title: Effects of a healthy Nordic diet on plasma 25-hydroxyvitamin D concentration in subjects with metabolic syndrome: a randomized, [corrected] controlled trial (SYSDIET).
abstract: OBJECTIVE
  At northern latitudes, vitamin D is not synthesized endogenously during winter, causing low plasma 25-hydroxyvitamin D (25(OH)D) concentrations. Therefore, we evaluated the effects of a healthy Nordic diet based on Nordic nutrition recommendations (NNR) on plasma 25(OH)D and explored its dietary predictors.
  
  
  METHODS
  In a Nordic multi-centre trial, subjects (n = 213) with metabolic syndrome were randomized to a control or a healthy Nordic diet favouring fish (≥300 g/week, including ≥200 g/week fatty fish), whole-grain products, berries, fruits, vegetables, rapeseed oil and low-fat dairy products. Plasma 25(OH)D and parathyroid hormone were analysed before and after 18- to 24-week intervention.
  
  
  RESULTS
  At baseline, 45 % had vitamin D inadequacy (<50 nmol/l), whereas 8 % had deficiency (<25 nmol/l). Dietary vitamin D intake was increased by the healthy Nordic diet (P < 0.001). The healthy Nordic and the control diet reduced the prevalence of vitamin D inadequacy by 42 % (P < 0.001) and 19 % (P = 0.002), respectively, without between-group difference (P = 0.142). Compared with control, plasma 25(OH)D (P = 0.208) and parathyroid hormone (P = 0.207) were not altered by the healthy Nordic diet. Predictors for 25(OH)D were intake of vitamin D, eicosapentaenoic acids (EPA), docosahexaenoic acids (DHA), vitamin D supplement, plasma EPA and plasma DHA. Nevertheless, only vitamin D intake and season predicted the 25(OH)D changes.
  
  
  CONCLUSIONS
  Consuming a healthy Nordic diet based on NNR increased vitamin D intake but not plasma 25(OH)D concentration. The reason why fish consumption did not improve vitamin D status might be that many fish are farmed and might contain little vitamin D or that frying fish may result in vitamin D extraction. Additional ways to improve vitamin D status in Nordic countries may be needed.
authors.affiliation: Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Tage-Hansens Gade 2, 8000, Århus C, Denmark, brader.lea@gmail.com.
authors.forename: Lea
authors.initials: L
authors.lastname: Brader
authors.forename: Lars
authors.initials: L
authors.lastname: Rejnmark
authors.forename: Carsten
authors.initials: C
authors.lastname: Carlberg
authors.forename: Ursula
authors.initials: U
authors.lastname: Schwab
authors.forename: Marjukka
authors.initials: M
authors.lastname: Kolehmainen
authors.forename: Fredrik
authors.initials: F
authors.lastname: Rosqvist
authors.forename: Lieselotte
authors.initials: L
authors.lastname: Cloetens
authors.forename: Mona
authors.initials: M
authors.lastname: Landin-Olsson
authors.forename: Ingibjorg
authors.initials: I
authors.lastname: Gunnarsdottir
authors.forename: Kaisa S
authors.initials: KS
authors.lastname: Poutanen
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Herzig
authors.forename: Ulf
authors.initials: U
authors.lastname: Risérus
authors.forename: Markku J
authors.initials: MJ
authors.lastname: Savolainen
authors.forename: Inga
authors.initials: I
authors.lastname: Thorsdottir
authors.forename: Matti
authors.initials: M
authors.lastname: Uusitupa
authors.forename: Kjeld
authors.initials: K
authors.lastname: Hermansen
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D003611:Dairy Products; D004032:Diet; D019587:Dietary Supplements; D004281:Docosahexaenoic Acids / Q000008:administration & dosage / Q000097:blood; D002523:Edible Grain; D015118:Eicosapentaenoic Acid / Q000008:administration & dosage / Q000097:blood; D005229:Fatty Acids, Monounsaturated; D005247:Feeding Behavior; D005260:Female; D005638:Fruit; D006801:Humans; D008019:Life Style; D008297:Male; D024821:Metabolic Syndrome / Q000097:blood* / Q000150:complications; D008875:Middle Aged; D015596:Nutrition Assessment; D009752:Nutritional Status; D010281:Parathyroid Hormone / Q000097:blood; D010938:Plant Oils; D000074262:Rapeseed Oil; D064167:Recommended Dietary Allowances / Q000331:legislation & jurisprudence; D011795:Surveys and Questionnaires; D014675:Vegetables; D014807:Vitamin D / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications
chemical_list: D005229:Fatty Acids, Monounsaturated; D010281:Parathyroid Hormone; D010938:Plant Oils; D000074262:Rapeseed Oil; D014807:Vitamin D; D004281:Docosahexaenoic Acids; C104450:25-hydroxyvitamin D; D015118:Eicosapentaenoic Acid