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Lookup NU author(s): Dr Othman Qadir, Emeritus Professor Chris SealORCiD, Ammar Ashor, Dr Mario Siervo, Dr Kirsten BrandtORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2022, The Author(s). Purpose: To compare acute effects on blood pressure (BP) of ingestion of visually similar lettuce with controlled high and low content of either nitrate or phenolic compounds. Methods: In a randomised cross-over design, 19 healthy participants (22–31 years) received 50 g of lettuce containing either 530 mg (8.4 mmol) nitrate + 11 mg (0.03 mmol) phenolic compounds (HNLP); or 3 mg nitrate (0.05 mmol) + 77 mg (0.2 mmol) phenolic compounds (LNHP), obtained by differential fertilisation. Ambulatory BP was recorded along with plasma, salivary and urinary nitrate and nitrite and plasma concentrations of cyclic guanosine monophosphate (cGMP), phenolic metabolites, Trolox equivalent antioxidant capacity (TEAC) and ferric reducing antioxidant power (FRAP). Results: Compared with LNHP, 3 h post ingestion of HNLP, plasma nitrate increased 0.31 ± (95%CI) 0.12 mM (+ 240%), and salivary nitrate 5.5 ± 1.4 mM (+ 910%); accumulated urinary nitrate excretion increased 188 ± 72 mg (+ 296%) (all P < 0.001). Systolic BP was reduced 4.9 ± 4.2 mmHg (P = 0.031) between 3 and 6 h after ingestion of HNLP compared with LNHP; systolic BP differences were negatively correlated (P = 0.004) with differences in saliva nitrate concentrations. LNHP increased plasma phenolics at 6 h, predominantly 3ʹ-methoxycinnamic acid-4ʹ-glucuronide (ferulic acid-4ʹ-glucuronide), 116%, 204 ± 138 nM more than HNLP (P = 0.001); increased cGMP 14% (P = 0.019); and reduced FRAP 3.1% (P = 0.009). Conclusion: The acute BP difference within 6 h of consumption matched the plasma/saliva nitrate peak, not the slower changes of plasma phenolics. This is the first double-blind controlled dietary intervention demonstrating differential effects on human physiology by consumption of an intact plant food, where compositional differences were obtained by controlling growing conditions, indicating potential opportunities for health claims relating to precision/vertical farming. Clinical trial registration: The trial was retrospectively registered on ClinicalTrials.gov, with identifier NCT02701959, on March 8, 2016.
Author(s): Qadir OK, Seal CJ, Ashor AW, Tassotti M, Mena P, Del Rio D, Siervo M, Brandt K
Publication type: Article
Publication status: Published
Journal: European Journal of Nutrition
Year: 2022
Volume: 61
Issue: 8
Pages: 4191-4203
Online publication date: 23/07/2022
Acceptance date: 08/07/2022
Date deposited: 12/08/2022
ISSN (print): 1436-6207
ISSN (electronic): 1436-6215
Publisher: Springer Nature
URL: https://doi.org/10.1007/s00394-022-02961-5
DOI: 10.1007/s00394-022-02961-5
PubMed id: 35871120
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