Diet and the metabolic syndrome : A cross-sectional study of 301 men from Stockholm County

Sammanfattning: The metabolic syndrome is a common condition that increases the risk of cardiovascular disease and type II diabetes. It is characterised by a clustering of metabolic disturbances such as abdominal obesity, dyslipoproteinemia, hypertension, and insulin resistance. Life style factors, including dietary habits, play an important role in the metabolic syndrome. To study the dietary intake of people under their normal living condition is, however, associated with difficulties. Underreporting (when the reported energy intake is too low to represent the habitual diet) is common in dietary surveys. Nevertheless, few studies have considered this when diet-disease relation-ships are reported. The objective of this thesis was to study the relationship between diet, in particular the quality of fat intake, and the metabolic syndrome, and to explore the possible effects of underreporting on these relationships. The analyses are based on a cross-sectional study of 301 healthy 63-year-old men with different fasting insulin levels. The men underwent a medical examination, which included taking blood samples and a biopsy of adipose tissue. Their food intake was assessed using a 7-day precoded, optically readable food record. The record booklet also contained space where the participants could record their intake in free text (=the manually coded part). The reported intake of protein, sodium and potassium was validated using 24-h urine collections. Individual physical activity levels were estimated and, according to the Goldberg equation, a cutoff was calculated for when the reported energy intake was too low to be due to chance. The men were divided by this means into underreporters and nonunderreporters. The results showed that underreporting of energy intake was common among healthy 63-year-old men (29 % were classified as underreporters) when the dietary intake was assessed using an estimated food record. The study indicates that under-reporting is a non-random phenomenon and that it is associated with particular kinds of foodstuffs. The manual part in the food recording was important since it contributed 20 % of the reported energy intake and affected the quality of the reported dietary intake. The findings suggest that to reduce the level of underreporting, emphasis should be placed on improving the recording of between-meal eating. The relationship between the intake of fats and the presence of components of the metabolic syndrome was different in underreporters and nonunderreporters. The results indicate that underreporters can both weaken associations and also introduce misleading associations. The relative content of the fatty acids 14:0, 15:0 and 17:0 in serum-phospholipids and adipose tissue were related to the intake of dairy fat but also to the intake of alcohol and physical activity. The findings suggest that these fatty acids should only be used as markers for dairy fat with caution. The thesis demonstrates that before drawing any conclusions about possible relation-ships between diet and disease a critical evaluation of what dietary data actually stand for must be carried out. This highlights an important issue that is of general concern to all those involved in nutritional research.