Vitamin D deficiency

Who I am
Louise Hay

Author and references


La vitamin D deficiencythe hypovitaminosis D, is the medical condition resulting from the absence of appropriate levels of vitamin D in the body; Appropriate levels of vitamin D are essential for good bone health and, according to recent studies, for good cardiovascular health.

Vitamin D deficiency can depend on various factors, including: an inadequate sun exposure, an insufficient dietary intake of the vitamin in question, the presence of kidney or liver disease, an increased requirement and the intake of some specific drugs.

The main consequences of vitamin D deficiency in humans are rickets, in young and very young subjects, and osteomalacia and osteoporosis, in adults.

To diagnose vitamin D deficiency, doctors resort to measuring blood levels of calcidiol, also known as 25-hydroxycalciferol.

The typical treatment of vitamin D deficiency consists of causal therapy and therapy aimed at immediately raising the vitamin deficiency levels.

Brief review of vitamin D

Also known as "sun vitamin", the vitamin D is a fat-soluble organic compound, similar in chemical structure to steroid hormones, appointed to perform important functions in the human body, including:

  • Promote the absorption of calcium in the intestine;
  • Maintain normal blood levels of calcium and phosphorus;
  • Promote the reabsorption of calcium and phosphorus in the kidney;
  • Strengthen the bones, through the deposition of calcium in the bone tissue;
  • Promote bone growth in children.

For humans, the natural supply of vitamin D depends on theexposure to sunlight - which allows the conversion in the skin of a specific precursor - and from the intake of some specific foods (ex: cod liver oil).
It should be noted that, in order to have the above effects, the vitamin D generated through exposure to sunlight and taken through the diet must undergo two hydroxylation reactions, which make it biologically active; such reactions take place in liver And in the Reindeer.


Under normal conditions, adequate exposure to sunlight is sufficient to meet the human body's need for vitamin D.

However, the application of sunscreen, fundamental especially at an early age to prevent skin cancer, it can almost completely limit skin synthesis of vitamin D

It is therefore for safety reasons that a certain intake of vitamin D is also recommended through the diet.

What is Vitamin D Deficiency?

La vitamin D deficiency it is the condition resulting from the absence of adequate amounts of vitamin D in the body.
In other words, it is the situation that reflects an insufficient level of vitamin D to keep the human body healthy.
In medicine, vitamin D deficiency is also known as hypovitaminosis D.


According to Harvard University, worldwide, vitamin D deficiency would affect about one billion people.


Vitamin D deficiency can have various causes; in fact, it can depend on:

  • Un insufficient food intake of the vitamin in question;
  • An in-depth inadequate sun exposure (in particular to UVB rays). This can be due to:
    • Reduced physical activity in the open air;
    • Dark skin;
    • Live in areas very distant from the equator;
    • Excessive use of sunscreen (a sunscreen with 15 protection blocks about 99% of the skin's production of vitamin D).
  • Un increased need for vitamin D;
  • Un impaired intestinal absorption;
  • The presence of medical conditions, such as liver disease or kidney disease, which compromise the conversion of biologically inactive vitamin D into its biologically active form (NB: remember that the liver and kidneys are the site where the aforementioned conversion takes place);
  • A therapy based on drugs which interfere with the normal metabolism of vitamin D (e.g. anticonvulsants, cholestyramine, glucocorticoids, antifungals, antivirals, anti-rejection drugs, etc.).

Risk factors

Several factors contribute to increasing the risk of vitamin D deficiency, including:

  • Cigarette smoking (because it alters the metabolism of vitamin D);
  • Advanced age (because, due to aging, the skin loses part of its productive efficiency);
  • Obesity (because adipose tissue sequesteres vitamin D and in this way reduces its bioavailability);
  • Taking drugs that interfere with the metabolism of vitamin D (eg anticonvulsants, glucocorticoids, etc.);
  • Dark skin (because it is accompanied by a lower cutaneous production efficiency);
  • Alcoholism (because it impairs the intestinal absorption of vitamin D);
  • Presence of osteoporosis;
  • Breastfeeding for long periods of time (because breast milk is a poor source of vitamin D)
  • Presence of Crohn's disease or celiac disease (because they compromise the absorption of vitamin D in the intestine);
  • Presence of gastric bypass (because it reduces the absorption efficiency of vitamin D along the digestive tract).

In addition to this, then, it is necessary to add (in some situations it is a repetition) that the lack of vitamin D is more frequent among:

  • Those who shy away from exposure to sunlight;
  • Anyone suffering from kidney failure or liver failure;
  • Anyone suffering from sarcoidosis, tuberculosis, histoplasmosis or some other granulomatous disease;
  • People with lymphoma, a type of blood cancer.
  • Patients with cystic fibrosis, chronic pancreatitis or primary biliary cirrhosis.

Symptoms and consequences

Vitamin D deficiency impairs it in different ways bone mineralization, which contributes to the development of diseases such as rickets, in children, andosteomalacia el 'Osteoporosis, in adults.
However, hypovitaminosis D is not limited to this: recently, in fact, experts have shown that its presence is associated with a non-negligible increase in cardiovascular risk and the predisposition to diseases, such as diabetes, hypertension, dyslipidemia e metabolic syndrome.
In light of this, therefore, it is possible to state that, if once vitamin D was associated exclusively with bone health, today - thanks to new knowledge in the scientific field - it is also important for many organs and body tissues other than bone tissue, in particular at the cardiovascular level.

What symptoms characterize vitamin D deficiency?

Vitamin D deficiency is a somewhat subtle condition, as it tends to reveal itself (with some symptoms) only when vitamin D levels are really very low.
That said, in an individual, symptomatic vitamin D deficiency can cause:

  • Bone pain
  • Joint pain
  • Muscle weakness
  • Muscle fasciculation disorders;
  • Brittle bones, which tend to deform in young people, or to break easily in adults;
  • Difficulty thinking clearly
  • Recurring fatigue.


In rickets there is a defect in bone mineralization, which over time leads to the collapse and deformation of the bones under the load of body weight and muscle tension. This explains why, in the stunted subject, the legs appear crooked, the jaw deformed, the rib cage sunken at the level of the sternum (pectus excavatum), the face particularly narrow and deformed.
Fortunately, the progressive improvement of sanitation conditions and the increasing spread of vitamin prophylaxis, since the neonatal period, have greatly reduced, compared to several decades ago, the spread of this vitamin D deficiency disease.
In any case, it is good practice to start the baby, already shortly after birth, to a healthy life in the open air, exposing him frequently and regularly to sunlight, without swaddling him excessively in the winter months and protecting him with special creams in case of prolonged sun exposure.


Rickets is more frequent in infants and children who belong to dark-skinned populations, as mentioned in other circumstances, it represents a factor favoring vitamin D deficiency.


Osteomalacia is a metabolic disease characterized by the macroscopic rarefaction of the bones, which, consequently, are painful and more prone to fractures.
Equivalent to rickets in young humans, osteomalacia reflects a defect in bone mineralization, a defect that may be due not only to an insufficient intake of vitamin D, but also of calcium and / or phosphorus.


Osteoporosis is a systemic skeletal disease that causes severe weakening of the bones. Responsible for a greater tendency to fractures, this weakening originates in the deterioration of the microarchitecture of the bone tissue and in the consequent reduction of bone mineral mass.
Although it also involves greater bone fragility and a prone to fractures, osteoporosis is notably different from osteomalacia. In fact, if in osteoporosis the mineralization process occurs correctly, in osteomalacia - as stated in the dedicated sub-chapter - the same process is defective.

Vitamin D deficiency, cardiovascular risk and more

At present, the role of vitamin D deficiency in the onset of cardiovascular diseases, hypertension, diabetes, dyslipidemia and metabolic syndrome. In fact, experts have yet to establish whether the vitamin deficiency in question acts directly, in determining the aforementioned pathological conditions, or should instead be associated with obesity (a proven risk factor for cardiovascular disease, hypertension, etc.) .
The doubts about this (direct involvement of vitamin D deficiency or mediated by obesity?) Derive from the demonstration that the obese have a greater tendency to have low circulating levels of vitamin D, compared to normal weight subjects, essentially for two reasons: sedentary life (which involves poor sun exposure) and vitamin sequestration in the adipose tissue.

Other consequences

In addition to compromising bone health and being a cardiovascular risk factor, vitamin D deficiency can have other consequences:

  • It is a potential cause of periodontitis, which is the inflammation of the bones that support the teeth. If it degenerates, periodontitis can cause tooth loss;
  • Ha immunosuppressive effects, that is, it is able to reduce the efficiency of the immune system. Therefore, the individual with a vitamin D deficiency is more prone to infections;
  • It can determine a state of insulin resistance, that is the condition for which the cells of the body have a low sensitivity to insulin;
  • Feelings of trough. At present, studies are underway to investigate the relationship between vitamin D deficiency and mood decay.


To know the levels of vitamin D present in a human, doctors measure the serum concentration of the 25-hydroxycalciferol, Also known as calcidiol o 25-OH-D.

25-hydroxycalciferol is the form in which vitamin D of solar and food origin circulates in the blood of the human being; in other words, vitamin D in the blood takes the form of 25-OH-D.
To express the concentration of 25-hydroxycalciferol, there are two units of measurement: the nanomole per liter, most commonly written as nmol/l, and the nanogrammo per millilitro, usually identified with ng / ml.

An individual has an adequate amount of vitamin D when the concentration of 25-OH-D is between 75 nmol / L (30ng / ml) and 200 nmol / L (80ng / ml). Doctors therefore begin to talk about vitamin D deficiency when the 25-OH-D concentration is less than 30 nmol / l (12 ng/ml).
The table below shows the ranges of 25-OH-D concentrations that are used to establish the level of vitamin D present in the human body:

Condition Concentration in nmol / l Concentration in ng / ml
insufficiency Tra 30 nmol / le 75 nmol / l Between 12 ng/ml and 30 ng/ml
Normality Tra 75 nmol / le 200 nmol / L Between 30 ng/ml and 80 ng/ml
Excess > 200 nmol / l > 80 ng/ml
Toxicity > 375 nmol / l > 150 ng/ml

What is the Vitamin D blood test called?

The test for measuring blood levels of vitamin D is called dosage of 25-OH-D.
To collect a blood sample to be subjected to the 25-OH-D dosage, a simple blood sample is sufficient.

Search for causes: why is it important?

Once the presence of a vitamin D deficiency has been ascertained, the affected individual will have to undergo aanamnesi accurate and other diagnostic tests, which are used by the attending physician to trace the triggering causes of the vitamin deficiency in question.
Only thanks to the knowledge of the causal factors it is possible to plan the most adequate therapy.


Vitamin D deficiency requires a causal therapy, ie aimed at counteracting the causes of the low levels of the vitamin in question, and a therapy aimed at restoring a normal level of the so-called "sunshine vitamin".
The causal therapy varies from patient to patient, depending on the triggering factor (here is the importance of knowing the precise causes of the deficiency); the therapy aimed at eliminating the deficiency, on the other hand, generally consists in a diet rich in foods naturally high in vitamin D or in foods fortified with the latter, and in the intake of specific supplements.
While causal therapy has long-term effects (therefore not immediate), therapy aimed at remedying the deficiency is designed specifically to act in the short term, as the persistence of low levels of vitamin D is, as we have seen, dangerous for Health.

Curiosity: who can use vitamin D supplementation?

Doctors may recommend a specific vitamin D supplement to pregnant and breastfeeding women, to infants fed breast milk (because, as already mentioned, poor in the vitamin in question) and, sometimes, to children and young people.
Regarding the dosages of the supplements, these depend on various factors, including the latitude of residence.

Causal Therapy Example

If the vitamin D deficiency is due to inadequate sun exposure, the causal therapy consists, quite simply, in changing your lifestyle and exposing yourself to the sun for at least 15-20 minutes a day, without protective sunscreen.

What and what are foods fortified in vitamin D?

Briefly, a food fortified in vitamin D is a food to which vitamin D has been added, to increase the intake of this nutrient by those who use it.
On the market, foods fortified in vitamin D include:

  • Milk;
  • Orange juice;
  • Soya milk;
  • Yogurt;
  • Breakfast cereals;
  • Margarine.

Which foods contain the most vitamin D?

Good dietary sources of vitamin D, highly recommended to remedy a deficiency of the aforementioned vitamin, are:

  • Cod liver oil;
  • Fish oils;
  • Fish such as salmon, trout, herring, swordfish, eel, mackerel, tuna, carp etc;
  • The egg yolk;
  • The milk;
  • Butter;
  • Mushrooms such as porcini and morel.

 Beware of high vitamin D intakes

It is necessary to remind readers that a high intake of vitamin D can give rise to phenomena of toxicity; therefore, before taking specific vitamin D supplements it is important to consult your doctor and rely on his advice.
The consequences (i.e. symptoms and signs) of a vitamin D overdose include:

  • Mineralization of non-bone tissues with diffuse calcifications in the affected organs;
  • Muscle twitching and spasms;
  • Muscle weakness
  • Vomiting, diarrhea or constipation, and headache
  • Loss of appetite and weight loss
  • Formation of kidney stones;
  • Confusion and disorientation;
  • Heart problems.


Correct prevention of vitamin D deficiency can be summarized in 4 points:

  • Sun exposure, without sunscreen, at least 15 minutes every day;
  • Include in the diet an adequate amount of foods high in vitamin D;
  • Resort to vitamin D supplements, if one of the two previous points is difficult to do;
  • Resort to foods fortified in vitamin D, if one of the first two points is difficult to do.

What strategies can older people adopt to prevent vitamin D deficiency and resulting bone disease?

The dietary requirement of vitamin D increases over the years, as the ability of the skin to synthesize the aforementioned vitamin and the ability of the kidneys to operate the last activation reaction decreases at the same time.
All this explains why doctors very often recommend one to the elderly vitamin D supplementation, through specific supplements or fish oils, to be combined perhaps with a calcium supplementation.
The purpose of these supplements is to maintain bone strength, decrease susceptibility to fractures and, ultimately, prevent vitamin D deficiency with all its consequences (osteomalacia and osteoporosis).

For further information: Osteoporosis Prevention
Audio Video Vitamin D deficiency
add a comment of Vitamin D deficiency
Comment sent successfully! We will review it in the next few hours.