Previous intervention studies have suggested an association between healthy Nordic diets – based on intake of wholegrain bread, oatmeal, apples/pears, root vegetables, cabbages and fish – and a reduced risk of cardiovascular disease.
The study, published in the Journal of Internal Medicine, analysed data from the Swedish Women’s Lifestyle and Health cohort study, which included 43,310 middle-aged women who completed a food frequency survey in 1991-92 with follow-up until the end of 2012.
Nearly 8,400 of the women developed heart disease during the follow-up period – but the researchers found no association between a healthy Nordic food index and heart disease risk, despite previous studies to the contrary.
“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 [at] a group of overall healthy women,” said first author Nina Roswall of the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, from which the study was led.
No negative scoring
The researchers also suggested that the discrepancy could be explained by the limited number of foods covered by the healthy Nordic food index, which includes just six food groups (the Mediterranean diet index includes nine), and no negative scoring for items thought to have an adverse effect on heart health.
“Adherence to the index was indeed previously associated with a higher intake of adverse dietary items such as processed meats and sodium, and total energy,” the study’s authors wrote.
Good news for former smokers?
The researchers also aimed to determine if the effect of a healthy Nordic diet was modified by smoking, drinking, BMI or age, and found that smoking was the only statistically significant factor – but only among former smokers, who were found to have a lower heart disease risk than current smokers or those who had never smoked.
Professor Elisabete Weiderpass, who supervised the study, said: “We did manage to show a beneficial effect of this diet among former smokers. 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.”
Source: Journal of Internal Medicine
Published online ahead of print doi: 10.1111/joim.12378
“No association between adherence to the healthy Nordic food index and cardiovascular disease amongst Swedish women: a cohort study”
Authors: N. Roswall, S. Sandin, R. Scragg, M. Löf, G. Skeie, A. Olsen, H.-O. Adami, and E. Weiderpass