There have been numerous studies showing that giving hens feed fortified with vitamin D increases the vitamin D content of their eggs. Yet there has been no research on the impact these bio-fortified eggs would have on humans eating them.
Research from the ODIN project – a four-year €7.95m research project backed by €6m in funding from the EU – sought to investigate this as a way to beat low vitamin D levels in winter.
The trial saw 55 healthy adults aged 45–70 given either up to two non-fortified eggs a week to eat; seven vitamin D3–enhanced eggs per week or seven eggs fortified with 25-hydroxyvitamin D over eight weeks in winter.
The results published in the American Journal of Clinical Nutrition showed significantly higher blood vitamin D levels in the participants given the fortified eggs.
“With the use of a within-group analysis, it was shown that, although serum 25(OH)D in the control group significantly decreased over winter […], there was no change in the two groups who consumed vitamin D–enhanced eggs[…],” the researchers wrote.
By the end of the experiment led by the University College Cork in Ireland, the percentage of participants with vitamin D blood levels below the UK threshold for deficiency (less than 25 nanomole per litre) was 22%, 0% and 0% for the control, vitamin D3 egg and 25(OH)D3 egg groups, respectively.
Earlier this year EFSA set an adequate intake (AI) level of 15 micrograms (µg) of vitamin D per day from food sources for adults and children to achieve a serum level of 50 nanomoles per litre (nmol / L).
For infants aged seven to 11 months, it set 10 µg per day.
EFSA said there was evidence for adults, infants and children of an increased risk of adverse musculoskeletal health outcomes at serum 25(OH)D concentrations below 50 nmol/L.
Adverse pregnancy-related health outcomes also increased below the same 50 nmol / L level, though it said available data was “widely variable”.
The researchers warned there was currently a “considerable mismatch” between recommended and actual vitamin D intake levels.
Indeed a previous paper from the ODIN project – which started in 2013 and involves 30 partner institutions from 18 countries overall – estimated 13% of the EU population are vitamin D deficient with serum levels of less than 30 nmol/L throughout the year.
Based on a sample of 55,844 Europeans, they found in October to March this rose to 17.7% and in April to November this fell to 8.3%.
Food fortification has been put forward as one way to combat this deficiency, with countries like Sweden creating lists of foods that must be fortified with the vitamin.
Meanwhile an increase in cases of rickets in the UK sparked debated on the need for similar initiatives on a mandatory or voluntary basis.
The researchers behind this latest ODIN study said ‘bioaddition’ of vitamin D was also an option in tackling deficiency.
“The use of ‘bioaddition’ which involves the addition of vitamin D to an animal’s diet to increase the vitamin D content in the resultant food, deserves serious consideration as it may produce foods that are more acceptable to consumers as well as increase the intake of various vitamin D compounds leading to improved vitamin D status.”
The ODIN researchers also investigated vitamin D2 from UV-irradiated yeast as a way to fortify bread.
However this method proved less promising.
The ODIN paper published earlier this year concluded that while Vitamin D2 from UV-irradiated yeast maybe a cheaper and more ecological way to fortify bread, there was poor bioavailability in humans.
Source: American Journal of Clinical Nutrition
Vol. 104 no. 3, pp. 629-637, doi:10.3945/ajcn.116.132530
“Vitamin D–enhanced eggs are protective of wintertime serum 25-hydroxyvitamin D in a randomized controlled trial of adults”
Authors:A. Hayes, S. Duffy, M. O’Grady, J. Jakobsen, K. Galvin, J. Teahan-Dillon, J. Kerry, A. Kelly, J. O’Doherty, S. Higgins, K. M. Seamans and K. D. Cashman