Vitamin D Deficiency Epidemic in Australia

Is There a Vitamin D Deficiency Epidemic in Australia, and if So, Is This a Major Contributing Factor to Disease and is vitamin D3 the new super nutrient? A summary of evidence.

 Russell Setright

Abstract

A review of published studies found that a significant number of Australians and New Zealanders have less than optimal serum vitamin D levels, with mild to moderate deficiency ranging from 33 to 84% depending on age, skin colour and/or those in residential care.

These studies have also reported a significant relationship between low vitamin D status and an increase in the prevalence of diseases including; diabetes, CVD, metabolic syndrome, osteoporosis, hypertension, certain cancers, several autoimmune diseases the Flu and all cause mortality. The data also suggest that normalising blood 25(OH)VitD levels by supplementation with vitamin D3 may have a positive effect in disease prevention.

Background

Ecological studies have suggested that mortality from several potentially life-threatening chronic diseases increase in incidence with a decreased exposure to sun light (Grant WB. Ecologic studies of solar UV-B radiation and cancer mortality rates. Recent Results Cancer Res. 2003;164:371-377) Because sun exposure is necessary for the synthesis of vitamin D in the skin, this review will show that the associations found between sun exposure, vitamin D intake and mortality(death) from several chronic conditions could be owing to variations in vitamin D status.

There are two forms of vitamin D that are important in humans: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Vitamin D2 is synthesized by plants and obtained by humans through diet. Vitamin D₃ is made in the skin when 7-dehydrocholesterol reacts with ultraviolet-B (UVB) rays from sunlight at wavelengths between 270–300 nm and stored in the blood as calcidiol (25-hydroxy-vitamin D). Both D2 and D3 precursors are hydroxylated in the kidneys and liver to form 25- hydroxyvitamin D (25(OH)vit.D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D. 1,25 (OH)2D, the biologically active (hormone) form that is tightly controlled by the body.

One of the functions of vitamin D is to maintain normal blood levels of calcium and phosphorus which helps form and maintain strong bones.

However, research also suggests that increased blood levels of 25(OH)VitD may provide protection from CVD, diabetes, osteoporosis, hypertension, certain cancers, and several autoimmune diseases.

The sun is a significant contributor to our daily production of vitamin D3. However, the amount of sun exposure required to produce enough vitamin D3 is dependent on a number of factors including, skin colour, latitude, types of clothing, body mass, age, cloud cover, atmospheric pollution. 

In Australia we are exposed to around 40% more UV rays than the equivalent latitude in the Northern Hemisphere and this creates a dilemma

(Madronich S, et al. Changes in biologically active ultraviolet radiation reaching the earth's surface. Photochem Photobiol B 1998;46:5-19).  

Is this increased UV exposure in the Southern Hemisphere and the resulting skin sun damage more detrimental to overall health than vitamin D deficiency?

There is evidence that excessive sun exposure increases the risk of skin damage, ageing and skin cancers. Excessive exposure to sunlight causing sunburn at any time in life increases a person's risk of developing skin cancer. However, people who experience intermittent exposure to high levels of UV radiation such as tanning on the beach on the weekend, appear to be at greater risk while those who experience continual exposure to lower levels even if the total dose of UV radiation is the same, have the lowest incidence of melanoma. That is, non-burning regular sun exposure such as obtained in the early morning and later in the afternoon seems to have a protective effect against skin cancer (Article, Prevention & Early Detection, Memorial Sloan-Kettering Cancer Centre 2008). And, a moderate amount of unblocked sunlight may actually be beneficial to most people, and could reduce the risk of many other diseases – including, paradoxically, melanoma itself.

Another example of this paradox is research from the University Of California School Of Medicine. This study found that higher incidence of melanoma occurred among Navy desk workers than among sailors who worked outdoors (Garland FC. et al. Occupational sunlight exposure and melanoma in the U.S. Navy. Arch Environ Health. 1990 Sep-Oct;45(5):261-7).

Also, a study (Nürnberg B, et al. 2008) from the Department of Dermatology, The Saarland University Hospital, Homburg, Germany that examined the progression of malignant melanoma reported. Basal 25-hydroxyvitamin D levels were lower in melanoma patients as compared to the control group. And progression of malignant melanoma was associated with  significantly reduced 25(OH)vit D serum levels. Their findings add to the growing body of evidence that 25(OH)vit D serum levels may be of importance for pathogenesis and progression of malignant melanoma (Nürnberg B, et al. Progression of malignant melanoma is associated with reduced 25-hydroxyvitamin D serum levels.Exp Dermatol. 2008 Jul;17(7):627).

As, the growing body of evidence supports the theory that  low blood serum levels of 25(OH)vit D is also associated with an increase of many diseases including CVD, diabetes, certain cancers, osteoporosis, muscular and bone strength and death from all causes

(Dobnig H, et al. Independent association of low serum 25-Hydroxyvitamin D with all cause mortality. Archives of Internal Medicine. 2008 Jun 23;168:1340-1349).

 A strategy of timed low dose sun exposure needs to be developed to maintain adequate vitamin D levels. However, given the vast difference in geographical location, skin type and ethnic origin we have in Australia a “One Fits All” program would be improbable.

As the data are supportive of maintaining adequate serum vitamin D levels, while at the same time reducing the risk of overexposure of UV rays from the sun.

Supplementation with vitamin D3 may be the best way of achieving both goals.

Vitamin D deficiencies in Australia

The data are consistent in that low blood serum levels of 25(OH)VitD (25-hydroxyvitamin D) is at an alarming rate in Australia. Those people with dark or olive skin, the elderly and veiled (80% may have mild deficiency) as well as those who wear protective clothing and always use sun screen have the greatest risk of vitamin D deficiency (FIG 1). In addition, those taking anticonvulsant medication or suffer from renal, hepatic or cardiopulmonary disease or those who have fat malabsorption syndromes (e.g., cystic fibrosis) or inflammatory bowel disease such as Crohn's disease, are at risk.  (Vitamin D, National Health and Medical Research Council 2010, Ministry of Health. Australian Government).FIG. 1

2: Proportion of women with serum vitamin D (25-hydroxyvitamin D3) levels under 22.5nmol/L, according to skin covering and skin colour
		Skin colour
Skin covering*	Very dark	Intermediate	Light	Total
Consistently covered	6/6 (100%)	1/2 (50%)	23/25  (92%)	30/33  (91%)
Inconsistently covered	3/5 (60%)	1/3 (33%)	18/24  (75%)	22/32  (69%)
Uncovered	2/2 (100%)	2/3 (67%)	0 (0)	4/5 (80%)
Total	11/13 (85%)	4/8 (50%)	41/49  (84%)	56/70  (80%)
*Consistently covered - women always covered up, including arms, hair and neck, when outdoors; inconsistently covered - women did not usually cover fully in their own garden; and uncovered - women did not generally cover their arms, hair and neck when outdoors.

Nozza J et al. MJA 2001; 175: 253-255

What are Serum 25(OH)VitD Norms?

It has already been established that low serum levels of vitamin D that is below 27.5nmol/Lt results in inadequate

mineralisation / demineralisation of the skeleton that is a contributing factor to rickets in young children.  (Vitamin D, National Health and Medical Research Council 2010, Ministry of Health. Australian Government) . In  a position statement, a Working Group from the Australian and New Zealand Bone and Mineral Society, the Endocrine Society of Australia and Osteoporosis Australia (2005) defined mild deficiency for adults as serum 25-OHvitD levels between 25 and 50nmol/L which may contribute to an increased risk of osteoporosis and less commonly  osteomalacia in adults (NHMRC).

The question often asked is, what blood serum 25(OH)VitD level is considered to be adequate?

Any level below 50nmol/Lt may also place an individual at high risk of vitamin D associated deficiency diseases and all cause mortality. Levels of vitamin D between 73 – 100 nmol/Lt would appear to be adequate.

One Prospective cohort study of 3258 consecutive male and female patients found that those with low levels of serum vitamin D had a 54% to 2.34 times increased risk mortality from any cause when compared to people with adequate levels  of around 72nmol/Lt. (Fig. 2)

Also, this study found that 25-hydroxyvitamin D levels that are in the lower 50% of the vitamin D range of the study population have an increased risk for all-cause mortality after adjustment for traditional cardiovascular risk factors. In subgroup analysis, the relationship of low 25-hydroxyvitamin D levels to mortality is consistent regardless of co-morbidity, physical activity level.

The researchers concluded that a low 25-hydroxyvitamin D level can be considered a strong risk indicator for death from any cause in men and women (Dobnig H, et al. Independent association of low serum 25-Hydroxyvitamin D with all cause mortality. Archives of Internal Medicine. 2008 Jun 23;168:1340-1349).

25(OH)VitD blood levels

(Dobnig H et al 2008)

Fig. 2    

25(OH)VitD Status	nmol/Lt
Deficient Highest Risk	‹ 37.4
Deficient High Risk	37.4 - 50
Insufficient Moderate Risk	50-72
Adequate Low Risk	›73