Prevalence of vitamin D deficiency in Southern NZ women

22nd January 2018

New Zealand women and their babies are at greater risk of vitamin D deficiency and current health guidelines fall short of curbing this detrimental trend, new University of Otago research shows.

The study, the first of its kind in the southern hemisphere, recruited 126 women through Dunedin’s Queen Mary Maternity Centre from 2011 to 2013. The findings, just published in the journal Nutrients, found rates of vitamin D deficiency were very high (evident in 65 per cent of mothers and 76 per cent of infants), and there was evidence of rickets in three infants.

Vitamin D is essential for foetal bone health, growth, and dental health. A lack of vitamin D is also associated with an increased risk of rickets in childhood.

Lead author Dr Ben Wheeler, of Dunedin School of Medicine’s Department of Women’s and Children’s Health, says the study raises “significant questions’’ around current public health policies, particularly for those living in southern New Zealand.

“Current policy does not appear effective at preventing vitamin D deficiency and its consequences.

“This is particularly an issue in New Zealand as living further south potentially decreases one’s ability to make vitamin D and the country has negligible vitamin D food fortification,’’ he says.

Present public health policy is to only consider vitamin D supplementation for pregnant women and breastfed infants who are considered “at risk’’ by having one or more of the following: naturally dark skin; complete sun avoidance; a sibling with rickets; liver or kidney disease, or taking certain medications that affect vitamin D levels; and infants who are breastfed over winter.

“The majority of New Zealand women and their children would not meet these risk criteria. However, our results show that in southern New Zealand, in traditionally low risk women and their infants, rates of deficiency are very high. In addition very severe deficiency in infants was also seen, something not previously seen in other similar international studies.’’

Dr Wheeler suggests strengthening of current New Zealand guidelines is needed.

“Further consideration should also be given to offering a fully funded universal supplement to New Zealand women and their children during pregnancy and lactation, particularly for those in the South Island.’’

Maternal vitamin D status during pregnancy is influenced by a range of factors, including season, skin colour, supplementation, latitude, and potential pregnancy-specific variations in metabolism.

Supplementation studies during pregnancy demonstrate significantly improved infant status at birth and beyond.

Publication details:

A Longitudinal Study of 25-Hydroxy Vitamin D and Parathyroid Hormone Status throughout Pregnancy and Exclusive Lactation in New Zealand Mothers and Their Infants at 45°S

Benjamin J. Wheeler, Barry J. Taylor, Michel de Lange, Michelle J. Harper, Shirley Jones, Adel Mekhail and Lisa A. Houghton.

Nutrients 2018, 10(1), 86; doi:10.3390/nu10010086

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