 IU per dose (5 x 1 capsule/tablet à 1.000 IU per day) for 80 days
intake in the form of a pharmacy-only product (e.g. 2 capsules/tablets à 5.000 IU per day) for 40 days
- intake of vitamin D tablets with a higher dosage, e.g. 20.000 IU per tablet (needs to be prescribed by a physician in most countries), 1 tablet per day for 20 days
Can you overdose vitamin D?
Can too much sunlight lead to an overdose?
A vitamin D-overdose, also called intoxication, is not possible from excessive sunbathing due to the body’s wide range of regulation processes which adapt to the body’s requirements and which also regulate the conversion into pre-vitamin D3. 
Simply put: when stores are full, the body stops the vitamin D-production in the skin.
Only high-dosage preparations and long-term oral intake can lead to possible side-effects such as build-up of calcium in your blood (hypercalcemia) and, in rare cases, severe organ damage.
In adults, toxic effects are suspected at doses of 500-1,000 µg/day if there is no lack of vitamin D (thus, within the optimal range of 61-90 ng/ml). This corresponds to 20,000-40,000 IE daily. 
Acute symptoms of an overdose are:
Nausea, vomiting, dizziness as well as cardiac arrhythmia, mental symptoms and disturbed consciousness. 
Long-term consequences are amongst others frequent urination, chronic thirst, muscle weakness, lack of appetite, weight loss and kidney stones. 
Summary: Too much sunlight cannot lead to an overdose due to the body’s regulation systems. High-dosage intake of more than 20,000-40,000 IE daily can in the long run - in case of an optimal blood level of 61-90 ng/ml - lead to negative effects on the body.
What makes a good supplement?
Due to the increasing awareness for the positive effects of vitamin D, the number and variety of vitamin D-preparations in the market has risen. The following question inevitably arises: which product helps best to effectively increase my 25 (OH) D-level?
Vitamin D3 or vitamin D2? Capsules, droplets or tablets?
The supplements should not be chosen randomly. Hereunder, we list some criteria that can help you find the most appropriate vitamin D-product:
An effective product should:
- contain vitamin D in its active form vitamin D3 (cholecalciferol). Vitamin D3 doesn’t need to be converted in the body in contrast to vitamin D2
- offer high bioavailability. This describes the quality (amount and extent) of the absorption of the active ingredient
- be dissolved in fatty substances as vitamin D3 is a fat-soluble vitamin. It can only be utilized by the body together with fat/oil.
- be enriched with MCT fats. Due to their fat matrix, they increase bioavailability and shelf life
- contain no or hardly any food additives. These can affect absorption and cause side effects. [36-38]
What should be considered when taking vitamin D-supplements?
Vitamin D can be taken on an empty stomach or with a meal. Its effect does not depend on the time of day. To help boost vitamin D-absorption, make sure to take your vitamin pill with some fat or oil in case the preparation doesn’t already contain it (as e.g. in case of droplets). Whether you take the vitamin D-supplement on a daily or weekly basis doesn’t influence its effect. [36-38]
Summary: What makes a good supplement?
active form: vitamin D3 (cholecalciferol)
contains fat or oil
contains no or hardly any food additives.
vegan, vegetarian, lactose-free, gluten-free
presentation in the form of capsules and droplets is most suitable
Vitamin D and vitamin K
A reasonable combination?
The vitamin-duo D and K are essential for maintaining bone health. A lack of these vitamins is associated with various chronic diseases. As is well known, vitamin K is important for blood coagulation. A deficiency entails, as for vitamin D, a reduced bone density and an increased risk of cardiovascular diseases. Both vitamins can have a protective effect against diabetes type 2. 
In prevention and therapy of osteoporosis it thus makes sense to combine vitamin D3 and vitamin K. 
Can additional intake of vitamin D optimize vitamin D3-absorption in the body?
At present, vitamin K2 as well as vitamin D are booming in the health industry. Current studies increasingly indicate the high benefits of vitamin K-supplementation in prevention and therapy of bone and vascular diseases.
The most important naturally occurring K-vitamins are vitamin K1 and vitamin K2. Vitamin K1 is in particular present in green leaf vegetables. Vitamin K2 is produced by intestinal bacteria. The demand for this vitamin is not exactly known. 
Vitamin K2 definitely offers various health benefits:
A supplementation of vitamin K2 can be useful for therapy of calcification in correlation with cardiovascular diseases. 
As prophylaxis for various organ tumors the daily intake of 800-1,000 international units (IE) is recommended.  This is, however, only valid in case of normal vitamin D-levels. If there is already a vitamin D-deficiency, this must be remedied at first before you strive for preventative protection.
Summary: Vitamin D has a huge impact on the risk of developing cancer. An optimal value of more than 50 ng/ml can contribute to the reduction of new cases of breast cancer by 50 %. In this light a regular check of the vitamin D-levels is a logical conclusion.
Vitamin D and depression
Depressions are one of the most frequent mental illnesses. In the world, more than 300 million people in each age group are affected and the number of new cases increases yearly. A depression differs from normal mood fluctuations and transient emotional reactions to daily challenges. Especially if they are prolonged and of average to strong intensity, depressions can become a severe risk to human health.  For therapy, antidepressants are often prescribed which are expensive and can cause side-effects. 
Studies have now proven the correlation between low vitamin D-levels and depression. People suffering from depression had by far lower vitamin D blood values that healthy people. [51, 52]
An enormous health problem could be improved by a correctly adjusted vitamin D-supplementation - which is cost-effective and above all without side-effects. 
Unfortunately, at present there are too few comparable studies to give a generalized recommendation on the nature and quantity of the preparations. But a majority of the studies indicates the effectiveness of vitamin D-preparations for reducing depressive symptoms. 
Vitamin D and hair loss
Hair loss is an issue in both men and women. People concerned have already tested different solutions from household remedies up to preparations with promising results. But are they addressing the problem at its source?
The thinning of hair as well as female diffuse hair loss is a frequent and challenging problem for dermatologists  as the reasons for hair loss are diverse.  One reason can be the lack of several nutrients which has a negative effect on the health of the hair root and thus on hair growth. 
Scientific investigations have shown that vitamin D plays a major role in hair follicles’ life cycle and is hence participating in active hair growth. 
The effects of vitamin D on hair growth
As a hormone, vitamin D promotes the production of receptors in the hair roots which stimulate growth. Hence, premature graying and hair loss can be reduced and sleeping roots can be put in operation. 
Summary: An optimal vitamin D-level and sufficient supply of B-vitamins and minerals can reduce hair loss and can stimulate new growth of hair roots.
Vitamin D and omega-3
The health advantages of vitamin D and omega-3 fatty acids are attracting increased attention in medical literature as well as in popular scientific publications. The sales of fish oil products expands and numerous foods are omega-3 enriched. 
The current regulations of the American Heart Association recommend eating fatty sea fish twice a week as prevention of cardiovascular diseases and to take up 1,000 mg omega-3 in the form of fish oil preparations. 
Studies also revealed a correlation between vitamin D-deficiency and cardiovascular diseases. Study participants with a vitamin D-deficiency value of less than 15 ng/ml have a 50 % higher risk of suffering a heart attack than study participants with an adequate level (> 30 ng/ml). 
Data resulting from studies, observational studies and / or secondary prevention studies indicate that vitamin D and omega-3 fatty acids can reduce the risk of cancer or cardiovascular diseases.
A large-scale study analysed the effect of vitamin D on chronic diseases and cancer. The objective is to determine an optimal vitamin D-dosage which has a preventive effect. The results are still pending. 
Summary: According to current studies, vitamin D and omega-3 fatty acids influence the risk to develop cardiovascular diseases or cancer. A vitamin D-value of less than 30 ng/ml should thus be avoided.
Vitamin D and migraine
About 80 % of people worldwide suffer from tension headache and migraine. Women are more often affected than men.  Migraine belongs to the recurrent severe headaches. It is assumed that the development of migraine attacks is correlating with inflammations of the nerves and blood vessels. 
The main characteristic of migraine attacks are headaches  that last from several hours to days  and are often intensive,  pulsating and unilateral.  Further symptoms are nausea, sometimes vomiting, light and noise sensitivity, neck pains and muscle tensions. 
According to the existing results, vitamin D-supplementation can reduce inflammation factors which are involved in migraine headaches. 
Currently, only few studies that analysed the correlation between migraine and vitamin D are available.
Existing research findings are inconsistent: Some studies show a positive correlation and others no correlation. Apart from this, there is a wide variety of studies that are showing in detail that higher vitamin D-levels help reduce inflammations in the body. Therefore, it is likely that vitamin D plays a role in the development of migraine attacks.
A recent study analysed the effect of vitamin D-supplementation on the symptoms of migraine patients. They concluded that vitamin D-intake can contribute to the reduction of the frequency of headache attacks. 
New research findings published in the International Journal of Clinical Practice suggest that vitamin D-levels and factors of vitamin D metabolism influence migraine. 
Summary: Available studies are contradictory. It is assumed that due to its anti-inflammatory function, vitamin D can reduce the development of migraine. Moreover, an optimal vitamin D-supply can reduce the symptoms of migraine.
Vitamin D and cardiovascular diseases
Vitamin D has even more to offer than its well-known effect on the skeleton and bone health. In fact, more and more influences of vitamin D on the state of health have been revealed. The enormous functional scope of vitamin D results from its participation in roughly 200 different enzymatic reactions of the body. Nearly every metabolic process is influenced by enzymes. Enzymes serve as a catalyst in the body, whereby metabolic processes are accelerated and can run with lower energy consumption than usual. 
Meaningful study situation:
In 2012, a study of the American Journal of Cardiology showed that vitamin D-deficiency can be considered a cause for higher mortality rates due to cardiovascular diseases. By administration of vitamin D-supplements, a reduction of these risks could be determined. Also, it was found out that vitamin D-deficiency is a risk factor for diseases of the blood vessels, for cardiac muscle problems and high blood pressure. 
These results were confirmed by another study with more than 40,000 participants. This study shows that vitamin D-values of less than 15 ng/ml - compared to >30 ng/ml - show a correlation with increased incidence of high blood pressure, elevated blood lipids, heart failures and strokes. 
Experts in the field of orthomolecular medicine recommend vitamin D-levels of 40 to 90 ng/ml for an optimal and preventive effect. 
Conclusion: A vitamin D-deficiency increases the risk of cardiovascular diseases, heart defects, diseases of the blood vessels and high blood pressure.
How does vitamin D influence cardiovascular diseases?
Vitamin D improves cardiac muscles and their strength. This happens through the reduction of thrombus formation as thrombi are eliminated by increased plasmin production. Plasmin helps the body to dissolve blood clots and thereby, for instance, protects against heart attacks and strokes. Thus, the pressure in the heart vessels is reduced and blood can circulate freely. Furthermore, vitamin D plays an important role in calcium and phosphorus metabolism. Vitamin D assures the incorporation of minerals in the bones. In case of vitamin D-deficiency, especially calcium is not incorporated correctly and this can result in calcification of the vessels. 
Summary: Vitamin D plays an important role in cardiovascular health. Therefore, everybody should strive for a vitamin D-level within the preventive range to avoid cardiovascular diseases. A regular check (at least twice a year) is the logical conclusion in order to identify a deficiency and, if necessary, to correct it.
Vitamin D and skin diseases
Skin diseases are a cumbersome topic and the psychological strain is high. Apart from external applications, like creams and lotions, also promising diets are chosen to improve neurodermatitis, acne and Co. But it may well be that the lack of just one vitamin causes the skin symptoms.
This was also assessed in recent studies. Vitamin D-deficiency plays a significant role in skin diseases such as neurodermatitis (atopic eczema), psoriasis or vitiligo. These can also be treated with UVB-rays in dermatological practices, as these rays are needed by the skin for vitamin D-synthesis. 
Neurodermatitis and vitamin D: What does scientific research say?
Studies show promising results in the field of vitamin D-preparations and neurodermatitis. According to a study conducted with 95 neurodermatitis patients, those with low vitamin D-levels more often had bacterial skin infections. [67, 68]
Psoriasis and vitamin D: What does scientific research say?
Another study researched the effects of high vitamin D-doses (by supplements) on the clinical course of psoriasis and vitiligo. It showed a positive effect from treatment with vitamin D in all nine patients aged 14 to 16 years. A repigmentation of 25-75 % could be achieved. Furthermore, it was found out that the calcium-levels increased in all patients through vitamin D-supplementation, in spite of their calcium-poor diet. Thus, a simple intake of vitamin D-preparations can impact positively on the course of psoriasis and Co. [68, 70]
Acne and vitamin D: What does scientific research say?
Moreover, it was proven that vitamin D3 (cholecalciferol) is important for wound healing as it is needed for the production of antimicrobial peptides which repel infectious micro-organisms. It not only protects the skin against infections, accelerates wound healing and promotes the formation of new cells but also plays a major role in the immune system. Vitamin D3 prevents the acne-skin from infections and contributes to its healing. [71, 72]
Summary: As vitamin D promotes the effect and absorption of calcium in the intestine, it is thus essential for a healthy skin. A high-dose therapy is thus effective and safe in patients with neurodermatitis, psoriasis and vitiligo.
A scientific study showed that through supplementation of vitamin K2 the proportion of carboxylated osteocalcin could be increased. This means that vitamin K2 is involved in the improvement of bone mineralization. 
But attention: In case of intake of vitamin-K antagonists, i.e. drugs that reduce blood clotting, the daily intake of vitamin K2 through supplements should not exceed 10 µg. 
Does an increase of vitamin D-levels cause vitamin K-deficiency?
Vitamin K2 and vitamin D3 are both involved in bone mineralization. They stimulate production and incorporation of osteocalcin, a peptide hormone. It is a marker of bone formation. 
Due to this common task the hypothesis is put forward that a rising vitamin D-level could cause vitamin K-deficiency. This leads to the conclusion that an additional intake of vitamin K2 is necessary, if vitamin D3 is taken.
At present, there is no clear scientific basis that vitamin K2 is recommended in addition to vitamin D3. Also large-scale studies did not record the influence of vitamin K. Only in case of cardiovascular diseases, vitamin K can be suitable as one aspect of an appropriate therapy. 
Leading researchers working with Prof. Dr. med. Michael F. Holick from the University Boston are agreeing on the fact that an additional intake of vitamin K2 in case of vitamin D3-supplementation is not necessary. 
Summary: From sole scientific perspective, a well-founded effect of vitamin K2 in addition to intake of vitamin D3 cannot be deduced due to the lack of studies. The studies available at present on the topic of vitamin D-absorption in the body have not researched the role of vitamin K2.
Vitamin D and cancer
The term ‘cancer’ is an umbrella term covering a plethora of malignant tumour diseases. What all of these have in common is the unscheduled and uncontrolled cellular proliferation of the tumour cells which can displace and destroy healthy tissue. 
Nearly 8 million people die from cancer each year.
That are 13 % of all deaths worldwide. The most common types of cancer are lung, stomach, colon, liver and breast cancer. In men, lung, colon and prostate cancer appear especially frequent. Whereas women most often battle against breast, lung and colon cancer. The frequency is given in descending order. According to the World Health Organization (WHO), more than 30 % of cancerous diseases could be avoided through prevention. 
What does scientific research say?
According to scientific data, vitamin D reduces the cancer risk; for example in case of colon cancer, by the regulation of the spreading and development of cells. A study conducted in 2004 with more than 16,000 patients determined that an increased vitamin D-level reduces the risk to develop some types of cancer. Through vitamin D-levels of more than 50 ng/ml a reduction of new cases of breast cancer by more than 50 % could be noticed.  Furthermore, studies in the field of cancer of the large intestine and rectum in correlation with vitamin D were evaluated. The risk of new cases of cancer was reduced by 46 %. 
This means: An optimal Vitamin D-level can reduce the risk of breast cancer and cancer of the large intestine and rectum by half!
Increased mortality and vitamin D-deficiency
Results of another study show that vitamin D-deficiencies correlate with increased mortality: The ESTHER*-study with nearly 9,600 men and women showed that the mortality in participants with low and very low vitamin D-levels compared to participants with sufficient vitamin D-levels was 1.2 times higher in men. In women, the risk was even 50 % higher. 
*ESTHER-study = Epidemiological study on the prevention, early detection and optimized therapy of chronic diseases in older people
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