Broccoli retunes metabolism, first evidence of mechanism
Diets rich in glucosinolates, such as glucoraphanin found in broccoli, can “retune” cellular processes that get disrupted as the body ages, and contribute to a reduced risk of cancer, according to the results of human studies undertaken at the Institute of Food Research in the UK.
The research, published in the American Journal of Clinical Nutrition on 31 July 2013, aimed to study what effects glucosinolate consumption has on metabolism. The researchers carried out human dietary intervention trials, which involved making controlled and very specific changes to people’s diets over a period of time.
Researchers randomly split 48 volunteers into three groups. Over a period of 12 weeks, one group ate high glucoraphanin broccoli, one group ate standard broccoli, and the third ate no broccoli.
The researchers measured 346 metabolites in the blood before and after the 12 week period. They found that people who ate the high glucoraphanin broccoli had improved metabolism, and most of them had reduced levels of fatty acids in the blood and other lipid compounds that are associated with inflammation.
Researchers concluded that this was because of a bioactive compound called sulforaphane that is derived from glucoraphanin. The compound switched on ‘antioxidant’ genes, which then reduced excessive ROS in the cells, enabling their metabolic machinery to work better.
The researchers said a number of studies have shown that diets rich in cruciferous vegetables like broccoli may reduce the risk of cancer, type 2 diabetes and other chronic diseases of ageing through the actions of glucosinolates, but this is “the first evidence from human intervention trials of the mechanism behind this positive effect”.
Inside each of the body’s cells are specialised structures called mitochondria, which act as the engines of the cell. Mitochondria either burn up dietary fats and sugars to make energy or export them to be used by the cell as the building blocks to make other compounds needed for health. Mitochondria can also convert fats and sugars into forms for storage, which is why eating too much can lead to weight gain. For good health, all the different metabolic activities need to be balanced.
Excessive fat or sugar in the diet can overload the mitochondrial machinery, which also works less efficiently as a person ages, especially if the person does not exercise sufficiently. This is because of the build-up of Reactive Oxygen Species (ROS) in the mitochondria that inhibit some of the metabolic processes. The mitochondria may also begin to produce other compounds that can cause chronic inflammation. Disturbed metabolism and badly functioning mitochondria are associated with the development of chronic diseases such as obesity, type 2 diabetes, cardiovascular disease and some forms of cancer.
The study will be followed up by another with a larger number of volunteers that will also look at metabolism and biomarkers of cardiovascular health.