July 31, 2013

expert reaction to substance found in broccoli, metabolism and ageing

 A study published in the American Journal of Clinical Nutrition has shown that diets rich in glucosinolates, such as glucoraphanin found in broccoli, may benefit metabolism.  

Catherine Collins, Principal Dietitian, St George’s Hospital NHS Trust, said:

 “Broccoli is a food with a well-established ‘health halo’ due to its glucosinolate content – a bitter plant substance that helps the liver boost its detoxifying enzymes to keep healthy. This study looked at glucoraphanin, another beneficial phytochemical found in broccoli, and compared the metabolic effects of a standard intake of frozen broccoli bred to have higher levels of glucoraphanin, compared to ordinary frozen broccoli. Frozen peas, which contain no glucoraphanin, were the green vegetable used as a ‘control’. Volunteers were asked to consume around 400g weekly of the frozen vegetable, equivalent to between 5-7 typical servings.

 “Blood cholesterol levels, one of three tests (the others being blood pressure and diabetes screening) that help predict risk of heart disease or stroke, remained unchanged by the dietary changes. Given the similar diets in the three groups in terms of dietary fat across the 12 weeks of study, this isn’t really surprising. However, researchers did find a major improvement at cell level, normally not measurable in routine health screening. The high glucoraphanin broccoli helped improve fat metabolism at cellular level.

 “What does this mean for broccoli lovers (or haters?). It adds to the evidence already there that cruciferous vegetables benefit health and possibly reduce the risk of chronic conditions such as cancer or cardiovascular disease. Don’t like broccoli, Brussels or cauliflower? Citrus fruits, soy, coffee and garlic have been shown to have similar cell benefits, although the mechanism of action may be different. Bottom line? Continue to eat your greens – or any other colours in the 5-a-day fruit and veg spectrum.”

Dr Gail Rees, Lecturer in Human Nutrition, Plymouth University, said:

 “This is an exciting study that demonstrates how eating broccoli benefits our metabolism. It is of huge scientific interest as we are now starting to unravel exactly which components of fruit and vegetables are responsible for good health and what the specific effects are.

 “The study published today in the American Journal of Clinical Nutrition is particularly important because it shows the advantages of eating regular but reasonable portion sizes of a special type of broccoli high in glucoraphanin. The study also demonstrates that the response to eating this type of broccoli is dependent on genetic makeup, so how beneficial it is to your health varies according to your genetics.

 “We must remember that there are thousands of bioactive components in fruit and vegetables and we need to have a mixture of different types daily. This novel type of broccoli, grown to have a high amount of this particular bioactive component, is not yet widely available in the UK and may have cost implications for consumers.

 “The best advice is to continue to consume at least five portions of different fruit and vegetables per day as part of a healthy diet. Reduction of cancer risk and healthy ageing are also dependent on decreasing alcohol and fat consumption, reducing smoking, lowering body weight and regular exercise. This study was carried out on 48 people so it was a fairly small study and may now need to be carried out on a larger sample size to ensure the results are representative of the wider population.”

  ‘A diet rich in high glucoraphanin broccoli interacts with genotype to reduce discordance in plasma metabolite profiles through modulating mitochondrial disfunction’ by Charlotte N Armah et al. was published in the American Journal of Clinical Nutrition.