Kruisbloemige groenten voor een sterk immuunsysteem*
Uit een studie, weliswaar met muizen blijkt het belang van het eten van kruisbloemige groenten voor een volledig functioneren van het
immuunsysteem. Voedingsstoffen in kruisbloemige groenten zoals
broccoli doen dit door de intra-epitheliale lymfocyten goed te laten werken. Intra-epitheliale lymfocyten (IEL’s)
zijn een heterogene populatie van naturalkillercellen en T-cellen die zich bevinden in het epitheelweefsel van o.a. de huid en de darmen. Deze IEL’s zijn de eerste verdediging in het epitheelweefsel van het lichaam zowel binnen als buiten. Uit de studie blijkt nu dat de hoeveelheid IEL’s afhankelijk van de zg. AhR’s (aryl koolwater receptoren), eiwitten die voorkomen in bijna alle cellen van mensen. Eerdere studies lieten al zien dat bioactieve stoffen in kruisbloemige groenten de hoeveelheid AhR’s flink verhoogd. Nu blijkt dat daardoor het aantal IEL’s ook flink vergroot wordt, bij weinig Ahr’s leven EIL’s veel korter en/of blijven niet in het epitheel. In de studie bleek bij gezonde muizen die 2-3 weken geen kruisbloemige groenten gegeten hadden wel 70-80% van de IEL’s verdwenen te zijn
waardoor ze een deel van hun immuunsysteem kwijt waren en darmontstekingen
ontwikkelden.
Eating Green Veggies Improves Immune Defenses
Researchers reporting online in the journal Cell, a Cell Press publication have found another good reason to eat your green vegetables, although it may or may not win any arguments with kids at the dinner table.
It turns out that green vegetables -- from bok choy to broccoli -- are the source of a chemical signal that is important to a fully functioning immune system. They do this by ensuring that immune cells in the gut and the skin known as intra-epithelial lymphocytes (IELs) function properly.
"It is still surprising to me," said Marc Veldhoen of The Babraham Institute in Cambridge. "I would have expected cells at the surface would play some role in the interaction with the outside world, but such a clear cut interaction with the diet was unexpected. After feeding otherwise healthy mice a vegetable-poor diet for two to three weeks, I was amazed to see 70 to 80 percent of these protective cells disappeared."
Those protective IELs exist as a network beneath the barrier of epithelial cells covering inner and outer body surfaces, where they are important as a first line of defense and in wound repair. Veldhoen's team now finds that the numbers of IELs depend on levels of a cell-surface protein called the aryl hydrocarbon receptor (AhR), which can be regulated by dietary ingredients found primarily in cruciferous vegetables. Mice lacking this receptor lose control over the microbes living on the intestinal surface, both in terms of their numbers and composition.
Earlier studies suggested that breakdown of cruciferous vegetables can yield a compound that can be converted into a molecule that triggers AhRs. The new work finds that mice fed a synthetic diet lacking this key compound experience a significant reduction in AhR activity and lose IELs. With reduced numbers of these key immune cells, animals showed lower levels of antimicrobial proteins, heightened immune activation and greater susceptibility to injury. When the researchers intentionally damaged the intestinal surface in animals that didn't have normal AhR activity, the mice were not as "quick to repair" that damage.
As an immunologist, Veldhoen says he hopes the findings will generate interest in the medical community, noting that some of the characteristics observed in the mice are consistent with those seen in patients with inflammatory bowel disease.
"It's tempting to extrapolate to humans," he said. "But there are many other factors that might play a role."
For the rest of us, he says, "it's already a good idea to eat your greens." Still, the results offer a molecular basis for the importance of cruciferous vegetable-derived phyto-nutrients as part of a healthy diet.
(November 2011)
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