Could eating broccoli slow the onset of arthritis?

"Broccoli could hold the key to preventing painful arthritis," the Daily Mail reports. But while the study the Mail reports on had promising results, it did not involve humans. The story is based on tests of a compound called sulforaphane on human and cow cartilage cells and artificially induced arthritis in mice.

Cartilage is the protective tissue found on the surface of joints that helps them to move smoothly. Damage and breakdown of cartilage can lead to osteoarthritis, which often causes severe symptoms of joint pain and swelling.

Sulforaphane is found in broccoli, and previous studies have suggested that it might help stop the breakdown of cartilage.

In this study, the researchers found that sulforaphane helped reduce the production of the enzymes that contribute to human cartilage breakdown. It was also found to protect bovine cartilage tissue from damage in the lab. The mice fed a sulforaphane-rich diet also had fewer signs of arthritis in their cartilage than controls.

Researchers now plan to study people with osteoarthritis who are awaiting joint surgery, testing the effects of eating "super broccoli", specially bred to release large amounts of sulforaphane. The results of this study will better indicate if eating broccoli can have a beneficial effect on osteoarthritis in people.

Where did the story come from?

The study was carried out by researchers from the University of East Anglia, the University of Oxford, and Norfolk and Norwich University Hospital. It was funded by the Biotechnology and Biological Sciences Research Council (BBSRC), Dunhill Medical Trust and Arthritis Research UK.

The study was published in the peer-reviewed journal, Arthritis and Rheumatism.

It was covered widely in the media, with many sources overplaying its results. Broccoli has not yet been found to be "key to beating [osteoarthritis]", as claimed in the Daily Express. BBC News took a more cautious approach, however, reporting that researchers believe broccoli may slow down arthritis.

What kind of research was this?

This was a laboratory and animal study. Researchers used three models to study the possible effect of the compound sulforaphane on cartilage. Sulforaphane is found in cruciferous vegetables, particularly broccoli.

The researchers say some research suggests a high intake of fruit and vegetables may prevent or slow down osteoarthritis. Sulforaphane has also been reported to:

• have anti-inflammatory properties
• protect against a form of inflammatory arthritis in mice
• reduce the production of enzymes that contribute to the breakdown of cartilage

Their study investigated the impact of sulforaphane on chondrocytes. These are cells that produce and maintain the proteins that form the structure of cartilage in mammals. 

What did the research involve?

The researchers constructed three different models to test the effect of sulforaphane on cartilage:

• They isolated and cultured chondrocytes taken from the cartilage of patients with osteoarthritis in the laboratory. They treated some of the cells with sulforaphane for 30 minutes, while some were left untreated. The cells were then treated with molecules called cytokines, which induce inflammation and normally increase the production of enzymes that break down cartilage. The researchers looked at whether the sulforaphane-treated cells produced as many of these enzymes as the untreated cells.
• The researchers also took cartilage tissue from cattle and again either treated it with sulforaphane or left it untreated before adding cytokines. They then looked at indicators of how much cartilage damage had occurred in treated and untreated samples.
• In the third model, they used two groups of mice: one group was fed a normal mouse diet and the other group a mouse diet plus sulforaphane. They were fed this way for two weeks before and after the researchers performed a surgical procedure on one of each mouse's knee joints to induce osteoarthritis-like changes. After two weeks the joints were then scored for signs of cartilage damage and osteoarthritis. 

What were the basic results?

The researchers found that:

• In the human cartilage cells treated with cytokines in the lab, sulforaphane reduced the production of enzymes involved in cartilage damage.
• Sulforaphane reduced the damage to bovine cartilage normally caused by cytokine treatment.
• Mice whose diet was supplemented with sulforaphane showed less arthritis-like cartilage damage after arthritis-inducing surgery than mice fed a normal diet.

How did the researchers interpret the results?

The researchers concluded that sulforaphane inhibits the production of key enzymes implicated in osteoarthritis. It has also been shown to protect against cartilage destruction at the cellular, tissue and whole animal level.

They suggest that a diet high in sulforaphane may help prevent or slow down the progress of arthritis in humans. 

In an accompanying press release, Ian Clark, professor of musculoskeletal biology at UEA and the lead researcher, said: "The results from this study are very promising …We now want to show this [sulforaphane treatment] works in humans. It would be very powerful if we could.

"This study is important because it is about how diet might work in osteoarthritis. Once you know that, you can look at other dietary compounds which could protect the joint, and ultimately you can advise people what they should be eating for joint health."

Conclusion

The results of this study suggest that sulforaphane, a chemical found in vegetables such as broccoli, could help reduce cartilage damage. As the authors point out, there is no drug cure for arthritis and if a common vegetable such as broccoli was found to be protective it would be very good news.

However, it is important to remember that this was a laboratory study involving human cells, cartilage samples from cows, and mice. The mice were fed a diet high in sulforaphane, rather than broccoli itself. There is a long way to go before scientists know if a diet high in broccoli or similar vegetables can prevent or slow down arthritis in humans.

The researchers are now planning a small trial of sulforaphane-rich broccoli in people with osteoarthritis waiting to undergo knee joint replacement surgery. The results of this trial will allow researchers to determine if the treatment shows effects on cartilage in humans. If this is successful, a larger clinical trial would be needed looking at the effect of broccoli on arthritis symptoms.

There is evidence that taking regular exercise and maintaining a healthy weight both help prevent osteoarthritis. Broccoli is full of nutrients and can form part of a healthy diet, but we can't yet be certain if it slows down or prevents arthritis.