Vitamin D

Consequences of Deficiency

Prolonged deficiency of vitamin D can cause, or increase the risk or severity of, a variety of diseases, including:

  • Rickets. A disease of childhood resulting in deformity or poor growth of the long bones. This is the best and longest-known result of vitamin D deficiency, and attempts to find a cure essentially led to the discovery of vitamin D itself.
  • Osteomalacia. A disease occurring in adults, similar in many ways to rickets in children, where thinning of the bones results in bone pain and fragility. It is also associated with muscle weakness.
  • Osteoporosis. A disease of old age, particularly prevalent in women, also causing bone fragility, but as a result of a reduction in bone mineral density. A vitamin D deficiency results in increased risk of fractures.
  • Muscle weakness and pain. Many adults and children with unexplained muscle and bone pain have been found to also be deficient in vitamin D, often severely so. Muscle weakness caused by vitamin D deficiency can lead to an increased risk of falls among the elderly, while restoration of proper vitamin D levels in deficient younger adults has been shown to improve athletic performance.
  • Cancer. There is growing evidence that vitamin D deficiency is linked to an increased risk of certain types of cancers, particularly colon, breast, and prostate. It is also associated with an increased risk of mortality from these cancers. There are also indications that vitamin D deficiency is associated with increased risk of skin cancers, and of mortality from the melanoma form.
  • Tuberculosis. Vitamin D helps the human body fight this deadly disease, so low vitamin D levels increase both the risk of infection, and its severity. Exposure to sunlight has also historically been used to treat the disease, before falling out of favour to modern drug treatments.
  • Heart disease and high blood pressure. Vitamin D improves the heart’s pumping strength and efficiency, so low vitamin D levels increase a person’s risk of heart disease. Vitamin D can also reduce blood pressure, especially in those with abnormally high pressure levels, and also helps reduce cholesterol levels.
  • Osteoarthritis and rheumatoid arthritis. There is growing evidence that adequate vitamin D levels can slow down the development of osteoarthritis, and reduce the risk of rheumatoid arthritis.
  • Diabetes. Low vitamin D levels reduce the body’s ability to properly produce and use insulin, and may therefore lead to increased risk of type 2 diabetes. Vitamin D deficiency in childhood is also associated with increased risk of type 1 diabetes later in life.
  • Autoimmune diseases. Vitamin D plays an important role in regulating the body’s immune system, and there is growing evidence that vitamin D deficiency is associated with several diseases in which the immune system attacks the body’s own tissues, such as multiple sclerosis (the protective sheath around the nerves is attacked), type 1 diabetes (the pancreatic cells that produce insulin are attacked), and rheumatoid arthritis (the tissues of the joints are attacked).
  • Skin conditions. Vitamin D can help in the treatment of skin conditions such as psoriasis, eczema and some types of acne. Exposure to sunlight (or artificial equivalent) or application by ointment are usually the most effective forms of vitamin D application in such cases; dietary intake is less effective because the vitamin doesn’t get to where it’s needed.
  • Mood and mental disorders. Vitamin D is important for brain function, including the generation of neurotransmitters such as serotonin, and deficiency is strongly associated with mood and mental function disorders such as schizophrenia, depression, and seasonal affective disorder (SAD).

Treatments aimed at increasing vitamin D levels, such as exposure to UVB or dietary supplements can also be effective in combating some of these diseases and conditions.

Incidence of Deficiency

Vitamin D deficiency is widespread, particularly among those living at higher latitudes, away from the tropics, and especially among darker-skinned people living at such latitudes. It is estimated that around 1 billion people worldwide are deficient in vitamin D to some extent, including around 90% of North Americans and 50% of Europeans.

The likelihood of deficiency, however, is not evenly distributed among a population. Groups at increased risk of vitamin D deficiency include:

  • Those with naturally dark skin, especially those living away from the tropics.
  • Those who wear fully-concealing clothing, such as Muslim women who wear a burka whenever they go out.
  • The elderly, since their vitamin D requirement increases with age while their ability to produce it decreases.
  • Those who don’t go outside much, or take excessive or unnecessary Sun protection or avoidance measures, including children and babies.
  • Pregnant and breast-feeding women, although it is their children who are at particular risk from their deficiency.
  • Babies who are exclusively breast-fed. Breast milk contains little vitamin D.
  • Those who are obese. Body fat tends to hold onto vitamin D – this is how it is stored over the winter – therefore excess fat tends to reduce the availability of vitamin D to the rest of the body.
  • Those who have certain diseases, such as chronic kidney or liver disease and intestinal disorders.

The use of sunscreen, by significantly reducing the UVB levels penetrating the skin, dramatically reduces the production of vitamin D. There is evidence that the success of the campaigns in Australia and New Zealand for Sun protection to reduce the incidence of skin cancers have, in encouraging Sun avoidance and excessive use of sunscreens and protective clothing, resulted in increased incidence of vitamin D deficiency, which is now also being linked with increased risk of skin cancer.

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