Metabolic modifications brought about by consumption of high-glucoraphanin broccoli may be behind the suggested health benefits and cancer-fighting ability of the cruciferous vegetable, according to a new clinical trial.
The study, led by researchers at the UK's Institute of Food Research (IFR) provides the first evidence from human studies for a possible mechanism behind the suggested ability of glucosinolates - such as glucoraphanin found in broccoli - to reduce the risks of chronic diseases and cancers.
Writing in the American Journal of Clinical Nutrition, the IFR-led research team noted that a number of studies have shown that diets rich in cruciferous vegetables may reduce the risk of cancer, type II diabetes and other chronic diseases of ageing through the actions of glucosinolates.
The new 12 week dietary intervention trial assessed the effect of glucosinolates on metabolism by randomising participants to consumption of either a high-glucoraphanin broccoli (Beneforté), standard broccoli or garden peas before analysing biomarkers of CVD risk and 347 plasma metabolites - finding that a high-glucoraphanin diet resulted in modified metabolism that may be linked to cellular processes of aging and the risk of chronic diseases.
"We consider that this study provides an important and original insight into how diets rich in cruciferous vegetables may be able to reduce the risk of cancer," said the research team - led by Richard Mithen of the IFR. "It also suggests that this protective effect is mediated by glucosinolates."
Mithen and his colleagues suggested that an increasing level of mitochondrial dysfunction caused by cellular aging leads to metabolic disturbances - causing imbalances between the anaplerotic and cataplerotic reactions "that are necessary to maintain the optimum balance between energy generation and the synthesis of fatty acids and other metabolites required for the maintenance of health."
"The nature of these changes within an individual depends on diet, physical activity, and genotype," they said. "A diet rich in cruciferous vegetables effectively retunes our metabolism by rebalancing anaplerosis and cataplerosis and restoring metabolic homeostasis."
"In this manner, cruciferous vegetables may be able to reduce the risk of many chronic diseases associated with aging."
The dietary intervention trial randomised 48 participants into three intervention groups; one group ate high glucoraphanin broccoli, one group ate standard broccoli, and the third ate garden peas instead of broccoli for a period of 12 weeks.
Mithen and his colleagues measured blood plasma levels of 346 metabolites before and after the 12 week period - finding that those who consumed the high glucoraphanin broccoli had improved metabolism, and reduced levels of fatty acids and other inflammation-related lipids in the blood.
The team concluded that their results were due to the bioactive compound sulforaphane - that is derived from glucoraphanin found in broccoli but is not found in peas. They suggested that sulforaphane switched on ‘antioxidant’ genes that helped to 're-tune' metabolism.
Source: American Journal of Clinical Nutrition
Published online ahead of print, doi: 10.3945/ajcn.113.065235
"A diet rich in high glucoraphanin broccoli interacts with genotype to reduce discordance in plasma metabolite profiles through modulating mitochondrial disfunction"
Authors: Charlotte N. Armah et al