The importance of vitamin D to our health remains a hot topic in research, and I understand that it can be confusing to know whether a vitamin D supplement or sunlight is best. I aim to answer recent questions that I have received about how much sun is required, skin cancer risk and supplement dosage.

Why do we need vitamin D?

Just recapping from my earlier post on vitamin D—this vitamin plays a role in the regulation of calcium and phosphate in the body, bone density and longevity. There is good research evidence supporting the role of vitamin D in reducing falls and bone fractures, as well as reducing all cause mortality.

Vitamin D is also thought to play a role in boosting our immune system, insulin action and preventing a number of chronic diseases, but further research is required to prove that there is a causal link to Vitamin D levels.

Do you need a vitamin D supplement?

Your healthcare practitioner may recommend a vitamin D supplement if your blood levels of vitamin D are below 50 nanomoles/litre (nmol/L) at the end of winter, or below 75 nmol/L at the end of summer. The blood test for vitamin D measures the level of 25-hydroxyvitamin D. This is the precursor to the active form of the vitamin, which is called 1, 25-hydroxyvitamin D, or Vitamin D3.

The 50 nmol/L value comes from research showing that the risk of falls and bone fractures increase below this level of vitamin D. A higher level is recommended at the end of summer because it will offset the effect of less sun exposure during winter. Vitamin D produced during summer can last up to 6 months.

Your healthcare practitioner will recommend the vitamin D supplement dosage. Vitamin D is often taken at a dose of 1000 IU (international units), but the dosage is dependent upon your blood levels. The supplement may take around 3 months to increase the level of vitamin D in the blood. This varies between individuals. I am also aware that some people taking a vitamin D supplement experience a plateauing of the vitamin D level in their blood. If you have any questions or concerns about your vitamin D supplement, then I highly recommend that you discuss them with your healthcare practitioner.

How much sun do you need to make vitamin D?

I can understand the confusion about whether to have time in the sun or not. We have been well educated in Australia about the risk of skin cancer, and have become wary of bearing our skin outdoors. Guidelines have been developed to meet our requirements for vitamin D, and also the prevention of skin cancer.

The sun exposure map will guide you on the amount of sunlight you require in winter and summer depending on where you live in Australia, and whether you have fair or dark skin. During summer the best times for sunlight exposure are just prior to 11am and just after 3pm. In winter, sun exposure at midday is recommended to maximise vitamin D production. People with fair skin require less time in the sun.

The UV index advises you on the amount of sun protection you require at different times during the day. A UV index of 3 or above can lead to skin damage and increase your risk of skin cancer. There are now websites and apps available to help you decide what’s required to reduce your risk.

Research indicates that sunlight may improve health and wellbeing via other mechanisms other than vitamin D. Sunlight improves our mood, decreases blood pressure, suppresses the immune system and helps regulate melatonin, which aids sleep.

Does sunscreen effect vitamin D production?

Research has shown that a thick layer of sunscreen reduces vitamin D production, but it has no adverse effect on levels of vitamin D in the blood. So don’t skip the sunscreen if you are concerned about vitamin D.

Further research studies are required to better understand the role of vitamin D in health and wellbeing. More studies are also needed to assess the impact of supplementation and sunlight exposure on levels of vitamin D in the body. In the mean time, do your best to follow the sunlight exposure guidelines, and speak to your healthcare practitioner if you are concerned about the health of your skin or your vitamin D levels. Have regular skin checks too, as advised by your practitioner.