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Craig Sinclair

Craig Sinclair

Director of Cancer Prevention
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Adequate vitamin D over winter

Experts — Posted 29/07/13

Keeping our vitamin D stores up during the winter months has a range of health benefits for our bones and muscles.

The sun's ultraviolet (UV) radiation is the major cause of skin cancer and the best source of vitamin D; essential for strong bones and overall health. It is important to take a balanced UV approach to help with vitamin D levels while minimising the risk of skin cancer.

Our bodies only store enough vitamin D to last between 30 and 60 days so some people who don’t get outside in the sun much during winter are at risk of having their vitamin D levels depleted over the colder months.

Sun exposure alone may not be a sufficient source of vitamin D for some sections of the population. Those most likely to be at risk of vitamin D deficiency include people with naturally very dark skin, individuals with little or no sun exposure including those that are housebound or institutionalised, those who wear concealing clothing for religious or cultural purposes, breastfed babies whose mothers are vitamin D-deficient and people with conditions or medications affecting vitamin D metabolism.

Low levels of vitamin D may have no obvious symptoms but without treatment, can have significant health effects. Vitamin D is crucial for bone and muscle development and in the prevention of osteoporosis. Low vitamin D and deficiency also causes bone and muscle pain, poor bone mineralisation (softer bones) leading to rickets (bone deformity) in children and osteomalacia in adults. There have been links with an increased risk of bowel cancer, heart disease, infections and auto-immune disease, although more research is needed for any conclusive evidence to be derived.

During summer, in the southern parts of Australia and all year round in the north, most of us need only a few minutes a day of mid-morning or mid-afternoon sun exposure to the face, arms and hands (or equivalent area) to help with vitamin D levels. Be extra cautious in the middle of the day when UV levels are most intense. People with naturally very dark skin may need 3-6 times this amount.

Regular use of sunscreen does not greatly decrease vitamin D levels over time. When sunscreen is tested in lab conditions it has been 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 more sunscreen spend more time in the sun, so naturally will have higher vitamin D levels and most people apply far less sunscreen than is recommended by manufacturers.

During winter, in the southern parts of Australia where UV radiation levels are below 3 all day, most of us need about 2-3 hours of midday winter sun exposure to the face, arms and hands (or equivalent area) spread over each week. The more skin you have exposed to the sun, the more vitamin D you’ll make, so roll up those sleeves. Keep yourself warm by walking fast or jogging. Daily exercise will assist your body with production of vitamin D.

Sun protection is not required unless near highly reflective surfaces such as snow, outside for extended periods or when the UV reaches 3 and above.

If you are worried that you do not get the recommended dose of sunshine during winter, visit your GP. Levels can be tested with a simple blood test and low levels can be treated with supplements.

Extra   For more information or to track your sun exposure for vitamin D using the free SunSmart app visit
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