The Truth about Broccoli Sprouts

It’s often cited by companies and influencers that broccoli sprouts contain 100 times more sulforaphane than mature broccoli. While everyone sharing this information probably has the best intentions, what the study actually said was 

“Unexpectedly, 3-day-old sprouts of cultivars of certain crucifers including broccoli and cauliflower contain 10–100 times higher levels of glucoraphanin (the Glucosinolate of sulforaphane) than do the corresponding mature plants."

Furthermore, In the quoted study, the amount of glucoraphanin in the broccoli sprouts was actually only 15.37 times as high as the mature plant, not 100 times.

This is what happens when people and companies are just repeating information they have heard from others or only read the abstract of a given study. This is a very common issue as we don’t generally verify the information provided by those we generally agree with.  An important thing to note about the above is that 100 times the level of glucoraphanin in most crucifers is still a very insignificant amount.

  1. Broccoli Sprouts do not contain Sulforaphane; they contain Glucoraphanin, which needs to be converted to sulforaphane by an enzyme called Myrosinase.
  2. Sulforaphane is an isothiocyanate product, not Glucosinolate.
  3. Broccoli Seeds actually contain higher levels of glucoraphanin than broccoli sprouts.
  4. Most crucifers are not rich sources of Glucoraphanin. They all contain different Glucosinolates, which are converted to different isothiocyanate products by Myrosinase, which is an enzyme stored in a separate cellular compartment from the Glucosinolate. This is why pureeing is important for dogs.
  5. Most of the more recent research has shown between 2-6 times more sulforaphane, with one study in Japan finding 10 times. 
    1. In these studies, the broccoli sprouts were processed so as to convert the glucoraphanin to Sulforaphane. They did not measure Glucoraphanin content.
  6. The amount of glucoraphanin in broccoli and other crucifers is heavily influenced by phenotype. IE some phenotypes of broccoli contain 100+Umol/g while others contain 5.38 Umol/g
  7. While we can’t say that no company selling seeds or sprouts is testing the amount of glucoraphanin, having spoken to several of them, most aren’t. This means it’s possible if not probable the sprouts or seeds you are purchasing are on the lower end for a number of reasons*.
  8. In one study that used broccoli sprouts purchased at a local store it came out to .84 umol/g. While this is still higher than the frozen broccoli and possibly the fresh broccoli at your grocery store, it is going to be relatively comparable to the broccoli you can get at your local farmers market, depending on the phenotype, growing conditions, and what other post-harvest methods they use.
    1. While in theory, organic fruits and vegetables can contain higher levels of different beneficial phytochemicals, this does not hold true for glucoraphanin.

Why the Seeds and Sprouts being sold are likely on the lower end.

Any company selling broccoli seeds for sprouting has an incentive to choose a variety based on ease of sprouting, as they don’t want to be blamed for it not sprouting and the cost of the actual seeds, not Glucoraphanin content.

Plants have been selectively bred for a number of specific traits. While relatively recently, there has been some attention placed on the phytochemicals within plants, most of the attention has revolved around

●       Heat/Cold Tolerance

●       Size

●       Germination Rate/Ease in Growing

●       Time to Market

●       Crop Yield

●       Aesthetics

●       Suitability for transport

●       Disease/Pest/Pathogen Resistance

Just as there can be unintended consequences associated with breeding for specific traits in dogs, some of these traits have likely resulted in lower concentrations of potentially beneficial compounds such as glucoraphanin.  In fact, one study that looked at the release date of specific broccoli phenotypes did find a decrease in the Glucosinolate content over time.

While we didn’t have the above sprouts tested for glucoraphanin content, based on the phenotype of the seeds used above, we can be relatively confident that the one on the left has around 2 times more glucoraphanin than the one in the middle, while it likely has 3 times more than the one on the right. The cost of these phenotypes means they can’t be realistically used for sprouting.

While Broccoli sprouts will still generally contain higher levels of glucoraphanin, it isn’t an astronomical difference, and given the palatability difference, it makes it a much closer call, especially If you can get fresh broccoli from a local farmer.

One major caveat is that broccoli sprouts are generally consumed raw, while broccoli is generally cooked to the point where the Myrosinase is no longer active, which means the only conversion will be from bacteria with Myrosinase-like activity.  There are things that can be done to enhance the conversion of different Glucosinolates to their isothiocyanate products, but that would be a post on its own.

While this post doesn’t cover the benefits of different isothiocyanate products, there does need to be some caution when talking about the effectiveness of different foods and herbs, especially in relation to different medications.

Some of the dosings required are just too high to be a realistic option due to palatability issues or just the amount required, as this also has an impact on quality of life. IE 100/mgs per KG/BW of a foul-tasting or bitter herb. So while in theory, it appears to be a great option while in reality, it isn’t a realistic option.   

If you are sprouting broccoli for yourself or your dog, contact the company and ask for the glucoraphanin content of the seeds you are buying. They likely won’t have an answer, but if enough people demand the glucoraphanin content, they may eventually start testing the seeds for glucoraphanin content. 

 

References 

Paśko P, Tyszka-Czochara M, Galanty A, et al. Comparative Study of Predominant Phytochemical Compounds and Proapoptotic Potential of Broccoli Sprouts and Florets. Plant Foods for Human Nutrition (Dordrecht, Netherlands). 2018 Jun;73(2):95-100. DOI: 10.1007/s11130-018-0665-2. PMID: 29675806; PMCID: PMC5956025.

Campas-Baypoli ON, Sánchez-Machado DI, Bueno-Solano C, Ramírez-Wong B, López-Cervantes J. HPLC method validation for measurement of sulforaphane level in broccoli by-products. Biomedical Chromatography : BMC. 2010 Apr;24(4):387-392. DOI: 10.1002/bmc.1303. PMID: 19650149.

López-Cervantes, J., Tirado-Noriega, L.G., Sánchez-Machado, D.I., Campas-Baypoli, O.N., Cantú-Soto, E.U. and Núñez-Gastélum, J.A. (2013), Biochemical composition of broccoli seeds and sprouts at different stages of seedling development. Int J Food Sci Technol, 48: 2267-2275. https://doi.org/10.1111/ijfs.12213

Nakagawa K, Umeda T, Higuchi O, et al. Evaporative light-scattering analysis of sulforaphane in broccoli samples: Quality of broccoli products regarding sulforaphane contents. Journal of Agricultural and Food Chemistry. 2006 Apr;54(7):2479-2483. DOI: 10.1021/jf051823g. PMID: 16569031.

Fahey JW, Zhang Y, Talalay P. Broccoli sprouts: an exceptionally rich source of inducers of enzymes that protect against chemical carcinogens. Proc Natl Acad Sci U S A. 1997 Sep 16;94(19):10367-72. doi: 10.1073/pnas.94.19.10367. PMID: 9294217; PMCID: PMC23369.

Bhandari SR, Jo JS, Lee JG. Comparison of Glucosinolate Profiles in Different Tissues of Nine Brassica Crops. Molecules. 2015 Aug 31;20(9):15827-41. doi: 10.3390/molecules200915827. PMID: 26334264; PMCID: PMC6331803.

Hahn C, Müller A, Kuhnert N, Albach D. Diversity of Kale (Brassica oleracea var. sabellica): Glucosinolate Content and Phylogenetic Relationships. J Agric Food Chem. 2016 Apr 27;64(16):3215-25. doi: 10.1021/acs.jafc.6b01000. Epub 2016 Apr 15. PMID: 27028789.

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