AbstractObjectiveTo investigate whether intakes of Ca, vitamin D, casein and whey are associated with periodontitis and to investigate the possibility of interactions between them.DesignCross-sectional study. An Internet-based, 267-item FFQ was used to assess dietary intake. Intakes of casein (32·0 g/d), whey proteins (9·6 g/d) and vitamin D (5·8 μg/d) were classified as withinv.above the 50th percentile. Ca intake was classified as withinv.below age-specific recommendations. Severe periodontitis was defined as having ≥2 inter-proximal sites with clinical attachment loss ≥6 mm (not on the same tooth) and ≥1 inter-proximal site with pocket depth ≥5 mm. Since vitamin D influences Ca absorption, models were stratified by lower and higher (<5·8v. ≥5·8 µg/d) vitamin D intake.SettingDanish Health Examination Survey (DANHES) 2007–2008.SubjectsAdult participants (n3287) in the oral health study of DANHES 2007–2008.ResultsIntakes of Ca within recommendations (OR=0·76; 95 % CI 0·58, 0·99), whey ≥9·6 g/d (OR=0·75; 95 % CI 0·58, 0·97) and casein ≥32 g/d (OR=0·75 95 % CI 0·58, 0·97) were associated with lower likelihood of severe periodontitis after adjustment for age, gender, education, smoking, sucrose intake, alcohol consumption, number of teeth, daily brushing, regular visits to the dentist and chronic illness, irrespective of vitamin D intake levels. Intake of vitamin D alone was not associated severe with periodontitis.ConclusionsIntakes of Ca, casein and whey protein were inversely associated with periodontitis. Consumption of foods rich in Ca, casein and whey (e.g. dairy foods) should be promoted, as they may contribute to the prevention of periodontitis. Further longitudinal studies are required to confirm these associations.