Key points about Vitamin D

  • We need vitamin D for strong bones, muscles and overall health.
  • Vitamin D is sometimes called the sunshine vitamin because our bodies produce it in response to sunlight.
  • It can also be found in some foods like fish, eggs and fortified dairy products.
  • If required, it can also be taken in supplement form.
Man reading book on beach in hat and sunglasses
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Vitamin D is important for the absorption of calcium from your stomach and for the functioning of calcium in your body. This helps your bones to stay healthy and your muscles to work well. 

  • Low levels of vitamin D are linked to bone conditions such as rickets in children and osteoporosis and osteomalacia in adults. 
  • Low vitamin D levels may also be linked to non-skeletal health conditions, such as colorectal cancer, cardiovascular disease and immune system problems. Researchers are looking into whether increasing vitamin D levels could help prevent any of these conditions, but the evidence is not clear at this stage.
  • Vitamin D has been shown to help reduce falls and fractures in older people in residential care. More research is needed to see if vitamin D could help reduce falls and fractures in other groups of people.
  • However, too much vitamin D replacement can lead to high levels, which can actually increase your risk of falls. For this reason, you should only take vitamin D as recommended and prescribed by a doctor. 

Vitamin D comes from sunlight, foods containing vitamin D and dietary supplements.

Two boys at sunny beach in Abel Tasman, New Zealand

Image credit: Healthify NZ

Sensible sun exposure

The body creates vitamin D from direct sunlight on the skin when outdoors. The sun’s ultra­vi­o­let B (UVB) rays inter­act with a pro­tein in the skin, con­vert­ing it into vit­a­min D. How much sun you need depends on: 

  • your skin colour
  • your age, weight and how mobile you are
  • your risk of skin cancer
  • how much vitamin D you get from your food
  • whether you are taking medications – some medications make your skin more sensitive to sunburn
  • where you are in New Zealand
  • the season and the time of day
  • certain medical conditions.

As little as 15 minutes under the sun (without sunscreen), 3 times a week enables your body to make enough vitamin D – but you need to be sensible. Exposing your skin to the sun increases your risks of skin cancer, so don't get sunburnt while you do it. Read more about sensible sun exposure.

Food sources of vitamin D

It's hard to get enough vitamin D through diet alone as what you eat and drink provides only about 5–10% of your vitamin D requirements. It's especially important to think about diet during the winter months when you have less exposure to the sun. Examples of good sources of vitamin D include oily fish (North Sea salmon, tuna, eel and warehou) and milk, yoghurt and margarine that have been fortified with vitamin D.

Dietary supplements

Vitamin D supplementation is not recommended for most New Zealanders. It is only helpful for people at risk of vitamin D deficiency. See below, who is most at risk of vitamin D deficiency.

Vitamin D is measured in micrograms written as µg, so 5 µg/day means 5 micrograms per day. The amount you need depends on your age and stage of life:

  • Infants to adults (aged 1–50 years): 5 µg/day.
  • Adults (aged 51–70 years): 10 µg/day.
  • Older adults (aged 70+ years): 15 µg/day.
  • Pregnant and breastfeeding women: 10 µg/day.

If you don't have enough vitamin D you may not notice any symptoms at first, but you may get:

  • aches
  • cramps
  • pain in your muscles.

An ongoing lack of vitamin D can increase your risk of weak, brittle bones and osteoporosis.

You are at higher risk of vitamin D deficiency if you:

  • have dark skin or a condition that prevents you getting sun exposure
  • wear clothing that covers your skin most of the time for cultural or religious reasons
  • have a condition that impairs absorption of vitamin D through your gut, such as Crohn's disease or coeliac disease
  • are of Māori, Pacific, African or Indian ethnicity
  • live in southern regions of New Zealand, which means you may experience short-lived vitamin D deficiency between the winter months of May and August
  • are confined indoors due to disability, age or illness (especially older people). 

Read more about vitamin D supplements in adults

Babies, children, teenagers, pregnant women or breastfeeding mothers are also at higher risk of vitamin D deficiency, as the need for vitamin D is higher in these groups. Read more about vitamin D supplements for babies and vitamin D in pregnancy.

Your doctor or healthcare provider may recommend a vitamin D test if you are at higher risk of vitamin D deficiency. A test is not always needed before your doctor prescribes a vitamin D supplement. Read more about vitamin D testing.(external link) 

It is rare to have toxic levels of vitamin D, but it can happen if you take high levels of vitamin D supplements over a long period of time. If you do this, there is some evidence this will have adverse effects, such as headaches and gastrointestinal disturbance, kidney stones, kidney failure and cardiac arrhythmia. For this reason, you should only take vitamin D supplements as recommended and prescribed by a doctor. Read more about vitamin D supplements for adults.

Clinical resources

25-hydroxy vitamin D testing for funded requests(external link)
Labtests Pathology, NZ, 2019 Vitamin D deficiency - investigation and management(external link) Starship Clinical Guidelines, NZ, 2017
Vitamin D and calcium supplementation in primary care: an update(external link) BPAC, NZ, 2016
Consensus statement on vitamin D and sun exposure in New Zealand(external link) Ministry of Health, NZ, 2012

See our page Skin cancer for healthcare providers

Vitamin D and COVID-19

There is some evidence of an association between vitamin D deficiency and increased severity of COVID-19. Ensure going into winter that people who are likely to have low vitamin D levels receive supplementation. This includes older people who are frail, housebound or living in residential care, people with dark skin pigmentation or people with obesity, chronic kidney disease, liver failure or another medical condition that affects vitamin D metabolism. There is no evidence it is effective in treating COVID-19.

Source: Griffin G, Hewison M, Hopkin J et al. Vitamin D and COVID-19: evidence and recommendations for supplementation(external link) Royal Society Open Science. Dec 2020; 7(12). 

Brochures

vitamin d

Vitamin D – factsheet

Refugee Health Network and Auckland District Health Board, 2012

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Credits: Healthify Editorial Team. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Dr Helen Kenealy, geriatrician and general physician, CMDHB

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