The tissue of cruciferous vegetables, such as broccoli, cauliflower, and cabbage, contain high levels of the plant chemicals glucosinolates. These are metabolized by the body into isothiocyanates (such as sulforaphane), which have been suggested to be powerful anti-cancer agents.
When eaten as a raw or lightly-cooked food, an enzyme called myrosinase in the broccoli help to break down the glucosinolates into two valuable compounds of intensive research interest – sulforaphane and erucin. The only sources we have for this enzyme is from the plant itself, or from our own microflora.
Tony Talalay, CEO at Brassica Protection Products LLC, which sells broccoli sprouts and broccoli seed extracts, told NutraIngredients-USA that the epidemiological data for the potential benefits of broccoli consumption is “really quite strong”.
Data from Johns Hopkins has shown that there is a great deal of variation in the chemoprotective effects between broccoli types, he said.
“Eating fresh sprouts is the best way to deliver this system.”
From sprout to supplement
However, it is well established that many processing techniques inactivate myrosinase (Food and Chemical Toxicology, Dec. 2011, Vol. 49, pp. 3287-3309). Recently, scientists from the University of Illinois and Oregon State University have separately questioned whether the lack of myrosinase in many of the commercially available broccoli dietary supplements undermines their ability to provide dietary sulforaphane, relative to the whole food.
In way of explanation, some people have suggested that pH may play a role and that taking the broccoli supplements with a glass of orange juice may not be the best approach.
Dr Elizabeth Jeffery from the University of Illinois’ Department of Food Science and Human Nutrition, a leading broccoli researcher, told NutraIngredients-USA that suggestions that pH may influence sulforaphane production from broccoli supplements (consuming the supplements with orange juice, for example) is not the greatest concern.
“It is true that during metabolism of glucosinolates in whole broccoli, a low pH has been associated with low sulforaphane formation" she said.
“But that is not the key problem in taking these supplements. The problem is the lack of the broccoli enzyme myrosinase - so metabolism of glucosinolates cannot occur at all, and no sulforaphane is made regardless of the pH, until the supplement gets all the way down to the colon. Even then, metabolism and release of sulforaphane is very poor in the colon.
“So the important issue is to have a product (or products) that provides myrosinase as well as glucosinolates - then you make sulforaphane early in the digestive process, absorb it and gain the great benefits that sulforaphane has to offer"
Supplement plus food?
Dr Jeffery explained that her group’s most recent work (Nutrition and Cancer, doi: 10.1080/01635581.2011.523495) looked at combining commercially available broccoli powder (with inactive myrosinase) with broccoli sprouts to boost the absorption of sulforaphane.
Many cruciferous vegetables are eaten raw, she noted, and they automatically still have the enzyme. The list is not restricted to broccoli or broccoli sprouts, but plants such as water cress, horse radish, cauliflower, and cabbage.
That’s not to say that all supplements contain inactive myrosinase. The Australian company Cell-Logic produces a supplement called EnduraCell which is said to contain active myrosinase. Dr Jeffery said that she has tested this product and that the myrosinase is indeed active.
Epidemiology vs practical
But how to tally the ‘strong’ evidence from epidemiology, where the majority (80-90%, according to Brassica Protection Products’ Talalay) of the broccoli consumed in those studies was cooked, and therefore contain inactive myrosinase, with the fact that active myrosinase may be needed?
Referring to the recent studies, , a spokesperson for Jarrow Formulas, which sells a broccoli extract product called BroccoMax that was used in the Oregon State study, told NutraIngredients-USA that: “These trials were one-offs and not findings based on consumption of the tested products over a period of days with normal diets.
“It must be kept clearly in mind that the broccoli extract supplement led to significant increases in markers for activity. Not surprisingly, the ingestion of broccoli sprouts gave greater yields of the markers and for reasons long available in the literature, to wit, without the presence of myrosinase, conversion of glucosinolate to sulforophane is dependent on bacterial action in the intestines and this takes place below the area of maximal uptake of sulforophane, which is the initial sections of the small intestine.
“Do sprouts give better yields? Of course, but few of us can or will regularly consume 40 grams of broccoli sprouts. Moreover, extracts of sprouts containing myrosinase have yet to be produced that are stable on a commercial scale,” added the Jarrow Formulas spokesperson.
Some products/ ingredients are available that claim to contain the active enzyme, or are standardized to contain a significant level of sulforophane (like Cyvex’s BroccoPhane and BroccoPlus ingredients, and the aforementioned EnduraCell product).
The spokesperson for Jarrow Formulas said the company is actively working on ways around “the limitations of current broccoli seed extracts in order to produce a supplement that more closely reproduces the sulforophane yield of ingested broccoli sprouts.
“Until this new approach has been perfected, the seed extract remains one means of improving access to the bioactive known as sulforophane.”