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Broccoli health benefits require the whole food, not supplements, says study

1 commentBy Nathan Gray , 12-Oct-2011
Last updated on 19-Oct-2011 at 17:45 GMT

The beneficial phytochemicals in broccoli are better absorbed when consumed as a whole food, not a supplement, say the researchers.
The beneficial phytochemicals in broccoli are better absorbed when consumed as a whole food, not a supplement, say the researchers.

Many of the health benefits associated with eating broccoli require consumption of the whole vegetables, because key phytonutrients are poorly absorbed and are of far less value if taken as a supplement, according to new research.

The study, published in the Journal of Agricultural and Food Chemistry, is said to be one of the first of its type to determine whether some of the healthy compounds found in cruciferous vegetables can be just as easily obtained through supplements.

"The issue of whether important nutrients can be obtained through whole foods or with supplements is never simple," said Emily Ho, associate professor at the Linus Pauling Institute at Oregon State University, USA – who led the research study.

“Consumption of a broccoli supplement results in significantly lower amounts of isothiocyanate metabolites that are excreted in the urine, which is likely due to the lack of myrosinase enzymes in the supplement,” said the researchers.

Without the enzyme, which is found in the whole food, Ho and her team found that that the body absorbs 5 times less sulforaphane metabolites, and 8-fold less of erucin metabolites,

“This finding has significant implications for people who consume broccoli supplements for the chemopreventive benefits and believe they are getting equivalent amounts of the bioactive isothiocyanates as if they were consuming fresh broccoli sprouts,” they added.

Broccoli benefit

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.

As such, the potential health benefits of broccoli have led to a range of commercial supplements on the market.

When eaten as a raw or lightly-cooked food, enzymes in the broccoli help to break down the glucosinolates into two valuable compounds of intensive research interest – sulforaphane and erucin.

Study details

Ho noted that small amounts of the myrosinase enzyme needed to break down glucosinolates are found in the human gut, but her teams findings show that they accomplish that task far less effectively than whole food consumption does.

She added that most supplements designed to provide these glucosinolates have the enzyme inactivated, so sulforaphane and erucin are not released as effectively.

There are a few supplements available with active myrosinase – whose function more closely resembles that of the whole food – but they are still being tested and not widely available, noted Ho.

"Some vitamins and nutrients, like the folic acid often recommended for pregnant women, are actually better-absorbed as a supplement than through food," said Ho.

"But the particular compounds that we believe give broccoli and related vegetables their health value need to come from the complete food," she said.

NPD potential?

Earlier this year, researchers from the University of Illinois recently reported combining broccoli supplements with broccoli sprouts to boost the absorption of sulforaphane.

“Data from the combination meal were interesting as they identified possible synergy among the sprouts and powder at early time point measurements of plasma and urine recovered metabolites,” wrote the U of I authors in Nutrition and Cancer (doi: 10.1080/01635581.2011.523495 ).

“The results show that combination improved availability, opening the door to development of products with enhanced chemoprotective potential.”

Source: Journal of Agricultural and Food Chemistry
Published online ahead of print, doi: 10.1021/jf202887c
Comparison of Isothiocyanate Metabolite Levels and Histone Deacetylase Activity in Human Subjects Consuming Broccoli Sprouts or Broccoli Supplement”
Authors: J.D. Clarke, K. Ried, D. Bella, S.J. Schwartz, J.F. Stevens, E. Ho

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1 comment (Comments are now closed)

Myrosinase-active supplements do exist

The findings of this study only apply to supplements of broccoli sprout 'extracts', not supplements made from 100% whole broccoli sprout powder.

When an 'extract' is made, the enzyme is necessarily deactivated and what remains is simply the glucoraphanin precursor compound. This has no ability of itself to produce sulforaphane, the active compound shown to be beneficial in human health. Although the gut microflora may have some ability to convert the precursor to active sulforaphane, studies show this ability is minimal and in some people (especially after taking antibiotics) there may be no conversion at all.

Most available broccoli sprout supplements are made from an extract which is unable to deliver what the consumer expects. This isn't clear when the supplement is purchased and so the expected benefits are not delivered.

However, if consumers search for '100% whole broccoli sprout powder', they will find myrosinase-active suppplements as both powder and capsules. Such supplements do produce sulforaphane when ingested.

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Posted by Christine Houghton
19 October 2011 | 22h59

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