Study questions beneficial effects of a Nordic diet on cardiovascular events

A new study led from Karolinska Institutet shows that although individual components of a healthy so-called Nordic diet previously have been linked to beneficial effects on cardiovascular health, as well as to other health effects, there is no evidence of an association with cardiovascular events in a general population. The study, which was conducted in in over 40,000 Swedish women, is being published in the Journal of Internal Medicine.

Cardiovascular disease, such as heart attack and stroke, is a leading cause of death worldwide, and it has long been known that dietary factors have an important influence on cardiovascular health. Previous studies have shown beneficial effects of a healthy Nordic diet – comprising whole grain bread and oatmeal, fruit (apples/pears), vegetables (root vegetables and cabbage) and fish – on short-term markers of cardiovascular health, for example lower blood pressure and weight loss. Several studies have also showed beneficial effects of individual components included in the Nordic diet on cardiovascular events. However, the current study is the first to investigate the overall, long-term association between a healthy Nordic diet and the incidence of cardiovascular disease in the general population.

The study was conducted in 43,310 middle-aged Swedish women. The participants answered questions in 1991/92 about their food intake, and the incidence of cardiovascular disease was recorded through the Swedish registries over approximately 20 years until the end of 2012. During the follow-up period, nearly 20% of the women developed cardiovascular disease. However, unexpectedly given the results of previous studies, the beneficial effect of a healthy Nordic diet did not register when looking at the incidence of concrete, cardiovascular events in the general population.

“The reason for this for this discrepancy could be that previous studies showing effect of a healthy Nordic diet were intervention trials, which means participants had a very high adherence to this particular diet and also were selected, high-risk persons in relation to developing cardiovascular disease, whereas the present study expected a lesser degree of adherence, and looked and a group of overall healthy women”, says first author Nina Roswall, PhD, at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet.

Alcohol consumption or smoking

An additional goal for the research team was to determine whether any relationship between the healthy Nordic diet and cardiovascular disease is modified by age, weight, alcohol consumption or smoking. Their results show that alcohol intake, weight (BMI) and age did not have any significant affect.

“We did manage to show a beneficial effect of this diet among former smokers”, says Professor Elisabete Weiderpass, PhD, who supervised the study. “However, this may be due to the fact that smoking cessation is associated with dietary changes towards a healthier lifestyle, which may have affected the results. It is also important to point out that further investigation is required to confirm these findings.”

Research organizations involved in this study, other than Karolinska Institutet, were the Danish Cancer Society Research Center, University of Auckland, New Zealand, Harvard School of Public Health, USA, Folkhälsan Research Center, Finland, The Cancer Registry of Norway, The Arctic University of Norway, and University of Tromsö, also in Norway. The investigation was supported by a grant from the Swedish Research Council.

Publication

No association between adherence to the healthy Nordic food index and cardiovascular disease among Swedish women – a cohort study
Roswall Nina, Sandin Sven, Scragg Robert, Löf Marie, Skeie Guri, Olsen Anja, Adami Hans-Olov, Weiderpass Elisabete
Journal of International Medicine, first published online 19 May 2015, DOI: 10.1111/joim.12378