{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,7]],"date-time":"2026-07-07T23:51:42Z","timestamp":1783468302665,"version":"3.55.0"},"reference-count":40,"publisher":"Wiley","issue":"2","license":[{"start":{"date-parts":[[2020,7,9]],"date-time":"2020-07-09T00:00:00Z","timestamp":1594252800000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Brit J Clinical Pharma"],"published-print":{"date-parts":[[2021,2]]},"abstract":"<jats:sec><jats:title>Aims<\/jats:title><jats:p>Dietary nitrate from sources such as beetroot juice lowers blood pressure (BP) via the nitrate\u2013nitrite\u2013nitric oxide (NO) pathway. However, NO and nitrite are inactivated via reoxidation to nitrate, potentially limiting their activity. Cytochrome P450\u20103A4 inhibition with troleandomycin prevents nitrite re\u2010oxidation to nitrate in rodent liver. Grapefruit juice contains the CYP3A4 inhibitor furanocoumarin. We therefore hypothesized that grapefruit juice would enhance BP\u2010lowering with beetroot juice by maintaining circulating [nitrite].<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>We performed a randomized, placebo\u2010controlled, 7\u2010hour crossover study in 11 healthy volunteers, attending on 3 occasions, receiving: a 70\u2010mL shot of active beetroot juice (Beet\u2010It) and either (i) 250 mL grapefruit juice (Active Beet+GFJ), or (ii) 250 mL water (Buxton, Active Beet+H<jats:sub>2<\/jats:sub>O); or (iii) Placebo Beet+GFJ.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>The addition of grapefruit juice to active beetroot juice lowered systolic BP (SBP): Active Beet+GFJ <jats:italic>vs<\/jats:italic> Active Beet+H<jats:sub>2<\/jats:sub>O (<jats:italic>P =<\/jats:italic> .02), and pulse pressure, PP (<jats:italic>P =<\/jats:italic> .0003). Peak mean differences in SBP and PP were seen at <jats:italic>T<\/jats:italic> = 5 hours: \u22123.3 mmHg (95% confidence interval [CI] \u22126.43 to \u22120.15) and at <jats:italic>T<\/jats:italic> = 2.5 hours: \u22124.2 mmHg (95% CI \u22120.3 to \u22128.2), respectively. Contrary to the hypothesis, plasma [nitrite] was lower with Active Beet+GFJ <jats:italic>vs<\/jats:italic> Active Beet+H<jats:sub>2<\/jats:sub>O (<jats:italic>P =<\/jats:italic> .006), as was salivary nitrite production (<jats:italic>P =<\/jats:italic> .002) and saliva volume (\u22120.34 mL\/min [95% CI \u22120.05 to \u22120.68]). The taste score of Beet+GFJ was 1.4\/10 points higher than Beet+H<jats:sub>2<\/jats:sub>O (<jats:italic>P =<\/jats:italic> .03).<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusion<\/jats:title><jats:p>Grapefruit juice enhanced beetroot juice's effect on lowering SBP and PP despite decreasing plasma [nitrite]. Besides suggesting more complex mechanisms, there is potential for maximising the clinical benefit of dietary nitrate and targeting isolated systolic hypertension.<\/jats:p><\/jats:sec>","DOI":"10.1111\/bcp.14420","type":"journal-article","created":{"date-parts":[[2020,6,10]],"date-time":"2020-06-10T13:19:31Z","timestamp":1591795171000},"page":"577-587","source":"Crossref","is-referenced-by-count":19,"title":["Grapefruit juice enhances the systolic blood pressure\u2010lowering effects of dietary nitrate\u2010containing beetroot juice"],"prefix":"10.1111","volume":"87","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2218-4763","authenticated-orcid":false,"given":"Kevin","family":"O'Gallagher","sequence":"first","affiliation":[{"name":"School of Cardiovascular Medicine and Sciences, Department of Clinical Pharmacology King's College London British Heart Foundation Centre of Research Excellence  London UK"},{"name":"Biomedical Research Centre, Clinical Research Facility Guy's and St 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