Why all the hype about vitamin D?

Craig Sinclair – Chair of Australia’s Public Health Committee and Director of the Prevention Division at Cancer Council Victoria

Published 30 May 2013

Craig Sinclair

Vitamin D is a hormone that controls calcium levels in the blood; crucial for bone and muscle development, and in the prevention of osteoporosis. Vitamin D deficiency may not result in any obvious symptoms, but without treatment it can have significant health effects and increase a person’s risk of musculoskeletal conditions such as:

  • Bone and muscle pain
  • Rickets (soft, weakened bones) in children
  • Osteopenia (weak, fragile bones – also known as osteomalacia or osteoporosis) in older adults.

There have also been links between low vitamin D and an increased risk of bowel cancer, heart disease, infections and auto-immune diseases, although more research is needed to determine whether increasing vitamin D levels can prevent these conditions.

Who’s at risk?

Sun exposure alone may not be a sufficient source of vitamin D for some sections of the population, particularly during the winter months. Those most likely to be at risk of vitamin D deficiency include:

  • People with naturally very dark skin
  • People with little or no sun exposure such as:
    • Older adults – especially the frail, who are in medium to long-term residential care, aged care or are housebound
    • People who wear covering clothing for religious and cultural reasons
    • People who deliberately avoid sun exposure for cosmetic or health reasons
    • People hospitalised or institutionalised for long periods
    • People with a disability or chronic disease that reduces their mobility
    • People in indoor occupations such as office workers, factory workers or night-shift workers.
  • Breastfed babies who fall into the risk categories above or have mothers with low vitamin D. Breast milk contains little vitamin D and infants depend on maternal stores initially. (Formula milk is fortified with vitamin D).
  • People with medical conditions or medications affecting vitamin D metabolism include obesity, end-stage liver disease, kidney disease, conditions that cause fat malabsorption (such as cystic fibrosis, coeliac disease and inflammatory bowel disease) and use of some drugs that increase the breakdown of vitamin D (such as rifampicin and some anticonvulsants).

When is supplementation needed?

Ultraviolet (UV) radiation from the sun is the best natural source of vitamin D and so a balanced UV exposure approach is often satisfactory. There are small amounts of vitamin D in some foods such as fish and eggs. Food however, only makes a small contribution (approximately 10%) to the body’s overall vitamin D levels and it is difficult to get enough vitamin D from diet alone.

For population groups at risk of low vitamin D, levels can be checked via a simple blood test and treated with supplements where required.

Sun exposure recommendations – getting the balance right

So how much sun is enough? The amount of UV exposure needed to maintain vitamin D levels depends on the time of year, location, skin type, day-to-day activity and individual circumstances.

SunSmart How much sun is enough map

When UV levels are low (below 3), get 2-3 hours per week of midday sun exposure. For example, in the southern parts of Australia, UV levels fall below 3 from May to August. At this time, most people need two to three hours of midday winter sun exposure to the face, arms, hands (or equivalent area of skin) spread over the week. People with naturally very dark skin, may require three to six times this amount of sun.

When UV levels are high (3 and above), get a few minutes of mid-morning or mid-afternoon sun exposure each day. UV levels are 3 or above for much of the day from September to April in the southern parts of Australia, and all year round in the north. When UV levels reach 3 and above sun protection is required. At this time, most people need just a few minutes of mid-morning or mid-afternoon sun exposure to the face, arms, hands (or equivalent area of skin). People with naturally very dark skin, may require three to six times this amount of sun. People with naturally very dark skin may not need to wear sunscreen, but should still protect their eyes from the sun, with sunglasses and/or a hat.

Does sunscreen hinder vitamin D absorption?

Sunscreen use whenever UV levels are three and above should not put people at risk of vitamin D deficiency. When sunscreen is tested in lab conditions it is shown to decrease vitamin D production, however regular use in real life has been shown to have little effect on vitamin D levels. This is probably because people who use sunscreen spend more time in the sun, so naturally they will have higher vitamin D levels.

Vitamin D Resources for clinical settings

SunSmart has a number of resources to assist medical professionals to confidently identify and treat patients low or deficient in Vitamin D.

A vitamin D tracker and sunscreen calculator tool are available at sunsmart.com.au and on the free SunSmart smartphone app. The tracker allows GPs to examine the sun exposure patterns of their individual patient/profiles to determine their vitamin D recommendations.

Also available are two new educational tools designed to provide GPs and other health professionals with increased knowledge and confidence to address sun exposure, Vitamin D and skin cancer prevention. A 15 minute expert video presenting a balanced message on vitamin D and sun protection and a one hour educational activity are also available.

More information available at: sunsmart.com.au/vitamin_d