Sulforaphane: Broccoli's Secret Weapon

Few would argue that regular consumption of vegetables is good for health. However, some vegetables pack more punch in terms of health benefit. For one, the Brassicas are king. With over 500 publications, what we know about broccoli might change your dinner plate.

It is widely accepted that dietary broccoli can protect against different types of cancer and possibly other chronic diseases. However, it can be hard to believe that in the rotating nutrition headline, post-truth world in which we find ourselves.

The Workhorse: Sulforaphane

Broccoli contains a number of beneficial components: vitamins E & C, carotenoids and antioxidant enzymes, and the flavonoids quercetin and kaempferol. The most studied components of broccoli are the isothiocyanates—a type of organosulfur compound. Of these, sulforaphane (SFH) is of great interest.

Interestingly enough, SFH is not available in the intact vegetable. The SFH pre-cursor glucoraphanin must be broken down to SFH by the enzyme myrosinase. How does this occur? By damage to the plant such as chewing, chopping, or smashing.           

Anti-inflammatory

Sulforaphane is considered by many to be responsible for the health benefits associated with broccoli. Many possible mechanisms have been studies to determine why. One compelling explanation is SFH’s ability to induce nuclear factor erythroid 2-related factor 2, or simply Nrf2. This is a protein that activates genes that protect against oxidative stress and inflammation. Other food components that act on Nrf2 are garlic, curcumin, and resveratrol. Nrf2 regulates 200 different genes in humans!

Another mechanism is SFH’s ability to upregulate phase II detoxification enzymes. These are our body’s natural detox system which clears carcinogens and reactive oxygen species (ROS). Phase II detoxification occurs at all times to metabolize medications, drugs, alcohol, xenobiotics, and other potentially toxic compounds we come in contact with. The phase II enzymes are crucial to handle these potentially toxic metabolites. They function to bind them with charged molecules such as glutathione (GSH), sulfate, glycine, or glucuronic acid.

Another potential reason for SFH’s health promoting benefits are through inhibition of NF-kB. This is a key protein in inhibiting cascades of inflammatory cytokines. Sulforaphane also fights inflammation by binding to free glutathione in the cell. This binding triggers the production of more glutathione—the master antioxidant—which quenches free reactive oxygen and nitrogen species (RO&NOS).

From Mice to Men

Rats with pancreatitis were fed broccoli (10% of their diet) and showed reductions and normalization in the pro-inflammatory cytokine IL-6, which drives pancreatitis. In human blood cells and colon cancer cells stimulated to release inflammatory cytokines, the introduction of pure SFH was able to mitigate inflammation by reducing concentrations of TNFa, IL-1, and IL-6. This finding has been repeated in several cell types.  In humans, men fed Brussels sprouts or cabbage in quantities of about 200g daily showed elevated levels of glutathione after just 6 days.

In 81 diabetic patients, given a 10g supplement of SFH daily for 4 weeks produced a 9% reduction in markers of oxidative stress and a 16% increase in total antioxidant capacity. In vitro studies have shown broccoli supplements affect natural killer cell activity in mouse and human cell lines. The SFH supplement increases NK destructive ability and overall activity.

Broccoli Beats H. pylori

A highly surprising study of patients infected with H. pylori were given broccoli sprouts 2x daily for 1 week. Nearly 80% of the subjects were cleared of infection immediately following, and 33% remained clear of infection at 42 days!

Hungry yet?

From Jeffery & Araya 2009

Sulforaphane and Autism

And even more surprising: double-blind, placebo-controlled study of 26 autistic children given a supplement of SFH. Of these, 17 (65%) improved significantly, most returned to baseline levels 4 weeks after terminating the supplement. Symptom improvement included reduced hyperactivity, less irritability, and better social responsiveness. The researchers made no speculation as to the mechanism of this supplement on the autistic condition. Could it be that supplementation was potent enough to reduce neuroinflammation associated with the condition?

Not For Everyone

If you have SIBO or other intestinal disorder, stay clear of the Brassicas until these issues are treated. Broccoli and the like are high in FODMAPS, which can worsen an already inflamed gut. However, to get the benefit of these foods without digestion, one can always supplement.

Young broccoli sprouts have the highest concentration of SFH precursors, glucoraphanin. Many broccoli sprout supplements are not bioavailable, however. The ideal broccoli sprout product must contain compartmentalized glucoraphanin and the enzyme myrosinase that reacts at the time of ingestion.

If you don’t struggle with digestive issues, eat Brassicas in abundance. Choose fresh over frozen, as they contain more glucoraphanin. In addition to broccoli choose cabbage, cauliflower, Brussels sprouts, bok choy, kale, collards, mustard greens, horseradish, wasabi, and watercress. Don’t boil. Boiling broccoli reduces the levels of sulforaphane exponentially with boiling time because it inactivates the crucial enzyme myrosinase. Eat raw. Steam. Stir-fry. Top with mustard seeds, horseradish, or wasabi which are good sources of myrosinase. Adding slightly cooking or pulverized mustard seeds to your broccoli protects against sulforaphane degradation.

References

Jeffery, E.H. & Araya, M. (2009) Physiological effects of broccoli consumption. Phytochem Rev. 8: 283.

Kapusta-Duch J. et al. (2012) The beneficial effects of Brassica vegetables on human health. Rocz Panstw Zakl Hig. 63(4):389-95.

Lynch, R., Diggins, E. L., Connors, S. L., Zimmerman, A. W., Singh, K., Liu, H., … Fahey, J. W. (2017). Sulforaphane from Broccoli Reduces Symptoms of Autism: A Follow-up Case Series from a Randomized Double-blind Study. Global Advances in Health and Medicine, 6, 2164957X1773582.

Ghawi, S. K., Methven, L., & Niranjan, K. (2013). The potential to intensify sulforaphane formation in cooked broccoli (Brassica oleracea var. italica) using mustard seeds (Sinapis alba). Food Chemistry, 138(2-3), 1734–1741.

Houghton, C. A., Fassett, R. G., & Coombes, J. S. (2013). Sulforaphane: translational research from laboratory bench to clinic. Nutrition Reviews, 71(11), 709–726.