Really, Soup Might Help in Osteoarthritis?

People with osteoarthritis (OA) appeared to benefit, in terms of knee pain and function, from a broccoli-laden soup, results from a small pilot trial indicated.

Patients who ate the broccoli soup for 12 weeks saw a reduction in mean Western Ontario-McMaster Universities Osteoarthritis Index (WOMAC) pain scores of 3.17 points, whereas scores for those assigned to a “placebo” soup increased by an average of 0.61 points, according to Rose K. Davidson, PhD, of the University of East Anglia in Norwich, England, and colleagues.

The mean difference of 4.2 points, out of the measure’s 20-point scale, was statistically significant (95% CI 1.0-7.4), as well as clinically relevant, the researchers reported in a medRxiv manuscript preprint, despite only having 18 patients in the trial.

Stressing that the study was meant primarily to establish feasibility, both for the soup product and the ability to test it in a formal trial, Davidson and colleagues declared it a great success.

“We report high participant acceptability, adherence, and retention for the study design. We show that it is feasible to collect dietary and biological samples for objective measures of compliance for the intervention and that blinding was sufficient,” they wrote.

“Notwithstanding the challenges of underpower we observed clear patterns for improved pain across a range of pain measures and the MCID [minimal clinically important difference] was met” both for WOMAC pain score and a separate measure of constant pain, they continued. “We demonstrate the intervention to be feasible, and a larger trial should be conducted.”

Davidson and colleagues were hoping to build on earlier evidence, mostly from in vitro and animal studies, that one particular nutrient in broccoli — glucoraphanin, along with its metabolite sulforaphane — may be an effective OA therapy. In mouse models, the researchers said, sulforaphane has “demonstrated a protective role in reducing inflammation and cartilage destruction.”

Putting broccoli in soup was the group’s approach to making it both palatable and standardizable as a nutraceutical (although self-reported broccoli haters were excluded). The vegetable is “widely accessible and can be used on a large scale,” they noted. But the acceptability and other requirements for scientific testing needed to be confirmed before proceeding with a true efficacy study.

Twenty-four patients were initially enrolled and randomized, with seven assigned to the broccoli soup, which was developed at the Institute of Food Research in Norwich (now part of the National Health Service’s Quadram Institute), and 17 to a control product. Both used a multi-vegetable soup base, which served as the placebo; the intervention soup also included broccoli extract, equivalent to 225 g of broccoli, or just about half a pound. Participants were instructed to eat 300 mL of the assigned soup once daily.

Patients were recruited from two centers in eastern England. To be eligible, patients needed Kellgren-Lawrence knee OA grades of 2-3 and to meet other standard criteria for a knee OA diagnosis. Individuals with knee surgery in the previous 6 months, or who were anticipating surgery during the study period, were excluded, as were those recently receiving intra-articular corticosteroid or hyaluronic acid injections.

Groups weren’t equally balanced: in the control group, mean patient age was 62 and close to 60% were women; among those assigned to the intervention, 70 was the mean age and just 43% were women. Also, duration of knee pain averaged 7 years for control participants versus 3 years in the intervention group.

Attrition was considerable during the 12-week trial: five participants in the control group and two assigned to the broccoli soup were lost to follow-up. But even with the diminished numbers, outcomes including WOMAC physical function and Measure of Intermittent and Constant Osteoarthritis Pain (ICOAP) scores favored the intervention after 12 weeks.

The mean difference for WOMAC function score was 1.94 points (95% CI 0.18-3.70). Changes in ICOAP constant pain scores were apparently quite variable, for the mean difference of 4.83 points at week 12 — from baseline values in the range of 6-8 — failed to reach statistical significance. But scale of this difference, given the ICOAP’s 20-point scale, allowed Davidson’s group to argue that this reflected a genuine effect.

Numerical advantages for the broccoli soup were also seen for other patient-reported measures of pain — overall, worst-day, and in other joints. Oddly, perhaps, there was little sign of a placebo effect with the control soup, as the majority of outcome measures showed only minor changes from baseline or worsening. Also, no benefit in WOMAC stiffness ratings could be discerned.

Limitations to the study included the small patient numbers and its conduct during the COVID-19 pandemic, which “curtailed data collection and restricted sample size below that originally planned,” the researchers commented.

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