Vitamin D Deficiency

What is vitamin D deficiency?

Vitamin D deficiency is also known as hypovitaminosis D. It is the most common nutritional deficiency worldwide,[1] affecting people of all age groups.[2]

Vitamin D is one of the most important vitamins ‒ essential compounds on which the body’s cells rely for normal development. Nearly every cell in the body has a receptor for vitamin D.[3]

Vitamin D levels in the body can be maintained in two ways:

  1. The body can, itself, make vitamin D from its resources of cholesterol. To do this, it needs access to sunlight.
  2. Vitamin D can be found in certain foods, such as fatty fish. (However, it is rare for a person to gain all the vitamin D that their body needs from food alone.)

Some of the most important functions of vitamin D include:

  • Maintenance of normal calcium and phosphate levels
  • Promotion of calcium absorption (essential for healthy bones and teeth)
  • Growth of cells and bones
  • Reduction of inflammation, such as can be caused by infection or injury

When a person has vitamin D deficiency, their cells become less efficient at carrying out processes such as growth and regeneration.

Symptoms of vitamin D deficiency

If the body does not contain sufficient vitamin D, this can give rise to a variety of health complications. Problems arising from vitamin D deficiency include fatigue, depressed mood and bone and muscle pain.

Vitamin D is particularly instrumental in maintaining healthy bones. The development or worsening of skeletal disorders ‒ such as osteoporosis in adults and rickets in children ‒ are therefore often linked to vitamin D deficiency.

Summary of the most important signs that a person may be affected by vitamin D deficiency:[4][5]

  • Bone pain, sometimes also felt as joint pain
  • Fatigue
  • Muscle pain
  • Hair loss
  • Being affected by frequent bacterial and viral infections
  • Mood changes such as a depressed mood
  • Wounds and injuries taking longer to heal
  • Weaker and/or easily breaking bones

Causes of vitamin D deficiency

The daily intake of vitamin D a person needs in order for their body to function optimally, depends on factors such as age, weight, skin color and their overall health. People whose bodies require a greater intake of vitamin D are at greater risk of experiencing vitamin D deficiency.

Being an infant or an elderly person, being obese, having darker skin and/or experiencing a health condition which compromises one’s ability to absorb vitamins properly (such as Coeliac disease or inflammatory bowel diseases) are all factors which may increase the daily quantity of vitamin D an individual requires.

Factors which increase the likelihood of being affected by vitamin D deficiency include:

  • Living in countries where there is little sun all year round
  • Having darker skin (the more pigmented a person’s skin is, the better it is able to produce melanin, which absorbs UVB radiation and reduces the synthesis of vitamin D)[6]
  • Wearing high-factor sunscreen
  • Spending the majority of one’s time indoors
  • Malabsorption as a result of conditions such as Coeliac disease which impede the normal uptake of nutrients
  • Avoiding foods which provide a source of vitamin D such as fatty fish and dairy products
  • Being obese
  • Being elderly

The main source of vitamin D is exposure to solar UVB radiation (from sunlight).[4] When the body is exposed to sunlight, it can manufacture vitamin D from cholesterol, a fatty substance synthesized by the liver and found in some foods. Anything that reduces a person’s access to solar UVB radiation will compromise the body’s ability to manufacture sufficient levels of vitamin D,[4] therefore eventually causing vitamin D deficiency.

Lacking vitamin D in one’s diet

The recommended daily intake of vitamin D is:[7]

  • 400 IU (international units) for children under one year
  • 600 IU for children, teens and adults up to age 70
  • 800 IU for pregnant people and adults over the age of 71

To increase a person’s chances of meeting the vitamin D target for their age group, healthcare professionals advise ensuring that one’s diet contains sources of vitamin D – which can be found in certain foods, especially in fatty fish, such as salmon or tuna, and certain dairy products, like milk and cheese.

However, most foods that contain vitamin D do not contain sufficient quantities to meet a person’s daily required intake. For this reason, many traditionally consumed sources of vitamin D (for example, formulated milk for infants, orange juice and soy milk) are fortified with the compound.

Failing to eat regular or sufficient quantities of vitamin-D-containing food (for example, because of following a vegan diet) increases the likelihood of developing vitamin D deficiency. Even with a vitamin-D-rich diet, it is not usually possible for a person to maintain sufficient levels of vitamin D in their body from food alone. For this reason, vitamin D deficiency is a very common problem worldwide.

Sourcing additional vitamin D

For some people, particularly those who ensure that their food contains vitamin D, exposure to sunlight will be sufficient for them to synthesize the rest of their recommended daily amount of vitamin D.

Many people – particularly those living far from the equator or whose lifestyles involve staying indoors and/or wearing clothes which cover most of the skin – may need to take supplements of vitamin D to meet their required daily amount.

Risks of vitamin D deficiency

It is important to consult a healthcare professional if one suspects vitamin D deficiency, because the condition increases the likelihood of developing certain problems. The most commonly experienced problems related to vitamin D deficiency are skeletal disorders (diseases related to the growth and strength of one’s bones). In children, vitamin D deficiency can cause rickets, a condition involving the weakening and softening of the bones. In adults, the equivalent to rickets is known as osteomalacia (soft bones).

Being deficient in vitamin D can also render the body less robust and heighten the likelihood of accidents occurring:

  • Vitamin D deficiency increases the likelihood of breaking a bone in people of any age
  • Elderly people with hypovitaminosis D are more likely to fall, trip or stumble

Health complications which are associated with vitamin D deficiency include:[8]

  • Osteomalacia (softening of the bones in adults) and osteoporosis (increased fragility of the bones)[9]
  • Rickets (softening of the bones in children)
  • Mental health conditions such as seasonal affective disorder (SAD) and depression[10]
  • Increased susceptibility to infections and illnesses
  • Glucose intolerance[11] and type 1 and type 2 diabetes[8]
  • Obesity
  • Hypertension (high blood pressure)[12]
  • Cardiovascular diseases (conditions affecting the heart) such as hypertension, heart failure and ischemic heart disease[13][14]
  • Cancer of the colon, breast or prostate[15]
  • Rheumatoid arthritis[16]
  • Multiple sclerosis[16][17]
  • Hair loss (alopecia)[18]
  • Tuberculosis[19]

Risks of vitamin D deficiency in children

Rickets (a condition involving the softening of the bones, so that the skeleton develops deformities) is a very common condition related to vitamin D deficiency and affects children worldwide.[20]

In children, vitamin D deficiency primarily causes skeletal diseases, because the growth of the skeleton demands certain levels of calcium, and lacking vitamin D impairs the body’s uptake of calcium. Vitamin D deficiency can therefore cause hypocalcemia (where the levels of calcium in the body are too low), which in turn can cause rickets and osteoporosis. Children experiencing hypocalcemia as a result of vitamin D deficiency may exhibit additional symptoms and health problems, such as seizures or tetany (muscle spasms).[21]

Risks of vitamin D deficiency in pregnancy and infancy

Vitamin D deficiency is linked to a range of complications relating to pregnancy and the health of the pregnant person and the newborn.

Complications which may arise for a pregnant person experiencing vitamin D deficiency include:[22]

  • Gestational diabetes and less efficient metabolism of glucose
  • Bacterial vaginosis
  • Preeclampsia
  • Premature birth
  • Increased likelihood of needing a cesarean delivery

A developing fetus’ need for vitamin D increases during the second half of pregnancy, when most of the bone growth prior to birth takes place. Because a developing fetus is entirely dependent on a passive transfer of vitamin D (from the pregnant person), it is important for pregnant people to ensure that their vitamin D intake is sufficient to support the needs of the fetus in addition to their own.

In newborns, vitamin D deficiency can lead to conditions including:

  • Low birth weight
  • Rickets
  • Abnormal bone growth
  • Increased likelihood of skeletal fractures

Breastfeeding and vitamin D deficiency

it is important to ensure that a breastfeeding person maintains adequate levels of vitamin D to support the healthy growth of a newborn in the postnatal period. For most newborns, breast milk is their primary source of vitamin D. However, not all breast milk will contain sufficient levels of vitamin D to provide an infant with their recommended vitamin D intake (400 IU per day). If the amount of vitamin D present in breast milk is not sufficient, It is possible for infants to develop vitamin D deficiency, particularly if they:

  • Lack exposure to sunlight (because of staying indoors, wearing clothing which usually covers most of the skin or living far from the equator)
  • Live in weather conditions with intense cloud covering
  • Live in a highly polluted area

The [American Academy of Pediatrics recommends that a daily supplement of 400 IU is given to all breastfeeding infants, to safeguard against vitamin D deficiency.

However, recent research indicates that if a mother takes a supplement with a sufficiently high concentration of vitamin D (around 6,400 IU), her breast milk will contain high enough levels of vitamin D to provide an infant with their recommended daily intake. This removes the need to give a supplement to an infant directly.

Risks of vitamin D deficiency in the elderly

People with vitamin D deficiency are likely to experience ageing more rapidly than those with sufficient vitamin D intake.

In the elderly, a deficit of vitamin D is associated with an increased likelihood that the health problems one does experience may be difficult to treat and/or result in death more likely than without a vitamin D deficiency. Among other factors, this is because elderly people who have vitamin D deficiency are also more likely to experience cognitive impairment, compromised muscle function and are more prone to falls.

Diagnosis

If vitamin D deficiency is suspected, it is important to visit a doctor in order to confirm the diagnosis, so that one can begin treatment as soon as possible and redress any problems incurred as a result of the deficiency.

It is not standard medical practice to screen symptomless people for vitamin D deficiency. Therefore, it is common for people to be unaware that they are vitamin D deficient, or that they need to take supplements, until they begin to experience health problems related to their vitamin D deficiency, such as hair loss, bone and/or muscle pain, fatigue or depression.

To confirm a suspected diagnosis of vitamin D deficiency, one’s doctor will perform a blood test (called 25-hydroxy vitamin D test) , measuring the serum 25(OH)D levels in the blood. This will determine whether a person has sufficient or insufficient levels of vitamin D.

If an individual is suspected of having had long-term vitamin d deficiency, doctors will also examine whether they display certain physical characteristics which are indicators of a deficiency.

Physical signs that a person may be affected by long-term vitamin d deficiency include:[23]

  • Widening of the ends of the bones
  • Skeletal deformities including bow legs and expanded rib-cage
  • Slow tooth development and/or early dental caries

In diagnosing vitamin D deficiency, a healthcare professional will also assess a person’s medical history, diet and lifestyle to ascertain whether they have a history of health problems which could be related to vitamin D deficiency, like chronic liver or chronic kidney disease, and how likely they are to access sufficient sources of vitamin D on a day-to-day basis.


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