“Broccoli sprouts are one of the richest dietary sources of sulforaphane, a compound that has been studied for its potential anti-cancer effects." (Secondary claims carried by the same post, assessed below: "One of the most powerful anti-cancer compounds isn't found in an expensive supplement. It's found in a vegetable that costs a few…”

On the concentration half of the claim: the 1997 PNAS paper by Fahey, Zhang and Talalay at Johns Hopkins reported that 3-day-old sprouts of certain crucifers, including broccoli, contain roughly 10 to 100 times higher levels of glucoraphanin (the glucosinolate precursor of sulforaphane) than the corresponding mature plants. Later food-science reviews describe broccoli sprouts as containing 10 to 100 times higher sulforaphane than mature plants and characterise them as the most potent known dietary source. A 2021 NIH-indexed review of sulforaphane states that among cruciferous vegetables, broccoli and broccoli sprouts contain the highest concentration of glucoraphanin. This part of the claim is well established and not seriously contested. On the research half of the claim: sulforaphane has indeed been studied extensively for possible anti-cancer effects. The 1997 PNAS paper itself reported that broccoli sprout extracts reduced the incidence, multiplicity and rate of development of mammary tumours in chemically treated rats. A 2023 systematic review identified eight randomized controlled trials of sulforaphane in human cancer patients, covering prostate, breast, pancreatic cancer and melanoma. On whether that research has demonstrated benefit in humans: it has not, at least not yet. NCI's fact sheet states that studies in humans have shown mixed results, and describes cohort studies generally finding no association between cruciferous vegetable intake and colorectal cancer risk, varying results for lung cancer, and a meta-analysis finding no association with breast cancer risk. The Linus Pauling Institute's position, as reflected in standard reference summaries of it, is that there is no good clinical evidence that consuming sulforaphane-rich vegetables or supplements provides benefit against cancer. The largest sulforaphane RCT, Cipolla 2015, randomized 78 men with rising PSA after radical prostatectomy to 60 mg stabilized free sulforaphane or placebo for six months. The pre-specified primary endpoint, a 0.012 log(ng/mL)/month reduction in log PSA slope, was not reached in the intention-to-treat analysis (p = 0.11). Secondary endpoints favoured sulforaphane: PSA doubling time was 28.9 months versus 15.5 months in placebo (+86%), and PSA increases above 20% at month 6 occurred in 44.4% of the sulforaphane group versus 71.8% of placebo (p = 0.0163). The authors described the result as showing promise, not as establishing efficacy. The Alumkal phase II single-arm trial (n=20, 200 micromol/day) missed its primary endpoint of a 50% PSA decline, achieved in only 1 of 20 patients. The 2023 systematic review concluded sulforaphane is a promising and safe agent, but explicitly noted it could not perform a meta-analysis because of methodological and clinical heterogeneity, did not apply GRADE certainty ratings because too few results and patients were available per outcome, and flagged high risks of bias and methodological weaknesses across the included trials. No trial has reported a reduction in cancer incidence or cancer mortality from sulforaphane or broccoli sprouts.