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The importance of an adequate vitamin D level cannot be underestimated.
Recent interest in the functions of vitamin D has highlighted several areas of health that require vitamin D.
It is estimated that around a quarter of the UK population are deficient in vitamin D and this is thought to play a role in a wide variety of health concerns.
We always take an evidence-based approach and in this article we take a look at the health implications of low vitamin D.
Vitamin D Sources
Very few foods are naturally rich in vitamin D. Foods like oily fish, egg yolks, meat, offal and UV treated mushrooms may contribute to overall levels, but the most significant source is from skin exposure to sunlight.
Around 15-20 minutes of sun exposure each day stimulates the body to synthesise vitamin D from cholesterol.
Once synthesised, the conversion to active vitamin D occurs in the liver and the kidneys.
A variety of factors may be playing a role in vitamin D deficiency including sun block, dark skin, climate, age, genetics and lifestyle habits such as shift work.
A vitamin D deficiency is normally diagnosed through a blood test.
Levels below 25nmol/L (10ng/ml) are classed as deficient (1).
Many experts advise that optimal levels for correct body functioning are around 70-80nmol/L (28-32ng/ml) (2,3).
Relationship With Health
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Bones
The link between vitamin D levels and bone health has long been known and it is essential for increasing intestinal absorption of bone supportive nutrients like calcium and phosphate.
In addition to this, vitamin D promotes healthy bone remodelling.
Classic signs of vitamin D deficiency in children include stunted growth, soft bones and deformed bones.
The condition rickets was common before fortification of foods and although the incidence of rickets reduced following fortification, a rise of rickets in children in the UK more recently has sparked concern.
In adults the condition is called osteomalacia.
A lack of vitamin D can also lead to osteopaenia and osteoporosis.
Both these conditions involve a loss in bone mineral density, although this is more pronounced in osteoporosis, and increasing fragility of bones.
In cases of osteoporosis, supplementation with vitamin D and calcium can significantly reduce the risk of fractures (4).
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Blood Sugar Balance
There is increasing evidence to show that vitamin D plays a role in blood sugar balance.
Evidence suggests that a person’s vitamin D status may impact the ability of the pancreas to sense glucose levels and respond appropriately, by secreting insulin (5).
Lifestyle conditions, such as Type 2 diabetes and metabolic syndrome, are characterised by insulin resistance – the inability of the cells to correctly recognise or respond to insulin.
This leads to uncontrolled and higher than normal blood glucose levels.
Low levels of vitamin D are linked to insulin resistance (6,7) and supplementing with vitamin D may not only improve insulin sensitivity but also reduce the risk of developing Type 2 diabetes by a third (8).
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Immune Defences
Vitamin D receptors are found in numerous parts of the body including the heart, stomach, skin, brain, breast and prostate (9).
Active vitamin D binds to the vitamin D receptor (VDR) which can regulate the expression of a variety of genes involved in many functions.
The VDR is expressed by most cells of the immune system and vitamin D is thought to have an immune modulatory effect.
This helps to enhance natural defences against foreign substances and pathogens (10).
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Autoimmune Disease
There is considerable evidence to show vitamin D may inhibit the development of autoimmune conditions.
Autoimmune conditions involve the immune system mistakenly attacking and destroying body tissues, instead of an invading pathogen.
This kind of response is under the control of specific immune cells, called T cells.
Vitamin D is now known to have a controlling influence on T cells, diminishing the autoimmune response.
Vitamin D deficiency seems to be involved in several autoimmune conditions including Type 1 diabetes (11), multiple sclerosis (12) and rheumatoid arthritis (13).
Supplementation with vitamin D has been shown to reduce the risk of Type 1 diabetes (14).
The clinical significance of supplementing vitamin D in other autoimmune conditions is not entirely clear, but based on the functions of vitamin D its interaction within the immune system, restoring deficiencies and maintaining an adequate vitamin D status may contribute to a reduction in the risk of developing disease.
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Cancer
There seems to be a clear link between vitamin D and cancer.
It has long been understood that people living in higher latitudes are more at risk of developing chronic diseases, including cancer (15,16,17).
Vitamin D is known to have regulating actions involved in cancer development, including cell proliferation and differentiation.
This may in effect reduce cancer cell growth and ‘kill off’ cancer cells (18).
In one study women with good vitamin D levels were 50% less likely to develop breast cancer (19).
The evidence in colon cancer is more compelling and a meta-analysis showed lower incidences of colon cancer with increasing vitamin D levels (20).
Studies show that survival in colon cancer is also linked to vitamin D status and risk of death from colon cancer may be reduced by 35% with higher vitamin D status (21).
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Cardiovascular Disease
There may be a link with vitamin D status and the risk of cardiovascular disease.
Vitamin D affects many actions in the body related to the development of cardiovascular issues including inflammation (22), calcium balance (calcification is a common occurrence in atherosclerosis) and blood pressure regulation (23).
Several studies have indicated that low vitamin D status may negatively affect blood pressure (24,25) and that supplementation to restore levels benefits blood pressure (26).
A 2003 study indicated that vitamin D deficiency in young adults may give rise to a greater risk of congestive heart failure (27).
Men with low vitamin D status have a higher risk of heart attack and other cardiovascular events compared to men with an adequate vitamin D levels (28,29).
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Neurodegenerative Conditions
Evidence is showing that vitamin D deficiency, or disruption to its metabolism, may be involved in degeneration of neurons which may lead to impaired cognitive functioning (30).
This link has led to some researchers postulating that the development of conditions like Alzheimer’s may be partly due to a long term vitamin D imbalance.
Studies do seem to indicate that low vitamin D levels are associated with dementia and Alzheimer’s (31).
In a memory clinic setting, outpatients who had supplemented with vitamin D to correct an underlying deficiency, saw improvements in several areas of cognitive function, including working memory, emotional control and problem solving (32).
The development of Parkinson’s is also associated with vitamin D status (33) and supplementation with vitamin D was shown to limit progression of the condition compared to placebo (34).
Vitamin D deficiency is surprisingly common.
Due to the fact that vitamin D influences many processes and systems this has wide ranging health implications.
Ensuring an adequate vitamin D level may be vital for preventing the onset of many health conditions, particularly with advancing age.
If you would like to know more about vitamin D, your levels and your health, guidance from an Amchara Personalised Health practitioner could be beneficial.
We’re dedicated to providing you with both insightful information and evidence-based content, all orientated towards the Personalised Health approach.
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