What does vitamin D do?
Vitamin D helps the body absorb the calcium it needs to keep the bones and muscles strong and healthy.
Sources of vitamin D
Most Australians get their vitamin D when they expose bare skin to ultraviolet B (UVB) light from the sun.
Food alone cannot provide an adequate amount of vitamin D and most people are reliant on sun exposure to reach recommended levels. Foods that contain small amounts of vitamin D include fatty fish (such as salmon, mackerel and herring), liver, eggs, margarines and some milk products. Infant formula is fortified with vitamin D in Australia.
Sun exposure and vitamin D
The amount of time you need in the sun depends on several things, including where you live, the season, time of day, your skin colour and the amount of skin exposed.
During summer, most people can get adequate vitamin D from just a few minutes outside. It’s important to avoid the high UV times, so mid-morning or mid-afternoon is best. During late autumn and winter in southern parts of Australia, when the UV index falls below 3 you should spend some time outdoors with the skin uncovered in the middle of the day.
Being physically active outside, such as gardening or going for a walk, can also boost your vitamin D levels. Always follow safe sun guidelines because too much sun can increase your risk of skin cancer and may cause the vitamin D in your skin to break down.
Never use a solarium to boost vitamin D levels because they emit dangerous levels of ultraviolet (UV) radiation that increase your risk of skin cancer.
What happens if I don't have enough vitamin D?
Moderate to severe vitamin D deficiency can lead to rickets (soft bones) in infants and children.
Low vitamin D levels can lead to osteoporosis and increase the risk of falls and fractures (broken bones) if you are over 50. Osteoporosis occurs when your bones lose calcium and other minerals, making them fragile and more likely to break. Vitamin D helps the body to absorb calcium, so if you don’t have enough, you can be at increased risk of developing osteoporosis.
People with very low levels of vitamin D (moderate to severe deficiency) are the most at risk of developing health problems.
A number of diseases have been linked to low vitamin D levels such as increased risk of death from cardiovascular disease, cognitive impairment in older adults, severe asthma in children and cancer. Research suggests that vitamin D could play a role in the prevention and treatment of a number of different conditions, including type1 and type 2 diabetes, hypertension, glucose intolerance and multiple sclerosis. Despite this, the evidence behind these claims is variable. Because of this Choosing Wisely Australia recommends that you do not need routine testing for vitamin D deficiency unless you are considered specifically at risk.
Who is at risk of vitamin D deficiency?
You may be at risk of vitamin D deficiency if you:
- stay mostly indoors for health, work or other reasons
- have naturally dark skin
- cover your body for religious or cultural reasons
- avoid the sun for skin protection or due to medical reasons
- are obese
- have a health condition that affects vitamin D absorption from your diet
- take medicines that cause vitamin D to break down
- were born to a vitamin D deficient mother
Do I need a vitamin D test?
You may need a vitamin D test if you are at risk of vitamin D deficiency.
A vitamin D test is a simple blood test that measures a form of vitamin D in your blood called 25-hydroxyvitamin D (25-OHD). This test is usually only done in people at risk of osteoporosis and needs an assessment and referral by a doctor.
Talk to your doctor if you think you need a vitamin D test.
The best time to test for vitamin D is at the end of winter or in early spring when your vitamin D levels are at their lowest.
How is vitamin D deficiency treated?
If you have a mild deficiency then your doctor may recommend a few simple things such as:
- increasing your sun exposure
- increasing calcium in the diet
- increasing physical activity
- taking a vitamin D supplement
If you have a moderate to severe deficiency then you might need to take a high-dose supplement and repeat the blood test in 3 months' time. Your doctor will discuss this course of treatment with you.
Some children and teenagers may need to be tested every year if they are identified as having a high risk of deficiency.
Vitamin D supplements
Most people don’t need vitamin D supplements. There can be side effects if you have too much vitamin D in your body. If you have been found to have vitamin D deficiency, talk to your doctor about whether you need supplements.
Vitamin D supplements are available over the counter and in different forms, including capsules, tablets, soluble tablets, chewable tablets, powder and liquids. Your doctor or pharmacist can advise you on the best one for you based on the strength of the medicine, the number and type of active ingredients it contains and your reason for taking it.
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Last reviewed: August 2020