Benefits from a diet rich in high glucoraphanin broccoli
Dietary advice to consume fruit and vegetables (F&V) every day is largely based upon observational data from epidemiological studies that have associated diets rich in F&V with a reduction in age related chronic illness1,2. The lack of F&V in the diet has been recognised for many years as being a risk factor for both cardiovascular disease (CVD) and some cancers, leading to the establishment of the 5-a-day UK campaign in 1994.
Health promoting properties of glucosinolates and isothiocyanates in cruciferous vegetables
Studies with cell and animal models have suggested that health promoting properties of cruciferous vegetables, in particular, may be mediated in part by the biological activity of isothiocyanates, derived from the sulphur-containing glycosides known as glucosinolates that accumulate within this group of vegetables2. In a previous study performed by our group, the Diet and Vascular Health (DVH) study, it was reported that 400g of cruciferous vegetable consumption over a 12 week period led to a clinically significant reduction in cardiovascular risk factors with a reduction in absolute risk identified in a group of participants consuming a new cultivar called high glucoraphanin (HG) broccoli (p=0.03).
The reduction in risk of CVD and cancer, observed in epidemiological studies associated with the consumption of cruciferous vegetables, tends to be amongst those individuals who eat several portions per week3,4, which is atypical of the general population. This implies that the level of isothiocyanates obtained from common dietary practices is insufficient to obtain health benefits.
A diet enriched with high HG Broccoli could reduce the risk of CVD
We have previously described the development of a novel cultivar of broccoli by conventional plant breeding that has a three-fold greater level of glucoraphanin than standard broccoli cultivars, and which delivers a three-fold greater level of the isothiocyanate sulforaphane to the systemic circulation5,6. The broccoli cultivars used although they are genotypically different are phenotypically the same resulting in flavour and all other sensory attributes being identical. Thus, to further explore the role of cruciferous vegetables and the potential role of glucosinolates and isothiocyanates in reducing risk of CVD, we have undertaken a dietary intervention study that will compare the effects of a diet enriched with a cultivar of standard broccoli (Parthenon) with that of a diet enriched with a commercially available cultivar of high glucoraphanin broccoli, Beneforté® broccoli.
The Broccoli and vAScular Health Study (BASH): In total 107 men and women were enrolled onto the BASH study between August 2012 and October 2013 in Reading and Norwich with 95 participants completing the study. Of the 95, 47 participants were allocated to HG broccoli and 48 to standard broccoli. Each group was asked to consume 4 portions (100g each) of their designated broccoli per week as part of their habitual diet. Blood samples were taken and blood pressure was assessed pre and post intervention.
Diet rich in high glucoraphanin broccoli reduces plasma LDL cholesterol
Participants consuming the HG broccoli had a significant reduction in plasma LDL-C compared to their own baseline level, but with no significant changes in HDL cholesterol, total cholesterol or TAG.
When data from the BASH study was combined with our previous study (DVH), the reduction in LDL-C by the HG broccoli was significantly greater (p=0.031) than that of the standard broccoli. There was no significant association between reduction in LDL-C and study, recruitment centre or sex.
The reduction in LDL-C by HG broccoli was not dependent upon baseline LDL levels (% ΔLDL-C = 5.8 – 2.6LDL-Cbaseline, r2=2.9%, p = 0.097), in contrast to that of standard broccoli which was significantly associated (% ΔLDL-C = 18.8 – 4.8LDLCbaseline, r2= 13.7%, p = 0.001). Once the data was reanalysed according to subgroups of participants with different baseline LDL-C, we observed a more moderate effect of standard broccoli at reducing LDL-C but only in participants who have higher baseline LDL-C.
In conclusion, the results of the two studies (DVH and BASH) would support the hypothesis that diets rich in broccoli reduce LDL-C, and indicate that the bioactive component is glucoraphanin. The HG broccoli reduced LDL-C by a similar amount to oat ß glucans and plant stanols. The mechanism by which this reduction occurs is likely to be due to suppression of cholesterol synthesis as opposed to suppression of cholesterol and/or bile acid absorption. This may suggest there may be additive LDL-C lowering effects through combining these different food items in the diet. This could contribute to more specific public health advice on the benefits of glucoraphanin containing vegetable consumption for CVD risk reduction.
Based on: Armah, C. N., Derdemezis, C., Traka, M. H., Dainty, J. R., Doleman, J. F., Saha, S., Leung, W., Potter, J. F., Lovegrove, J. A. and Mithen, R. F. (2015), Diet rich in
high glucoraphanin broccoli reduces plasma LDL cholesterol: Evidence from randomised controlled trials. Mol. Nutr. Food Res., 59: 918–926. doi: 10.1002/mnfr.201400863
- Lampe JW. Health effects of vegetables and fruit: assessing mechanisms of action in human experimental studies. Am J Clin Nutr 1999;70(3 Suppl):475S-90S.
- Traka M, Mithen R. Glucosinolates, isothiocyanates and human health. Phytochem Rev 2009;8(1):269-82.
- Cornelis MC, El-Sohemy A, Campos H. GSTT1 genotype modifies the association between cruciferous vegetable intake and the risk of myocardial infarction. Am J Clin Nutr 2007;86(3):752-8.
- Zhang X, Shu XO, Xiang YB, Yang G, Li H, Gao J, et al. Cruciferous vegetable consumption is associated with a reduced risk of total and cardiovascular disease mortality. Am J Clin Nutr 2011;94(1):240-6.
- Mithen R, Faulkner K, Magrath R, Rose P, Williamson G, Marquez J. Development of isothiocyanate-enriched broccoli, and its enhanced ability to induce phase 2 detoxification enzymes in mammalian cells. Theor. Appl. Genet. 2003;106(4):727-34.
- Gasper AV, Al-Janobi A, Smith JA, Bacon JR, Fortun P, Atherton C, et al. Glutathione S-transferase M1 polymorphism and metabolism of sulforaphane from standard and high-glucosinolate broccoli. Am J Clin Nutr 2005;82(6):1283-91.