By Daniel Roytas MHSc (Nut), BHSc (Nat), Dip. RM, MANTA
Despite living on the sunniest continent on Earth1, 25% of all Australians are thought to be vitamin D deficient2. Rather than acquiring vitamin D from sensible amounts of sun exposure to maintain optimal levels of vitamin D, it seems the Australian public have turned towards supplementation instead. As of 2010, there were 89 vitamin D manufacturers selling 195 different vitamin D products in Australia. Almost 60 million vitamin D products were sold that year, totalling an eye watering $89.3 million3. Why is all of this money being spent on something that we can literally get for free, right outside our front door?
Could it be that the public health initiatives around sun safety have worked too well? A 2011 paper published in the Medical Journal of Australia found that it is relatively difficult to obtain the equivalent of just 1000 IU (1 capsule worth) of vitamin D from sun exposure when adhering to sun smart recommendations4. Whilst these recommendations have been developed with the best intentions, they have driven unnecessary fear in to the hearts and minds of the Australian people, so much so, that many young people are afraid of going out in to the sun5. It is important to mention that whilst sensible amounts of sun exposure are beneficial, prolonged periods or excessive exposure are damaging to human health.
Dr. Robyn Lucas, an epidemiologist at the National Centre for Epidemiology and Population Health in Canberra stated in a 2008 article published in the Journal of Environmental Health Perspective that diseases arising from excessive sun exposure are usually benign and typically occur in older people6. She went on to say that despite their high prevalence, skin cancers are associated with a relatively low burden of disease6. In that same paper, Dr. Alberto Ascherio an epidemiologist from the Harvard School of Public Health stated that moderate sun exposure (believe it or not) is more beneficial for human health than trying to avoid it6. In fact, sun exposure is associated with protective effects against cardiovascular disease, type 2 diabetes, Alzheimer’s disease, multiple sclerosis7, prostate, breast, colorectal8 and other gastrointestinal cancers9. These beneficial effects are due to mechanisms beyond the stimulation of vitamin D synthesis8, which supports research suggesting UV exposure is superior to vitamin D supplementation at reducing the risk of disease10.
Ultraviolet-B radiation exposure (UV-B) from sunshine is the principle source of vitamin D in humans11. One whole body minimum erythema dose (faint skin redness) can generate the equivalent dose of 10 000 – 25 000 IU12. Just 7 minutes of sun exposure outside of the hours of 10 am – 3 pm in Summer and between 7 – 40 minutes at midday during Winter, is sufficient to maintain adequate vitamin D levels when at least 15% of the skin (arms and hands) is exposed13. Therefore, a low vitamin D level might be a good indicator of an individual’s lifestyle habits. That is, that they are spending too much time in doors and not enough time outdoors in the fresh air, enjoying the sun. It is worthwhile to note that UV-B radiation does not penetrate glass, so exposure to sunshine indoors through an office window does not increase vitamin D levels14.
This is probably a good time to mention that vitamin D, isn’t actually a vitamin, it is a pleiotropic steroid hormone15. We shouldn’t let the word “vitamin” fool us. Ask yourself, what other hormone do you take religiously every single day, without a second thought about the potential effects it’s having on your health? It is responsible for the regulation and function of more than 1000 different genes and governs basically every single tissue in the body6. It is not known precisely how many genes vitamin d actually regulates and what the true effect of the supplemental vitamin D on our genes is. Our body and the sun have worked this complex inter-relationship out over millennia, however the reality of the matter is that we have no idea what’s really occurring at a genetic level with supplementation. It defies belief that we could be so naïve to think that a synthetic vitamin manufactured in a laboratory (or other exogenous forms) and crammed in to a soft-gel capsule with various other excipients, could take the place of an endogenously produced substance that is formed by a reaction catalysed by the sun. The human body shares an innate relationship with the sun, something not even the wonders of modern medicine may ever come to fully comprehend.
Many readers may not be aware of this, but before vitamin D was popularised as a supplement for humans, it was (and still is) used as the main active ingredient in many commercially available rat poisons and possum baits, albeit at very high doses16. In high doses, vitamin D has also been shown to be lethal to dogs, cats and birds16. How can we be absolutely sure, that even at the ‘recommended dose’, vitamin D supplements are not having potentially long term, deleterious effects on our health? The mechanism by which vitamin D toxicity causes death, is by inducing hypercalcemia via increasing calcium absorption from the small intestine, increasing calcium mobilisation from bones and by inhibiting renal calcium excretion16. In humans, vitamin D toxicity induced hypercalcemia results in systemic calcification of soft tissue, leading to renal failure, cardiac abnormalities, hypertension, central nervous system depression, and gastro-intestinal dysfunction17. It should be noted that the reports in the literature of vitamin D toxicity are not common.
Serum levels of vitamin D (specifically 25(OH)D) plateau at around 150 nmol/L in response to sun light (UV-B) exposure. This is an in-built self-defense mechanism that prevents sun induced vitamin D toxicity as UV-B prevents excessive cutaneous pre-vitamin and vitamin D production18. Therefore vitamin D toxicity can only be caused by the prolonged ingestion of fortified food and supplementation at high doses over prolonged periods of time19. There are numerous reports of errors in food fortification of vitamin D, where individuals were exposed to excessive levels of vitamin D leading to toxicity20. For example, a New Zealand study found that only 8 out of 14 products had vitamin D levels within 10% of the listed label dose21. A US study found that only a third of all capsules analysed in the study contained vitamin D levels within 10% of the listed dose22. Discrepancies between the listed dose and the actual dose of a range of supplements are responsible for many cases of toxicity reported in the literature. Furthermore, as vitamin D supplements are readily available over the counter, there is a risk for consumers to inappropriately self-medicate which could lead to toxicity, particularly when there is already adequate sun exposure and consumption of fortified foods23.
Vitamin D is commonly prescribed to patients with vitamin D deficiency, however vitamin D supplementation in such individuals may not necessarily address the underlying cause, and could be equated to putting a band-aid on a gaping wound. In fact, despite vitamin D deficiency being implicated as the cause of disease, there is scant evidence elucidating the pathogenesis24,25. It has been proposed that vitamin D deficiency is a direct consequence of disease and not a cause of illness26. In fact, vitamin D deficiency may be a marker of deteriorating health, ageing and inflammation, which explains why deficiency could be observed in a wide range of disorders24,27,28.
Some evidence actually suggests that a chronic inflammatory process caused by persistent bacterial infections24,29 and chronic disease28 may be the cause of low vitamin D. Paradoxically, whilst inflammation reduces vitamin D levels, supplementation seems to have a negligible effect on ameliorating inflammation24,27. There is also some evidence indicating that vitamin D could actually up-regulate inflammation24,29. This is analogous to throwing timber on a raging fire. We know that the body has a self-defence mechanism, where during states of inflammation and infection, it sequesters iron inside the tissue to prevent excessive levels of oxidative stress30. Could it be, that a similar mechanism exists with vitamin D and we have been adding fuel to the fire this whole time through supplementation without realising it? The other train of thought, is that a low vitamin D might actually be an indicator of absence of disease, however further research is required24.
Furthermore, it has been postulated that adiposity accounts for the lower vitamin D levels seen in overweight & obese individuals due to its sequestration within excess adipose tissue31. With 30% of the Australian population now obese and 67% overweight32, could this be one reason why there is high prevalence of vitamin D deficiency in Australia?2.
Medicare funded Vitamin D testing is an interesting topic. In 2010, it was reported vitamin D testing cost Medicare $96.7 million, a 95-fold increase compared to the amount spent a decade earlier33. Incredibly the cost peaked at $151 million in 201234, which dwarfs the $12.7 million worth of funding by the Australian Government to Cancer Australia that same year35. Consequently, vitamin D testing was restricted to specific, at risk population groups the following year to reduce the expenditure as the cost-benefit analysis did not support widespread use of this test as it is of low clinical value34. Where has the need for such testing come from?
Understanding the true nature of deficiency is complicated by the fact that vitamin D tests may not be as accurate as we think. Despite the dramatic increase in vitamin D testing, there is considerable uncertainty about the accuracy of these tests36. A report presented at a conference of the Endocrine Society in 2012 stated that at least 40% of all vitamin D tests are inaccurate37. Furthermore, there is no agreement amongst peak regulatory bodies around what actually constitutes vitamin D deficiency24, nor what the optimal serum concentrations should be38. How then, as practitioners, do we interpret the results of a test in a clinically meaningful way?
Surely, despite all of the aforementioned data presented here, there is still a place for vitamin D to be prescribed for patients with a frank deficiency? One of the most common reasons vitamin D is prescribed is in order to reduce the risk of osteoporosis and associated fractures by improving bone mineral density39. Despite commonly held perceptions by clinicians, there is in fact, little evidence to support the use of vitamin D in such cases. A considerable number of systematic reviews and meta-analyses investigating the musculoskeletal effects of vitamin D supplementation have found that it provides very little or no clinically significant benefit (with or without calcium supplementation) in improving bone mineral density or reducing fracture risk40–46. A 2020 paper published in the Journal of Bone and Mineral Research found that long term, high dose vitamin D supplementation actually reduces bone mineral density and muscle strength in postmenopausal females47, the very population group that vitamin D is promoted to protect.
It’s time to get people back out in to the sun and to throw those vitamin D pills in the bin on their way out of the house.
Note: This article is for general information purposes only. It does not constitute as health advice and does not take the place of consulting with your primary health care practitioner.