Vitamin D

Vitamin D is important for strong bones, muscles and overall health. Ultraviolet (UV) radiation from the sun is needed for the body to make vitamin D in the skin, and it is the best natural source. Some sun exposure helps you maintain adequate vitamin D levels, but too much UV radiation can cause sunburn, skin and eye damage, and skin cancer.

The body can only absorb a limited amount of vitamin D at a time. Spending extra time in the sun will not raise your vitamin D levels, but it will increase your risk of skin cancer.

Sources of vitamin D#

The main sources of vitamin D are:

• sunlight (UV radiation) on the skin – the most important source
• some foods – these provide only a small amount (about 5 to 10 per cent), and it is difficult to get enough from diet alone
• vitamin D supplements

Regular physical activity also assists with the body’s production of vitamin D.

Food sources of vitamin D include:

• fatty fish, such as salmon
• eggs
• margarine and some milks, which have vitamin D added
• some cereals, which have vitamin D added

Sun exposure, UV and vitamin D#

UV levels vary with the time of year, time of day, latitude and location. The amount of sun you need for healthy vitamin D levels, and the amount of sun protection you need to avoid harm, both depend on how strong the UV is where you live.

Sun protection is recommended whenever the UV level reaches 3 or above. In some places, UV is 3 or above every day throughout the year; in others, it falls below 3 during cooler months. “Daily sun protection times” indicate the hours when the UV level is forecast to be 3 or above. You can check the forecast sun protection times for your location through a local weather or UV forecast service.

When the UV level is 3 or above for much of the day, use a combination of sun protection measures, including:

• shade
• a broad-spectrum, water-resistant sunscreen of SPF 30 or higher
• a wide-brimmed hat
• cool, covering clothing
• sunglasses

During these periods, most people only need a few minutes outdoors on most days to make enough vitamin D. Sensible sun protection should not put people at risk of vitamin D deficiency.

When UV levels are low (below 3), routine sun protection is generally not needed, unless you work outdoors, are near highly reflective surfaces such as snow, or are outside for extended periods. During these times, spending time outdoors in the middle of the day with some skin uncovered helps maintain vitamin D levels.

Overexposure to UV is never recommended, even for people who have vitamin D deficiency.

Vitamin D deficiency#

Vitamin D deficiency does not always cause obvious symptoms, but without treatment it can have significant health effects. Some people experience bone and muscle pain, and softening of the bones.

It is important to achieve a good peak bone mass early in life. Vitamin D deficiency can reduce bone density and increase the risk of:

• osteoporosis
• falls and bone fractures (especially in older people)
• rickets in infants and children – a preventable bone disease
• osteomalacia in adults

Vitamin D deficiency can also be associated with low levels of calcium.

Who is at risk#

You may be at greater risk of vitamin D deficiency if you:

• have naturally very dark skin – the pigment (melanin) in dark skin can partially block UV radiation from being absorbed
• spend long periods indoors with limited sun exposure (such as nightshift workers, or people who are housebound or in residential care)
• avoid the sun because of previous skin cancers or sensitive skin
• wear covering clothing that conceals the body (for example, for religious or cultural reasons)
• are obese
• have a condition that affects vitamin D metabolism or absorption – such as end-stage liver disease, kidney (renal) disease, or fat malabsorption syndromes (such as cystic fibrosis, celiac disease and inflammatory bowel disease)
• take medication that affects vitamin D absorption
• are a breastfed baby of a mother who is vitamin D deficient (formula milk is fortified with vitamin D)

Treating vitamin D deficiency#

If you are at risk of, or concerned about, vitamin D deficiency, seek advice from your doctor. Your doctor may suggest a blood test to check your vitamin D levels.

Treatment options include improved sunlight exposure, diet and exercise. If you are found to have a deficiency, your doctor may recommend vitamin D supplements, which should be taken strictly as directed. Your doctor may also give advice on getting enough calcium.

Once vitamin D deficiency has been treated, the aim is to maintain normal vitamin D levels.

Key points#

• Spending extra time in the sun will not raise vitamin D levels, but it will increase your risk of skin cancer.
• Sensible sun protection should not put people at risk of vitamin D deficiency.
• It is important to achieve a good peak bone mass early in life.
• If you are at risk of vitamin D deficiency, seek advice from your doctor.
• Treatment options for vitamin D deficiency include improved sunlight exposure, diet and exercise.

Where to get help#