Fish Tacos to Radish Pickles: It's all about the sulforaphane
Written by Jacob Schor, ND, FABNO, AANP Board Member
I wrote recently about the appropriateness of eating coleslaw with fried fish, and that information has been on my mind since. As a quick recap, it was reported in March of this year that frying fish creates far more cancer causing heterocyclic amines then previously thought, levels that compete with the worst found in a barbecued steak, a potential cause of cancer that we have worried about for years. Cruciferous vegetables, including broccoli and cabbage, can, if prepared correctly, produce a chemical called sulforaphane that neutralizes the harmful effects of these heterocyclic amines.1
Sulforaphane production is tricky; it requires the mixing of two separate constituents in these vegetables, a chemical called glucoraphanin and an enzyme called myrosinase. Like many other enzymes, myrosinase is sensitive to temperature; heat can destroy it. Sulforaphane yield from any particular food is unpredictable, varying greatly with cooking methods and this has given rise to inconsistent results in human cancer trials. This problem of varying sulforaphane levels has been the subject of a number of papers over the last year so that we are getting a sense of how to increase the anticancer effect of these foods.
Just about a year ago to the day a paper by Saha et al reported that frozen broccoli added to soup yielded about one tenth the increase in blood levels of sulforaphane in human volunteers than if fresh broccoli was used. According to the authors, “…the reduction was shown to be due to destruction of myrosinase activity by the commercial blanching-freezing process”. Gut bacteria were apparently responsible for converting what small amounts of sulforaphane were found.2
Then along come Drosz and Jeffery writing in the September 2013 issue of the Journal of Food Science with a clever idea. They aren't ready to discard frozen broccoli as a good food to eat. Frozen broccoli is cheaper than fresh broccoli, has a longer shelf life and is easier and faster to cook. All attributes favored by the food scientists who were my colleagues at one point. Following Saha's lead they assumed the myrosinase was destroyed during the blanching process that the broccoli undergoes prior to being frozen. They experimented with lower blanching temperatures reducing the temperature from the standard 86° C to 76° C. At the lower temperature most of the lipoxygenase enzymes responsible for product spoilage were destroyed yet the majority of the myrosinase was left intact; as a result, over 80% of the potential sulforaphane formation occurred.
They found another trick to increasing sulforaphane content of frozen broccoli, they added active myrosinase back in. They report to my surprise that daikon radish root is a good source of heat stable myrosinase. Daikon radish root supported sulforaphane formation even when heated to 25° C for 10 min, plenty of time to cook frozen broccoli through and through. What's more it doesn't take much (0.025% daikon), not enough to even notice.3
Thus don't be surprised to find daikon radish on the label of frozen broccoli packages at some point in the future. In the meantime, there is a simple way to insure full sulforaphane production when eating cooked cruciferous vegetables, eat a bit of daikon radish with the meal.
Two easy ways to eat more daikon radish:
Simple add to any coleslaw.
1/2 lb carrots (julienned or cut into thin match-like strips)
1/2 lb radish (daikon, cut same as carrots)
4 cups water (warm enough to dissolve the salt and sugar)
3 tbs sugar ?
2 tbs salt
6 tbs rice vinegar
In large pitcher or large bowl, mix water, vinegar, sugar and salt till everything is dissolved and combined well.
Place carrots and daikon in a clean, sterile jar and fill with vinegar mixture till jar is full.
Cover jars and set in the refrigerator to pickle for about 3 days. Pickles can last for about 3 weeks in the fridge.
[Recipe from “White on Rice Couple”]
1. Khan MR, Busquets R, Saurina J, Hernández S, Puignou L. Identification of seafood as an important dietary source of heterocyclic amines by chemometry and chromatography-mass spectrometry. Chem Res Toxicol. 2013 Jun 17;26(6):1014-22.
2. Saha S, Hollands W, Teucher B, Needs PW, Narbad A, Ortori CA, Barrett DA, Rossiter JT, Mithen RF, Kroon PA. Isothiocyanate concentrations and interconversion of sulforaphane to erucin in human subjects after consumption of commercial frozen broccoli compared to fresh broccoli. Mol Nutr Food Res. 2012 Dec;56(12):1906-16. doi: 10.1002/mnfr.201200225. Epub 2012 Oct 27.
3. Dosz EB, Jeffery EH. Modifying the processing and handling of frozen broccoli for increased sulforaphane formation. J Food Sci. 2013 Sep;78(9):H1459-63. doi: 10.1111/1750-3841.12221. Epub 2013 Aug 5.
The image is a Wikipediaand Wikimedia Commons image is from the user Chris 73 and is freely available online under the creative commons cc-by-sa 3.0 license.