Farmed fish not have enough vitamin D to increase levels – RCT Feb 2014

Effects of a healthy Nordic diet on plasma 25-hydroxyvitamin D concentration in subjects with metabolic syndrome: a randomized, placebo-controlled trial (SYSDIET).

Eur J Nutr. 2014 Feb 26.
Brader L1, Rejnmark L, Carlberg C, Schwab U, Kolehmainen M, Rosqvist F, Cloetens L, Landin-Olsson M, Gunnarsdottir I, Poutanen KS, Herzig KH, Risérus U, Savolainen MJ, Thorsdottir I, Uusitupa M, Hermansen K.

PURPOSE:
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.

CONCLUSION:
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.

PMID: 24570029

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https://doi.org/10.1007/s00394-014-0674-3

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I wonder when they are going to get around to adding Vitamin D to the diets of farmed fish

See also VitaminDWiki

• Food Sources of Vitamin D category listing has 112 items along with related searches
• 11,000 IU vitamin D daily from traditional Norwegian diet of cod, cod liver, cod-liver oil, and roe – 2004 before fish farming
• A balanced diet is no longer enough – supplements needed - VitaminDWiki Oct 2012