Boosting plant food polyphenol concentration by saline eustress as supplement strategies for the prevention of metabolic syndrome: an example of randomized interventional trial in the adult population

Abstract

Introduction: Phenolic compounds in lettuce can increase by the application of positive stress (eustress) such as moderate saline stress. Phenolic compounds possess antioxidant capacity that is a key factor in the detoxification of excess reactive oxygen species. A double-blinded randomized interventional and placebo- controlled study design was carried out to compare the effect of daily dietary eustress lettuce ingestion in hepatic, lipid, bone, glucose, and iron metabolism.

Methods: Forty-two healthy volunteers, 19 female and 23 male participants, were divided into two groups. Participants were randomized into a polyphenol-enriched treatment (PET) arm or control arm. Each arm consumed 100 g/day of control or eustress (polyphenols enriched treatment = PET) lettuce for 12 days. Primary study outcomes were serological analysis for assessing hepatic, lipid, bone, iron, and glucose markers at baseline and after 12 days. Secondary outcomes assessed body composition.

Results: Salinity stress reduced plant yield but increased caffeic acid (+467%), chlorogenic acid (+320%), quercetin (+538%), and rutin (+1,095%) concentrations. The intake of PET lettuce reduced PTH, low-density lipoprotein (LDL), cholesterol, alanine transaminase (ALT), and aspartate transaminase (AST) enzyme levels and increased vitamin D and phosphate levels, while iron and glucose metabolism were unaffected.

Discussion: Supplementation with eustress lettuce by increasing polyphenols concentration ameliorates hepatic, lipid, and bone homeostasis. Body composition was not affected.

Clinical trial registration: https://classic.clinicaltrials.gov/ct2/show/NCT06002672, identifier: NCT06002672.

Keywords: MetS; body homeostasis; diet; functional food; lettuce; nutritional intervention; phytochemicals.