New research has found that if you want the health benefits associated with eating broccoli or other cruciferous vegetables, you need to eat the real thing, not rely on a supplement.
Key phytochemicals, called glucosinates, in these vegetables is poorly absorbed if taken as a supplement. Glucosinates in cruciferous vegetables are thought to help reduce the risk of prostate, breast, lung and colorectal cancer.
The study, from the Linus Pauling Institute at Oregon State University, is 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 answer is no.
The reason is that a necessary enzyme in broccoli, called myrosinase, is missing from most of the supplement forms of glucosinates. Without this enzyme, the study found that the body actually absorbs five times less of one important phytochemical and eight times less of another.
Intensive cooking has similar effects. If broccoli is overcooked, its health value declines because much of the enzyme is destroyed. However, if it is lightly cooked for two or three minutes, or steamed until it's still a little crunchy, it retains adequate levels of the necessary enzyme.
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.
Studies have indicated that sulforaphane, in particular, may help to detoxify carcinogens, and also activate tumour suppressor genes so they can perform their proper function.
Most supplements designed to provide these glucosinolates have the enzyme inactivated, so the sulforaphane is not released as efficiently. There are a few supplements available with active myrosinase but they are still being tested and not widely available
Although broccoli has the highest levels of glucosinolates, they are also found in cauliflower, cabbage, kale and other cruciferous vegetables.
Bottom line: if you want to reap the health benefits of broccoli, eat your veggies.
Source: Journal of Agricultural and Food Chemistry, September 19, 2011.
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