According to a 2012 national population-based study of Australians aged 25–95 years, 73 per cent of the population had vitamin D levels that were below the ideal range according to blood levels, with nearly one-third of the population being deficient and four per cent of the population having a severe vitamin D deficiency.
Alongside this, the prevalence of deficiency was more common among women than men and vitamin D status also decreased with age. This study also found that levels of vitamin D decreased greatly during winter and spring, with 58 per cent of women and 35 per cent of men in southern regions of Australia being deficient during this time.
With many of us thinking that we are going to get all the vitamin D we need from the sun this may not be the case, with many of us living and working indoors more now than ever before. From October to March, 10–15 minutes of unprotected sunlight exposure to 15 per cent of the body outside of the hours of 10am to 3pm, 2–3 times per week is sufficient for adequate synthesis of vitamin D. However, due to lowered levels of sunlight between March and October, up to one hour is required to maintain adequate vitamin D synthesis during the cooler months. However the above statistics reflects that we are struggling to reach this amount of time outdoors.
Due to the primary source of vitamin D being through sunlight exposure, reduced sunlight experienced during winter – particularly in Victoria – reduces the levels that your body will be able to produce and therefore your vitamin D status may be diminished. For this reason, testing of vitamin D levels prior to winter is extremely important to ensure you are aware of, and maintaining, your levels throughout the cooler months as needed.
Doctors often refer to having ‘optimal’ levels of vitamin D when concentrations within the blood are within the reference range. But studies have indicated that even levels within this range can result in deficiency symptoms and impaired vitamin D functioning within the body. For this reason, it is important to ensure your levels are considered to be within the ideal range of >100nmol/L to optimise body function and prevent associated deficiency conditions.
Groups at higher risk of vitamin D deficiency:
· people who avoid dairy and processed foods (sources of fortified vitamin D)
· people who are unable to attain sunlight exposure
· dark-skinned individuals
· pregnant women
· elderly people
· people with malabsorption conditions such as: irritable bowel syndrome, Crohn’s disease and ulcerative colitis
Vitamin D plays a number of import roles within your body which enable normal functioning of a range of metabolic and physiological functions. Insufficient levels of this nutrient can result in disruption to these functions, leading to detrimental effects on our health and also giving rise to various disease states, particularly related to our immune system.
A number of studies have found links between vitamin D deficiency and adverse health outcomes such as cardiovascular disease, autoimmune diseases, diabetes, cancer and an increased risk of mortality. Vitamin D has been shown to be particularly beneficial for our immunity, our fertility and during pregnancy and for our musculoskeletal system.
(1) Hechtman, L. 2012, Clinical naturopathic medicine, Elsevier Australia, Chatswood
(3) Braun, L. & Cohen, M. 2010, Herbs & natural supplements: An evidence-based guide, Elsevier Australia, Sydney
(5) Gropper, S. & Smith, J.L. 2016, Advanced nutrition and human metabolism, 6th ed Wadsworth, Cengage Learning