Why is broccoli good for you?

“Eating steamed broccoli reduces the risk of a heart attack by boosting the body’s ability to fight off cell damage”, The Daily Telegraph reported.

New research suggests that a mechanism involving antioxidants found in the Brassicaceae family of vegetables (cauliflower, broccoli, cabbage and Brussels sprouts) prevents the build-up of free radicals. Excessive production of free radicals can harm cells and even trigger cancers. The paper quotes other researchers who have long believed that antioxidant substances have health benefits. However, many studies have failed to show an effect.

The rats which were fed broccoli during this study showed some changes in proteins and heart function compared to those fed only water. However, without knowing if the activation of heart-protective proteins in response to antioxidants would be the same in humans, it would be premature to claim that eating broccoli specifically reduces your chance of a heart attack, as opposed to a healthy eating pattern in general.

Where did the story come from?

Subhendu Mukherjee and two colleagues at the Cardiovascular Research Center, University of Connecticut School of Medicine in the US, carried out this research. The study was published in the scientific journal The Journal of Agricultural and Food Chemistry.

What kind of scientific study was this?

This was a laboratory study conducted in rats which investigated whether eating broccoli could be beneficial to the heart. The researchers suspected this might be the case as broccoli contains high amounts of selenium, an inorganic chemical that is thought to mop up free radicals and glucosinolates (organic compounds derived from sugar and also found in many other green vegetables). Glucosinates are toxic in high doses, but are converted to sulphoraphanes by chewing and these are thought to protect against cancer and heart disease.

The researchers fed broccoli (in a slurry made with water) to a group of six rats, while six control animals were fed only water. After 30 days, the hearts of the animals were removed and the blood supply cut off for 30 minutes, followed by two hours where the blood flow was returned. This was intended to be the experimental equivalent of a heart attack. The researchers then performed a variety of tests on the hearts and the heart muscle cells.

What were the results of the study?

When compared to the control group, the rats which were fed broccoli showed improved heart muscle function after the experimental heart attack: they had a smaller amount of dead heart muscle and heart muscle cells. These changes were accompanied by changes in several proteins found in the cell nuclei, and other chemicals thought to protect the heart.

What interpretations did the researchers draw from these results?

The researchers report that the experimental heart attack led to the death of heart muscle cells by causing a change in the mitochondria within these cells and the release of a protein that ‘programmes’ the cell for death. Broccoli consumption appeared to reduce the number of heart muscle cells programmed for cell death and also the levels of protein released, which indicated that it was able to generate some kind of “anti-cell death” signal. They examined several components of these pathways and claim that broccoli appears to rescue the heart muscle in the experimental model heart attack through some form of survival pathway.

What does the NHS Knowledge Service make of this study?

This study has investigated the pathways thought to protect heart muscle from cell death during a heart attack, using a rat model of the disease.

The researchers claim that broccoli is a unique vegetable in this respect, and implied in the title of their paper that their results might apply to mammals in general. However, how these results apply to heart attacks in humans remains to be seen. It is also not known whether these results could be achieved with other vegetable diets in rats.

Until further research can confirm these findings, the best advice may be to protect heart muscle by following conventional advice: eat healthy food, engage in moderate physical activity and avoid smoking. There is also no harm in eating broccoli as part of a healthy, balanced diet.

Sir Muir Gray adds...

We already have enough evidence to eat broccoli often; 5 a day could include broccoli every day.