Mario Siervo1,2, Kirsten Brandt3, Othman K Qadir1,4, Chris J Seal1, Ammar W Ashor1,5, Michele Tassotti6, Pedro Mena6, Daniele Del Rio6,7. 1. Human Nutrition Research Centre, Population Health Sciences Institute, William Leech Building, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK. 2. School of Life Sciences, Queen's Medical Centre, Nottingham University, Nottingham, NG7 2UH, UK. 3. Human Nutrition Research Centre, Population Health Sciences Institute, William Leech Building, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK. kirsten.brandt@ncl.ac.uk. 4. Food Science and Quality Control Department, College of Agricultural Engineering Sciences, University of Sulaimani, 46001, Sulaymaniah, Kurdistan Region, Iraq. 5. Department of Internal Medicine, College of Medicine, Mustansiriyah University, Baghdad, Iraq. 6. Human Nutrition Unit, Department of Food and Drugs, University of Parma, Medical School Building C, Via Volturno, 39, 43125, Parma, Italy. 7. School of Advanced Studies on Food and Nutrition, University of Parma, Parma, Italy.
Abstract
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 3'-methoxycinnamic acid-4'-glucuronide (ferulic acid-4'-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.
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 3'-methoxycinnamic acid-4'-glucuronide (ferulic acid-4'-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.
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