Benefits
Detoxication of Airborne Pollutants: Benzene and Acrolein Excretion
In two placebo-controlled trials in Qidong, China, a broccoli sprout drink raised urinary excretion of benzene breakdown products by 61% over 12 weeks (291 adults; acrolein up 23%, crotonaldehyde unchanged) and by 63% over 10 days at full strength (170 adults), while half and one-fifth strengths did not differ from placebo. Health outcomes were not measured.
Oxidative Stress Markers
In 81 adults with type 2 diabetes, 5 or 10 g a day of broccoli sprout powder for 4 weeks lowered MDA and oxidized LDL and raised total antioxidant capacity compared with placebo. Total oxidant status did not change. In 40 adults with asthma, 100 g a day of whole fresh sprouts for 3 days did not switch on antioxidant genes or lower oxidative stress markers versus alfalfa sprouts. Both trials were short.
Insulin Sensitivity Markers
In the same 4-week trial in 81 adults with type 2 diabetes, 10 g a day of broccoli sprout powder lowered fasting insulin and insulin resistance (HOMA-IR) compared with placebo, with a borderline result (p = 0.05); 5 g a day did not. This is one small, short trial in people with a diagnosed condition.
LDL Cholesterol and High-Glucoraphanin Broccoli Eaten as Food
Whole broccoli eaten as food, not an extract: in two double-blind trials (130 adults), LDL cholesterol fell 7.1% and 5.1% from baseline after 12 weeks of 400 g a week of high-glucoraphanin broccoli, with no significant change on standard broccoli; the varieties differed significantly only with both studies pooled. The licensee of the patented broccoli co-funded the work.
Myrosinase and Sulforaphane Yield
Sprouts or seeds given with their own active myrosinase delivered 3 to 4 times more sulforaphane than glucoraphanin given without active myrosinase, which relies on gut bacteria. A review found many sprout supplements lack active myrosinase without saying so on the label. In a crossover trial, glucoraphanin-rich and sulforaphane-rich drinks did not differ in pollutant excretion.
Mechanism of action
Glucoraphanin to Sulforaphane Conversion
In intact broccoli, glucoraphanin and myrosinase are stored apart; chewing or crushing brings them together and myrosinase releases sulforaphane. Heat inactivates myrosinase, leaving conversion to gut bacteria, which yields far less sulforaphane in people, as shown in bioavailability studies.
NRF2 Pathway Activation
Sulforaphane is a strong inducer of NRF2, the transcription factor that switches on a battery of the cell's own protective genes, as summarized in a review of laboratory and clinical work. In one 3-day trial of whole sprouts in adults with asthma, these genes were not switched on in blood or nasal cells.
Phase II Enzyme Induction
Sulforaphane induces glutathione S-transferases and other protective enzymes that attach glutathione to reactive chemicals so they can be excreted in urine as mercapturic acids. The Qidong trials measured this as higher urinary excretion of glutathione-derived conjugates of benzene and acrolein.
Clinical trials
Randomized placebo-controlled trial of three strengths of a broccoli sprout beverage for 10 days; the full strength (the only one to beat placebo) gave 600 micromol glucoraphanin plus 40 micromol sulforaphane from broccoli sprout powders, the same drink as the 12-week trial; outcome urinary benzene mercapturic acids; NIH funded; registered as NCT02656420. (Chen et al. 2019, Am J Clin Nutr)
170 adults in Qidong, China, exposed to airborne pollutants (55 placebo; 25 full, 35 half and 55 one-fifth strength).
Benzene mercapturic acid excretion rose 63.2% with the full-strength drink, which produced about 25 micromol a day of urinary sulforaphane metabolites. The half (+11.3%) and one-fifth (-6.4%) strengths did not differ from placebo.
Randomized crossover trial of a glucoraphanin-rich and a sulforaphane-rich broccoli sprout beverage, 7 days each with a 5-day washout, without a placebo arm; outcome urinary mercapturic acids (glutathione-derived conjugates). (Kensler et al. 2012, Carcinogenesis)
50 healthy adults in He Zuo Township, Qidong, China.
Excretion of the mercapturic acids of acrolein, crotonaldehyde and benzene rose 20 to 50% compared with each person's own baseline (no placebo comparison). The two drinks did not differ significantly.
4-week double-blind placebo-controlled randomized trial of 10 g/day or 5 g/day broccoli sprout powder. (Bahadoran et al. 2011, Eur J Clin Nutr)
81 adults with type 2 diabetes (63 analyzed).
MDA, oxidized LDL and the oxidative stress index fell and total antioxidant capacity rose compared with placebo; total oxidant status did not change.
4-week randomized double-blind trial of 10 g/day or 5 g/day broccoli sprout powder versus placebo. (Bahadoran et al. 2012, Int J Food Sci Nutr)
81 adults with type 2 diabetes (72 completed, 63 analyzed).
10 g/day lowered serum insulin and HOMA-IR compared with placebo (p = 0.05 for treatment effect).
Double-blind randomized trial of 100 g/day fresh broccoli sprouts eaten as food (a whole-food material, not an extract) versus alfalfa sprouts as the comparison food for 3 days; outcomes included exhaled nitric oxide (primary), antioxidant gene expression and oxidative stress biomarkers. (Sudini et al. 2016, J Allergy Clin Immunol Pract)
40 adults aged 18 to 50 with asthma and indoor allergen sensitization.
No benefit versus alfalfa sprouts: exhaled nitric oxide (the primary outcome), protective gene expression in blood and nasal cells, blood stress and inflammation markers, and lung function did not improve, despite a marked rise in serum sulforaphane.
Two independent double-blind randomized parallel dietary trials of 400 g/week high-glucoraphanin broccoli versus standard broccoli (frozen florets eaten as food; a whole-food material, not an extract) for 12 weeks; co-funded by Seminis Vegetable Seeds, which licenses the patented high-glucoraphanin broccoli, and one author is a named inventor. (Armah et al. 2015, Mol Nutr Food Res)
130 adults (37 and 93 in the two studies).
LDL cholesterol fell 7.1% (study 1, 37 adults) and 5.1% (study 2, 93 adults) from baseline with high-glucoraphanin broccoli and did not change significantly with standard broccoli; the difference between the two broccolis was significant only when both studies were pooled (P = 0.031).
Randomized trial of 70 g/day fresh broccoli sprouts eaten as food (420 micromol glucoraphanin; a whole-food material, not an extract) versus the same weight of alfalfa sprouts as the comparison food for 8 weeks, alongside mouse experiments; the abstract reports changes within each group. (Yanaka et al. 2009, Cancer Prev Res (Phila))
48 adults with H. pylori infection.
Urea breath test, stool antigen and serum pepsinogens fell with broccoli sprouts but not with alfalfa sprouts, and returned to baseline 2 months after stopping.
15-week randomized double-blind placebo-controlled trial of Avmacol tablets (broccoli seed extract glucoraphanin plus broccoli sprout extract as the myrosinase source) dosed to yield about 2.2 micromol sulforaphane per kg a day, with open-label and no-treatment extensions; tablets supplied by Nutramax; US Department of Defense funded; one author later advised Brassica Protection Products, a glucoraphanin supplier, and another is named on a Johns Hopkins patent on sulforaphane for autism. (Zimmerman et al. 2021, Mol Autism)
57 children aged 3 to 12 with autism spectrum disorder (45 analyzed).
The primary outcome (Ohio Autism Clinical Impressions Scale) did not differ from placebo at 7 or 15 weeks. One secondary caregiver scale (Aberrant Behavior Checklist) improved at 15 weeks; the Social Responsiveness Scale did not. No side effects were serious; rare insomnia, irritability and taste intolerance occurred.
12-week randomized placebo-controlled trial with one active arm: a beverage of glucoraphanin-rich and sulforaphane-rich broccoli sprout extract powders giving 600 micromol glucoraphanin plus 40 micromol sulforaphane daily; outcome urinary mercapturic acids (glutathione-derived conjugates) of benzene, acrolein and crotonaldehyde; NIH funded; the authors declared no conflicts. (Egner et al. 2014, Cancer Prev Res (Phila))
291 adults in a rural township in Qidong, China, with substantial exposure to airborne pollutants.
Benzene mercapturic acid excretion rose 61% and acrolein 23% versus placebo (P 0.01 or less), but crotonaldehyde did not change. Sulforaphane uptake did not decline over 12 weeks. A biomarker outcome; health outcomes were not measured.