Untargeted ¹H-NMR Metabolomics Identifies Candidate Metabolic Changes Associated with Watercress (Nasturtium...

Background/Objectives: Watercress (Nasturtium officinale R.Br.) is a glucosinolate-rich cruciferous vegetable with reported cardioprotective properties. However, previous human studies have relied on targeted clinical and biochemical biomarkers, limiting insight into its broader metabolic effects. This exploratory study investigated plasma metabolomic changes associated with watercress supplementation in adults with low-to-moderate cardiovascular risk using untargeted proton nuclear magnetic resonance (¹H-NMR) spectroscopy. Methods: In this randomized, single-blind, placebo-controlled pilot trial (Thai Clinical Trials Registry: TCTR20251119004), 26 participants aged 40-59 years received dried watercress capsules (8 g/day; approximately 195 mg glucosinolates/day) or placebo for 28 days. Fasting plasma samples collected at baseline and Day 28 underwent untargeted ¹H-NMR profiling. Partial least squares-discriminant analysis (PLS-DA) assessed group discrimination, while Kyoto Encyclopedia of Genes and Genomes (KEGG)-based pathway enrichment and topology analyses identified perturbed metabolic pathways. Results: A total of 209 plasma metabolites were identified. PLS-DA demonstrated modest discrimination between groups (Q² = 0.268), with 27 discriminant metabolites (variable importance in projection > 1.5) involving amino acid, nucleotide, carbohydrate, and gut microbial metabolism. Eighteen metabolic pathways were significantly perturbed, particularly galactose and fructose/mannose metabolism (p < 0.001), together with glycerolipid, purine, glycolysis/gluconeogenesis, and tryptophan metabolism. Watercress supplementation reduced metabolites associated with oxidative DNA damage, inflammatory kynurenine metabolism, and microbial co-metabolism, while increasing glycine and dimethylglycine and altered gut microbial activity. Conventional biomarkers showed a significant decrease in low-density lipoprotein cholesterol but no consistent effects on other lipids. Conclusions: Watercress supplementation was associated with coordinated metabolic alterations across multiple pathways, generating mechanistic hypotheses for its antioxidant and cardiometabolic effects. These findings are exploratory and warrant confirmation in larger, adequately powered clinical trials.