Sulforaphane, an isothiocyanate compound derived from cruciferous plants such as broccoli and kale, was first discovered in the late 1950s and noted for its antimicrobial qualities. The molecule was largely forgotten until 1992, when it was re-discovered by the late Dr. Paul Talalay and his then student, Dr. Yuesheng Zhang. Talalay and Zhang noted that sulforaphane demonstrated the remarkable capability to switch on intrinsic protective mechanisms that defend cells against cancer and other environmental insults in a hormetic-type response.

Dr. Jed Fahey joined the research in 1994. His findings revealed that sulforaphane is an artifact of isolation: The molecule isn't present in the plants from which it is derived. Rather, it is an end-product of a simple chemical reaction that occurs when the plants sustain damage – whether by insect attack, food preparation techniques, or human consumption. The reaction involves an enzyme (myrosinase) and a precursor molecule (glucoraphanin). Glucoraphanin is a type of glucosinolate. Although many glucosinolates exist in nature – primarily in cruciferous plants – Fahey discovered that young broccoli plants (the sprouts) contain 10 to 100 times more glucoraphanin than any other plant.

Nearly three decades of cell, rodent, and human studies have since yielded a robust library of evidence demonstrating sulforaphane's beneficial effects, thrusting the molecule into the lexicons of the lay public, who seek strategies to optimize well-being and prolong healthspan.

Determining the optimal source and dose of sulforaphane poses challenges

Many questions have arisen regarding the optimal source (food versus supplements), formulation, and dosage of sulforaphane. A critical aspect of this discussion centers on glucoraphanin content in broccoli sprouts versus mature broccoli, which varies across species and cultivar and is influenced by factors such as soil and growing conditions, harvest time, and post-harvest storage.

Although clinical studies have assessed the merits of sulforaphane in a wide range of chronic and infectious diseases, including autism, aflatoxin toxicity, air pollution detoxication, cancer, cardiovascular disease, diabetes, neurodegenerative disease, Helicobacter pylori infection, and many others, doses in these studies have varied markedly in terms of quantity and whether supplied as glucoraphanin (the precursor) or sulforaphane (the end product). In general, however, data suggest that a dose range of 5 to 60 milligrams of sulforaphane daily will likely yield the greatest health effects.

Myrosinase factors into this discussion, as well. The enzyme is heat-sensitive and rapidly denatures during normal cooking processes. Adding ground mustard seed (which is rich in myrosinase) to cooked vegetables provides a culinary workaround to myrosinase losses incurred during cooking. Food preparation techniques that employ shorter cooking times and less water favor myrosinase stability and retention

But myrosinases are also found in the human gut, where they are produced by commensal bacteria that reside there. These bacterial myrosinases providing a fail-safe mechanism for sulforaphane production by converting unhydrolyzed glucoraphanin to sulforaphane. However, the conversion process is highly variable and subject to differences in commensal microbiota composition, the use of antimicrobial agents, or other factors that alter or reduce the gut microbial population.

Optimal glucoraphanin content in broccoli sprouts starts at the source

Key players in the glucoraphanin variability in broccoli sprouts are the seeds from which the tiny plants germinate. Seeds are inherently rich sources of phytochemicals. They house all the nutrients and protective compounds (such as glucoraphanin) the future plant will require as it sprouts and begins to grow. Although many seed vendors provide quality seeds that are free of pesticides and have high germination rates, determining the glucoraphanin content in broccoli seeds requires laboratory analysis that may be cost-prohibitive for most home growers.

"...you would get the highest levels of glucoraphanin from just eating broccoli seeds. [But] there's also a possibility of getting an overload of erucic acid…" - Dr. Jed Fahey Click To Tweet

The putative glucoraphanin abundance in broccoli seeds implies that consuming the seeds (rather than sprouting them) provides a better means of obtaining the end product. However, broccoli seeds are rich in erucic acid, an omega-9 fatty acid that exerts detrimental effects on heart tissue in rodents and is classified as a natural toxicant. Although prudence is warranted when consuming broccoli seeds directly, their bitter taste may provide a natural deterrent to copious consumption.

Sulforaphane optimizes glutathione, serving as a nutritional "seatbelt"

But consumption of this non-nutrient appears to be important – even essential – for optimal health. Sulforaphane promotes the production of glutathione, a powerful antioxidant that facilitates the body's excretion of a wide range of toxic substances, including pesticides, aflatoxin, and air pollutants. Glutathione binds with many of these toxins and forms mercapturic acids, which can be excreted and measured in urine.

Robust clinical evidence has demonstrated that sulforaphane is beneficial for people who live in areas where air quality is poor due to pollution levels. An intervention study in Qidong, China, an area known for its high levels of air pollution, found that sulforaphane markedly increased the production of mercapturic acid metabolites of benzene and acrolein, known carcinogens present in air pollution. These effects manifested within 24 hours of sulforaphane administration in a dose-dependent manner.

More importantly, however, these effects were sustained – even after several months – demonstrating that sulforaphane did not exhaust the body's capacity to protect itself from environmental threats and suggesting that regular consumption of sulforaphane in foods or dietary supplements provides a kind of nutritional "seatbelt" that protects against future toxic exposures. These findings have relevance for people living in the western part of the United States, where forest fires, which are sources of many airborne pollutants, are common.

Sulforaphane's protective effects extend to the brain.

A growing body evidence suggests that sulforaphane's protective effects extend to the brain. Glutathione is a likely mediator of these effects, as evidenced by data from preclinical models of glutathione deficiency and supported by magnetic resonance spectroscopy studies showing increased glutathione levels in the brains of people who receive sulforaphane.

But other mechanisms might be at play in the brain. Sulforaphane appears to enhance brain derived neurotrophic factor (a protein that controls and promotes the growth of new neurons) and inhibits histone deacetylation (an epigenetic modification that influences gene expression). Other evidence demonstrates that sulforaphane provides protection from methylglyoxal, a critical player in the pathogenesis of advanced glycation end products, commonly referred to as AGEs. AGE formation is a prominent feature of diabetes and a major contributor to amyloid-beta aggregation in the brain.

Sulforaphane may exert opposing effects on cancer.

Sulforaphane appears to preferentially target certain tissues, especially those of the prostate, breast, and bladder, where it exerts pharmacological effects that provide protection against cancer. The bladder, in particular, serves as a reservoir for byproducts of sulforaphane metabolism, including a variety of glutathione-derived conjugates.

These antioxidant compounds eventually end up in the urine, which is temporarily stored in the bladder prior to elimination, providing a unique environment in which to study the effects of sulforaphane and its metabolic byproducts on bladder tissue. Although human trials are lacking, some animal research suggests that sulforaphane and its byproducts protect against bladder cancer.

But the mechanisms by which sulforaphane exerts its cancer-preventive effects may backfire in existing cancers. The current state of the science regarding sulforaphane as a chemotherapeutic measure is meager and points to its role in prevention rather than treatment.

Sprouting offers a natural, cost-effective means of obtaining sulforaphane.

Sprouting is the natural process by which seeds germinate. It is inexpensive, easy to do, and requires very few supplies or even a green thumb. The process often yields far more edible product than most people can consume before quality and safety are compromised. Freezing is a practical strategy for storing sprouts for future use. An added bonus is that freezing and thawing sprouts activates myrosinase, further enhancing their value.

Not everyone can grow (or loves) broccoli sprouts.

We might be a little bit sad about that, but the truth is...

Growing sprouts may prove logistically challenging for some people! Not everyone cares for broccoli sprouts' flavor, which is largely due to their glucosinolate content. In general, the glucosinolates in cruciferous vegetables are described alternately as sharp, pungent, acrid, astringent, or lachrymatory (tear-inducing), but they are most widely regarded – in some cases inaccurately – as bitter. Whereas the glucosinolates in some vegetables are notably bitter, those found in broccoli and broccoli sprouts are much milder.

Nevertheless, for many people, the taste of broccoli sprouts is off-putting – a problem first noted during clinical trials in China in which compliance was crucial. Attempts to disguise the flavor of the broccoli sprout teas used in the trials eventually led them to enlist flavor analysis expertise. The end result was a palatable – and culturally acceptable – beverage, spiked with pineapple and lime. American palates may find a sweeter concoction more tolerable.

An easier, but less cost-effective solution that requires no masking is found in supplementation. Dietary supplements carry inherent risks, however, so choosing a supplement that contains the desired product – glucoraphanin or stabilized sulforaphane – will likely yield the desired results. Choosing a supplement manufacturer with a proven track record of safety is important, too. Some dietary supplements have been used in clinical studies of autism and prostate cancer, lending credence to their efficacy and safety.

"If you're counting on your gut's...your intestinal tract's myrosinase to do all of the conversion for a supplement, you're probably going to want to take a higher level of glucoraphanin. And if you're getting a product that has myrosinase in it, you don't need as much glucoraphanin because some of that conversion is theoretically going to happen based on what you've provided in the supplement tablet." -Dr. Jed Fahey Click To Tweet

Sulforaphane does not meaningfully interfere with thyroid function.

Some anti-nutritional effects of isothiocyanates have been reported. One example is seen in progoitrin, a glucosinolate found in cabbage, rapeseed, and kale. Progoitrin is hydrolyzed to goitrin, which is named for its antithyroid effects. Goitrin blocks tyrosine iodination and inhibits thyroxine (thyroid hormone) formation. Long-term ingestion of goitrin is associated with goiter formation in mammals, a phenomenon first observed in rabbits and described as “cabbage” goiter.

But broccoli sprouts carry little risk of goitrogenic effects. A 12-week study in China assessed the effects of daily sulforaphane consumption on thyroid status, hormone status, and autoimmune status and found that the compound elicited no adverse effects on thyroid function. Normal consumption of isothiocyanate-rich foods and supplements poses little risks to humans.

This episode provides answers to many of the questions submitted by the FMF family regarding sulforaphane, particularly those surrounding dosing, duration of effects, and its hormetic effects. It also addresses a wide range of concerns about sprouting broccoli seeds at home, including harvesting, storing, and consuming home-grown sprouts.

Companion guide

The video serves as a companion to our 15-page Sprouting Guide.

The Sprouting guide is an illustrated manual to the basics of sprouting that includes a brief summary of the science of sulforaphane, and the video shows easy to follow steps for cleaning and growing broccoli sprouts.

• Get the sprouting guide by clicking here now.

Additional sulforaphane and sprouting resources

• Podcast interview: Jed Fahey, ScD, on Isothiocyanates, the Nrf2 Pathway, Moringa, & Sulforaphane Supplementation
• Podcast interview: New Omega-3, sulforaphane research, and more! [Dr. Rhonda Patrick on the Kevin Rose Show]
• Episode: How sulforaphane benefits human health

In this episode, Dr. Fahey mentions the following companies, websites, and supplements:

• Brassica Protection Products
• Cullman Chemoprotection Center
• Crucera SGS® (Thorne)
• Oncoplex® (Xymogen)
• Avmacol®
• Vision Defense® (Swanson)
• MaxN-Fuze®
• MitoCORE® (Ortho Molecular Products)

[Disclosure: FoundMyFitness does not have financial interest in any of the aforementioned products or companies. Dr. Fahey plays a minor consulting role for Brassica Protection Products articulated at 00:03:20 and 01:22:58. Additionally, Dr. Fahey is an advisor for Kuli Kuli.]