Hoe krijg je de meeste gezondheidsvoordelen van broccoli?*
Uit twee studies blijkt het belang van het eten van broccoli zelf, een goede bereiding van broccoli en voor een optimale opname in het lichaam een goede combinatie van kruisbloemige groenten.
Broccoli staat bekend om de meeste glucosinolaten te bevatten van alle kruisbloemige
groenten. De studie van het Linus Pauling instituut laat zien dat bij nagenoeg alle supplementen van broccoli met glucosinolaten het enzym myrosinase ontbreekt waardoor de opname van gezonde stoffen wel 5 tot 8 keer minder wordt. Ook koken doet veel van de voordelen teniet. Rauw of kort stomen doet alle voordelen behouden en worden belangrijke stoffen als
sulforafaan en urecin gevormd. Uit de andere studie blijkt dat om de maximale gezondheidsvoordelen uit broccoli te halen broccoli het best gecombineerd kan worden met andere groenten die veel van het enzym myrosinase inzich hebben, zoals vooral jonge spruiten van broccoli,
mosterd, mierikswortel en wasabi. Daardoor worden niet alleen veel meer gezonde stoffen
(isothiocyanaten) gevormd maar de opname in het lichaam gebeurt veel beter en sneller en al in het eerste gedeelte van de dunne darm. Anders gebeurt dat pas in de dikke darm, duurt het langer en wordt duidelijk minder opgenomen.
Health Benefits of Broccoli Require the Whole Food, Not Supplements
New research has found that if you want some of the many 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 supplement.
The study, published by scientists in 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.
And not only do you need to eat the whole foods, you have to go easy on cooking them.
"The issue of whether important nutrients can be obtained through whole foods or with supplements is never simple," said Emily Ho, an OSU associate professor in the OSU School of Biological and Population Health Sciences, and principal investigator with the Linus Pauling Institute.
"Some vitamins and nutrients, like the folic acid often recommended for pregnant women, are actually better-absorbed as a supplement than through food," Ho said. "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, Ho said. 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.
The new study was published in the Journal of Agricultural and Food Chemistry. It was supported by the National Institutes of Health.
Broccoli has been of particular interest to scientists because it contains the highest levels of certain glucosinolates, a class of phytochemicals that many believe may reduce 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, may help 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. There are a few supplements available with active myrosinase, and whose function more closely resembles that of the whole food, but they are still being tested and not widely available, Ho said.
Small amounts of the myrosinase enzyme needed to break down glucosinolates are found in the human gut, but the new research showed they accomplish that task far less effectively than does whole food consumption.
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, Ho said.
Many people take a variety of vitamins, minerals and phytochemicals as supplements, and many of them are efficacious in that form, researchers say. Higher and optimal levels of popular supplements such as vitamins C, E, and fish oil, for instance, can be difficult to obtain through diet alone. Some researchers believe that millions of people around the world have deficient levels of vitamin D, because they don't get enough in their diet or through sun exposure.
But for now, if people want the real health benefits of broccoli, there's a simple guideline.
Eat your vegetables.
More evidence that spicing up broccoli boosts its cancer-fighting power
Teaming fresh broccoli with a spicy food that contains the enzyme myrosinase significantly enhances each food’s individual cancer-fighting power and ensures that absorption takes place in the upper part of the digestive system where you’ll get the maximum health benefit, suggests a new University of Illinois study.
“To get this effect, spice up your broccoli with broccoli sprouts, mustard, horseradish, or wasabi. The spicier, the better; that means it’s being effective,” said Elizabeth Jeffery, a U of I professor of nutrition.
In the study, when fresh broccoli sprouts were eaten with broccoli powder, the scientists were able to measure bioactive compounds in the blood 30 minutes later. When these peaked at three hours, they were much higher when the foods were eaten together than when either was eaten alone. Urine samples corroborated the blood results, said Jenna Cramer, lead author of the study.
It’s no secret that many people cook the benefits right out of broccoli instead of steaming it lightly for two to four minutes to protect its healthful properties, she said.
“However, this study shows that even if broccoli is overcooked, you can still boost its benefits by pairing it with another food that contains myrosinase,” she said.
Myrosinase is the enzyme necessary to form sulforaphane, the vegetable’s cancer-preventive component, co-author Margarita Teran-Garcia explained.
Note what happened with the fresh broccoli sprouts and broccoli powder eaten in this experiment. The powder doesn’t contain myrosinase, but it does contain the precursor to the anti-cancer agent sulforaphane. Eaten together, the sprouts were able to lend their myrosinase to the powder. As predicted, both foods produced sulforaphane and provided greater anti-cancer benefit, Jeffery said.
Other foods that will boost broccoli’s benefits if they are paired together include radishes, cabbage, arugula, watercress, and Brussels sprouts.
“Here’s another benefit of protecting and enhancing the myrosinase in your foods,” Jeffery said. “If myrosinase is present, sulforaphane is released in the ilium, the first part of your digestive system. Absorption happens well and quickly there, which is why we saw bioactivity in 30 minutes.”
An earlier Jeffery study showed that microbiota are capable of releasing sulforaphane in the lower gut, but absorption happens more slowly in the colon than in the upper intestine, she said.
Scientists say that as little as three to five servings of broccoli a week provide a cancer-protective benefit.
“But it pays to spice it up for added benefits and find ways to make it appealing so you don’t mind eating it if you’re not a broccoli fan. I add fresh broccoli sprouts to sandwiches and add them as one of my pizza toppings after the pie is out of the oven,” Cramer
said. The study is available pre-publication online in the British Journal of Nutrition
(Oktober 2011)
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