Broccoli voor een goed immuunsysteem en tegen kanker*
Uit twee studies blijkt dat broccoli in het bijzonder de jonge spruiten heel gezond zijn.
Uit de ene studie blijkt dat de bioactieve stof sulforafaan in broccoli en in andere
kruisbloemige groenten goed is om het immuunsysteem op peil te houden dat anders door het ouder worden achteruitgaat. Een van de belangrijkste oorzaken van het ouder worden is de oxidatieschade in de weefsels en organen veroorzaakt door vrije radicalen. Sulforafaan als sterke antioxidant zorgt ervoor dat die schade sterk verminderd wordt.
Uit een andere studie, weliswaar met dieren, blijkt dat extracten van broccoli de kans op het ontstaan van blaaskanker wel met de helft kunnen verminderen. Bovendien zijn er
veel minder kankergezwellen en zijn deze ook aanzienlijk kleiner.
Broccoli May Help Boost The Aging Immune System
Eat your broccoli! That's the advice from UCLA researchers who have found that a chemical in broccoli and other cruciferous vegetables may hold a key to restoring the body's immunity, which declines as we age.
Published in the online edition of the Journal of Allergy and Clinical Immunology, the study findings show that sulforaphane, a chemical in broccoli, switches on a set of antioxidant genes and enzymes in specific immune cells, which then combat the injurious effects of molecules known as free radicals that can damage cells and lead to disease.
Free radicals are byproducts of normal body processes, such as the metabolic conversion of food into energy, and can also enter the body through small particles present in polluted air. A supercharged form of oxygen, these molecules can cause oxidative tissue damage, leading to disease for example, triggering the inflammation process that causes clogged arteries. Oxidative damage to body tissues and organs is thought to be one of the major causes of
aging.
"The mysteries of aging have always intrigued man," said Dr. Andre Nel, the study's principal investigator and chief of nanomedicine at the David Geffen School of Medicine at UCLA. "While we have known for some time that free radicals are important in aging, most of the past attention has focused on the mechanisms that produce free radicals rather than addressing the pathways used by the body to suppress their
production."
A dynamic equilibrium exists in the body between the mechanisms that lead to increased free radical production and those antioxidant pathways that help combat free radicals.
"Our study contributes to the growing understanding of the importance of these antioxidant defense pathways that the body uses to fight free radicals," said Nel, a practicing clinical allergist and immunologist at the Geffen School. "Insight into these processes points to ways in which we may be able to alleviate the effects of
aging."
The delicate balance between pro-oxidant and antioxidant forces in the body could determine the outcome of many disease processes that are associated with aging, including cardiovascular disease, degenerative joint diseases and diabetes, as well as the decline in efficiency of the immune system's ability to protect against infectious
agents.
"As we age, the ability of the immune system to fight disease and infections and protect against cancer wears down as a result of the impact of oxygen radicals on the immune system," Nel said.
According to the UCLA study, the ability of aged tissues to reinvigorate their antioxidant defense can play an important role in reversing much of the negative impact of free radicals on the immune system. However, until this current study, the extent to which antioxidant defense can impact the aging process in the immune system was not properly understood.
"Our defense against oxidative stress damage may determine at what rate we age, how it will manifest and how to interfere in those processes," Nel said. "In particular, our study shows that a chemical present in broccoli is capable of stimulating a wide range of antioxidant defense pathways and may be able to interfere with the age-related decline in immune
function."
The UCLA team not only found that the direct administration of sulforaphane in broccoli reversed the decline in cellular immune function in old mice, but they witnessed similar results when they took individual immune cells from old mice, treated those cells with the chemical outside the body and then placed the treated cells back into a recipient
animal.
In particular, the scientists discovered that dendritic cells, which introduce infectious agents and foreign substances to the immune system, were particularly effective in restoring immune function in aged animals when treated with
sulforaphane.
"We found that treating older mice with sulforaphane increased the immune response to the level of younger mice," said Hyon-Jeen Kim, first author and research scientist at the Geffen School.
To investigate how the chemical in broccoli increased the immune system's response, the UCLA group confirmed that sulforaphane interacts with a protein called Nrf2, which serves as a master regulator of the body's overall antioxidant response and is capable of switching on hundreds of antioxidant and rejuvenating genes and
enzymes.
Nel said that the chemistry leading to activation of this gene-regulation pathway could be a platform for drug discovery and vaccine development to boost the decline of immune function in elderly people.
"This is a radical new way of thinking in how to increase the immune function of elderly people to possibly protect against viral infections and cancer," Nel said. "We may have uncovered a new mechanism by which to boost vaccine responses by using a nutrient chemical to impact oxidant stress pathways in the immune
system."
Kim said that although there is a decline in Nrf2 activity with aging, this pathway remains accessible to chemicals like sulforaphane that are capable of restoring some of the ravages of aging by boosting antioxidant
pathways.
The next step is further study to see how these findings would translate to humans.
"Dietary antioxidants have been shown to have important effects on immune function, and with further study, we may be adding broccoli and other cruciferous vegetables to that list," Nel said.
For now, Nel suggests including these vegetables as part of a healthy diet.
Nel said that these findings offer a window into how the immune system ages.
"We may find that combating free radicals is only part of the answer. It may prove to be a more multifaceted process and interplay between pro- and antioxidant forces," he
said.
The study was funded by the National Institute on Aging, the UCLA Claude D. Pepper Older Adults Independence Center, and the National Institute of Allergy and Infectious Diseases.
Other study authors included Berenice Barajas and Dr. Meiying Wang.
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http://www.ucla.edu
Extract of broccoli sprouts may protect against bladder cancer
A concentrated extract of freeze dried broccoli sprouts cut development of bladder tumors in an animal model by more than half, according to a report in Cancer Research, a journal of the American Association for Cancer Research.
This finding reinforces human epidemiologic studies that have suggested that eating cruciferous vegetables like broccoli is associated with reduced risk for bladder cancer, according to the study's senior investigator, Yuesheng Zhang, MD, PhD, professor of oncology at Roswell Park Cancer Institute. "Although this is an animal study, it provides potent evidence that eating vegetables is beneficial in bladder cancer prevention," he said.
There is strong evidence that the protective action of cruciferous vegetables derives at least in part from isothyiocyanates (ITCs), a group of phytochemicals with well-known cancer preventive activities."The bladder is particularly responsive to this group of natural chemicals," Zhang said. "In our experiments, the broccoli sprout ITCs after oral administration were selectively delivered to the bladder tissues through urinary excretion."
Other cruciferous vegetables with ITCs include mature broccoli, cabbage, kale, collard greens and others. Broccoli sprouts have approximately 30 times more ITCs than mature broccoli, and the sprout extract used by the researchers contains approximately 600 times as much.
Although animals that had the most protection against development of bladder cancer were given high doses of the extract, Zhang said humans at increased risk for this cancer likely do not need to eat huge amounts of broccoli sprouts in order to derive protective benefits.
"Epidemiologic studies have shown that dietary ITCs and cruciferous vegetable intake are inversely associated with bladder cancer risk in humans. It is possible that ITC doses much lower than those given to the rats in this study may be adequate for bladder cancer prevention," he said.
Zhang and his colleagues tested the ability of the concentrate to prevent bladder tumors in five groups of rats. The first group acted as a control, while the second group was given only the broccoli extract to test for safety. The remaining three groups were given a chemical, N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) in drinking water, which induces bladder cancer. Two of these groups were given the broccoli extract in diet, beginning two weeks before the carcinogenic chemical was delivered.
In the control group and the group given only the extract, no tumors developed, and there was no toxicity from the extract in the rats.
About 96 percent of animals given only BBN developed an average of almost two tumors each of varying sizes. By comparison, about 74 percent of animals given a low dose of the extract developed cancer, and the number of tumors per rat was 1.39. The group given the high dose of extract had even fewer tumors. About 38 percent of this high-dose group developed cancer, and the average number of tumors per animal was only .46 and, unlike the other animals, the majority were very small in size.
The study was funded by the Vital Vegetables Research Program of Australia and New Zealand, the National Cancer Institute and the Roswell Park Alliance Foundation.
http://www.aacr.org (April
2008)
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