Supplement
Sulforaphane (Broccoli Sprout Extract)
Glucose control and insulin resistance in type 2 diabetes, on small short trials: one 4-week Tehran trial of 10 g/day broccoli sprout powder lowered insulin and HOMA-IR, and a Swedish trial of a concentrated sprout extract lowered fasting glucose and HbA1c A blood test that reflects average blood sugar over the previous two to three months. in obese patients with poorly controlled diabetes, a subgroup.
Grade C: human trials exist, but they are small, mixed or not yet repeated. This is not a finding that it does not work. How to read a grade →
Sulforaphane is a compound from broccoli sprouts. It has been tested for blood sugar in people with type 2 diabetes. In two small, short studies, it lowered insulin or improved blood sugar, though one result came from only part of the group. In people with prediabetes, it did not meet its main goal. So the evidence is early and mixed.
A letter describes the human evidence, not the product, the manufacturer, or the ingredient's worth.
See the full evidence record →Trials report an average. This box says whether any trial on this record looked at who the result applies to, and what it found.
For this record's Grade C · Subgroup tested, effect differedAxelsson et al. (2017; PMID PubMed ID: the permanent number the US National Library of Medicine gives a published paper. Each one links to that paper's record on PubMed. 28615356) found lower fasting glucose and HbA1c only in a subgroup, obese patients with poorly controlled diabetes. The same group's prediabetes trial (PMID 39929977) missed its prespecified primary endpoint The one outcome a trial names in advance as its main test. Results on other outcomes carry less weight.. A subgroup result shows who the effect appeared in within these trials. It does not change the letter.
Glucose control and insulin resistance in type 2 diabetes on small, short trials, one a subgroup result; a prediabetes trial missed its primary.
How this letter has changed · latest: October 2026 · Corrected
best_use led with NRF2 activation and claimed neuroprotective, cancer-preventive and cardiometabolic effects that no cited randomized trial measured; the record's own NRF2 trial (Wise et al., 2016; PMID 27832073) was null and a hemodialysis crossover A trial design in which each participant receives both the treatment and the comparison, one after the other, and serves as their own control. (Ribeiro et al., 2024; PMID 37619675) found no change in NRF2 mRNA, with one small positive in non-dialysis kidney disease (PMID 38772511). The field now states glucose control in type 2 diabetes, the only clinical question the trials address. Added: Dwibedi et al. (2025; PMID 39929977), the Lund group's prediabetes trial that missed its prespecified primary endpoint with patent and stock interests disclosed; Christiansen et al. (2010; PMID 20805984), no effect on endothelial function or blood pressure in hypertension. Axelsson 2017 (PMID 28615356) is now described as a subgroup result, and PMIDs 22537070, 21559038 and 22325157 as one 81-patient Tehran trial reported three times. The dose field now names what was studied rather than a 10 to 40 mg label. C unchanged. Applied the written grade definition under the editor's standing instruction of October 2026 (Arnold Sandlow, D.C.).PMID 20805984 PMID 27832073 PMID 28615356 PMID 37619675 PMID 38772511 PMID 39929977
Every change to a letter on this site is dated and published. The full evidence log →
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EBL earns no commission on any supplement it grades. A purchase made through the dispensary link below pays EBL nothing, the practitioner discount goes to you in full. The dispensary is Fullscript, a practitioner dispensary, and many of the professional-grade brands in it are sold mainly through practitioners rather than in health food stores. Grades are assigned by published rubric before any commercial relationship exists and are never influenced by one. Full disclosure.
As studied: 10 g/day broccoli sprout powder for 4 weeks (Tehran; sulforaphane content not stated in the reports) and a concentrated broccoli sprout extract (Sweden). Products labeled 10 to 40 mg sulforaphane equivalent have not been tested on these endpoints at that labeling.
The glycemic trials used broccoli sprout powder or a concentrated broccoli sprout extract. Glucoraphanin is a precursor converted to sulforaphane by myrosinase, and products differ in whether they supply active myrosinase; no trial on these endpoints compared forms.
The cited trials gave sulforaphane or broccoli sprout powder daily (PMID 22537070, PMID 21559038, PMID 27832073, PMID 25313065). They do not state a time of day or whether doses were taken with food.
Checked against the full report for 1 of the 4 cited studies, and the published summary for the rest. What the cited trials did, not a schedule. Every supplement, by trial timing →
How to buy this: quality criteria, not a brand
10–40mg active sulforaphane/day.
Glucoraphanin plus myrosinase, or sprouted-broccoli-seed products, glucoraphanin alone needs gut bacteria to convert.
Glucoraphanin content and active myrosinase stated on the label, with the sulforaphane yield; any USP or NSF third-party seal.
Glucoraphanin with no myrosinase; no active-sulforaphane yield on the label.
The grade and these criteria are set only from human trials. Any purchase link is convenience and does not affect the grade.
Pregnancy, on absence of data at concentrated doses. High doses cause GI upset and rash. The goitrogenic concern attached to brassicas does not extend meaningfully to isolated sulforaphane at studied doses.
CYP1A2 induction at high doses would lower blood levels of drugs cleared that way. Human dietary trials have measured that induction from cruciferous vegetables; none has measured it from isolated sulforaphane at a supplement dose, so the size of the effect from a capsule is unknown. Sulforaphane is a nuclear factor erythroid-2 activator, so the general antioxidant-during-chemotherapy caution applies as an oncology decision.
No trial has given sulforaphane during chemotherapy; the one trial in cancer patients ran before surgery instead. Sulforaphane has been given to cancer patients in a randomized trial, but not during treatment: a presurgical window study gave broccoli sprout extract for two weeks before surgery in 30 postmenopausal breast cancer patients and measured tissue biomarkers A measurable sign in the body, such as a blood test value, used to track a condition or the effect of a treatment., not treatment efficacy. That design deliberately avoids the question this conflict text raises. So the caution here is entirely class-level and mechanistic. The class-level human evidence is real but it is not about this compound. Neither study tested it, and neither result is statistically significant Unlikely to be explained by chance alone at the threshold the study set. It says nothing about whether the difference is large enough to matter. on its own: the breast cancer analysis was observational Research that watches what people already do rather than assigning a treatment. It can show that two things travel together, not that one causes the other. within a randomized trial and its antioxidant signal did not reach significance, and the head and neck trial's recurrence signal was a trend. Two independent trends in the same direction, on hard endpoints An outcome that matters directly to a person and is counted without judgment, such as death, heart attack, stroke or fracture., in a setting where the mechanism predicts exactly that direction, is why the caution exists. It is not a measured effect for any supplement here. Wang et al. (Molecular Nutrition and Food Research, 2022;66(12):e2101094; PMID 35475592): randomized presurgical window-of-opportunity trial, 30 postmenopausal breast cancer patients, isothiocyanate-rich broccoli sprout extract at 200 micromol per day for two weeks versus placebo An inactive substitute made to look like the real treatment, so participants cannot tell which one they received., with biomarker endpoints in tumor tissue. Ambrosone et al. (Journal of Clinical Oncology, 2020;38(8):804-814; PMID 31855498): prospective study of 1,134 patients ancillary to the randomized SWOG S0221 breast cancer trial; any antioxidant use both before and during chemotherapy carried an adjusted hazard ratio How often an event happened in the treated group compared with the control group over the same period. A ratio of 0.80 means 20 percent fewer events. for recurrence of 1.41 (95% CI 0.98 to 2.04, P = .06). Bairati et al. (Journal of Clinical Oncology, 2005;23(24):5805-13; PMID 16027437): randomized double-blind Neither the participants nor the people assessing them know who received the real treatment until the trial ends. placebo-controlled trial, 540 head and neck cancer patients given alpha-tocopherol and beta-carotene during radiotherapy; acute adverse effects fell, and local recurrence tended to rise (hazard ratio 1.37, 95% CI 0.93 to 2.02).
CYP1A2 induction is measured in humans for cruciferous vegetables, not for isolated sulforaphane. A systematic review A review that searches for every study on a question using a method set in advance, then assesses them together. and meta-analysis A study that pools the numbers from several trials into one combined estimate. of human dietary intervention trials found that eating cruciferous vegetables induces CYP1A2 activity in vivo, while noting disagreement between reports and that the clinical significance of the resulting diet-drug interactions is unclear. What no trial has done is give isolated sulforaphane at a supplement dose and measure the same thing. So the direction is established in people and the magnitude from a capsule is not, which is a different statement from calling it a laboratory finding. Eagles et al. (Clinical Pharmacology and Therapeutics, 2020;108(2):212-227; PMID 32086800): systematic review and meta-analysis of dietary intervention trials in humans on the effects of cruciferous vegetable-enriched diets on drug metabolism.
The trials measured the clinical target rather than any sulforaphane-specific biomarker; no validated sulforaphane marker exists.
Primary evidenceEleven papers, each linked to its PubMed record.
Bahadoran et al. (Int J Food Sci Nutr, 2012; PMID 22537070): 81 patients with type 2 diabetes in Tehran, 10 or 5 g/day broccoli sprout powder or placebo for 4 weeks; serum insulin and HOMA-IR fell at 10 g/day. The same trial was reported twice more: Bahadoran et al. (Eur J Clin Nutr, 2011; PMID 21559038) on oxidative stress markers and Bahadoran et al. (Diabetes Res Clin Pract, 2012; PMID 22325157) on triglycerides and oxidized LDL Low-density lipoprotein cholesterol, the cholesterol fraction most closely tied to plaque in the arteries.. Three papers, one 81-patient trial; they do not replicate each other. Axelsson et al. (Sci Transl Med, 2017; PMID 28615356): a concentrated broccoli sprout extract reduced fasting glucose and HbA1c in obese patients with dysregulated type 2 diabetes, which the abstract states as the group in which the effect appeared, so it is a subgroup result. Dwibedi et al. (Nat Microbiol, 2025; PMID 39929977): the same Lund group, 74 drug-naive adults with prediabetes, 12 weeks; the prespecified primary endpoint (a 0.3 mmol/L fall in fasting glucose) was missed, with an overall fall of 0.2 mmol/L; two authors hold patents on sulforaphane for hepatic glucose production licensed to a company in which one holds stock, and the extract's manufacturer supplied the product and placebo. NULL FINDINGS on the mechanism: Wise et al. (PLoS One, 2016; PMID 27832073), 89 patients with COPD, 4 weeks, no effect on Nrf2 target gene expression; Ribeiro et al. (J Ren Nutr, 2024; PMID 37619675), 30 hemodialysis patients, crossover, no change in NRF2 or NF-kB mRNA; Ribeiro et al. (Free Radic Biol Med, 2024; PMID 38772511), non-dialysis chronic kidney disease, NRF2 and NQO1 mRNA rose at 400 micrograms/day for one month, the one positive. Christiansen et al. (PLoS One, 2010; PMID 20805984): 40 adults with hypertension, 10 g/day dried broccoli sprouts for 4 weeks; no improvement in flow-mediated dilation or blood pressure. Singh et al. (Proc Natl Acad Sci U S A, 2014; PMID 25313065): randomized placebo-controlled trial in autism spectrum disorder, a different population and question, not graded here. Egner et al. (Cancer Prev Res (Phila), 2011; PMID 21372038): bioavailability The share of a dose that reaches the bloodstream in a form the body can use. crossover of two sprout beverages in Qidong, China; grades nothing. Grade C: small, short, partly subgroup-driven and inconsistent surrogate results.
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(sulforaphane[tiab] OR "broccoli sprout"[tiab]) AND (glucose[tiab] OR diabetes[tiab] OR prediabetes[tiab]) AND randomized controlled trial[pt] AND humans[mesh]Grades move when new trials publish. A free monthly email lists every grade EBL moved, with the reason and the trial behind it: the sign-up is on the Evidence Log →