Carbohydrates in the diet of Finnish adults : focus on intake assessment and associations with other dietary components and obesity

In the modern abundant food environment, the relationship between dietary carbohydrates and health outcomes is complex. The main aims of this thesis were to investigate the role of added sugar intake in the diet, and the relationship between dietary carbohydrates, the dietary glycaemic index (GI) and load (GL) and obesity. Another aim was to examine the dietary assessment methodology from the dietary carbohydrates perspective. This study was based on health examination surveys in the Finnish adult population conducted in 2000-2007: the DILGOM Study, the National FINRISK/FINDIET 2007 Study, the Health 2000 Survey and the Helsinki Birth Cohort Study (overall n=13 800, age 25+). The examinations included measured anthropometrics and questionnaires. The habitual diet was assessed with a food frequency questionnaire (FFQ). Food records served as a reference method in FFQ validation. Food GI values were based on a previous Finnish epidemiological GI database and were documented using international controlled vocabularies used in the Finnish national food composition database (Fineli). Intake of added sugars was estimated based on sucrose and fructose derived from foods other than fruits, berries, vegetables, and 100% fruit juices. On average, 40% of sucrose and fructose were from natural sources and the remaining 60% were added sugars. Subjects in the highest added sugar intake quartile were younger and had lower fibre, fruit, vegetable, rye, and fish intakes than subjects in the lowest added sugar intake quartile. Added sugar intake was associated positively with the intake of butter and butter mixtures. These results support the recommendation for the restriction of added sugars in the diet. In the meta-analysis of three cross-sectional studies (n=12 342), 23% of the subjects were classified as obese (body mass index, BMI ≥ 30 kg/m2). The likelihood of being obese was 35% lower in the highest quartile of total carbohydrate intake than in the lowest quartile. Total sucrose intake and dietary GL were also inversely associated with obesity. Dietary GI and fibre intake were not associated with obesity. Prospective cohort studies are needed to assess possible temporal relations. Instead of sucrose only, added sugars should be investigated. Between-method Spearman rank-correlation coefficients ranged from 0.27 (total sugars, men) to 0.70 (lactose, men). Based on the two methods, 73% of the subjects were correctly classified into the same or adjacent carbohydrate intake distribution quintile. Between-method agreement improved with decreasing age and with higher education, especially in women. The ability of the FFQ in ranking subjects according to most carbohydrate-related exposures is on the same level as in the international literature. However, sex, age and education represent important confounding factors. The origin and derivation methods of the GI values were successfully documented with the controlled vocabularies generally used in Fineli. This provides a foundation for the comparison of GI databases in international contexts.