Vitamin D deficiency: symptoms, causes and treatment
Tired, weak muscles, constantly catching colds in winter? More than half of adults in Germany fall below the recommended vitamin D level, and even more from October to March. Which symptoms are typical, which blood value matters, how much sun is enough, and when a supplement makes sense.
Aktualisiert 10 September 2026 · 15 Min. Lesezeit · 18 Quellen
The essentials in 30 seconds
That's 800 IU, for everyone aged one and over (DGE). This value only applies if the skin produces no vitamin D at all, so mainly in winter.
During these months, UV-B radiation in Germany is too weak for skin production. The stores built up over summer have to last.
That's how much of your supply comes from the skin with enough sun. Food only provides 2 to 4 µg a day, even with fish.
Below 30 nmol/l (12 ng/ml) counts as a deficiency, from 50 nmol/l (20 ng/ml) as sufficient. Measure first, then dose, never the other way round.
Vitamin D deficiency symptoms: how to recognise it
Vitamin D deficiency rarely announces itself with one clear sign. Most symptoms are non-specific: tired, worn out, sore muscles, more frequent infections. That's exactly why it's often only discovered through a blood test, or not at all. In Germany, more than half of adults fall below the level the DGE and BfR consider sufficient, even more in winter. No symptom will tell you whether you're one of them, only your 25(OH)D value can (chapter 4). This list helps you spot your own pattern.
Early signs: tiredness, muscle weakness, pain
Vitamin D controls how much calcium moves from the gut into the blood and from there into the bones. If it's missing for months, newly formed bone no longer mineralises properly. Doctors call this osteomalacia, or bone softening. It hurts: a dull, deep ache, often in the lower back, pelvis, hips and thighs, sometimes in the shin or breastbone under pressure. Alongside this comes muscle weakness, mainly affecting the thighs. Climbing stairs and getting up from sitting become difficult, and older people fall more often. Calf cramps and muscle pain are also part of the picture.
Tiredness is the symptom most people search for first. To be honest, it's linked to low levels in observational studies, but a cause-and-effect link hasn't been proven, as the BfR explicitly states. If you're exhausted in February, there are many possible reasons, vitamin D being just one of them. It's different for children: a severe deficiency during growth leads to rickets, with bowed legs, a soft back of the skull and delayed growth. In Germany, this has become rare thanks to vitamin D prophylaxis in the first year of life.
Vitamin D deficiency: eye symptoms
Dry, burning or irritated eyes appear on many symptom lists, and there is actually data on this: a meta-analysis of ten studies with almost 19,000 people found that people with dry eyes had vitamin D levels around 4 ng/ml lower on average, reported more complaints and produced less tear fluid. This is a correlation, not proven causation: whether vitamin D triggers dry eye or whether both are linked to the same lifestyle remains open. What doesn't belong in this picture: visual disturbances, blurred vision or flashes of light. These have other causes and belong in an eye specialist's office, not in a vitamin D test.
Vitamin D deficiency and mental health: depression and winter blues
Low vitamin D levels and low mood often occur together, especially in winter, when both depend on light. Research has only half-answered the question of whether vitamin D really lifts mood: a meta-analysis of 41 randomised trials with over 53,000 participants found a small positive effect on depressive symptoms, mainly from 2,000 IU a day, but rated the certainty of this finding as very low. What this means for you: vitamin D doesn't replace treatment for depression. If a deficiency is confirmed, replenishing it can be one building block, but no more than that.
Have your 25(OH)D level checked if you have bone pain together with muscle weakness, falls or cramps, or if children show delayed growth or bowed legs. This also applies without symptoms for risk groups: people needing care, people with darker skin or covering clothing, chronic bowel, liver or kidney disease, or those taking anti-epileptic medication.
Hair loss, skin and weight
Hair loss, dry skin and weight gain are often reported alongside low vitamin D levels. The BfR sums up the situation soberly: the link has been observed, but a clear cause-and-effect relationship hasn't been proven for these non-specific symptoms. For hair loss, there are far more common reasons, above all iron deficiency, thyroid issues and hormonal changes. So if you're losing hair, don't just get your vitamin D checked, get your ferritin checked too. With weight, it tends to work the other way round, more on that in chapter 2.
Vitamin D deficiency causes: Where the deficiency comes from
Vitamin D is the only vitamin the body makes itself, with the help of UV-B radiation on the skin. With enough sun, 80 to 90% of your supply comes from this self-production, while food only contributes 10 to 20%, around 2 to 4 µg a day. This already points to the main cause of a deficiency: too little sun on too little skin. Everything else, age, skin type, clothing, excess weight, illness, only amplifies this one effect. How much you actually need depends on your age and life situation.
Too little sun: October to March
Skin production needs UV-B, which only reaches the ground when the sun is high enough. In Germany, that's roughly from April to September around midday. From October to March, radiation is too weak even under a blue sky, and levels drop for almost everyone, according to the BfS and BfR. In the national health survey DEGS1, one in four adults fell below 30 nmol/l in winter, while in summer only half reached a sufficient level. On top of that comes everyday life: office, car, working from home. Window glass lets through hardly any UV-B, and light at your desk doesn't count. If you spend the whole summer indoors, you'll head into winter with empty stores.
Age, skin type, clothing, medication
From around age 65, the skin produces less than half of what it managed in younger years. Add in the need for care or little physical activity, and deficiency becomes almost the norm: the BfR names residents of care facilities as a group for whom general supplementation should be considered. Darker skin contains more melanin and needs considerably more UV-B for the same amount of vitamin D. Covering clothing, for whatever reason, acts like winter in summer. Sunscreen also reduces production, but is essential during longer sun exposure. On the illness side, there's chronic bowel disease like coeliac disease and Crohn's disease (vitamin D, being fat-soluble, is poorly absorbed), liver and kidney disease (activation is impaired), and medication, above all anti-epileptics, which speed up breakdown.
Vitamin D deficiency and weight gain
The usual search is: does vitamin D deficiency make you fat? The data suggests the opposite. People with a high body fat percentage have lower vitamin D levels, because the fat-soluble vitamin gets distributed across more tissue. A study of 686 adults showed that this dilution effect fully explains the difference, not storage in fat itself. The practical consequence: if you weigh more, you need a higher dose to replenish your levels, and excess weight is a risk factor for deficiency. There's no evidence that a deficiency itself causes weight gain or a bigger belly (BfR). So if you want to lose weight, don't rely on vitamin D, instead fix the deficiency, because it slows down muscle strength and drive.
The body stores vitamin D in fat and muscle tissue and releases it during exercise. That's why the BfR recommends outdoor activity even in winter: it helps you tap into your summer reserves, even when the sun isn't delivering anything new right now.
Risk groups at a glance
- People who rarely go outside: those needing care, the chronically ill, office and shift workers without an outdoor lunch break
- Older adults from 65, especially with limited mobility
- People with dark skin or covering clothing
- Infants, because they shouldn't be in the sun and breast milk contains hardly any vitamin D
- People with severe obesity
- Chronic bowel, liver and kidney disease, taking anti-epileptic medication
How vitamin D works in your body
Three stages from the skin to the bone. If you know them, you'll understand why sunshine matters more than your plate, why the blood value is called 25(OH)D, and why too much does just as much harm as too little.
Formation in the skin
UV-B radiation converts a cholesterol precursor in the skin into vitamin D3. In Germany, this only works from around April to September around midday. Window glass, clothing and strong sun protection let through hardly any UV-B, and in winter there's none at all. Vitamin D3 (fish, egg) and D2 (mushrooms) from food are absorbed via the small intestine.
Storage: 25(OH)D
The liver converts this into 25-hydroxyvitamin D, the storage and transport form with a long half-life. This is exactly the value the lab measures, because it reflects both sources: skin and food. The surplus from summer is stored in fat and muscle tissue and released again during exercise.
Effect: calcitriol
The kidney activates the storage form into calcitriol. This draws calcium from the gut into the blood, hardens the bones and acts on muscle and immune cells. If it's missing, the calcium in food stays unused, bones become soft and muscles weak. Too much, only possible through supplements, drives blood calcium up.
Vitamin D level: how a deficiency is diagnosed
What's measured isn't the active hormone but the storage form 25-hydroxyvitamin D, or 25(OH)D for short. It has a long half-life, isn't subject to hormonal counter-regulation, and reflects sun exposure and diet over the past few weeks. The units can be confusing: German labs sometimes report nmol/l, sometimes ng/ml. The conversion is simple: ng/ml times 2.5 equals nmol/l. It's also confusing that labs set different thresholds: some class anything under 75 nmol/l (30 ng/ml) as undersupplied, others only below 50 nmol/l (20 ng/ml). The DGE, BfR, EFSA and the US National Academy consider 50 nmol/l sufficient, and in 2024 the Endocrine Society withdrew its old target of 30 ng/ml. So for most people, a result above 50 nmol/l is no reason to top up.
The three levels of vitamin D status
-
1
Deficient25(OH)D < 30 nmol/l (< 12 ng/ml)
Risk of osteomalacia and rickets. Muscle weakness, bone pain, and in children growth disturbances. This needs topping up, at a doctor-prescribed dose.
-
2
Suboptimal30–50 nmol/l (12–20 ng/ml)
Not everyone in this range is undersupplied, needs vary individually. Typical in winter. Sun in summer, 20 µg a day for risk groups.
-
3
Sufficient≥ 50 nmol/l (≥ 20 ng/ml)
Covers the needs for bone health even with high individual requirements. Studies show no added benefit from topping up beyond this.
Thresholds according to BfR, DGE and EFSA (guidance from the former Institute of Medicine). Values above 100 nmol/l bring no proven benefit; overdose is only possible through supplements (chapter 5).
Who should get tested? Not everyone. In 2024 the Endocrine Society explicitly advised against routine testing for healthy adults under 75, because screening without symptoms doesn't measurably improve health. Testing makes sense if you have symptoms from chapter 1, belong to a risk group from chapter 2, or before taking any higher-dose supplement. If there's a valid clinical reason, health insurance covers it; as an optional service, testing usually costs 20 to 30 euros.
Vitamin D deficiency test: self-test from the pharmacy
Dried-blood home tests measure the same thing as the lab, using a drop of blood from your fingertip. They're useful if you keep two things in mind. First, the time of year: the value is lowest at the end of March and highest in September. A test right after a beach holiday tells you nothing about your winter levels. Second, the method: automated immunoassays, used by many labs and home tests, detect vitamin D2 less accurately than D3. If you eat a plant-based diet and get most of your vitamin D2 from mushrooms or fortified products, your measured value could come out too low (BfR). A single result is a clue, not a verdict. If the result is low, confirmation and dosing belong in the hands of a doctor.
Blood value: ng/ml × 2.5 = nmol/l (20 ng/ml = 50 nmol/l). Dose: 1 µg = 40 IU, 20 µg = 800 IU, 100 µg = 4,000 IU. The IU figure appears on supplements, the µg figure in DGE values.
Fixing a vitamin D deficiency: what really helps
Treatment follows the cause, and that's almost always: too little sun. So it has two halves. From April to September, midday sun is the best source: expose your face, hands and arms two to three times a week for half the time it would take to burn, without sunscreen, but never until your skin reddens. From October to March, the sun delivers nothing, so a supplement takes over. According to the BfR, 20 µg (800 IU) a day achieves sufficient status without any sun at all, that's the dose for risk groups and winter. In the case of a confirmed deficiency below 30 nmol/l, that's not enough to top up your stores. Then your doctor will prescribe a higher dose for 8 to 12 weeks, depending on your starting value and body weight, followed by a check-up. Such loading doses are medicine, not self-care. Take vitamin D with a meal containing fat, since it's fat-soluble.
Vitamin D3 or D2, daily or weekly
D3 (cholecalciferol) is the form your skin produces itself, and it raises blood levels more reliably than D2 from mushrooms; vegan D3 is derived from lichen. The evidence on frequency is clear: daily, low-dose beats rare and high-dose. In 2024 the Endocrine Society favoured daily dosing. In the large meta-analysis on respiratory infections, vitamin D only protected when given daily or weekly without a bolus. Yearly or monthly high-dose bolus doses actually led to more falls and fractures in studies, which is why the BfR advises against them.
In summer, midday sun is the best source; in winter, 20 micrograms a day is enough. Anything beyond that without a measured value isn't prevention, it's a risk.
Joerg Hauke, Nutrition expert, technical review of this article
How long does it take to fix the deficiency
Nothing works in days. With a doctor-prescribed dose, the 25(OH)D value rises into the target range over about 8 to 12 weeks; a first check after 4 to 6 weeks makes sense. Muscle strength and cramps often improve within the first few weeks, but soft bone takes months to remineralise. Without a supplement, stores only refill with the spring sun from April, and a winter with empty reserves stays a winter with empty reserves.
-
Week 0
Test, don't guess
Get 25(OH)D tested if you have symptoms or risk factors. Don't take a high dose of any supplement on a hunch.
-
Weeks 1–8
Refill stores
Determine the dose with your doctor based on your level and body weight, daily with a fatty meal, no weekly or monthly bolus doses.
-
After 8–12 weeks
Check-up
Check your level, switch to a maintenance dose. Muscle strength is usually already better; bone pain takes longer.
-
After that
Maintain
April to September, midday sun on face, hands and arms. October to March, 20 µg a day if you belong to a risk group.
Vitamin D overdose: when it becomes too much
Overdosing from sun exposure is impossible, since the skin regulates production itself. With supplements, it's a different story. In 2023, the EFSA confirmed the tolerable upper limit for adults at 100 µg (4,000 IU) a day, and 50 µg for children aged 1 to 10. According to the BfR, staying above this long-term risks reduced bone density, more falls, and, in people with heart conditions, worse heart function. At even higher amounts, blood calcium rises: nausea, muscle weakness, heart rhythm disturbances, weight loss, and in the long run kidney stones and kidney damage. Products with 10,000 or 20,000 IU per dose aren't dietary supplements, they belong in medical hands with blood monitoring. For self-care, the BfR recommends supplements with a maximum of 20 µg (800 IU) a day.
Large studies with over 2,000 participants show: if you're already adequately supplied, extra vitamin D brings no benefit, not for bones, heart, cancer or falls. High doses without a measured blood level bring no health gain, only added risk.
Große Studien mit über 2.000 Teilnehmenden zeigen: Wer ausreichend versorgt ist, hat von zusätzlichem Vitamin D keinen Nutzen, weder für Knochen noch für Herz, Krebs oder Stürze. Hochdosis ohne Blutwert bringt kein Plus an Gesundheit, nur an Risiko.
Vitamin D foods: what belongs on your plate
Vitamin D is found in only a few foods, almost all of them animal-based: oily sea fish, egg yolk, and trace amounts in liver, butter and cheese. On the plant side, only mushrooms remain, and only if they've seen light. That's why the typical German diet provides just 2 to 4 µg a day, a tenth to a fifth of the amount needed without sun. The ranking below shows where you'll still find the most, per 100 g and as it lands on the plate.
Vitamin D per 100 g: top 10 plant-based and animal-based
Values per 100 g, USDA FoodData Central SR Legacy. Mushrooms provide vitamin D2, and only if they've seen light: regular cultivated button mushrooms reach 0.2 µg, UV-treated ones reach 26 µg. In portions: 100 g chanterelles 5.3 µg, 200 ml fortified soy drink 2.4 µg, 10 g fortified margarine 0.3 to 0.8 µg (2.5 to 7.5 µg per 100 g in Germany, DGE). Nuts, seeds, grains, vegetables and fruit contain virtually no vitamin D.
Sun beats plate
Even if you eat oily fish twice a week, as the BfR recommends for vitamin D, omega-3 and iodine, you still won't reach 20 µg a day on average. That's not a reason to skip it, just a bit of perspective: food is the supplement, skin is the main source, and in winter a supplement steps in.
Das ist keine Aufforderung, es zu lassen, sondern eine Einordnung: Essen ist die Ergänzung, die Haut ist die Hauptquelle, und im Winter springt ein Präparat ein.
pro Tag liefert die übliche Ernährung, ein Zehntel bis Fünftel des Bedarfs ohne Sonne
der Versorgung entstehen in der Haut, wenn du regelmäßig zur Mittagszeit rausgehst
Was die Bildung fördert und was sie bremst
Weil die Haut die Hauptquelle ist, geht es weniger um Kombinationen auf dem Teller als um das, was zwischen Sonne und Haut passiert. Glas, Kleidung und Schatten lassen kein UV-B durch. Ein hoher Lichtschutzfaktor schützt vor Sonnenbrand und senkt zugleich die Bildung, deshalb reicht für die kurze Mittagssonne die halbe Sonnenbrandzeit ohne Creme. Das Solarium liefert vor allem UV-A und erhöht das Hautkrebsrisiko; BfS und BfR raten davon ab. Auf dem Teller zählt nur eines: Vitamin D ist fettlöslich, Präparat und Pilze also mit etwas Fett essen.
Vitamin D in everyday life: fortified foods and drinks
Since hardly anyone eats fish daily, fortified foods are the norm in many countries. In Germany, fortifying everyday foods requires approval; mainly margarine and spreads (2.5 to 7.5 µg per 100 g), plant-based drinks, and, for a few years now, UV-treated mushrooms, yeast and milk are permitted. The BfR considers targeted fortification useful, but not blanket fortification. A second option is drinkable meals with defined nutrient amounts: one bottle of Saturo provides 1.5 µg of vitamin D, 30% of the reference intake, plus calcium, which vitamin D needs to reach the bones. Not a substitute for sun or for a supplement if you're deficient, but a reliable contribution on days when fish isn't on the menu.
Trinkmahlzeit: eine vollwertige Mahlzeit aus der Flasche
26 Vitamine und Mineralstoffe, darunter Vitamin D und Calcium. Vitamin D trägt zur Erhaltung normaler Knochen und einer normalen Muskelfunktion bei. Referenzwert für Vitamin D: 5 µg pro Tag (NRV). Für Tage, an denen Fisch nicht auf dem Plan steht.
Winter, pregnancy, older age, vegan: who needs to pay extra attention
Vitamin D deficiency in winter
Winter is the normal case for deficiency, not the exception. In the national health survey, one in four adults was below 30 nmol/l from October to March, while in summer only half reached a sufficient level. What helps: build up your summer reserves by really getting outside from April to September, stay active outdoors daily even in winter, since this releases stored vitamin D, and for risk groups, 20 µg a day from October to March. If you're regularly ill, tired and tense in February, get tested once and you'll know for sure.
Pregnancy and infants
The same 20 µg applies during pregnancy as usual, but with one difference: since 2024 the Endocrine Society has recommended supplementation for pregnant women, because studies found lower rates of pre-eclampsia, preterm birth and low birth weight, although the evidence is of low certainty. No routine testing is needed for this. After birth, prevention takes over: infants shouldn't be in the sun, and breast milk contains hardly any vitamin D. That's why in Germany they're given 10 to 12.5 µg (400 to 500 IU) daily until their second early summer, as a tablet or drops.
From 65: bones, falls, care
In older age, three things come together: the skin produces less than half as much, many people go outside less often, and bone density naturally declines anyway. Deficiency is therefore widespread among people needing care; the BfR recommends considering a general dose of 20 µg a day for residents of care facilities. The Endocrine Society recommends supplementation for everyone from age 75, since it may reduce mortality. What vitamin D doesn't do for healthy older adults was shown by the VITAL study.
Vegan and vegetarian
If you don't eat fish or eggs, you get almost nothing from food anyway, which makes little difference given the average of 2 to 4 µg. The sun is just as effective for vegans as for everyone else, and it's just as absent in winter. Plant-based sources are UV-treated mushrooms, fortified plant-based drinks and margarine, plus supplements with D2 from mushrooms or vegan D3 from lichen. Two notes: D3 raises blood levels more reliably than D2, and standard immunoassays detect D2 less accurately, so lab values can come out too low with pure D2 intake (BfR).
Consequences of vitamin D deficiency: bones, muscles, immune system
Left untreated, a severe deficiency leads to osteomalacia in adults, rickets in children, and contributes to osteoporosis in old age. Muscle weakness increases the risk of falls. The picture for the immune system is more nuanced: an analysis of 25 studies with over 11,000 people found that daily or weekly vitamin D reduced respiratory infections by about 12%, and by as much as 70% in people with very low starting levels below 25 nmol/l. An updated 2021 analysis of 46 studies confirmed a small protective effect, most notable at daily doses of 400 to 1,000 IU. For cancer, cardiovascular disease and diabetes, however, the large studies found no benefit in people who were already well supplied. In short: fixing a deficiency is worth it, topping up beyond that isn't.
Frequently asked questions about vitamin D deficiency
What are vitamin D robbers?
There are no foods that rob you of vitamin D. What lowers your level is a lack of UV-B radiation: the months from October to March, glass, clothing, and high sun protection during short sun exposure. On top of that come age, dark skin, a high body fat percentage (vitamin D spreads through more tissue), chronic bowel, liver and kidney disease, and medications like anti-epileptics, which speed up its breakdown.
How long does it take to replenish vitamin D?
With a doctor-prescribed dose, the 25(OH)D value rises into the target range within about 8 to 12 weeks; a first check after 4 to 6 weeks makes sense. Muscle weakness and cramps often improve within the first few weeks, but bones take months. Without a supplement, stores only refill with the spring sun from April.
What does cholesterol have to do with vitamin D?
Vitamin D3 forms in the skin from a cholesterol precursor, 7-dehydrocholesterol, as soon as UV-B hits it. But a high cholesterol level in the blood doesn't mean more vitamin D, and vitamin D supplements don't demonstrably lower cholesterol. The two values are chemically linked, but not in everyday practice.
Is 10,000 IU of vitamin D a day too much?
Yes, if taken long-term. 10,000 IU is 250 µg, two and a half times the EFSA upper limit of 100 µg (4,000 IU) for adults. Over the long run, this risks raised calcium levels, kidney stones and a decrease in bone density. Doses like this belong under medical supervision, only for correcting a proven deficiency. 3,000 IU (75 µg) is below the upper limit, but unnecessary without a measured deficiency; the BfR recommends no more than 20 µg (800 IU) a day for self-supplementation.
Should you take vitamin D daily or weekly?
Both raise your blood level, but the evidence favours a low daily dose. In 2024, the Endocrine Society preferred daily dosing, and in meta-analyses on respiratory infections, vitamin D only had a protective effect without bolus doses. Monthly or yearly high doses led to more falls and fractures in studies, so the BfR advises against them.
Does vitamin D3 always need vitamin K2 alongside it?
There's no official recommendation for combining the two – the BfR doesn't mention K2 at all in its vitamin D FAQ. The idea behind it, that K2 directs calcium absorbed via vitamin D into the bones instead of the blood vessels, has no proven benefit at typical doses of up to 20 µg, since these don't raise calcium levels. If you take a vitamin K antagonist blood thinner, don't take K2 without talking to your doctor first.
What hurts with a vitamin D deficiency? Can it cause leg pain?
Yes. Typical signs are dull, deep bone pain in the pelvis, hips, thighs, shins and lower back, because bone doesn't mineralise properly when you're deficient. On top of that come muscle weakness in the thighs, calf cramps and tenderness when pressing on the shin or breastbone. Tension and joint pain are also reported, but these are non-specific.
Which blood values point to a vitamin D deficiency?
The key marker is 25-hydroxyvitamin D: below 30 nmol/l (12 ng/ml) counts as deficient, 30 to 50 as suboptimal, and 50 nmol/l (20 ng/ml) or above as sufficient. With severe deficiency, calcium and phosphate in the blood can also be low, while alkaline phosphatase and parathyroid hormone can be raised. Active calcitriol is only measured for specific questions.
Sources · 18 sources anzeigen
- German Nutrition Society (DGE): Reference values for nutrient intake, vitamin D (calciferols). Estimated values in the absence of endogenous synthesis, derived 2012.
- German Nutrition Society (DGE): Selected questions and answers on vitamin D. As of 30.09.2025.
- German Federal Institute for Risk Assessment (BfR): Vitamin D – sun and exercise support good supply. FAQ dated 30 December 2025.
- Federal Office for Radiation Protection (BfS) and 19 professional societies: Consensus recommendation on UV radiation and vitamin D. 2012.
- Institute for Quality and Efficiency in Health Care (IQWiG): Vitamin D deficiency. gesundheitsinformation.de, as of 15.11.2023.
- Rabenberg M., Scheidt-Nave C., Busch M. A., Rieckmann N., Hintzpeter B., Mensink G. B. M.: Vitamin D status among adults in Germany – results from the German Health Interview and Examination Survey for Adults (DEGS1). BMC Public Health 2015; 15: 641.
- Rabenberg M. et al.: Implications of standardization of serum 25-hydroxyvitamin D data for the evaluation of vitamin D status in Germany, including a temporal analysis. BMC Public Health 2018; 18: 845.
- Demay M. B. et al.: Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology & Metabolism 2024; 109(8): 1907–1947.
- Holick M. F. et al.: Evaluation, Treatment, and Prevention of Vitamin D Deficiency: an Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology & Metabolism 2011; 96(7): 1911–1930.
- EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA): Scientific opinion on the tolerable upper intake level for vitamin D, including the derivation of a conversion factor for calcidiol monohydrate. EFSA Journal 2023; 21(8): e08145.
- LeBoff M. S. et al.: Supplemental Vitamin D and Incident Fractures in Midlife and Older Adults (VITAL). New England Journal of Medicine 2022; 387(4): 299–309.
- Martineau A. R. et al.: Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ 2017; 356: i6583.
- Jolliffe D. A. et al.: Vitamin D supplementation to prevent acute respiratory infections: a systematic review and meta-analysis of aggregate data from randomised controlled trials. Lancet Diabetes & Endocrinology 2021; 9(5): 276–292.
- Mikola T. et al.: The effect of vitamin D supplementation on depressive symptoms in adults: A systematic review and meta-analysis of randomized controlled trials. Critical Reviews in Food Science and Nutrition 2023; 63(33): 11784–11801.
- Liu J., Dong Y., Wang Y.: Vitamin D deficiency is associated with dry eye syndrome: a systematic review and meta-analysis. Acta Ophthalmologica 2020; 98(8): 749–754.
- Drincic A. T., Armas L. A. G., Van Diest E. E., Heaney R. P.: Volumetric dilution, rather than sequestration best explains the low vitamin D status of obesity. Obesity 2012; 20(7): 1444–1448.
- Cardwell G., Bornman J. F., James A. P., Black L. J.: A Review of Mushrooms as a Potential Source of Dietary Vitamin D. Nutrients 2018; 10(10): 1498.
- U.S. Department of Agriculture, Agricultural Research Service: FoodData Central, SR Legacy Release (2018). Vitamin D content (D2 + D3) per 100 g.
Writing for Saturo since 2019 about nutrition, nutrients and how good nutritional supply actually works in everyday life.
Hat diesen Artikel am 10. September 2026 auf fachliche Richtigkeit geprüft. This content doesn't replace medical advice.
Iron deficiency: symptoms, causes and treatment
Tired, pale, hair loss: why iron deficiency is the most common nutrient deficiency in the world, which blood value matters and what helps fast.
Weiterlesen · 13 Min
New from the guide
New articles, updates and tips straight to your inbox. Easy to understand, expert-checked, no spam.
Danke! Bitte bestätige die Anmeldung in deinem Postfach.