Scientists from King’s College London have discovered that grapefruit juice may enhance the blood pressure–lowering effects of beetroot juice.
Beetroot is naturally rich in folate (vitamin B9), an essential nutrient that supports cell growth and helps protect blood vessels from damage, reducing the risk of heart disease and stroke.
Beets are also high in dietary nitrates, which the body converts into nitric oxide—a compound that relaxes and widens blood vessels, thereby lowering blood pressure.
Previous research has shown that nitrate-rich beetroot juice can effectively reduce blood pressure in both healthy adults and those with hypertension.
Grapefruit, meanwhile, is low in calories and packed with nutrients, especially vitamins A and C. It is also low on the glycemic index, meaning it provides important nutrients without strongly affecting blood sugar levels.
Its combination of fiber, potassium, lycopene, vitamin C, and choline has been linked to improved heart health.
In this study, researchers set out to determine whether grapefruit juice could amplify the blood-pressure-lowering effects of beetroot juice by helping maintain circulating nitrite levels. Earlier studies suggested that grapefruit juice may slow the metabolic conversion of nitrate to nitrite, thereby preserving more of the compounds that help regulate blood pressure.
The team conducted a controlled experiment involving 11 healthy volunteers, each participating in three separate test sessions. The participants received either a 70-mL shot of active beetroot juice (“Beet-It”) combined with 250 mL of grapefruit juice; active beetroot juice with 250 mL of water; or a placebo drink containing neither beetroot juice nor grapefruit juice.
Results showed that adding grapefruit juice to beetroot juice significantly lowered systolic blood pressure and pulse pressure compared with beetroot juice mixed with water. Systolic blood pressure—the top number in a blood pressure reading—measures the force inside arteries when the heart beats. Pulse pressure represents the difference between systolic and diastolic pressure and is another important marker of cardiovascular health.
Five hours after consuming the combination of beetroot juice and grapefruit juice, participants experienced an average reduction of 3.3 mmHg in systolic blood pressure. A stronger effect appeared two and a half hours after consumption, when systolic pressure fell by an average of 4.2 mmHg.
Notably, these improvements occurred even though grapefruit juice reduced nitrite levels in the blood, a finding that contradicts expectations based on earlier studies. Despite this, the overall cardiovascular effect was enhanced.
The researchers concluded that grapefruit juice can boost the blood-pressure-lowering impact of beetroot juice, improving both systolic blood pressure and pulse pressure.
The study, led by Kevin O’Gallagher and colleagues, was published in the British Journal of Clinical Pharmacology.
