Posted on 16 January 2012 - 12:00pm
Vitamin D plays an essential role in maintaining overall good health and a lack of it is linked to several disorders. SOURCESVERY few nutrients seem to play such an important role in health promotion than vitamin D, which is also referred to as the ‘sunshine’ vitamin.
Many of us tend to believe that we can get enough of this nutrient via direct exposure to the sun or from our diet.
People working in offices and/or who wear long pants and sleeves can be rather deficient in vitamin D, which has been linked to various health disorders which affect up to two-thirds of the population (Dowd, 2008).
» Production of vitamin D
Skin exposed to adequate sunlight (UVB ray) produces vitamin D3 (cholecalciferol) from the body’s cholesterol.
The darker our skin is, the less the amount of sunlight penetrating it, hence, lowering the body’s production of this vitamin.
Our liver then converts vitamin D3 to 25-hydroxyvitaminD (calcidiol or 25[OH]D) through its enzyme vitamin D-25-hydroxylase.
Finally, calcidiol is transformed in our kidney into the highly-active 1,25-dihydroxyvitamin D (calcitriol) through its enzyme 25-hydroxyvitamin D3-1alpha-hydroxylase (1-OHase).
» Calcitriol, a major health promoter
This converted nutrient raises calcium and phosphorus absorption in our intestine; induces osteoclast (cell associated with absorption and removal of bone) maturation for our skeletal restructuring; increases calcium deposition in our bones; and reduces levels of our parathyroid hormone (PTH).
Calcitriol works like a steroid hormone that targets more than 1,000 of our genes. Consequently, cells of almost all major organs in our body have vitamin D receptors that respond to calcitriol.
» Foods rich in vitamin D
They include Chinese (shiitake) mushroom dried – 474 IU per oz; cod liver oil – 450 IU per 1tsp; herring fish with liver – 461 IU per oz; sardines, canned in oil – 142 IU per oz; mackerel, fresh – 115 IU per oz; tuna, canned in oil – 100 IU per oz; eel, cooked – 57 IU per oz; one whole egg – 20 IU; and one egg yolk – 100 IU.
While cow’s milk and its derivatives contain this vitamin, a substantial number of Asians are known to be allergic to milk sugar lactose.
Any food item which you are allergic to may be treated by your body as a ‘foreign’ or toxic substance.
Fish may actually contain toxins and heavy metals. Egg white can also cause allergic reactions in some individuals while its yolk may elevate one’s serum ferritin.
» Prevention of chronic health disorders
Vitamin D regulates skeletal and tooth growth during our early years. It induces bone-formation during childhood and acts as a bone-turnover regulator during our adulthood.
High blood pressure, insulin resistance (pre-diabetes) and cardiovascular disease may be linked to vitamin D deficiency since it helps lower stress hormones and abdominal fat, raises insulin production and reduces inflammation that can damage arteries.
Those with blood vitamin D (25[OH]D) levels lower than half of the low optimal range are 11 times more likely to suffer from mood disorders and three times more likely to have impaired cognition.
This vitamin works with the DHA fat to facilitate our learning process.
The risk of heart attack doubles if calcidiol levels are less than 34ng/ml or 85nmol/L. Higher PTH levels carry increased risk for heart attack and hypertension as well as ischemic stroke.
Adjunct nutritional therapy targets the 15 known vitamin D-sensitive cancers: gastro-intestinal (colon, oesophageal, gastric, gallbladder, pancreatic, rectal, small intestine); urogenital (bladder, kidney, prostate); female (breast, endometrial, ovarian); and blood (Hodgkin’s lymphoma, non-Hodgkin’s lymphomas). This list can also be extended to the lungs (Grant et al, 2002).
Vitamin D plays a part in arresting malignant cell growth, and it is also anti-inflammatory. Its metabolites have inhibitory action on initiation and progression of cancers.
Vitamin D also slows down our cells’ life cycle, hence, reducing the number of mistakes in its DNA replication. It promotes apoptosis (natural cell death) and turns on our tumour-suppressor genes.
Study suggests that just 2,000 IU per day of this vitamin can reduce risk of type 1 diabetes by some 80% in young infants.
Other autoimmune diseases associated with vitamin D deficiency include multiple sclerosis, Grave’s disease, lupus, rheumatoid arthritis and spondylitis.
The inverse relation with multiple sclerosis risk was particularly strong for calcidiol levels measured before age 20 years.
Generally, it is true that our immune defence is largely determined during our several months in the womb and during our early childhood. Supplementation recommended by nutritional therapists is usually in the form of vitamin D3, not D2.
Depending on cod liver oil for this vitamin can lead to an excess intake of oil-soluble vitamin A.
While it is said that the healthful Chinese mushroom helps enhance our immune system, it is unclear to what extent this benefit is attributed to its vitamin D content, besides its rich source of tumour-suppressing polysaccharides.
http://www.thesundaily.my/news/267111
