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Is it time to shine for vitamin D? – by guest expert Tim Crowe

Vitamin D is attracting more than its fair share of attention in both the scientific and public spotlight. Long known for its role in keeping bones healthy, there is a growing list of health benefits being linked to this so called ‘sunshine vitamin’. Sorting the health from the hype can be a little tricky…that’s why we asked our latest guest to give us the Scoop.

About our expert

Associate Professor Tim Crowe is based in the School of Exercise and Nutrition Sciences at Deakin University and is also an Accredited Practising Dietitian. Tim teaches about the role of nutrition in disease prevention and management, particularly diabetes and cancer. His research areas include specialised nutrition in the prevention of surgical complications, malnutrition and nutrition support in wound healing. He is very active in the media and also writes for many magazines and websites. Checkout his nutrition blog and connect with him on Twitter @CroweTim

The list of disease links to vitamin D is long and includes diabetes, cardiovascular disease, multiple sclerosis, obesity, autoimmune diseases, cancer, respiratory diseases, and even some mental health conditions such as schizophrenia. The field of research is fast-moving so it is hard to determine where the truth may lie.

As most of you probably know, vitamin D is one of those rarer nutrients where only a few foods contain it. Fortunately, we can make all we need from sun exposure, which makes up more than 80 percent of the vitamin D in our body.

Despite our sunny climate, vitamin D deficiency is now considered a major public health issue in Australia and New Zealand. Groups such as the housebound, community-dwelling older people, disabled people, those in residential care, dark-skinned people (particularly those modestly dressed), and people who regularly avoid sun exposure or work indoors are all at risk of developing deficiency. Infants born to deficient mothers are also a serious concern.

Bone and Muscle Health

The most clearly established role of vitamin D is to keep calcium and phosphate levels in balance, and with that comes healthy bones and good muscle function. Severe vitamin D deficiency causes impaired bone mineralisation, resulting in rickets in children and osteomalacia in adults. Osteomalacia results in bone and muscle pains, and an increased risk of fractures.

It is not just healthy bones that vitamin D helps with. Muscle has specific receptors for vitamin D which promote muscle protein synthesis and muscle growth. Vitamin D deficiency can affect a person’s balance which if combined with poor muscle strength, puts a person at greater risk of falling and potentially a life-threatening bone fracture.

Source: via Emma on Pinterest



A role for vitamin D as a potential agent in the prevention of cancer is an emerging area of research. A higher risk of developing and dying from three of the most common cancers seen in western countries (breast, prostate and colon cancer) has been linked with living at higher latitudes, likely because of the result of reduced exposure to sunlight. Observational studies of large groups of people followed over time also point to a link between low levels of vitamin D and cancer. Although observational studies cannot prove a cause-and-effect relationship, the weight of evidence is growing and is pointing in the right direction.


The seasonal nature of influenza outbreaks is one that is not entirely understood by medical researchers. One interesting theory is that vitamin D could explain the connection, because influenza is more common in the winter during times of less sunlight.

Studies looking at vitamin D supplementation and the prevention of osteoporosis gave an interesting finding that people taking vitamin D supplements were three-times less likely to report cold and flu symptoms. Other studies have seen a correlation between low vitamin D levels and higher influenza risk. Providing higher quality evidence, a purpose-designed clinical trial found that children given a daily vitamin D supplement during winter were 42% less likely to become infected with seasonal flu compared to those who were given a placebo.

If the findings from the recent influenza research were confirmed in larger trials, it opens the door to an effective way to boost the immune system of people going into the flu season, especially those at greatest risk of being infected.


But wait there’s more….

Interest in vitamin D also extends to cardiovascular where rates of disease are higher in countries at higher latitudes, and during winter months where sunlight exposure is less. Vitamin D is also an important part of the body’s immune system, with low levels linked to autoimmune diseases including type 1 diabetes and multiple sclerosis.

Bottom line?

Despite strong correlations between vitamin D and a range of diseases, the latest research represents only a thumbnail sketch of the bigger picture. As scientists build upon this research, it potentially could mean a future where the sun is seen more as a friend than a foe – at least in small doses.

Vitamin D’s role in human health is diverse, ranging from its important role in bone health to more speculative roles such as cancer prevention. The promising findings from new areas of vitamin D research need to be tempered with the quality of research studies behind them until more definitive clinical trials are undertaken.

Considering that we rely on UV radiation, a known cancer causing agent, to synthesise the majority of our vitamin D, this creates a major public health dilemma of how to balance health benefits against disease risk. Adopting a food fortification policy, as seen in some countries, or wide-spread supplementation in at-risk groups may be the most practical measure to alleviate suboptimal vitamin D levels in many people today.

Editor’s comment:

Thanks Tim and congrats on your fantastic blog.  Scoop readers may also like our archive post on how to get the balance right with sun exposure.  I also love new vitamin D rich mushrooms……how about you lovely readers?  How do you get your D’s?  Do you have a question for our expert, Tim?

  • Di Munns

    Hi Tim, I know Vit D was not checked regularly on blood tests a while back but seems to be more common now with increased awareness of the potential problems you have outlined. What level or range is ideal? I often see levels just within range however I know a higher level is advised. I often refer a client back to their GP to discuss supplementation and because the level has just sraped through, the GP says it ‘s fine?? Please expand……Di Munns, APD

  • Hi Di – a serum 25-hydroxyvitamin D level ≥ 50 nmol/L at the end of
    winter (10–20 nmol/L higher at the end of summer to allow for seasonal
    decrease) is considered optimal – taken from a position statement published in MJA on vitamin D and health in adults which is free access

    A position statement for infants, children and adolescents has also just been published

  • Scott.

    Hi Tim. Those of us spending time in freezing conditions need to get Vit. D from something other than the sun. Do you have some recommendations?


  • Hi Scott – the ‘problem’ with dietary vitamin D is that you only find it in a limited range of foods such as oily fish (herring, mackerel, salmon), eggs, a small amount in dairy,
    and UV-irradiated mushrooms. For someone with either overt or sub-clinical deficiency who can’t get enough sun, then it does indicate the use of supplements

  • Trish

    I am recovering from breast cancer but I was told checking my vit D was not relevant. what should I ask in getting it checked and what is recommended each day as a supplement ?

  • Hi Trish – it would be best to get advice from your doctor regarding the need for testing of vitamin D levels and from there, if required, advice on the type and amount of vitamin D supplements (or injections) would be considered as there is no one generic answer to your question on this.

    Kind regards


  • EmmaStirling

    Great question Di

  • EmmaStirling

    HI Trish sorry to hear about your breast cancer. It’s possible that your medical team wanted you to focus on recovery for now and that vitamin D may have been seen to be a lower priority….but as Tim says it’s worth asking again as time goes on. You may also like to read our archive post on eating tips for cancer survivors that my good friend, oncology expert Dr Jane Read wrote for Scoop:

  • EmmaStirling

    Hi Tim I’m wondering if you could elaborate please on supplement dosage…I’ve heard of people taking mega doses of vit D for conditions like MS. We know with supps you can have too much of a good thing, what’s your advice?

  • Good question Emma. The Upper Level of Intake from the Nutrient Reference Values for vitamin D is set at 3200 IU/day (IU = International Units) – typical dosage in vitamin D supplements is 1000 IU so is well under this.

    Adults under 70 years of age need at least 600 IU/day and above 70 years it is 800 IU though of course both sun and food can provide this so does not mean that supplements are always needed.

    Interestingly, a monthly vitamin D single dose of tens of thousands IUs via injection or a single tablet of similar dosage have been used in some studies to give an ongoing level of protection without any adverse issues.

    Treatment of a diagnosed deficiency would aim to provide 3000-5000 IU per day for several weeks and for someone with deficiency, advice on dosage (which can vary over time once maintenance levels are factored in) should be from your doctor.

  • EmmaStirling

    Great thanks Tim

  • Brett Parker

    Hi Tim. Thank you for some great information. As a current N & D student at Griffith University and I am becoming more and more aware of Vit D deficiency in the public. I am also concerned about myself! If I am not in a class, i am at work, or at home studying. It’s ironic that in our sun drenched country we are often indoors these days, and then when we go out doors, we “slip, slop slap”!

    Regarding fortification of milk with Vitamin D. I read that it is mandatory to add vitamin D to milk in Canada under the Food and Drugs act. Do you think we are at such a stage in Australia, or should it remain voluntary for milk manufacturers? Interestingly too, I read that when fat is removed from full cream to produce skim milk during the separation process, vitamin A is lost. Thus in Canada is is mandatory to add vitamin A to skim milk. Do you have any thoughts on this?

    Thank you for your insightful article. Look forward to reading more in the future!

    Brett Parker

  • Thanks for your great comments Brett. Mandatory food fortification with vitamin D is increasingly being discussed at a public health level. In the face of now recognised wide-spread clinical and sub-clinical deficiency in many population groups (and will grow with an ageing population and migration from certain regions of the world such as sub-Sahara Africa and Muslim countries) then is something that I would be leaning to support, especially as evidence for its role in many diseases grows.

    Regarding your comment on vitamin A, I have no real strong views as is not really a ‘nutrient of concern’ in Australia. Vitamin A is found in many animal foods as preformed vitamin A and in fruits and vegetables as provitamin A so losing some in the processing of low-fat milk is not really a great issue that I lose much sleep over.

  • lovenutritionlivelife

    Great article Tim! Must say I learnt alot from a assignment in year 3 at Deakin during Diet and Disease we had to do back in the day on Vitamin D and the processes associated. Has helped me alot in my further study of Dietetics! Interesting article indeed and thank you for the fantastic post.


  • Thanks for the feedback Steph and pleased to read your past Diet and Disease work has proven fruitful ‘in the real world’ – we always aimed for everything presented in that unit to be as relevant to current evidence and practice as possible! Keep up the great work with your blog.

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