PhD defence - Karina Arnberg

Karina Arnberg is defending her PhD thesis

The effects of milk and milk proteins on risk factors of metabolic syndrome in overweight adolescents

Time

1 November 2013 at 10:00

Venue

Auditorium A1-01.01 (Festauditoriet), Bülowsvej 17, 1870 Frederiksberg

Opponents

Associate Professor Anders Sjödin (chair), Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Denmark

Professor Inga Thorsdottir, Unit for Nutrition Research, School of Helath Sciences, University of Iceland & Universityt Hospital, Iceland

Professor Bjørn Richelsen, Department of Endocrinology and Metabolism, Aarhus University, Denmark

Supervisors

Associate professor Christian Mølgaard, Department of Nutrition, Exercise and Sports, University of Copenhagen, Denmark

Professor Kim F. Michaelsen, Department of Nutrition, Exercise and Sports, University of Copenhagen, Denmark

About the thesis

This PhD is based on data from an intervention study with milk and milk proteins conducted in Danish adolescents with overweight. There is a high prevalence of overweight in Danish adolescents. Metabolic syndrome is a cluster of risk factors related to overweight and believed to increase the risk of type-2 diabetes and atherosclerotic cardiovascular diseases.

Overweight children have higher concentrations of the metabolic syndrome risk factors than normal weight children and the pathological condition underlying cardiovascular diseases, called atherosclerosis, seems to start in childhood. A well-functioning artery wall is important for preventing the atherosclerotic process. Little is, however, known about lifestyle factors related to the function of the artery wall in children.

Therefore the baseline data from the intervention study were used to study dietary and lifestyle predictors of arterial stiffness in the adolescents. The analyses showed that increased physical activity was related to an improved arterial function whereas central adiposity and a high protein intake were related to increased arterial stiffness.

In the intervention study, the adolescents with habitual low milk intakes were randomized to drink 1L skimmed milk, whey, casein or water for three months. The background for the intervention is that milk is an important source of protein in the Western diet and epidemiological studies in children have shown that children drinking low amounts of milk have higher concentrations of the metabolic risk factors than children having a high milk intake.

The aim of the intervention study was to examine whether it is beneficial for overweight adolescents with a habitual low milk intake to increase the consumption of low fat milk and whether a potential beneficial effect is caused by whey or casein.

The data from the intervention study showed that skimmed milk, whey and casein increased the age-adjusted BMI despite that there were no changes in energy intake. Also, the whey and casein group had increased insulin secretion measured by the C-peptide concentration. The results also showed that a high intake of casein decreased the diastolic blood pressure by approximately 2 mm Hg independent of the increased BMI.

The reductions in DBP following casein consumption may likely be beneficial in terms of preventing cardiovascular diseases. Otherwise, this study does not support increasing the intake of whey and casein for prevention of cardiovascular diseases in overweight children. Also, this study indicates that increasing the intake of skimmed milk to 1L per day is not advice-able due to the apparent increase in body weight. Drinking water showed to be harmless and may even be beneficial in overweight adolescents.

2013, 112 pages, ISBN 978 87 7611 653 8