New research published in the European Journal of Nutrition has found that a Nordic diet high in fish consumption does not improve vitamin D levels.
Vitamin D deficiency is common among populations living at northern latitudes. This is because in northern regions, for most of the time during the year, the angle of the sun doesn’t allow for much ultraviolet-B radiation to reach the Earth’s surface. Ultraviolet-B radiation is needed for vitamin D production in human skin.
This means that for the majority of the year, people living in northern latitudes must rely on other sources for vitamin D.
Researchers recently conducted a randomized trial to see if a healthy diet based on Nordic nutrition recommendations (NNR) could be an adequate source of vitamin D. The NNR is a publication produced every year which establishes recommended intakes of nutrients in Nordic countries.
They recruited 213 people with metabolic syndrome from the SYSDIET study cohort. The SYSDIET study consists of multiple research projects based on a multi-center cohort designed to see how changing the Nordic diet can improve health and prevent metabolic syndrome, diabetes, and other diseases.
The participants were randomized to receive either a healthy Nordic diet or a control diet for 18-24 weeks. The Nordic diet consisted of a high intake of fatty fish, which is a known dietary source of vitamin D, as well as whole-grain products, fruits, vegetables, and low-fat dairy products.
The researchers found that the Nordic diet, when compared with the control diet, did not change the participants’ vitamin D levels.
“Consuming a healthy Nordic diet based on NNR increased vitamin D intake but not plasma 25(OH)D concentration,” the researchers stated.
Supplementing with vitamin D is the best option when sun exposure isn’t possible. While some foods do contain vitamin D, it is not enough to rely on diet alone to obtain healthy levels.
Brader, L. Effects of a healthy Nordic diet on plasma 25-hydroxyvitamin D concentration in subjects with metabolic syndrome: a randomized, placebo-controlled trial (SYSDIET). European Journal of Nutrition, 2014.