Broccoli compound boost for immune health
benefits, may also counter the decline in the body's immune system
associated with age, says a new study from UCLA.
The compound sulforaphane was found to activate a set of antioxidant genes and enzymes in specific immune cells, which then combat the detrimental effects of free radicals that can damage cells and lead to disease, reports the study in the Journal of Allergy and Clinical Immunology .
"Our defence against oxidative stress damage may determine at what rate we age, how it will manifest and how to interfere in those processes," explained lead researcher Andre Nel from the University of California, Los Angeles (UCLA).
"In particular, our study shows that a chemical present in broccoli is capable of stimulating a wide range of antioxidant defence pathways and may be able to interfere with the age-related decline in immune function."
Broccoli and mice Using mice as test animals, the UCLA researchers administered sulforaphane (nine micromoles per day per mouse) for five days before being challenged with infection, and for a further 11 days.
Direct administration of broccoli compounds resulted in a reversal in the age-related decline in immune function in old mice.
Similar results were also obtained when individual immune cells were taken from old mice, exposed to sulforaphane and then injected back into the animal.
"We found that treating older mice with sulforaphane increased the immune response to the level of younger mice," said lead author Hyon-Jeen Kim.
In particular, sulfurophane was found to restore immune function in the older animals by directhe 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.
Antioxidant boost Previous studies have reported that sulforaphane works by inducing the body's natural phase-2 enzyme antioxidant defences, and the researchers looked at the Nrf2 pathway, said to be the most sensitive oxidative stress response, and a master regulator of the body's overall antioxidant response, capable of switching on hundreds of antioxidant and rejuvenating genes and enzymes.
"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," added Nel.
The researchers report that, while there is a natural decline in the activity of Nrf2 with ageing, the pathway did remain accessible to compounds like sulforaphane that are capable of restoring some of the ravages of ageing by boosting antioxidant pathways.
"This finding could be of major significance in preventing or reversing the effects of immune senescence in elderly human subjects," wrote the authors.
"Dietary antioxidants have been shown to have important effects on immune function, including improvement of contact hypersensitivity (CHS) and vaccination responses in human subjects.
To this list we can now add broccoli and other cruciferous vegetables that are deserving of a human trial," they added.
In the meantime, Nel suggested including these vegetables as part of a healthy diet.
And looking to the future, Nel said that free radicals may only be part of the answer.
"It may prove to be a more multifaceted process and interplay between pro- and antioxidant forces," he said.
Moreover, the chemistry leading to activation of this gene-regulation pathway could be offer a means to combine pharmaceutical science and nutrition, suggested the researchers.
"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," said Nel.
"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."
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.
History of sulforaphane In 1992 researchers from John Hopkins University School of Medicine were the first to isolate sulforaphane glucosinolate (SGS) - the precursor to sulforaphane - and subsequently created Brassica Protection Products to develop and commercialise the broccolis sprouts in the US.
In December 2005 British researchers announced the development of Super Broccoli, which contains three times the levels of sulforaphane than normal mature broccoli, but still less than that found in the three-day old sprouts.
Source: Journal of Allergy and Clinical Immunology (Elsevier) Published online ahead of print 5 March 2008, doi:10.1016/j.jaci.2008.01.016 "Nrf2 activation by sulforaphane restores the age-related decrease of TH1 immunity: Role of dendritic cells" Authors: H.-J. Kim, B. Barajas, M. Wang, A.E. Nel
