Sulforaphane

What is sulforaphane?

Sulforaphane (SFN) is a naturally occurring isothiocyanate found in cruciferous vegetables, most abundantly in broccoli sprouts. It doesn't exist in the plant itself. Instead, it forms when the precursor compound glucoraphanin meets the enzyme myrosinase during chewing, chopping, or gut bacterial metabolism ^[1]. First isolated by Johns Hopkins researchers in 1992, sulforaphane has since accumulated over 3,000 published studies, making it one of the most researched phytochemicals in nutritional science ^[2].

How sulforaphane activates the NRF2 pathway

The primary mechanism behind sulforaphane benefits is its activation of the NRF2 (nuclear factor erythroid 2-related factor 2) signaling pathway. Under normal conditions, the transcription factor NRF2 is kept inactive by the protein KEAP1. Sulforaphane modifies KEAP1, freeing NRF2 to enter the cell nucleus and switch on over 200 cytoprotective genes involved in antioxidant defense, detoxification, and anti-inflammatory responses ^[3]. This makes sulforaphane one of the most powerful indirect antioxidants known. It upregulates the body's own protective enzymes rather than simply scavenging free radicals like vitamin C or E. As we age, NRF2 activity naturally declines, contributing to increased oxidative stress and chronic inflammation. Research shows sulforaphane can counteract this age-related NRF2 decline, which is why it has attracted so much attention in longevity science ^[4].

Sulforaphane benefits backed by clinical trials

A comprehensive 2025 review of all published clinical trials found that sulforaphane has measurable effects across several health domains ^[9]. In cancer prevention, a Phase II clinical trial in former smokers showed that sulforaphane supplementation reduced the Ki-67 proliferation marker by 20% in bronchial tissue, while the placebo group saw a 65% increase ^[6]. Sulforaphane also acts as a histone deacetylase (HDAC) inhibitor, an established mechanism in cancer chemoprevention.

For blood sugar regulation, a randomized controlled trial with 103 type 2 diabetes patients found that 12 weeks of broccoli sprout extract significantly reduced fasting blood glucose and HbA1c levels, particularly in obese participants ^[10]. A 2025 follow-up trial in prediabetic individuals confirmed these results, with sulforaphane reducing fasting blood sugar through NRF2-mediated suppression of hepatic glucose production ^[11].

In brain health, animal studies demonstrate that sulforaphane crosses the blood-brain barrier and reduces amyloid-beta deposits, neuroinflammation, and oxidative damage relevant to Alzheimer's disease ^[7]. Small clinical trials have also shown symptomatic improvements in autism spectrum disorder and cognitive benefits in schizophrenia ^[9]. Sulforaphane further supports cardiovascular health, with a systematic review and meta-analysis finding that broccoli sprout supplementation can lower blood pressure and improve lipid profiles ^[12].

Foods high in sulforaphane

Broccoli sprouts are the richest food source, containing 10 to 100 times more glucoraphanin than mature broccoli heads, depending on cultivar and growing conditions ^[1]. Three-day-old sprouts deliver the highest concentrations. Other sulforaphane-rich foods include mature broccoli, Brussels sprouts, kale, cauliflower, cabbage, and watercress.

Cooking destroys the myrosinase enzyme needed for sulforaphane conversion. To maximize intake from cooked broccoli, add a pinch of mustard seed powder after cooking. This provides exogenous myrosinase and can increase sulforaphane bioavailability by up to fourfold ^[5]. Steaming broccoli for one to three minutes preserves more myrosinase than boiling or microwaving.

Sulforaphane supplements and dosage

For those who can't consume broccoli sprouts regularly, sulforaphane supplements offer an alternative. Effective study doses typically range from 10 to 60 mg of sulforaphane daily. When choosing a supplement, look for products standardized to actual sulforaphane content or those combining glucoraphanin with myrosinase for enhanced conversion. A 2024 Phase I pharmacokinetic trial of enteric-coated stabilized sulforaphane (SFX-01) confirmed good safety and tolerability in healthy adults ^[13]. Supplements containing stabilized sulforaphane or broccoli sprout extracts with verified myrosinase activity tend to have better bioavailability ^[8].

Sulforaphane is generally well tolerated. The most common side effects are mild gastrointestinal discomfort, occasional heartburn, and a characteristic burning sensation in the throat at higher doses. People with thyroid conditions should consult their physician, as high doses of cruciferous-derived compounds can interfere with iodine uptake.