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Sulforaphane and Myrosinase
May 9, 2011
Jacob Schor, ND, FABNO
Over the past half dozen years numerous studies have been published suggesting a health benefit can be derived from a food derived chemical called sulforaphane. We’ve mentioned it numerous times over the years, especially in connection with broccoli sprouts. These sprouts are probably the best source for getting sulforaphane in the diet.
While the majority of research has suggested sulforaphane is useful in preventing and treating cancer recent research is creating a strong argument for also using it in treating chronic obstructive pulmonary disease. A recent newsletter reviewed some of this research.
There is another recent study on sulforaphane of interest. Published earlier this year Cramer and Jeffery report on a small clinical trial they undertook feeding volunteers various combinations of dried broccoli powder and broccoli sprout powder. Though the study only had 4 participants, the resultant data nevertheless still provide useful information. Over a period of several weeks, these 4 young men were fed either broccoli sprout powder, broccoli powder, a combination of both or a placebo. These powders were mixed into a breakfast of Kahi cereal and yogurt.
Blood and urine samples were collected and analyzed for sulforaphane levels to see which powder supplement increased sulforaphane levels the most. Results were reported as percentages of the initial glucoraphanin in the powder was converted into sulforaphane.
Broccoli sprouts produced the highest 24 hour recovery of sulforaphane, 74% while the combination of sprouts and broccoli powder produced 49% and the broccoli powder alone only 19%.
Given the quantity of research suggesting that the phytochemical sulforaphane plays a desirable role in promoting health, it behooves us in many situations to consume foods or supplements that will supply it. This study by Cramer and Jeffery adds valuable information on how to do so.
Cruciferous plants use sulforaphane to ward off bacterial, viral and fungal infection. Despite this antibiotic-like effect, sulforaphane probably acts by triggering benefit in people via a hormetic effect, “… at the subtoxic doses ingested by humans that consume the plants, the phytochemicals induce mild cellular stress responses.”
Plants often store their noxious chemicals in inert form, activating them only as needed. In the case of sulforaphane, as in many other parallel plant systems, the activating enzymes are stored in nearby cell vacuoles and are released only when the cells are damaged. An example that is easy to relate to are the reactions in garlic when it is crushed. Once the cell walls are ruptured, the cells release the enzyme alliinase. This enzyme catalyzes the reaction in which alliin is converted into allicin. In the case of cruciferous vegetables, the chemicals have different names but the process is similar. Glucoraphanin is the stored form of the chemical. The enzyme myrosinase is released when the cells are damaged and it converts glucoraphanin into sulforaphane.
Thus to get sulforaphane from the diet requires the chemical reaction between glucoraphanin and the enzyme myrosinase. If cruciferous vegetables are cooked before they are eaten, the heat destroys the myrosinase enzyme and very little sulforaphane is produced.
Fermentation by intestinal bacteria can also catalzye this reaction though not very efficiently.
Nutritional supplements that contain cruciferous vegetable concentrates are popular. Unless otherwise stated, assume they contain only glucoraphanin and not sulforaphane. While attracting consumer attention and sounding healthy, these provide little benefit. That is unless they contain myrosinase enzyme with which to catalyze the reaction to sulforaphane. We can not assume that they do.
Tang et al in their bladder cancer study from June 2005 illustrate the value of active sulforaphane.
In seeking correlations in diet and cancer recurrence, they found no association between consumption of cooked cruciferous vegetables and bladder cancer. On the other hand, individuals who ate one or more servings of raw broccoli a month had less than half the risk of their bladder cancer returning compared to those that ate broccoli less often. Remember, cooking destroys myrosinase, and without it little sulforaphane is produced.
Cramer and Jeffrey used air-dried broccoli sprouts to provide the myrosinase enzyme in this study. About 4/5 of the glucorophanine in the broccoli sprouts is converted into sulforaphane during eating and digestion because the sprouts contain active enzyme. Combining broccoli sprout powder with broccoli powder that contains no active enzyme converted half of the glucoraphanin in the broccoli powder into sulforaphane. Consuming just broccoli powder still produced a little sulforaphane through intestinal fermentation; about one fifth of the glucoraphanin was converted. Obviously it would be to one’s advantage to consume foods containing active myrosinase whenever eating foods containing glucoraphanin.
There are a number of possible food sources for myrosinase. Daikon radishes, common in Japanese salads, contain significant amounts of myrosinase but most of it is in the skin, a part of the plant typically not eaten. Myrosinase is also present in rapeseed but is purposefully deactivated by heating before the seeds are pressed to make canola oil. Just because the chemicals produced by this enzyme provide medical benefit does not mean that we like the way they taste.
This current study by Cramer and Jeffrey brings out the importance of myrosinase. Powdered or cooked vegetables even if they contain glucoraphanin are of little benefit unless converted to sulforaphane. As suppliers begin to add cruciferous vegetable extracts to their product lines, we should question them about myrosinase content or sulforaphane yield. We should encourage testing for and labeling the enzyme levels for these products. If myrosinase is not present, these powders provide little benefit. Watch for products containing myrosinase. Someday, we may have myrosinase containing digestives or condiments intended to be taken along with cooked cruciferous vegetables. Such a practice may increase the potential benefit of these foods.
Broccoli and COPD http://denvernaturopathic.com/broccoliandCOPD.htm
Broccoli and Bladder Cancer Recurrence Risk: http://denvernaturopathic.com/rawbroccoliandbladdercancer.htm
Cramer JM, Jeffery EH. Sulforaphane absorption and excretion following ingestion of a semi-purified broccoli powder rich in glucoraphanin and broccoli sprouts in healthy men. Nutr Cancer. 2011;63(2):196-201.
Johansson NL, Pavia CS, Chiao JW. Growth inhibition of a spectrum of bacterial and fungal pathogens by sulforaphane, an isothiocyanate product found in broccoli and other cruciferous vegetables. Planta Med. 2008 Jun;74(7):747-50.
Son TG, Camandola S, Mattson MP. Hormetic dietary phytochemicals. Neuromolecular Med. 2008;10(4):236-46.
Tang L, Zirpoli GR, Guru K, Moysich KB, Zhang Y, Ambrosone CB, et al. Intake of Cruciferous Vegetables Modifies Bladder Cancer Survival. Cancer Epidemiol Biomarkers Prev. 2010 Jun 15.
Nakamura Y, Nakamura K, Asai Y, Wada T, Tanaka K, Matsuo T, et al. Comparison of the glucosinolate-myrosinase systems among daikon (Raphanus sativus, Japanese white radish) varieties. J Agric Food Chem. 2008 Apr 23;56(8):2702-7.