You need vitamin D for strong bones, muscles and overall health. Make sure you get enough from sunlight and your diet.
- Vitamin D helps your bones to stay healthy and your muscles to work well.
- It is produced by your body in response to the sun, and it can also be found in some foods like fish, eggs and fortified dairy products.
- If you don't get enough of it, you may get aches, cramps and pain in your muscles and your bones may become soft and break more easily.
- About 5% of adults in New Zealand are deficient in vitamin D. A further 27% are below the recommended blood level of vitamin D.
- People with darker skin, who spend less time outside or who have health conditions that make it hard to absorb nutrients are more at risk of vitamin D deficiency.
- Vitamin D supplementation is not recommended for most New Zealanders, only those who are at risk of deficiency.
Why is vitamin D important?
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.
What happens if you don't have enough vitamin D?
If you do not have enough vitamin D you may not notice any symptoms at first, but you may get:
- pain in your muscles.
An ongoing lack of vitamin D can increase your risk of weak, brittle bones and osteoporosis.
Can you have too much vitamin D?
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 as recommended and prescribed by a doctor.
What is the link between vitamin D and winter health?
Vitamin D is sometimes called the sunshine vitamin because your body produces it in response to sunlight. In winter we get less sun and more flu. Researchers have been looking into whether the two might be related. Some studies have found signs of people with lower vitamin D levels being more likely to get colds and flu, but more research is needed.
However, if you have low levels of vitamins D, you may be walking around with a weakened immune system, which can leave you susceptible to viral infections, like colds and the flu.
Who is most at risk of vitamin D deficiency?
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).
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.
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.
How much vitamin D do I need?
The amount of vitamin D you need depends on your age and stage of life.
Life stage and age
Vitamin D (µg/day)
Infants and toddlers: 1–3 years
Children and adolescents: 4–18 years
Adults: 19–50 years
Adults: 51–70 years
Adults: 70+ years
Pregnant and breastfeeding women: 14–50 years
Where does vitamin D come from?
Sensible sun exposure
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 your diet alone.
Vitamin D is found in small quantities in a few foods such as eggs, liver and fatty fish (North Sea salmon, herring and mackerel).
Some foods may also have vitamin D added. These include:
- margarine and fat spreads
- some reduced-fat dairy products (eg, milk, dried milk and yogurt)
- plant-based dairy substitutes (eg, soy drinks).
Vitamin D supplementation is not recommended for most New Zealanders. It is only helpful for people at risk of vitamin D deficiency. Read more about vitamin D supplementation.
Do I need a vitamin D test?
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: Do I need a vitamin test? Choosing Wisely, NZ
Food and nutrition guidelines for healthy New Zealanders Ministry of Health, NZ
Vitamin D Ministry of Health, NZ
Consensus statement on vitamin D and sun exposure in New Zealand Cancer Society and Ministry of Health, NZ
- Vitamin D and calcium supplementation in primary care: an update BPAC, NZ, 2016
- Vitamin D New Zealand Formulary
- Association between serum 25-hydroxyvitamin D level and upper respiratory tract infection in the Third National Health and Nutrition Examination Survey. Arch. Intern. Med. 2008;169(4):384–90.
- Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren American Journal of Clinical Nutrition, 2010.
- Randomized trial of vitamin D supplementation and risk of acute respiratory tract infection in Mongolia Pediatrics. PMID 22908115.
- Young MRI, Xiong Y. Influence of vitamin D on cancer risk and treatment: Why the variability? Trends Cancer Res. 2018; 13: 43–53.
- Vitamin D supplementation: Navigating the debate BPAC, NZ, 2011
- Vitamin D is essential for good health Health Quality and Safety Commission, NZ, 2018
|Dr Helen Kenealy is a geriatrician and general physician working at Counties Manukau DHB. She has a broad range of interests and has worked in a variety of settings including inpatient rehabilitation, orthgeriatrics and community geriatrics.|