The potential health benefits of tart cherries have made tart cherries and tart cherry juice concentrate a popular topic for discussion and research. Plus, tart cherry juice has the advantage of being fairly easy to drink and to access.
Tart cherry juice concentrate is a particularly interesting area because there has been so much research into the topic – partly because the cherry industry is interested in promoting the health benefits wherever possible.
Essentially, tart cherry juice concentrate is just a more concentrated version of tart cherry juice. So, it tends to have a stronger flavor and contain more healthy compounds than the same amount of tart cherry juice. So, any benefits of tart cherry juice concentrate are also likely to be present for tart cherry juice itself, it's just that you would have to consume more juice to get the benefits.
There have been a number of studies focusing on how tart cherry juice concentrate may affect inflammation but another interesting area is the connection between tart cherry juice and heart disease.
A very recent study (Keane et al., 2016), published in the American Journal of Clinical Nutrition, looked into this very topic. The outcomes of the study have been making waves in social media and some news sites, as the study showed that tart cherry juice significantly lowered blood pressure.
In this post, I want to look at the study itself, because headlines tell us relatively little about the outcomes of a study and how well it was designed.
The Study Itself
The first thing to note about this study was that it was supported by the Cherry Marketing Institute. This doesn’t necessarily mean that the study was biased in any way. However, it is always important to take a harder look at any research that is sponsored by industry. After all, with this type of study support, there is some pressure to look harder for positive results.
The study design is referred to as Latin square design. This is actually a fairly efficient research design, even though it isn’t frequently used. At the same time, the authors used a placebo and assigned participants randomly to groups. Those approaches helped to decrease the risk for error.
The study did only contain 15 participants, but the authors used a washout-based design. This meant that participants would be in one treatment, then no treatment for a period (at least 14 days, in this case). After that, they would be placed in a different group.
From their analyses, the authors argued that 14 days was sufficient to ensure that all the compounds from tart cherry juice had left the bloodstream.
For the study, participants either consumed 60 ml of tart cherry concentrate or 60 ml of a fruit-flavored cordial. In both cases, the drink was diluted with 100 ml of water before consumption.
The authors then collected blood samples from participants at 1, 2, 3, 5 and 8 hours after the concentrate had been consumed. The key outcomes that the authors looked at were blood pressure, arterial stiffness and microvascular vasodilation.
As a result of the study, the authors found that blood pressure was significantly lower in participants who had consumed the tart cherry juice, but only 3 hours or less after the consumption.
While the reduction was relatively small (7%), the authors argued that this was more than enough to significantly decrease heart disease risk.
Strengths and Limitations
The outcomes of this study do lend some support to ideas that tart cherry juice can help to reduce heart disease risk. Indeed, the anthocyanins in tart cherries are associated with a decreased risk of heart attacks (1).
However, the results of this particular study were far from conclusive.
One of the first limitations was the sample size. In general, a higher sample size contributes to a stronger study. In this case, the study just involved 15 participants, which is very low. That small sample size makes it difficult to be confident in the study outcomes.
While it is true that the study found a significant decrease in blood pressure, the outcomes are not as relevant as the authors imply.
In particular, the study only saw a 7% reduction in blood pressure. They argued that this outcome was enough to decrease the risk of heart disease (by 23%). However, the information about reduction in heart disease risk came from a different study, which looked at the impacts of reducing blood pressure for 5 years.
Yet, the study at hand was extremely short-term, only looking at a change in blood pressure up to 8 hours after consumption of the tart cherry juice. Indeed, the observed significant change in blood pressure occurred at the 3-hour mark.
This means that the study couldn’t even determine whether tart cherry juice had a long-term effect on blood pressure. Without that information, there isn’t any way to accurately say what impact tart cherry juice would have on heart disease.
There is also one other important factor to consider with the study.
The authors looked at outcomes in patients with early hypertension. This means that their blood pressure was elevated but not to the extent that they would be placed on blood pressure medication.
As part of their discussion, the authors argued that the effects of tart cherry juice on the participants was similar to the effects of blood pressure medications. Yet, participants with this type of hypertension wouldn’t be given blood pressure medications – and the effect of medications might be different on them than on the general population.
Implications of the Study
In general, this research study was fairly low quality and doesn’t have enough data to show whether or not tart cherry juice has any impact on heart disease risk. However, the authors were able to show that in the short-term, the tart cherry juice was able to lower blood pressure significantly.
This does mean that there is potential for tart cherry juice to have a long-term effect on blood pressure and heart disease risk. But, more in-depth research is needed to show whether or not this is the case.
Nevertheless, the outcomes of the research do suggest that tart cherry juice may be a good addition to the diet if you are concerned about your blood pressure. After all, natural products like this tend to have few side effects, which is much better than most medications.
That potential certainly makes tart cherry juice worth trying, particularly as you don’t really lose anything if it doesn’t help with your blood pressure. Besides that, tart cherry juice has been connected to other benefits. For example, the site Dreaming and Sleeping looks at how tart cherry juice may promote sleep. The site Healthy and Natural World highlights additional potential benefits.
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What do you think of tart cherry juice? Have you tried it?