The importance of vitamin D
Vitamin D is a group of vitamins essential for maintaining health and well-being. Low vitamin D levels have been linked to a variety of health conditions, including:
- Bone diseases (e.g. osteoporosis, osteomalacia and rickets - especially in children)
- Cardiovascular disease
- Reduced immune system function
Vitamin D can be obtained from foods like fish, eggs and milk, but most of our vitamin D is produced in the skin in the form of vitamin D3, or 'cholecalciferol' when it is exposed to the UVB radiation in sunlight.
One in twenty adults have vitamin D deficiency
About 4.9 percent of New Zealand adults had vitamin D deficiency in 2008/09 . This included 0.2 percent of adults with severe deficiency. A further one in four adults (27.1 percent) were below recommended levels of vitamin D.
The following population groups had higher levels of vitamin D deficiency:
- Pacific adults
- people who lived in the most socioeconomically deprived areas (NZDep2006 quintile 5)
- people who were obese.
Men and women had similar levels of vitamin D deficiency. Rates were also similar across age groups.
Risk factors for vitamin D deficiency
- Having naturally darker skin. This includes Māori and Pacific Islanders as well as people from Africa, the Indian subcontinent and the Middle East
- Lacking regular sun exposure, either through wearing clothing that covers much of your skin, limiting exposure as you have a high risk of skin cancer, or simply spending a lot of time indoors
- Living in the South Island, with the risk increasing the further south you live
- Certain liver and kidney diseases and medications can also affect vitamin D levels.
People are more at risk in winter and in the South Island
Vitamin D deficiency is more common in late winter and early spring (August to October) in New Zealand. This is because UV levels are lower during these months, and people are less likely to get exposure to the sun.
In particular, people living in the South Island are more at risk of vitamin D deficiency during late winter and spring.
Information about the data
Prevalence of Vitamin D deficiency
Source: Vitamin D Status of New Zealand Adults . Data come from the 2008/09 New Zealand Adult Nutrition Survey. Vitamin D deficiency was based on blood samples collected as part of the survey.
Definition: Proportion of the adult population (aged 15+ years) who have vitamin D deficiency. This is defined as a serum 25-OHD level less than 25.0 nmol/L. Severe deficiency was defined as a serum 25-OHD level less than 12.5 nmol/L. The Ministry of Health recommends that individuals have an annual mean vitamin D (serum 25-OHD) level of 50.0 nmol/L or greater.
1. Ministry of Health. 2012. Vitamin D Status of New Zealand Adults: Findings from the 2008/09 New Zealand Adult Nutrition Survey. Wellington: Ministry of Health.