A broccoli seed extract containing a sulforaphane precursor reduced the number of cold symptom days in adults susceptible to colds. Digest
Colds undermine the health and well-being of millions each year, yet few effective strategies exist to prevent infection or cut recovery time. Researchers in Japan tested whether a broccoli seed extract that supplies sulforaphane glucosinolate, a precursor of the phytochemical sulforaphane, could lessen cold symptoms in people who say they catch colds easily.
The trial enrolled 66 healthy Japanese adults and randomly assigned them to take either the extract (100 mg sulforaphane glucosinolate per day) or a placebo powder for eight weeks.
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Broccoli seed extract improved several outcomes:
On average, participants taking the extract reported 8 fewer days with cold symptoms than placebo.
Symptom days made up 22 percent of all days in the extract group compared with 36 percent in placebo.
The longest stretch of consecutive symptom days was shorter with the extract, but this result was not statistically significant.
Two immune scores tended to improve slightly in the extract group, both linked to T cells, the white blood cells that fight virus-infected cells.
No side effects were reported.
The study's findings align with experimental evidence that sulforaphane modulates immune activity. Sulforaphane activates Nrf2, a protein that turns on antioxidant and antiviral defense genes. It may also raise levels of heme oxygenase-1, an enzyme that helps cells respond to viral infection. Together these changes could explain why participants taking the extract reported fewer days with cold symptoms. However, the findings are based on a single small demographic group, which restricts their generalizability. The study also relied on self-reported symptoms rather than medical examinations, and did not include measurements of sulforaphane blood levels or biomarkers such as cytokines or gene expression that could clarify the mechanisms. Future studies in broader populations with mechanistic assessments are needed to confirm and extend these findings. Learn more about the health benefits of sulforaphane in Episode #29, featuring sulforaphane expert Jed Fahey, ScD.