Vitamin D (Calciferol)

December 27, 2011 by  
Filed under Vitamins

Keywords: bone health, mineral absorption, anti-inflammatory, anti-infection

Functions

  • Anti-inflammatory effects
  • Bone health
  • Calcium metabolism
  • Cancer prevention
  • Cell differentiation
  • Immune system modulation
  • Kidney metabolism
  • Mineral absorption
  • Protects against infection

Good food sources

  • Butter
  • Cod liver oil
  • Halibut liver oil
  • Herrings
  • Kippers
  • Mackerel
  • Salmon
  • Sardines
  • Tuna

Deficiency symptoms

  • Deafness
  • Infections
  • Osteoporosis: loss of bone minerals, with brittleness, bones easily broken
  • Osteomalacia: softening of bones with bone pain and tenderness
  • Possibly multiple sclerosis and other auto-immune diseases and cancers since vitamin D is needed for the self-destruction of cytokine-producing or mutated cells
  • Rickets (in children): softening and deformity of the bones, bowed legs, knee pains and poor growth
  • Weakness of some muscles (e.g. in climbing stairs), waddling gait. Probably caused by muscle degeneration (muscles turning into fat).

Preventing deficiency

Recent research has shown that 90% of the US pigmented populace and nearly 75% of the white populace suffer from vitamin D deficiency. (Adams JS, Hewison M. Update in vitamin D. J Clin Endocrinol Metab. 2010 Feb;95(2):471-8. Review.) Similar rates occur in the UK and other cold climates.

Vitamin D can be produced in the body from the action of sunlight on the skin, therefore when exposure to the sun is sufficient, dietary sources of vitamin D are not required. Uncovering the skin when outdoors allows the body to absorb more sunlight to make vitamin D. However in cold climates, the high energy photons needed for vitamin D synthesis in the skin are absent for up to five months of the year. Vitamin D synthesis in the skin also declines with age.

Vitamin D is taken from the skin to the liver where it is turned into its active form. Final activation takes place in the kidney and other tissues. The active form of vitamin D is known as vitamin D3 and has many hormone-like effects.

There is evidence that isoflavones found in soy foods can  improve the activation of vitamin D by liver enzymes.

People at risk of vitamin d defiency

Vegans living in cold climates should take particular care not to become deficient in vitamin D and it may be best to err on the side of caution and take vitamin D supplements, especially during the winter months. This especially applies to dark-skinned people, who have a reduced ability to produce vitamin D from sunlight. Using sun-screen lotions to block ultraviolet light also blocks vitamin D synthesis in the skin and the presence in the body of so-called ‘heavy’ (toxic) metals can block the activation of vitamin D by the kidneys.

People who live in nursing homes, prisons and other institutions, and house-bound people such as the disabled, sick or elderly, are at risk of developing vitamin D deficiency if they do not get enough of this vitamin in dietary form. The bioavailability of vitamin D also decreases in the elderly.

People who eat a very low-fat diet may be at risk of vitamin D deficiency not only because vitamin D is only naturally present in fatty foods such as cream, cheese and fish oil, but because vitamin D can only be absorbed when a meal contains some oil or fat levels. People who have a dietary fat malabsorption problem can also develop vitamin D deficiency.

Non-vegetarians who avoid dairy products should instead regularly eat liver and oily fish such as herrings, mackerel and salmon.

Vitamin d deficiency and the immune system

There is growing evidence that vitamin D strongly influences immune system function:

  • Activated macrophages produce vitamin D3
  • Cells in the immune system cells have vitamin D receptors
  • Poor vitamin D nutrition seems to increase susceptibility to chronic infections
  • At least five studies show  that the higher your vitamin D level, the lower your risk of contracting colds, flu, and other respiratory tract infections
  • Vaccines offer better protection when administered together with vitamin D.

Auto-immunity consists of chronic activation of the immune system, producing inflammation that is not resolved and goes on to cause tissue damage. Examples of auto-immune diseases include multiple sclerosis, thyroiditis, insulin-dependent diabetes mellitus and inflammatory bowel disease. Animal studies suggest that the immune system is less able to switch  itself off when vitamin D3 is deficient. When vitamin D deficiency is corrected, immune cells become more sensitive to instructions to ‘self-destruct’. (Hayes CE, Nashold FE, Spach KM, Pedersen LB. The immunological functions of the vitamin D endocrine system. Cell Mol Biol (Noisy-le-grand). 2003 Mar;49(2):277-300. Department of Biochemistry, University of Wisconsin-Madison, USA.)

Vitamin d and cancer

There is now much evidence that vitamin D is effective in preventing several forms of cancer, especially breast and colon cancers.  The evidence is now so strong that the Canadian Cancer Society has begun endorsing vitamin D supplementation as a cancer-prevention therapy.

Comments

Vitamin D3 (cholecalciferol) is the natural form of vitamin D, found in food and produced in the body. Vitamin D2 (ergocalciferol), which is often used in supplementation products, is an inferior, artificial form.

Information compiled by Linda Lazarides
Naturopathic Nutritionist, Author, Educator

Linda Lazarides is Course Director of the School of Modern Naturopathy and author of eight books on health, nutrition and naturopathy.

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