Vitamin D-the great help to our health!

March 17, 2015

 

Vitamin D is an essential nutrient, but it is more like a hormone than a vitamin itself. It has innumerable functions throughout the body, although its fame is linked to its requirement for proper skeleton formation and prevention of rickets. In fact, Vitamin D deficiency causes growth retardation and rickets in children and will precipitate and exacerbate osteopenia, osteoporosis and increase risk of fractures in adults. 

 

This is due to the fact that one well known function of vitamin D is to enhance the efficiency of calcium (as well as Magnesium and Phosphorus) absorption from the intestine. Besides this action, though, vitamin D is key to several other functions in the body, from muscular performance to immune system function, from kidney function to cardiovascular health to fertility


Vitamin D promotes insulin secretion (preventing diabetes), inhibits adaptive immunity but promotes innate immunity (protecting from autoimmune diseases and infections), inhibits cell proliferation and enhances cell self-death (protecting from cancer), alters cardiac contractility, stimulates sex hormones production. Vitamin D has an important effect on reproduction in both women and men: it might influence production of sex hormones (estradiol and progesterone) in women and men, and it is positively associated with semen quality.


Notwithstanding its importance, many people (an estimated 1 billion) are vitamin D deficient (D3 level less than 20 ng/ml), i.e. they do not even have the minimal amount of it for correct functioning of these body systems. This is recognized as one of the most common medical conditions in children and adults. Doctors are starting to accept vit D’s important role and prescribe it, although mainly to prevent osteoporosis in post-menopause women.
 

But its need of supplementation does not end here.
 

It is calculated that approximately 90% of all vitamin D needed has to be formed in the skin under the effect of ultraviolet radiation UV B. This might be one reason for it being so low in so many people: strict sun protection, predicated in the past 30 years or so to supposedly prevent skin cancers, causes vitamin D-deficiency. 


Use of sunscreens: not only do synthetic sunscreens effectively block the healing benefits of the sun, by blocking UVB rays, but they also become absorbed into the skin where they create several potential health problems. Moreover, synthetic sunscreens create a false sense of security by disabling the skin's early reaction for overexposure, the sunburn, which creates other health problems. When sunburn, the skin gets damaged by sun rays through creation of free radicals, which are responsible, among other things, for premature ageing and some cancers. That is why it is a good idea to counter these free radicals with antioxidants in the diet.

 

The synthesis of vitamin D in the skin is a function of skin pigmentation (at darker skin corresponds a lower synthesis, thus less vitamion D) and of the solar angle, which depends on latitude, season, and time of day. Melanin absorbs 99.9% of the UVB photons into heat that is easily dissipated, which effectively avoids radiation damage that contributes to cell damage. The remaining photons are used for the transformation of 7-dehydrocholesterol found in the skin to the previtamin D3.


This 0.1% of photons use is extremely rapid and robust. The obtained forms of pre-vitamin D (D3) is biologically inactive and require activation in the liver and kidneys. 

 

For Vitamin D production in the skin UVBs of between 290 and 313 nanometers of wave length are necessary. However,  such wavelength is not present at this (New Zealand) latitude between April and September approximately. This is why supplementation is strongly recommended in the fall-winter period. This is one of the best ways to strengthen the immune system, especially against flu infections. It also helps relieve seasonal depression and fatigue. Vitamin D is in fact necessary for the production of serotonin and dopamin, the neurotransmitters of happiness.


It is believed that, besides the recent  lower sun exposure, also protein losses, gastrointestinal malabsorption (so common in our times) and defective skin synthesis might contribute to the elevated number of people with suboptimal level of such vitamin.
 

Insufficient dietary intake might be another cause: vitamin D is found in eggs and oily fish. Eggs have been (unjustly) receiving a bad name with the appearance of the cholesterol fright of the past 20 years and oily fish do not get highly consumed by the general population, except probably among Inuit. Also, farmed salmon (the most commonly eaten one) has a mean content of vitamin D of approximately 25% of the mean content found in wild caught salmon. Vitamin D content in food is however minimal importance when compared to vitamin D production from the skin-sun reaction.


Association of vitamin D-deficiency has been found with various diseases including cancer (especially breast, ovarian, prostate, colorectal, multiple myeloma and Hodgkins lymphoma, pancreas, leukemia), heart failure, bone diseases, autoimmune diseases (Multiple Sclerosis, autoimmune thyroid diseases, Systemic Sclerosis, Systemic Lupus Erythematosus , Rheumatoid Arthritis, Chron’s disease), chronic kidney disease, infectious diseases, cardiovascular diseases and hypertension, type II diabetes, infertility, muscular diseases (myopathies, risk of falling, fibromyalgia), asthma and neurological disorders (cognitive performance, depression, Alzheimer’s, schizophrenia).
 

A series of studies have suggested that low vitamin D increases risk of cancer: in a recent study researchers from Northwestern University found that vitamin D deficiency can increase the risk of aggressive prostate cancer in some men by nearly 500 percent. Lung cancer patients have a better prognosis with vit D3 enhancement by high sun exposure. 

 

Vitamin D supplementation can also increase survival of chronic kidney disease patients. In general, and this is what science reveals, higher vitamin D levels are associated with lower overall mortality.

We hope that this article educated on the beneficial effects of moderate sunlight for providing us the vitamin D requirement for good health. For people who are not exposed to sunlight, a supplement is recommended: at present, most experts agree that daily intake of 1000- to 5000 IU vitamin D in adults and 400 IU in children could reduce the incidence of vitamin D-deficiency-related diseases.

 

So finally, avoid getting sunburn, but do not avoid the sun: train your skin in spring with the morning to midday sun, exposing your body 15-20 minutes at first and then longer times, without sun protection. Use the coloring of the skin as a gauge for safety against overexposure.  

 

 

 

References

Stewart A, Roecklein KA, Tanner S, Kimlin MG. Possible contributions of skin pigmentation and vitamin D in a polyfactorial model of seasonal affective disorder. Med Hypotheses. 2014 Nov;83(5):517-25.

 

K.S. Vimaleswaran et al. Causal relationship between obesity and vitamin D status: Bi-directional mendelian randomization analysis of multiple cohorts. PLos medicine. Volume 10, February 2013, p. e1001383.

 

Garland CF. Vitamin D supplement doses and serum 25-hydroxyvitamin D in the range associated with cancer prevention. Anticancer res. 2011 Feb ;31(2):607-11.

 

 

Cannell JJ.  On the epidemoloy of influenza. Virol.  2008;5-29.

 

Grant    WB,  Garland CF, Holick MF.  Comparisons  of estimated economic burdens due to insufficient solar ultraviolet irradiance and vitamin D and excess solar UV  irradiance for the United  States.  Photochem Photobiol 2005 ; 81 : 1276-86 2.  

 

25 (OH) vitamin D level in Crohn's disease: association with sun exposure & disease activity. The Indian journal of medical research, 2009

Childhood asthma may be a consequence of vitamin D deficiency. Current opinion in allergy and clinical immunology, 2009 


Dietary intake of vitamin D and cognition in older women: a large population based study. Neurology, 2010

Disease specific definitions of vitamin D deficiency need to be established in autoimmune and non autoimmune chronic diseases: a retrospective comparison of three chronic diseases. Arthritis research & therapy, 2010

Factors that influence the cutaneous synthesis and dietary sources of vitamin D.Archives of biochemistry and biophysics, 2007

Interaction of factors related to the metabolic syndrome and vitamin D on risk of prostate cancer. Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology, 2007

Is Vitamin D Deficiency Associated With Heart Failure? A Review of Current Evidence. Journal of cardiovascular pharmacology and therapeutics, 2011

Melanoma and vitamin D. Molecular oncology, 2011

Nonclassic actions of vitamin D. The Journal of clinical endocrinology and metabolism, 2009

Protective and toxic effects of vitamin D on vascular calcification: clinical implications. Molecular aspects of medicine, 2008

Role of vitamin d in insulin secretion and insulin sensitivity for glucose homeostasis. International journal of endocrinology, 2010

Scientific documentation of the relationship of vitamin D deficiency and the development of cancer. Journal of environmental pathology, toxicology and oncology : official organ of the International Society for Environmental Toxicology and Cancer, 2009

Seasonal and geographical variations in lung cancer prognosis in Norway. Does Vitamin D from the sun play a role? Lung cancer, 2007

Serum vitamin D concentrations are related to depression in young adult US population: the Third National Health and Nutrition Examination Survey. International archives of medicine, 2010

Skin cancer prevention and UV protection: how to avoid vitamin D deficiency? The British journal of dermatology, 2009

The role of vitamin D in cancer prevention: does UV protection conflict with the need to raise low levels of vitamin D? Deutsches Ärzteblatt international, 2010

Very low levels of vitamin D in systemic sclerosis patients. Clinical rheumatology, 2010

Vitamin D and autoimmune thyroid diseases. Cellular & molecular immunology, 2011

Vitamin D and host resistance to infection? Putting the cart in front of the horse. Experimental biology and medicine (Maywood, N.J.), 2010

Vitamin D and skeletal muscle tissue and function. Molecular aspects of medicine, 2008

Vitamin D biology: from the discovery to its significance in chronic kidney disease. Journal of renal nutrition : the official journal of the Council on Renal Nutrition of the National Kidney Foundation, 2011

Vitamin D deficiency in fibromyalgia. The Journal of the Pakistan Medical Association, 2010

Vitamin D, neurocognitive functioning and immunocompetence. Current opinion in clinical nutrition and metabolic care, 2011

Vitamin D: considerations in the continued development as an agent for cancer prevention and therapy. Cancer journal, 2010

Vitamin D and fertility: a systematic review. European Journal of Endocrinology 2012

 

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