Impact of a (poly)phenol-rich extract from the brown algae Ascophyllum nodosum on DNA damage and antioxidant activity in an overweight or obese population: a randomized controlled trial

Am J Clin Nutr. 2018 Oct 1;108(4):688-700. doi: 10.1093/ajcn/nqy147.


Background: Epidemiologic evidence suggests that a diet rich in (poly)phenols has beneficial effects on many chronic diseases. Brown seaweed is a rich source of (poly)phenols.

Objective: The aim of this study was to investigate the bioavailability and effect of a brown seaweed (Ascophyllum nodosum) (poly)phenol extract on DNA damage, oxidative stress, and inflammation in vivo.

Design: A randomized, double-blind, placebo-controlled crossover trial was conducted in 80 participants aged 30-65 y with a body mass index (in kg/m2) ≥25. The participants consumed either a 400-mg capsule containing 100 mg seaweed (poly)phenol and 300 mg maltodextrin or a 400-mg maltodextrin placebo control capsule daily for an 8-wk period. Bioactivity was assessed with a panel of blood-based markers including lymphocyte DNA damage, plasma oxidant capacity, C-reactive protein (CRP), and inflammatory cytokines. To explore the bioavailability of seaweed phenolics, an untargeted metabolomics analysis of urine and plasma samples after seaweed consumption was determined by ultra-high-performance liquid chromatography-high-resolution mass spectrometry.

Results: Consumption of the seaweed (poly)phenols resulted in a modest decrease in DNA damage but only in a subset of the total population who were obese. There were no significant changes in CRP, antioxidant status, or inflammatory cytokines. We identified phlorotannin metabolites that are considered potential biomarkers of seaweed consumption including pyrogallol/phloroglucinol-sulfate, hydroxytrifurahol A-glucuronide, dioxinodehydroeckol-glucuronide, diphlorethol sulfates, C-O-C dimer of phloroglucinol sulfate, and C-O-C dimer of phloroglucinol.

Conclusions: To the best of our knowledge, this work represents the first comprehensive study investigating the bioactivity and bioavailability of seaweed (poly)phenolics in human participants. We identified several potential biomarkers of seaweed consumption. Intriguingly, the modest improvements in DNA damage were observed only in the obese subset of the total population. The subgroup analysis should be considered exploratory because it was not preplanned; therefore, it was not powered adequately. Elucidation of the biology underpinning this observation will require participant stratification according to weight in future studies. This trial was registered at as NCT02295878.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Antioxidants / pharmacology*
  • Ascophyllum / chemistry*
  • Biological Availability
  • C-Reactive Protein / metabolism
  • Cross-Over Studies
  • Cytokines / blood
  • DNA Damage / drug effects*
  • Diet*
  • Double-Blind Method
  • Female
  • Humans
  • Inflammation / blood
  • Male
  • Middle Aged
  • Obesity* / genetics
  • Obesity* / metabolism
  • Obesity* / pathology
  • Overweight
  • Oxidative Stress / drug effects
  • Plant Extracts / pharmacology
  • Polyphenols / pharmacology*
  • Seaweed / chemistry*
  • Tannins / blood
  • Tannins / pharmacology


  • Antioxidants
  • Cytokines
  • Plant Extracts
  • Polyphenols
  • Tannins
  • C-Reactive Protein

Associated data