Everything you need to know about Vitamin D

Vitamin D

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What you can achieve by taking it
Healthy bones
Vitamin D is essential to increase and maintain the mineral content of the bones.
Maintains muscle strength
It supports the intake of minerals in the muscle and therefore it prevents muscle weakness.
Supports joint health
It allows the proper function of the joints and prevents the progress of degradation processes by enhancing mineral intake.
Boosts the immune system
Proper absorption and supply of nutrients are essential for the functioning of the immune system; they are facilitated by vitamin D.

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Vitamin D is a fat-soluble vitamin. The name of vitamin D, like many other vitamins, doesn’t refer to one compound; it refers to several steroid derivative compounds (the vitamin itself is not a sterane structure). Vitamin D is considered to be a hormone and a vitamin as well, since the body is able to synthetize it and it plays a major role in several life functions. The body is able to synthetize it from the sunlight, but it’s deficiency can be supplemented with the diet as well. It has two main forms: D3-cholecalciferol and D2-ergocalciferol. D3 can be synthesized in the skin from 7-dehydrocholesterol, as a result of exposure to UV-B radiation. D3 and D2 may be ingested from foodstuffs of animal origin, while ergocalciferol is produced from plant ergosterol and therefore D2 may be ingested from foodstuffs of plant and fungus origin; these are used for the industrial production as well. The bioactivity of the two forms is similar. Vitamin from the diet or dermal synthesis is inactive; it is transported to the liver by the blood, where calcidiol (25-hydroxycholecalciferol) is produced. The most active form, calcitriol (1.25-dihydroxycholecalciferol) is produced in the kidneys by further enzymatic process. The synthesis is twice as intense in young people than in older people; therefore the risk of deficiency is increased in them. The vitamin acts by binding to the intracellular vitamin D receptor (VDR).

Approximately 50-80% of the ingested vitamin is absorbed. A few minutes of sunbathing a day covers the needs; it can even cover the vitamin needs during the winter.

It regulates growth, development and bone regeneration by controlling calcium and phosphor absorption from the intestines.

It promotes calcium absorption; when required it releases calcium from the bones to increase the blood level; it is also responsible for the increased resorption in the kidneys.

The proper vitamin D intake is essential for the optimal function of the bones, joints and teeth. Vitamin D deficiency in childhood causes rickets which is characterized by inappropriate bone and joint development and muscle weakness; in adults it is characterized by osteomalacia (softening of the bones) which is accompanied by easy fracturing of the bones, muscle weakness and muscle cramps.

Supplementation is required in case of inappropriate nutrition or special diet. It applies in particular to post menopausal women, who are much more likely to develop osteoporosis. The prevention and treatment of osteoporosis requires combined vitamin D and calcium supplementation, since this combination may inhibit or decrease the loss of bone mass, the development of low bone density and the worsening of the present condition. Approximately 1000-1500 mg calcium and 400 IU (International Unit) of vitamin D is used for this purpose, but you have to consult with your physician (since the required dose is influenced by the health condition, medication and illnesses, and drug interaction may develop). This combination is efficient even in case of corticosteroid induced bone loss. Dairy products contain calcium and vitamin D as well; they have a beneficial effect on bone metabolism. Strict vegetarian diet and dark skin color may increase the risk of deficiency, as well as liver and kidney diseases (lack of activation). Inflammatory bowel diseases increase the risk of insufficient intake. Its presence is beneficial for sperm production and insulin synthesis. Vitamin D supports the function of the immune system and inhibits the autoimmune processes (smaller risk of type 1 diabetes, multiple sclerosis, etc.). It may be important in the prevention of cancer (colorectal carcinoma, breast cancer), although extreme doses are not beneficial. Derivatives of vitamin D are used in the treatment of psoriasis. The risk of hypertension may be decreased by proper intake.

Why it is worth using

  • Athletes often use vitamin D supplements to prevent injury induced arthritis.
  • Athletes and non-athletes prefer to use multivitamin products containing vitamin D during low fat diet to prevent vitamin deficiency.

Further benefits

Healthy bones
It prevents the development and worsening of osteoarthritis (bone disease with the signs of chronic arthritis and pain) and osteoporosis (reduction of bone density), since it inhibits bone and joint degeneration.

How to use it

A few minutes of sunbathing a day covers the needs ; it can even cover the vitamin needs during the winter. The recommended daily intake is 200-400 IU (5-10 mcg). The required dose may increase when you are not exposed to sunlight often or at all. Let us not forget that excessive sun exposure may increase the risk of skin cancer. The prevention and treatment of osteoporosis requires combined vitamin D and calcium supplementation, since it can inhibit or decrease the loss of bone mass, the development of low bone density and the worsening of the present condition. Approximately 1000-1500 mg calcium and 400 IU of vitamin D is used for this purpose, but you have to consult with your physician (since the required dose is influenced by the health condition, medication and illnesses, and drug interaction may develop). It can be used locally in the treatment of psoriasis. Compounds and medications influencing fat absorption may block its absorption, therefore the needs may increase.

Timing: It should be taken with meals.

Synergy occurs in its effect: when combined, vitamin D increases calcium absorption significantly.

Natural sources

The human body is able to produce vitamin D from the sunlight; liver, cod liver oil, butter and yolk are good dietary sources of it, therefore the deficiency can be supplemented by consuming these food. Margarine is artificially fortified with vitamin D. Let us not forget that the food rich in vitamin D is also rich in fat. Approximately 50-80% of the ingested vitamin is absorbed.

The vitamin D content of certain food (per 100 g):

Cow's milk: 0.40 mcg
Butter: 15 mcg
Egg yolk: 10 mcg
Liver: 3-4 mcg
Cod liver oil: 250 mcg

Possible side effects

Constipation, vomiting, headache, loss of appetite, diarrhea, arrhythmia and bone weakness may develop when excess amounts of vitamin D are used. Calcification of soft tissues (e.g. muscles) and kidney stone may also develop. Care must be taken not to exceed the recommended daily dose with the different multivitamin products and diet.

Safety: Its use in the recommended dose is safe. Prolonged intake of vitamin D in doses higher than 1800 IU may increase the calcium level in the blood, therefore kidney stone may occur and excess deposits of calcium may develop in soft tissues.

Update:The recent recommendation of professional associations is 1500-2000 IU daily for adults during the winter months as nutritional supplement. The dose is higher in overweight people, even 3-4000 IU may be recommended.

Close medical supervision is required for the supplementation in sarcoidosis and hyperthyroidism. Supplements should be used under medical supervision during the pregnancy and nursing. Combination with thiazide diuretics may lead to excessive calcium levels in the blood. It should not be used in hypercalcemia (high calcium level) either. Consult your physician if you use heart medicines (digoxin, glycosides).

Contraindication: It is not on any lists.

The history of vitamin D

Signs of vitamin D deficiency have long been known. Rickets, the well-known name of the deficiency was common during the Industrial Revolution when the disease affected a significant proportion of children. Trousseau discovered the beneficial effect of cod liver oil in the treatment of rickets in 1860, but this effect was considered to vitamin A for a long time. In 1925 Hess and Weinstock have demonstrated that UV radiation stimulates the production of an antirachitic material in the skin. The structure of the vitamin was established 10 years later.

Q & A on vitamin D

May vitamin D deficiency develop in case of a strict vegetarian diet?

Yes, there is a real risk. It may be prevented with appropriate exposure to sunlight (excessive exposure should be avoided!) or vitamin supplementation.

Can I take multivitamin products with vitamin D content during pregnancy?

Vitamin and mineral supplements should be used under medical supervision and after consulting with a dietitian during the pregnancy, taking into account the individual dietary characteristics. Otherwise, there is no significant risk if you don’t take more than the recommended daily dose.

Can the combination of vitamin D and calcium prevent osteoporosis?

The combination is not able to prevent it, but it can support the prevention and the treatment. The osteoporosis is a multifactorial disease. The use of mineral and vitamin supplements together with proper physical activity and protein intake contributes to slow the progress of bone loss, therefore it may be beneficial. You should follow your physician’s instructions in case of a progressed disease or increased risk.


Bíró-Lindner: Tápanyagtáblázat, Medicina (Table of Nutrients), Budapest, 1999

Michael T. Murray: Encyclopedia of Nutritional Supplements, Prima Health, USA, 1996

Bolla Erika: A D- és K-vitamin, a csontépítés kulcsai (Vitamin D and Vitamin K, the key elements of bone formation), Élelmezésvezetők lapja August-September, 2001.

Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety. Am J Clin Nutr 69: 842–856, 1999.

Moon JC. A brief history of vitamin D toxicity. J Appl Nutr 49: 18–31, 1997.

Dawson-Hughes B, Harris S, Krall E, et al. Effect of calcium and vitamin D supplementation on bone density in men and women 65 years of age or older. N Engl J Med 337(10): 670–673, 1997

Buckley LM, Leib ES, Cartularo KS, et al. Calcium and vitamin D3 supplementation prevents bone loss in the spine secondary to low-dose corticosteroids in patients with rheumatoid arthritis. A randomized, double-blind, placebo-controlled trial. Ann Intern Med 125: 961–968, 1996.

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