Vitamin D deficiency

Vitamin D is a fat-soluble vitamin that helps the body absorb calcium, which is important for bone formation. It also has important functions in the muscular, nervous, and immune systems. The body can obtain vitamin D from the skin after exposure to sunlight, from the diet, and supplements. The recommended dietary allowance (RDA) of vitamin D IS 600 IU for ages 1-70 and 800 IU for those older than 70. Individuals with a higher risk of vitamin D deficiency may require more and should consult with their health care providers.

Vitamin D deficiency or hypovitaminosis D is when the level of Vitamin D in the body is lower than normal. It most commonly occurs in individuals who have inadequate exposure to sunlight but it can also occur due to decreased vitamin D in the diet, impaired absorption of vitamin D from the gastrointestinal tract, problems in the liver or kidney that impair conversion of vitamin D to its active form in the body or intake of drugs that interfere with the ability to absorb or convert vitamin D.

Risk Factors

Risk factors for developing vitamin D deficiency include:

  • Breastfeeding infants, as human milk is not a good source of vitamin D.
  • Older age individuals are more at risk as their skin does not make vitamin D as efficiently as when they were young. The ability of their kidney to convert vitamin D into its active form also decreases.
  • Dark-skinned individuals, due to the higher level of melanin pigment, have a decreased ability to make vitamin D from the sun.
  • People who suffer from intestinal malabsorptive disorders like Crohn’s disease or celiac disease cannot properly absorb the fat-soluble vitamin D.
  • Obese individuals also may suffer from hypovitaminosis as their body fat binds some vitamin D and prevents in form entering the circulation.
  • A complication of gastric bypass surgery
  • Osteoporosis
  • Chronic kidney or liver disease
  • Hyperparathyroidism
  • Granulomatous diseases like sarcoidosis, tuberculosis, histoplasmosis
  • People who take drugs that interfere with the metabolism of vitamin D such as anti-seizure drugs, cholestyramine, glucocorticoids, antifungal drugs, and HIV medicines also increase the risk.

Associated diseases

Severe deficiency of vitamin D can cause several diseases including:

  • Osteoporosis: Deficiency of vitamin D can cause decreased bone mineral density and increased susceptibility to fractures, a condition known as osteoporosis.
  • Osteomalacia. The deficiency of vitamin D in adults leads to osteomalacia in which there are proximal muscle weakness and increased bone fragility and pain.
  • Rickets: Vitamin D deficiency in children characterized by impaired growth and deformed bones. There is a higher risk in African American infants and children.
  • Muscle pain, weakness, and fasciculations (twitching)
  • Light-headedness
  • Periodontitis: It is bone loss due to local inflammation that can lead to loss of teeth.
  • Pre-eclampsia: Vitamin D deficiency in women has been shown to have an association with the development of pre-eclampsia during pregnancy. Vitamin D deficiency in the mother may also lead to overt bone diseases in the baby before birth and impaired quality of bone after birth.
  • Schizophrenia: Deficiency of vitamin D is also associated with schizophrenia. Vitamin D deficiency in the mother during the prenatal period can cause neurodevelopmental defects in the brain that are seen in schizophrenia.

Relation to COVID-19

The severity of coronavirus infection is determined by the presence of complications that involve underlying inflammation in the body. Vitamin D metabolites provide an important antiviral activity in the body. Decreased vitamin D is associated with a rise in inflammatory mediators in the body and an increased risk of upper and lower respiratory tract infections. Vitamin D deficiency is also associated with thrombosis which is a frequent complication of COVID-19.  Obesity and diabetes are common risk factors for hypovitaminosis D and have also been reported to increase the mortality of COVID-19. The overlap between the risk factors between vitamin D deficiency and severe COVID-19 infection has prompted researchers to suspect that vitamin D supplementation could prevent or improve the outcome of COVID-19.



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