Do cruciferous vegetables lower blood pressure? - BHF

Oct 15, 2024

You might have heard that eating more fruit and vegetables can help to reduce high blood pressure. But could a certain group of vegetables be particularly effective?

Published 14 October 2024

In September, several UK newspapers reported that eating cruciferous vegetables like broccoli, cabbage and cauliflower every day could lower blood pressure, and in doing so lower the risk of a heart attack or stroke.

They described these vegetables as ‘superfoods’ on the back of a study that suggested eating them every day for a fortnight reduced blood pressure in people with high blood pressure more than if they ate root and squash vegetables, such as potato and carrot.

The study included 17 adults from Perth, Australia, who were aged 68 on average. All of them had mildly high blood pressure and were asked to eat 4 servings of soup made of either cruciferous or root and squash vegetables every day for 2 weeks.

The cruciferous vegetable soup contained broccoli, cauliflower, cabbage and kale, while the root and squash vegetable soup was made of potato, pumpkin, carrot and sweet potato.

The researchers measured participants’ systolic blood pressure (the top number on a blood pressure reading) for 24 hours before the start of the trial and at the end of the 2 weeks.

They found systolic blood pressure readings among those who had the cruciferous vegetable soup had fallen 2.5mmHg more on average between the start and end of the study, than those who had the root and squash vegetable soup.

The researchers suggested that this difference in systolic blood pressure could offer a 5 per cent lower risk of them having a major heart or circulatory event, such as a heart attack or stroke.

This difference in blood pressure took place independently, as both groups of participants also lost similar amounts of weight, which is known to help lower blood pressure, reported the Australian researchers in the journal BMC Medicine.

The research team carried out the study because previous research has linked cruciferous vegetables to a lower risk of having heart and circulatory conditions.

For example, a 2017 research paper in The International Journal of Epidemiology found that across 8 different studies, people who ate the most cruciferous vegetables had a 12 per cent lower risk of heart and circulatory disease (cardiovascular disease) than those who ate the least.

The researchers behind the new study wanted to investigate if this association was caused by cruciferous vegetables’ effect on high blood pressure, which is 1 of the main risk factors for cardiovascular conditions like coronary heart disease, heart attack and stroke.

They also cited a 2021 review in The Lancet of 48 trials that looked at the effect of blood pressure medicines on reducing major heart events. It found lowering systolic blood pressure by 5mmHg for 4 years cut the risk of having a heart attack or stroke by around 10 per cent.

In their study, the researchers used this data to suggest that the 2.5mmHg difference in blood pressure between people who ate cruciferous vegetables, and those who ate root and squash vegetables, could lead to a 5 per cent risk lower risk of heart attack or stroke.

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A big limitation of the study was how small the number of participants was.

It included just 17 people aged 56 to 72 with mild to moderate high systolic blood pressure of between 120mmHg and 160mmHg.

Most of the group were White and female, with only 2 men and 1 person from Asian descent. This means the results cannot be applied to a larger population.

Furthermore, the study only showed that cruciferous vegetables were linked to a larger fall in blood pressure than root and squash vegetables. This does not prove they are more effective at lowering blood pressure than other types of vegetables, such as leafy greens.

Finally, it only lasted for 2 weeks, so we do not know if eating cruciferous vegetables would continue to reduce blood pressure more than root and squash vegetables in the long term.

The research was covered by a few media outlets in the UK, including the Daily Express.

Their headline called cruciferous vegetables a ‘superfood’. This is misleading as it could imply that these vegetables alone can reduce blood pressure to healthy levels, which the study did not show.

The article also quoted the study’s authors Emma Connolly, PhD candidate, and Lauren Blekkenhorst, PhD RNutr, with the Nutrition and Health Innovation Research Institute at Edith Cowan University, as telling Medical News Today: “We found a 2.5mmHg reduction in 24-hour ambulatory systolic blood pressure.”

However, the Daily Express did not explain that this ‘2.5 mmHg reduction’ was the average difference between the blood pressures of those who ate cruciferous vegetables compared to those who ate root and squash vegetables, not how much their blood pressure fell from their usual levels.

We know that all vegetables contain nutrients that can help to lower blood pressure, so it’s no surprise that people’s blood pressure was lower after eating more cruciferous vegetables.

But while this small study suggests that root and squash vegetables could be less effective at lowering blood pressure, it’s also worth noting that potatoes, which do not count as 1 of your 5 recommended portions of fruit and vegetables a day, made up 40 per cent of the root vegetable soup.

If you’re trying to lower your blood pressure, instead of focusing on just 1 group, try to eat more fruit and vegetables in general. Getting a range of different types and colours in your diet can give you a wider variety of nutrients.

Regular exercise and cutting down on alcohol and salt can help you lower blood pressure too.

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