New research has found that a key cancer-fighting chemical in broccoli and cabbage cannot be easily absorbed in supplement form.
To obtain some important health benefits associated with eating broccoli or other cruciferous vegetables, you need to eat the real thing - a key phytochemical in these vegetables is poorly absorbed and of far less value if taken as a pill.
The study, published by scientists in the Linus Pauling Institute, 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. They found that the answer was no, not only do you need to eat the whole foods; you have to go easy on cooking them too.
The principal investigator of the study said:
"The issue of whether important nutrients can be obtained through whole foods or with supplements is never simple."
"Some vitamins and nutrients, like the folic acid often recommended for pregnant women, are actually better-absorbed as a supplement than through food,"
"Adequate levels of nutrients like vitamin D are often difficult to obtain in most diets. But the particular compounds that we believe give broccoli and related vegetables their health value need to come from the complete food."
The reason, researchers concluded, is that a necessary enzyme called myrosinase is missing from most of the supplement forms of glucosinolates, a valuable phytochemical in cruciferous vegetables. Without this enzyme found in the whole food, the study found that the body actually absorbs five times less of one important compound and eight times less of another.
Intensive cooking does pretty much the same thing, according to the researchers. If broccoli is cooked until it's soft and mushy, its health value plummets. However, it can still be lightly cooked for two or three minutes, or steamed until it's still a little crunchy, and retain adequate levels of the necessary enzyme.
Broccoli Is A Superfood
Cruciferous vegetables like broccoli are of great interest to scientists because they contain high levels of a class of phytochemicals called glucosinolates. These important compounds are associated with reducing the risk of prostate, breast, lung and colorectal cancer. 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, helps to detoxify carcinogens, and also activate tumor 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.
Although broccoli has the highest levels of glucosinolates, they are also found in cauliflower, cabbage, kale and other cruciferous vegetables. The same cooking recommendations would apply to those foods to best retain their health benefits according to the researchers.
The study author added that higher and optimal levels of key nutrients such as vitamins C, D, E, and fish oil, for instance, can be difficult to obtain through diet alone.
But to obtain the real health benefits of broccoli and other cruciferous vegetables, they must be eaten as whole foods.
Research Paper Details:
Clarke JD, Riedl K, Bella D, et al. Comparison of Isothiocyanate Metabolite Levels and Histone Deacetylase Activity in Human Subjects Consuming broccoli sprouts or broccoli Supplement. Journal of Agricultural and Food Chemistry, 2011.