Underpowered or negative? A crucial distinction. Reply to Dollerup OL, Treebak JT, Jessen N [letter]

  • Niels J. Connell
  • Riekelt H. Houtkooper
  • Patrick SchrauwenEmail author


Clinical trial Human NAD+ metabolism 

To the Editor: Jessen and colleagues [1] have commented on our recent review of NAD+ metabolism in Diabetologia [2]. In their letter, they comment on the discussion and citation of a clinical trial that they performed, in which dietary nicotinamide riboside was supplemented in obese men to assess the effects on whole body insulin sensitivity [3].

We concede to the argument made by Jessen and colleagues that it is important to make a clear distinction between endpoints when citing clinical trials, as this may otherwise lead to unwanted assumptions regarding the endpoint(s) that are discussed. In our review, we did not have the intention to suggest that the study by Dollerup et al [3] was underpowered for its primary endpoint, insulin sensitivity, but unfortunately omitted to add ‘for these secondary endpoints’, for which we do apologise. Nevertheless, the overall message and conclusion of our review does not change and we agree with Jessen and colleagues that more human studies are needed to test the efficacy of dietary supplements in rigorously designed human clinical trials.


Contribution statement

All authors were responsible for drafting the article and revising it critically for important intellectual content. All authors approved the version to be published.

Duality of interest

The authors declare that there is no duality of interest associated with this manuscript.


  1. 1.
    Dollerup OL, Treebak JT, Jessen N (2019) Underpowered or negative? A crucial distinction. Diabetologia.
  2. 2.
    Connell NJ, Houtkooper RH, Schrauwen P (2019) NAD+ metabolism as a target for metabolic health: have we found the silver bullet? Diabetologia.
  3. 3.
    Dollerup OL, Christensen B, Svart M et al (2018) A randomized placebo-controlled clinical trial of nicotinamide riboside in obese men: safety, insulin-sensitivity, and lipid-mobilizing effects. Am J Clin Nutr 108(2):343–353. CrossRefPubMedGoogle Scholar

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • Niels J. Connell
    • 1
  • Riekelt H. Houtkooper
    • 2
  • Patrick Schrauwen
    • 1
    Email author
  1. 1.Department of Nutrition and Movement Sciences, NUTRIM School for Nutrition and Translational Research in MetabolismMaastricht UniversityMaastrichtthe Netherlands
  2. 2.Laboratory Genetic Metabolic Diseases, Amsterdam Gastroenterology and Metabolism, Amsterdam UMCUniversity of AmsterdamAmsterdamthe Netherlands

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