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Older New Zealanders might remember receiving a daily dose of cod liver oil as children. But do you remember why? Cod liver oil is a rich source of vitamin D, and was considered an easy way of preventing rickets, a bone-softening condition causing bowed legs or knock knees in children.
Today, a low blood level of vitamin D may not be severe enough to cause rickets, but it may increase the risk of bone fractures due to its important role in bone health where it is essential for calcium absorption from food. Concern about vitamin D deficiency has re-emerged in New Zealand as a result of health messages to reduce sun exposure and encouragement to use ultraviolet (UV) sun screens, reducing the skin’s ability to produce vitamin D.
How much vitamin D do we need?
AI* Vitamin D (µg/day)
Infants and toddlers
Children and adolescents
Pregnant and breastfeeding women
Who needs more and why?
Older people, particularly those who are housebound with limited exposure to sunlight.
Those with a darker skin colour, e.g. Māori and Pacific Islanders, or people who are veiled.
Those living in the South Island during the winter.
Which foods contain vitamin D?
Vitamin D is in oily fish, such as canned tuna and salmon, eggs, lean meat and dairy products. There are now margarines, milks and yoghurts fortified with vitamin D available in New Zealand.
Vitamin D deficiency
Unlike any other nutrient, most vitamin D (up to 80%) is formed as a result of sunlight exposure on our skin. The most recent national surveys showed about one in three New Zealand children had too little vitamin D in their blood; nearer a half of adults.
During summer, being outdoors before 11am and after 4pm should allow enough sunlight to be absorbed to meet your vitamin D needs. We still need to practice good sun protection (sunscreen, hats and coverage) during the summer months. In winter, longer periods are required, around 30 minutes per day, with those people living in the south island of New Zealand needing more exposure because of the lower UV levels.
Talk to your doctor if you are concerned about your vitamin D levels or if you have limited exposure to the sun.