Researchers in Finland looked at whether an apple polyphenol extract could improve arterial health in 60 volunteers who had mildly raised blood pressure.
Atherosclerosis is a build-up of fatty material on the inside wall of arteries. Over time, this material becomes fibrous and the arterial walls lose their elasticity, so atherosclerosis is sometimes referred to as a “hardening of the arteries”. The build-up of deposits also narrows the vessels, which can eventually lead to health problems such as angina, heart attack, or stroke. Atherosclerotic changes can begin in childhood and progress slowly and silently over many years before any symptoms are noticed. The endothelial cells which line the arteries are key to regulating and maintaining healthy arteries. If they become damaged, then atherosclerotic changes may occur.
There are several risk factors for atherosclerosis, including hypertension (high blood pressure), smoking, type 2 diabetes, being overweight, and physical inactivity. Maintaining a healthy lifestyle helps to reduce the risk of atherosclerosis.
There has been interest in whether certain dietary supplements can improve arterial health. In some experiments, epicatechin – a subgroup of flavonoids – has been shown to have a protective effect on the heart. Several clinical studies have shown that cocoa, which is a rich source of flavanols and catechins, improves endothelial cell function. Researchers in Finland examined the effects of an apple polyphenol extract, high in epicatechin, on endothelial cell function in volunteers with mild hypertension. They recently reported their findings in Nutrition Journal.
The researchers included a total of 60 volunteers with mild hypertension who were otherwise healthy. They randomly assigned the volunteers to receive a daily capsule of either the apple polyphenol extract or placebo for four weeks. There was then a rest period of four weeks with no treatment (washout period), following which the groups swapped over to receive the apple polyphenol extract or placebo for four weeks (the opposite of what they had previously received). The scientists tested endothelial function at the beginning and end of each four week study period.
Flow-Mediated Vasodilation (FMD)
A technique called flow-mediated vasodilation (FMD) can be used to test the health and function of the endothelial cells. This uses ultrasound to measure the blood vessel dilation response in the brachial artery of the forearm (the vessel that is normally used to measure blood pressure) after a blood pressure cuff distal to it has been inflated and then released. FMD can be used to study the effects of potential treatments on endothelial cell function.
The Finish researchers used FMD of the brachial artery to examine the effects of the apple polyphenol extract. They performed FMD measurements on the volunteers before and after they received either the apple polyphenol extract or placebo capsule at each study visit.
Improvement in FMD of the Brachial Artery
With the apple polyphenol extract, a significant immediate improvement in FMD of the brachial artery from baseline was seen on both treatment visits. However, the improvement was not statistically significant when compared to the placebo group. The overall long-term effect of the apple polyphenol extract on FMD of the brachial artery was not significantly different from placebo.
No Significant Effects Compared to Placebo
The researchers concluded that although there was an immediate improvement in FMD measurements after taking the apple polyphenol extract, this was not significantly different from placebo in this group of volunteers with mild hypertension. This was due to an unexpected improvement effect on FMD measurements by the placebo capsules. The overall long-term effects of the apple polyphenol extract were no different to placebo.
The researchers noted that there was a large variation in FMD measurements, and some volunteers had measurements within the normal range despite having mild hypertension. A more selective study of a larger number of subjects may be needed to see any statistically significant effect and further studies should consider this in the design.
Written by Julie McShane, Medical Writer
Reference: Saarenhovi M, Salo P, Scheinen M, et al. The effect of an apple polyphenol extract rich in epicatechin and flavan-3-ol oligomers on brachial artery flow mediated vasodilatory function in volunteers with elevated blood pressure. Nutrition Journal (2017) 16:73. DOI 10.1186/s12937-017-0291-0.