Sulforaphane is a biochemical nutrient found naturally in broccoli and many other cruciferous vegetables. It is created by a reaction between the enzyme myrosinase and glucoraphanin, one of the forms of glucosinolates found in cruciferous vegetables that is readily converted to sulforaphane.
Researchers have found that sulforaphane has some very wide-ranging healthful properties. Anybody seeking to maximize their health should consume a considerable amount of sulforaphane in their diet from foods or supplements. Cruciferous vegetables such as broccoli are among the best sources of sulforaphane. Sprouts are better sources than mature plants. Differences in food preparation have a vast impact on the amounts of sulforaphane available from foods.
Sulforaphane Fights Atherosclerosis and Cardiovascular Diseases
Inflammation in the lining of blood vessels is believed to be an early factor in the development of atherosclerosis. The clogging of the arteries and veins of the human circulatory system due to atherosclerosis is a contributing factor in strokes, heart attacks, DVT (deep vein thrombosis) blood clots, and many other cardiovascular health conditions. New research shows that some of the most susceptible areas of the arteries are those with bends or branching shapes. It appears this is due to how they lack the active version of a protective protein known as Nrf2. That’s because the Nrf2 in these areas is often bound to other proteins that inactivate it. Sulforaphane, found naturally in broccoli and many other cruciferous vegetables, helps turn on the Nrf2 and thereby reduce the risk of inflammation and consequent injuries.
Sulforaphone also helps fight other inflammatory processes related cardiovascular diseases. It has been found to inhibit the activity of several inflammatory molecules found in the human body including NF-kB (Nuclear Factor kappa B), prostaglandin E2, and nitric oxide. It appears to help induce enzyme detoxification of upper respiratory pathway contaminants such as pollutants and pollens. And it helps block the production of TNF-a (Tumor Necrosis Factor alpha) in some immune cells that contributes to inflammatory conditions such as rheumatoid arthritis.
Sulforaphane Helps Reduce Diabetic Health Damage
There is some evidence that sulforaphane can help prevent damages from high glucose levels found in diabetics. It appears to do so both by the Nrf2 protein activation mentioned above and also by greatly reducing ROS (reactive oxygen species) levels by boosting the production of the endogeneous antioxidant glutathione peroxidase and the enzyme transkelotase. More research is being done on its applicability in diabetes treatment.
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Sulforaphane Exhibits Broad Spectrum Antibacterial Activity
Researchers have found that sulforaphane acts to impeded the growth of many harmful bacteria including Escherichia Coli and Salmonella, common sources of food poisoning and urinary tract infections in humans. Another bacterial target susceptible to sulforaphane is Helicobacter pylori which is responsible for many ulcers and also a suspected cause of gastrointestinal cancers. A 2009 Japanese study of broccoli’s effect on Helicobacter pylori found that consumption of about 70 grams (2.5 ounces) of broccoli sprouts daily for two months reduced Helicobacter pylori colonization in the stomach by about 40%. Infection returned to previous levels two months after discontinuation of the broccoli sprouts, so continuous use is probably necessary for anybody who is struggling with ulcers and related medical problems caused by the bacteria.
Other infectious bacteria strains impeded by sulforaphane include shigella (responsible for dysentery), staphylococcus aureus (implicated in many kind of infections ranging from minor skin infections to deadly pneumonia), streptococcus pyogenes, pseudomonas aeroginosa, and cryptococcus neoformans.
Sulforaphane Acts As A Cancer Chemopreventative
Sulforaphane is also being researched for use in cancer prevention and treatment. A study titled Sulforaphane, a dietary component of broccoli/broccoli sprouts, inhibits breast cancer stem cells in 2010 showed that sulforaphane treatment reduced breast tumor growth in live mice. Other studies discuss how sulporaphane inhibits breast cancer stem cells and inhibits oral carcinoma cell migration.
The study Phytochemicals Resveratrol and Sulforaphane as Potential Agents for Enhancing the Anti-Tumor Activities of Conventional Cancer Therapies suggests combining sulforaphane with anti-cancer drugs to potentiate them at lower dosages and reduce the risk of side effects.
Isothiocyanates I3C (indole 3 carbinol) and DIM (diindolylmethane) are other common biochemicals found in broccoli that are also responsible for reputed cancer preventative effects. A recent paper entitled Selective Depletion of Mutant p53 by Cancer Chemopreventive Isothiocyanates and Their Structure−Activity Relationships discusses one of the cancer preventative mechanisms they offer involves their interaction with the p53 tumor suppressor gene to help keep healthy cells from becoming cancerous. The study, run by Fung-Lung Chung and colleagues at Georgetown University and Columbia University, examined the effects of several types of isothiocyanates on cancer cells from colon, breast, and lung cancer tumors.
There is some concern that extraordinarily high dosages of certain isothiocyanates other than sulforaphane, for example benzyl isothiocyanate and phenethyl isothiocyanate, could increase the risk for bladder cancer in the presence of certain chemical carcinogens. However, most studies have found that sulforaphane is beneficial at typical dosages for chemoprotective effects against chemical carcinogens. This may suggest that taking supplements containing significant quantities of preformed sulforaphane may be preferable over eating extraordinarily large quantities of cruciferous vegetables.
Good Food Sources of Sulforaphane
The best food source of sulforaphane is generally broccoli sprouts, but it is also found in mature broccoli and other cruciferous vegetables in substantial quantities. Many sources say sprouts offer about 10 to 100 times the concentration of sulforaphane versus mature plants. Mature plants have much higher concentrations of indoles, another class of compounds with reputed effects on cancer prevention and hormone balancing.
A recent study points to how combining broccoli sprouts and broccoli powder almost doubles the amount of sulforaphane absorbed by the body. This may be due to how mature plants have more sulforaphane precursors such as glucoraphanin that can be converted to sulforaphane in a healthy digestive tract. Given the difference in indoles, also, it likely makes sense to consume both sprouts and mature plants to get the benefits of both.
Some of the best sources of sulforaphane include:
- Broccoli sprouts
- Cauliflower sprouts
- Brussel sprouts
- Collard greens
- Mustard greens
- Wasabi (a Japanese food)
Not all supplements and foods are equally good at getting sulforaphane into the body. The enzymes myrosinase reacts with glucoraphanin (also known as sulforaphane glucosinolate), one of the glucosinolates found in cruciferous vegetables, transforming it into sulforaphane. This happens when the microscopic sacs containing these compounds are broken open, allowing them to react. Physical damage such as chewing and cutting and light steaming tend to break open the sacs and allow the reaction to proceed to generate sulforaphane without destroying most of the myrosinase before it can react. Human intestinal microflora may be able to convert some of the glucoraphanin into sulforaphane, also, but people who have digestive health problems are likely to be unable to convert much of it unless there is myrosinase enzyme available in the foods or supplements to assist. Many broccoli products lack significant amounts of myrosinase, so when choosing supplements it may be best to pick products that include some standardized amount of sulforaphane versus those that simply list glucosinolates among their components without specifying sulforaphane.
Preparing Broccoli to Maximize Sulforaphane Availability
The myrosinase enzyme is inactivated or destroyed via overcooking for long durations or at high temperatures, leading to little available sulforaphane from such foods. As much as 90% of the potentially available sulforaphane may be eliminated from foods by overcooking. Unfortunately, that means a yummy broccoli soup you like so much is probably a poor source of sulforaphane.
This might lead you to consider eating your broccoli raw. However, sulforaphane in raw broccoli can be poorly available because the myrosinase and glucoraphanin are bound up and unable to react to create sulforaphane. Cutting, chopping, and crushing raw broccoli frees the myrosinase and glucoraphanin allowing sulforaphane to be generated. Probably the best possible way to prepare cruciferous vegetables for maximum sulforaphane benefit is to finely chop or grate them raw and then eat them shortly thereafter.
Lightly steaming broccoli also helps to free up the myrosinase and glucoraphanin to create bioavailable sulforaphane, but it is easy to overcook and deplete the food of useful sulforaphane. Microwave cooking is thought to be less effective at making the sulforaphane bioavailable than steamer cooking.
When you cook cruciferous vegetables, many of the glucosinolates dissolve into the cooking water. This is part of why steaming is advantageous because there is little water involved. You could choose to drink the cooking water as it will have many glucosinolates in it.
Broccoli is by far the best researched source of sulforaphane. Similar guidelines likely apply to preparing other cruciferous vegatables to maximize their beneficial sulforaphane, but further research is needed to substantiate this conclusively.
A recent Chinese study on bioavailability of sulforaphane from two broccoli sprout beverages shows that beverages with high levels of glucoraphanin tend to produce lower elevations in sulforaphane that last longer whereas those with high levels of sulforaphane attain higher concentrations but they wash out more quickly. The authors conclude that it is probably more effective to mix glucoraphanin and sulforaphane in foods and supplements to achieve best effect by reaching both high peak concentrations of sulforaphane in the body and sustaining lower levels for longer periods of time.
Some suggest total daily dosages of sulforaphane should be around 50mg to 100mg for optimal effect. It is my belief that such suggestions are referring to sulforaphane glucosinolate which can be converted to sulforaphane in the body, not to sulforaphane directly. Many supplements include only 400 micrograms to 2 milligrams of sulforaphane itself. Others include various glucosinolates but their ingredient lists make no mention of preformed sulforaphane. It is important to realize that the body’s ability to convert glucosinolates to sulforaphane depends upon adequate myrosinase and/or healthy gut bacteria populations.
Please be clear that you have to pay very close attention to terminology to be sure of your understanding of a research paper or supplement label as some refer to sulforaphane and others refers to sulforaphane glucosinolate which are not the same compounds. Often these materials use “SGS” as an abbrevation for sulforaphane glucosinolate. A product that claims that it offers 400 mcg (micrograms) of sulforaphane may actually be more potent than one which claims it offers 5 mg of SGS or sulforaphane glucosinolate, even though 5 mg is certainly a larger mass than 400 micrograms.
There are a couple of supplements available with larger dosages of sulforaphane precursors at 30mg per capsule from Jarrow Formulations and Xymogen (shown to the left). Both of these products list sulforaphane glucosinolate, not sulforaphane, as a component of their formulations. The Xymogen product also contains a number of other Nrf2 activators such as pterostilbene, a compound similar to resveratrol but with bioavailability claimed to be much higher.
As sulforaphane is rapidly absorbed and metabolized, it’s important to take multiple doses per day for sustained effect.
Foods have highly variable quantities of sulforaphane and its glucosinolate precursors. Most of them are rich in glucosinolates but have little preformed sulforaphane. In a healthy digestive tract, bacteria will convert many of the glucosinolates to sulforaphane, especially if there is plenty of myrosinase enzyme in the food because it is raw and has been broken up into very small pieces. If you have digestive problems related to use of antiobiotics wiping out your digestive tract bacteria, it’s likely that little conversion to sulforaphane will take place. You may want to investigate using probiotrics and prebiotics to rebuild the healthy digestive tract flora and select glucosinolate and sulforaphane supplements that contain significant quantities of preformed sulforaphane.
Some studies show that a 100 gram (3 ounce) serving of broccoli sprouts offers about 250 mg of sulforaphane glucosinolate (glucoraphanin). If you can obtain fresh broccoli sprouts that are clean and in fresh and crunchy condition, this might be one of the best sources of the nutrient as it is easy to put them on salads and sandwiches. Raw salads including mature chopped broccoli, cauliflower, and cabbage are another good source, but you have to consume far more of them to get the same amount of sulforaphane.
Here are some estimated quantities of glucosinolates in various raw vegetables:
Brussel sprouts – 1/2 cup (44g) has about 104mg
Garden cress – 1/2 cup (25g) has about 98mg
Mustard greens – 1/2 cup chopped (28g) has about 79mg
Turnip – 1/2 cup chopped into cubes (65g) has about 60mg
Savoy cabbage – 1/2 cup chopped (45g) has about 35mg
Kale – 1 cup chopped (67g) has about 67mg
Watercress – 1 cup chopped (34g) has about 32mg
Kohlrabi – 1/2 cup chopped (67g) has about 31 mg
Red cabbage – 1/2 cup chopped (45g) has about 29mg
Broccoli (mature) – 1/2 cup chopped (44g) has about 27mg
Horseradish – 1 tablespoon (15g) has about 24mg
Cauliflower (mature) – 1/2 cup chipped (50g) has about 22mg
Bok choy or Bok choi – 1/2 cup chopped (35g) has about 19mg
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