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10 February, 2010

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Vitamin D

Vitamin D plays an important role in helping the body to absorb calcium through the small intestine. Our bodies need calcium to help them develop and maintain healthy bones, muscles and teeth. Ultraviolet (UV) radiation from the sun is the best natural source of vitamin D.

Most people get enough vitamin D through exposure to sunlight during normal day-to-day outdoor activities. However, some people have very low levels of daily sun exposure. This can lead to low vitamin D and, in some cases, longer term deficiency.

It is important to remember that too much sun exposure can increase the risk of skin cancer. You need to find a sensible balance between sun exposure and protection.

There are very small amounts of vitamin D in some foods and drinks, but it is difficult to get enough vitamin D from diet alone. Only a few foods (such as fish and eggs) naturally contain vitamin D. Margarine and some types of milk have added vitamin D, but most people only get 10–25 per cent of their vitamin D from food.

Health effects of low vitamin D
Low vitamin D and vitamin D deficiency may have no obvious symptoms but, without treatment, they can have significant health effects. They can increase a person’s risk of musculoskeletal conditions such as:

Bone and muscle pain
Rickets (soft, weakened bones) in children
Osteomalacia (weak, fragile bones) in older adults.

Low vitamin D also contributes to osteoporosis.

Vitamin D deficiency has recently been linked to various types of cancers (particularly colon cancer), heart disease, stroke, altered immunity and autoimmune diseases; however, more research is needed to confirm this link.

At-risk groups
People who are at risk of low vitamin D and deficiency include:

People with naturally very dark skin. The pigment in skin (melanin) acts as a filter to UVB (Ultraviolet B) radiation and reduces the amount of vitamin D the body makes (synthesises).
People with little or no sun exposure. This group includes:
Older adults – people who are frail, in medium to long-term residential or aged care and housebound people
People who wear concealing clothing for religious and cultural purposes
People who deliberately avoid sun exposure for cosmetic or health reasons
People at high risk of skin cancers
People who are in hospital for long periods
People with a disability or chronic disease
People in occupations with little sun exposure such as taxi drivers, factory workers or night-shift workers.
Breast-fed babies with other low vitamin D risk factors. Breast milk is the best type of feed for babies, but it does not contain much vitamin D. Babies get their initial store of vitamin D from their mothers, so they are at risk of low vitamin D if their mother has low vitamin D.

Sun exposure and vitamin D
Most Victorians with fair to olive skin get enough vitamin D through ‘incidental’ sun exposure during normal daily outside activities (from September through to April), even if they apply sunscreen. People with naturally very dark skin need 3–6 times the exposure time and may require supplements, depending on their vitamin D levels.

It is important to know when sun protection is required throughout the year in Victoria and when it’s safe to get some UV exposure to maintain vitamin D levels. This is generally when the UV Index is below 3.
Sun protection in Victoria

In Victoria

Fair to olive skin
(Fitzpatrick skin types I–IV)

Higher risk of skin cancer

Naturally very dark skin
(Fitzpatrick skin types V–VI: rarely or never burns)

Higher risk of low vitamin D

From September to April
– when average UV levels are 3 and above

UV exposure: A few minutes of sun exposure to the face, arms and hands (or equivalent area of skin) before 10am or after 3pm on most days of the week should provide enough vitamin D.
Sun protection: Sun protection is needed during these months.

UV exposure: Need 3–6 times the level of exposure compared to people with fair to olive skin.

Supplements may be required.

Sun protection: It is not really necessary for people with this skin type to wear sunscreen but they should still wear a hat and sunglasses.

From May to August
– when average UV levels are below 3

UV exposure: Approximately 2–3 hours of sun exposure to the face, arms and hands (or equivalent area of skin) across the week should help maintain vitamin D levels.
Sun protection: Sun protection is not needed unless you are in alpine regions or near highly reflective surfaces such as snow and water.

UV exposure: Need 3–6 times the level of exposure compared to people with fair to olive skin.

Supplements may be required.

Sun protection: Sun protection is not needed but eye protection is important near highly reflective surfaces such as snow and water.

See your doctor
See your doctor if you think you may be at risk of vitamin D deficiency. A simple blood test can assess your risk. If you are at risk, make sure you have regular medical check-ups to monitor your levels. The doctor may recommend that you take vitamin D supplements. If so, take the supplements strictly as directed.

Where to get help

Your doctor
Maternal and Child Health nurse
An Accredited Practising Dietitian, contact the Dietitians Association of Australia
Nurse-on-Call Tel. 1300 606 024 – for expert health information and advice 24 hours, 7 days
SunSmart

Things to remember

The sun is the best natural source of vitamin D.
Some people are at increased risk of low vitamin D: this includes people with naturally very dark skin and people who have very low exposure to sunlight, such as those who cover their skin for cultural or religious purposes or spend most of their time indoors.
Low vitamin D increases the risk of rickets in children and osteomalacia in older adults.
People with low vitamin D also need adequate calcium in their diet.
Low vitamin D can be a long-term problem. Once low vitamin D is treated, the aim is to maintain normal vitamin D levels. People with risk factors for low vitamin D should have their levels checked every year and may need lifelong supplements

You might also be interested in:
Calcium.
Orienteering - preventing injury.
Rickets.
Vitamin and mineral supplements.
Vitamins - common misconceptions.

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