Vitamin D deficiency

Generality

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

The application of sunscreens, essential especially at an early age to prevent skin cancer, can almost completely limit the skin synthesis of vitamin D.

The main consequences of vitamin D deficiency in human beings are rickets in young and very young people, and osteomalacia and osteoporosis in adults.

To diagnose vitamin D deficiency, doctors use calcidiol, also known as 25-hydroxicalciferol, to measure blood levels.

The typical treatment of vitamin D deficiency consists in a causal therapy and in a therapy aimed at reviving deficient vitamin levels immediately.

Brief review of vitamin D

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

• Promote the absorption of calcium in the intestine;
• Maintain blood calcium and phosphorus levels normally;
• Promote the reabsorption of calcium and phosphorus in the kidneys;
• 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 exposure to sunlight - which allows the conversion of a specific precursor to the skin - and from the intake of some specific foods (eg, the oil of cod liver).

It is important to point out that, in order to have the above effects, vitamin D generated by exposure to sunlight and taken through the diet must undergo two hydroxylation reactions, which make it biologically active ; such reactions take place in the liver and kidneys .

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

However, for safety reasons, doctors still recommend a certain intake of vitamin D also through diet.

What is vitamin D deficiency?

Vitamin D deficiency 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 a level of vitamin D that is insufficient to keep the human body healthy.

In medicine, vitamin D deficiency is also known as hypovitaminosis D.

Epidemiology

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

Causes

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

• An insufficient dietary intake of the vitamin in question;
• Inadequate exposure to the sun (in particular to UVB rays). This may be due to:
• Reduced physical activity in the open air;
• Dark skin;
• Living in areas far away from the equator;
• Excessive use of sunscreen (a sunscreen with protection 15 blocks about 99% of the vitamin D skin production).
• An increase in vitamin D requirements ;
• An altered intestinal absorption ;
• The presence of medical conditions, such as liver diseases or kidney diseases, which compromise the conversion of biologically inactive vitamin D into its biologically active form (NB: remember that the liver and kidneys are the place where the aforementioned conversion takes place) ;
• A therapy based on drugs that interfere with the normal metabolism of vitamin D (eg: anticonvulsants, cholestyramine, glucocorticoids, antifungals, antivirals, anti-rejection drugs, etc.).

Risk factors

Several factors increase 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 sequesters 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 lower skin production efficiency);
• Alcoholism (because it compromises 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 impair the absorption of vitamin D in the intestine);
• Presence of gastric bypass (because it reduces the absorption efficiency of vitamin D along the pathways of the digestive system).

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:

• Who shuns exposure to sunlight;
• Those suffering from kidney failure or liver failure;
• Those who suffer from sarcoidosis, tuberculosis, histoplasmosis or some other granulomatous disease;
• Lymphoma patients, a type of blood cancer.
• Patients with cystic fibrosis, chronic pancreatitis or primary biliary cirrhosis.

Symptoms and consequences

Vitamin D deficiency compromises bone mineralization in different ways, which contributes to the development of diseases such as rickets, in children, and osteomalacia and osteoporosis, in adults.

However, hypovitaminosis D is not limited to this: recently, in fact, experts have shown that its presence is associated with a not inconsiderable increase in cardiovascular risk and predisposition to diseases, such as diabetes, hypertension, dyslipidemia and metabolic syndrome .

In light of this, therefore, it is possible to state that, if once the vitamin D was associated exclusively to bone health, today - thanks to new knowledge in the scientific field - it is also important for many organs and body tissues other than bone, in particular at the cardiovascular level.

What symptoms characterize vitamin D deficiency?

Vitamin D deficiency is a somewhat insidious condition, as it tends to reveal itself (with some symptoms) only when the levels of vitamin D are very low.

Having said that, in an individual, the lack of symptomatic vitamin D can cause:

• Bone pain;
• Joint pain;
• Muscle weakness;
• Muscle fasciculation disorders;
• Bones fragile, which tend to deform, in subjects of young age, or to break easily, in adult subjects;
• Difficulty thinking clearly;
• Recurrent fatigue.

Rickets

In rickets there is a defect in bone mineralization, which over time results in the failure and deformation of the bones under the load of body weight and muscle tension. This explains why, in the rachitic subject, the legs appear distorted, the jaw is deformed, the thoracic chest is hollow at the level of the sternum ( pectus excavatum ), the face is particularly narrow and deformed.

Fortunately, the progressive improvement of hygienic-sanitary conditions and the ever increasing diffusion of vitamin prophylaxis, since the neonatal period, have greatly reduced, compared to several decades ago, the spread of this vitamin D deficiency disease.

However, it is good practice to start the child, shortly after birth, to a healthy life in the open air, exposing it frequently and regularly to sunlight, without excessively bandaging it in the winter months and protecting it with special creams in case of prolonged sun exposure.

Curiosity

Rickets are more common in newborns and black children, due to dark skin which, as mentioned in other circumstances, is a factor favoring vitamin D deficiency.

Osteomalacia

Osteomalacia is a metabolic disease characterized by macroscopic rarefaction of the bones, which, consequently, are painful and more prone to fractures.

Equivalent to rickets in human beings at a young age, osteomalacia reflects a defect in bone mineralization, a defect that may be due not only to an insufficient intake of vitamin D, but also to calcium and / or phosphorus.

Osteoporosis

Osteoporosis is a systemic disease of the skeleton that causes a strong weakening of the bones. Responsible for a greater tendency to fractures, this weakening finds its origin in the deterioration of the microarchitecture of the bone tissue and in the consequent reduction of the bone mineral mass .

Although it also involves a greater fragility of bone and an inclination to fractures, osteoporosis is significantly different from osteomalacia. In fact, if in osteoporosis the process of mineralization occurs correctly, in osteomalacia - as it has been stated in the dedicated subchapter - 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 disease, hypertension, diabetes, dyslipidemia and the metabolic syndrome is still unclear. Experts, in fact, 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.) .

Doubts about this (direct involvement of vitamin D deficiency or mediated by obesity?) Derive from the demonstration that obese people 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 adipose tissue.

Other consequences

In addition to impairing bone health and representing 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;
• It has immunodepressive effects, ie 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, ie the condition that the cells of the body show a poor sensitivity to insulin;
• Feelings of depression . At present, studies are underway to investigate the relationship between vitamin D deficiency and mood decline.

Diagnosis

To learn about the levels of vitamin D present in a human being, doctors measure the serum concentration of 25-hydroxicalciferol, also known as calcidiol or 25-OH-D .

25-hydroxicalciferol is the form in which vitamin D of solar and food origin circulates in the blood of human beings; in other words, in the blood, vitamin D takes on the appearance of 25-OH-D.

To express the concentration of 25-hydroxicalciferol, there are two units of measurement: the nanomole per liter, written more commonly as nmol / l, and the nanogram per milliliter, 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). Therefore, doctors begin to talk about vitamin D deficiency, when the concentration of 25-OH-D is less than 30 nmol / l (12 ng / ml).

The table below shows the 25-OH-D concentration ranges used to determine the level of vitamin D present in the human body:

What is the name of the vitamin D blood test?

The test for measuring blood levels of vitamin D is called 25-OH-D .

A simple blood sample is sufficient for collecting a blood sample to be dosed with 25-OH-D.

Search for causes: why is it important?

Once the presence of a vitamin D deficiency has been ascertained, the individual concerned must undergo a careful medical history and other diagnostic tests, which are necessary for the treating physician to trace the causes triggering the vitamin deficiency in question.

Only through knowledge of causal factors is it possible to plan the most appropriate therapy.

Therapy

Vitamin D deficiency requires a causal therapy, that is 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 "sun vitamin".

The causal therapy varies from patient to patient, depending on the trigger (this explains the importance of knowing the precise causes of the deficiency); the therapy aimed at eliminating the deficiency, on the other hand, generally consists of a dietary regime rich in foods naturally high in vitamin D or foods fortified with the latter, and in taking specific supplements.

While causal therapy has long-term effects (therefore not immediate), the therapy aimed at remedying the deficiency is specifically designed to act in the short term, as the persistence of low levels of vitamin D is, as we have seen, dangerous for Health.

Curiosity: the integration of vitamin D to whom can it be used?

Doctors could recommend a specific supplementation of vitamin D to pregnant and breast-feeding women, to infants fed with breast milk (because, as already mentioned, poor in the vitamin in question) and, sometimes, to children and boys.

Regarding the dosages of the integrations, these depend on various factors, including the latitude of residence.

Example of causal therapy

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

What and what are foods fortified with vitamin D?

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

The following are among the foods fortified in vitamin D:

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

Which foods contain more 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 porcino and spugnolo.

Beware of high vitamin D intakes

Readers should be reminded that a high intake of vitamin D can cause toxicity ; therefore, before taking specific vitamin D supplements it is important to consult your doctor and rely on his advice.

The consequences (ie the symptoms and signs) of an overdose of vitamin D include:

• Mineralization of non-bone tissues with diffused calcifications at the level of the organs concerned;
• Twitching and muscle spasms;
• Muscle weakness;
• Vomiting, diarrhea or constipation, and headache;
• Loss of appetite and loss of body weight;
• Formation of kidney stones;
• Confusion and disorientation;
• Heart problems.

Prevention

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

• Exposure to the sun, without sunscreen, at least 15 minutes every day;
• Include in the diet an adequate amount of foods high in vitamin D;
• Use vitamin D supplements, if one of the two previous points is hardly viable;
• Use foods fortified with vitamin D, if one of the first two points is hardly viable.

What strategies can the elderly adopt to prevent vitamin D deficiency and consequent bone diseases?

The dietary need for vitamin D increases over the years, as the ability of the skin to synthesize the aforementioned vitamin and the ability of the kidneys to make the last activation reaction decreases.

All this explains why, for the elderly, doctors very often recommend supplementation with vitamin D, using specific supplements or fish oils, to be combined perhaps with calcium supplementation.

The purpose of these supplements is to keep the bones in strength, to decrease the susceptibility to fractures and, ultimately, to prevent vitamin D deficiency with all its consequences (osteomalacia and osteoporosis).

To learn more: Osteoporosis prevention