Beetroot juice has become popular among people interested in heart health because it can help lower blood pressure.
Now, researchers at King’s College London have found that drinking it with grapefruit juice may make that effect stronger. The early findings suggest that the two drinks may work together in an unexpected way.
High blood pressure is one of the world’s most common health problems. It makes the heart work harder and, over many years, can damage blood vessels and increase the risk of heart attack, stroke and kidney disease. Because it often causes no symptoms, many people do not realize they have it.
Diet can play an important role in controlling blood pressure alongside exercise, weight management and prescribed medicines.
Beetroot has attracted particular attention because it contains large amounts of nitrate, a natural substance also found in leafy green vegetables. The body can turn nitrate into substances that help blood vessels relax and widen.
When blood vessels widen, blood can flow through them more easily and pressure may fall. Previous research has found that nitrate-rich beetroot juice can produce modest reductions in blood pressure. Beetroot also provides nutrients such as folate, which is important for normal cell function and blood vessel health.
Grapefruit contains vitamin C, potassium, fiber and several plant compounds. Researchers wondered whether it could change the way the body processes nitrate from beetroot. Earlier work suggested grapefruit might slow part of the process that converts nitrate into nitrite in the blood.
Kevin O’Gallagher and colleagues tested the idea in 11 healthy volunteers. Participants received different drinks on separate occasions, including a 70-milliliter shot of nitrate-rich beetroot juice combined with 250 milliliters of grapefruit juice. Other conditions included beetroot juice with water and a placebo drink.
The researchers measured blood pressure for several hours after the drinks were consumed. The beetroot and grapefruit combination lowered blood pressure more than beetroot juice mixed with water. The effect was seen particularly in systolic blood pressure.
Systolic pressure is the first and higher number in a blood pressure reading. It measures pressure in the arteries when the heart contracts and pushes blood around the body. About two and a half hours after the combined drink, systolic pressure was 4.2 mmHg lower.
The effect did not disappear immediately. Five hours after drinking the combination, systolic blood pressure remained about 3.3 mmHg lower. The researchers also observed a reduction in pulse pressure, which is the difference between the systolic and diastolic readings.
One of the most interesting results was that grapefruit appeared to reduce nitrite levels in the blood while still strengthening the blood-pressure effect. That was not what might have been expected from the usual explanation of how dietary nitrate works. The researchers therefore do not yet know exactly why the combination produced a stronger response.
The study was published in the British Journal of Clinical Pharmacology. It provides an interesting clue about how foods can interact inside the body, but it is far too small to show that people with high blood pressure should start drinking grapefruit and beetroot juice together. Only 11 healthy people took part.
Healthy volunteers can also respond differently from older adults or people who already have hypertension, diabetes or heart disease. Larger and longer studies are needed to see whether the effect is consistent and whether regular consumption provides meaningful benefits. Researchers also need to understand the biological mechanism behind the finding.
There is another important reason for caution. Grapefruit can change how the body processes a number of prescription medicines, sometimes causing drug levels to become too high or too low. These interactions can involve medicines used for cholesterol, heart conditions and other health problems.
People taking prescription medicines should therefore check with a doctor or pharmacist before regularly adding grapefruit or large amounts of grapefruit juice to their diet. They should also not replace prescribed blood pressure treatment with juice based on this early study. High blood pressure often needs long-term medical management.
The research fits into a much larger body of evidence showing that overall eating patterns matter for cardiovascular health. Diets rich in vegetables, fruit, whole grains, beans, nuts and other minimally processed foods can support healthier blood pressure. Reducing excess salt is also particularly important for many people.
The study is intriguing because the combination produced a measurable effect within hours and because the result did not follow the expected nitrate pathway.
However, the tiny sample means the size of the benefit could change substantially when many more people are studied. It is best viewed as an early experiment that creates a useful question for future research.
If larger trials confirm the result, scientists may learn more about how different foods influence the way nitrate affects blood vessels. That could eventually help researchers design dietary approaches that support blood pressure control.
For now, beetroot remains an interesting heart-healthy food, while grapefruit should be consumed with extra care by anyone taking medicines that can interact with it.
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