12 January - 20 June 2016

Grapes may reduce risk of heart failure associated with hypertension

8 May 13

A study published in the Journal of Nutritional Biochemistry has investigated the mechanism for how grapes reduce heart failure associated with hypertension.  The study by Seymour et al notes that grapes contain commonly consumed flavonoids, including anthocyanins, flavan-3-ols (eg catechin, epicatechin, proanthocyanins) and flavonols (quercetin, kaempferol, isorhamnetin).  The authors note that as a whole food, grapes may represent a simple experimental model for a phytochemical rich diet.  Seymour et al fed heart failure-prone rats one of four diets (a low salt diet, a low salt diet with 3% w/w added grape powder, a high salt diet, or a high salt diet with 3% w/w added grape powder) for 18 weeks.   The rats were fed 20g of powdered diet per day.   The amount of supplemented grape powder added to the diets was calculated as the equivalent of 8-9 human servings per day of phytochemical-containing vegetables and fruits as used in the Dietary Approaches to Stop Hypertension (DASH) diet.  The DASH diet which is rich in fruits and vegetables, low-fat dairy and whole grains has been reported to reduce blood pressure.  During intervention the team measured blood pressure bi-monthly and carried out echocardiograms monthly.  At the end of intervention, the rats were sacrificed and their hearts analysed.  The scientists analysed the left ventricle of the heart as this chamber is most impacted by oxidative stress.  Parameters measured included cardiac fibrosis, oxidative damage, DNA binding activity, cardiac glutathione amongst others. Seymour et al found that grape intake significantly reduced systolic blood pressure in hypertensive rats, having an effect at week 4.   Salt intake was associated with cardiac hypertrophy and increased cardiac hydroxyproline content, an index of collagen content and fibrosis.  The grape intake reduced these effects in the high salt group.  However there were no difference between the low salt diet and the low salt diet supplemented with grape powder.  The high salt diet increased relative wall thickness, but the high salt diet with grape powder reduced this effect.  Mild or early diastolic dysfunction parameters increased in the high salt diet, however again the high salt diet with the grape powder attenuated these.  Furthermore, the mechanism of action was uncovered: grape intake "turned on" antioxidant defence pathways, increasing the activity of related genes that boost production of glutathione, which is the most abundant cellular antioxidant in the heart.  Seymour et al note that glutathione deficiency has been observed in human heart failure and may be a marker of early heart failure.  The researchers state that their findings suggest that regular phytochemical intake may therefore increase cardiac resistance to cardiac pathology caused by prolonged hypertension.

RSSL’s Functional Ingredients Laboratory can offer anthocyanin analysis by colorimetric methods or HPLC in a range of foods and beverages. For more information please contact Customer Services on Freephone 0800 243482 or email enquiries@rssl.com

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