Tart cherries (Prunus cerasus) don’t get quite as much love as their sweet counterparts – other than in baked goods like cherry pie and black forest cake. But they just might deserve a little more attention from you, because science has revealed that there are interesting health benefits associated with the fruit. Tart cherries are a rich source of phenolic compounds, which have been shown to exert amazing physiological effects when consumed, including reducing inflammation, alleviating oxidative stress, and even speeding up exercise recovery. Oddly enough, tart cherries are also one of the most abundant natural sources of melatonin, and consuming them has been found to improve sleep.
Additionally, we know from prior research that some of these compounds can modulate vascular cells in vitro – which has caused scientists to wonder if adding fruit like tart cherries to the diet could lower blood pressure through its effects on our blood vessels. As we’ve discussed before in previous blogs, high blood pressure is a pervasive health issue, affecting as many as 1 in 3 adults in the US. So there is a lot of interest in finding ways to address it via lifestyle.
But as we all know, applying chemicals to cells in a petri dish does not necessarily translate to real life. So, researchers from Northumbria University designed a trial to put it to the test in humans. Let’s take a look at what happened.
The investigators recruited 15 healthy men with mildly elevated blood pressure – at or above 130/90 mmHg. To put that into perspective, we define normal blood pressure to be at 120/80 mmHg or lower. So these men were not severely hypertensive, but they were at a level that has been found to be associated with higher risk of cardiovascular issues. And prehypertension – as the name implies – often gets worse over time.
Participants were randomly assigned to one of two conditions:
- Experimental group: Drank 60 mL (2 ounces) of tart cherry concentrate
- Placebo group: Drank 60 mL (2 ounces) of a fruit-flavored soft drink (which contained almost no actual fruit components)
The researchers measured blood pressure and took blood samples before the drinks were consumed, then continued to measure at hourly intervals after administering the drinks.
So what happened?
Participants who drank the cherry juice experienced a peak drop in blood pressure of around 7 mmHg, relative to the placebo.
That may not sound like a whole lot but small changes like this can make a surprisingly big difference. Data from pharmaceutical trials has suggested that a reduction of just 5-6 mmHG over a period of five years may be enough to reduce risk of stroke by 38% and risk of coronary artery disease by 23%.
This level of reduction, in fact, is comparable to the blood-pressure lowering effect of an antihypertensive drug (bendrofluazide or propranolol). Pretty impressive.
What is special about tart cherries?
As I said earlier, the fruit is rich in a wide range of phytochemicals that affect us in myriad ways when we eat them. The team ran analyses of the cherry juice concentrate and the fruit soda placebo. Sure enough, the cherry juice was distinctly rich in phenolic compounds, compared to the placebo, and exhibited high antioxidant activity. The researchers attributed the effects on blood pressure to downstream metabolites from anthocyanins in the cherries, which had previously been shown to improve vascular function.
Even more telling, the cherry juice group experienced the greatest reductions in blood pressure specifically when participants’ blood levels of plasma phenolic acid were highest. So it sure looks like these compounds were playing an important role in the vascular changes.
Before you go and stock up on tart cherry juice, it is worth noting that this study (like all studies) has some limitations.
First of all, the study only measured acute effects on blood pressure over a few hours. What if the men’s blood pressure rebounds back up later in the day, as plasma phenolic acid levels go back down to baseline?
Secondly, remember that this trial tested 15 otherwise healthy young men with mean blood pressure of 137/82 – which is elevated, but not especially high. The effect is still clinically valuable over the long term, but we should cautious when attempting to extrapolate these findings to people with very high blood pressure or who are older and less healthy.
Despite the aforementioned limitations, I really like this study. One thing I appreciate is that the researchers didn’t use a supplement containing a super high concentration of phenolic compounds. Those types of studies are interesting and useful, but to me they represent a pharmaceutical – rather than a nutritional – intervention. Instead, they used a realistic amount of juice (2 ounces) that pretty much anyone could handle. Whole tart cherries would work too – you can usually find them in the frozen fruit section at the grocery year round.
But an even better thing about the study is the findings are probably not limited to tart cherry juice. The anthocyanins that were putatively responsible for the drop in blood pressure are found in a wide range of fruits and vegetables, not just cherries.
This is probably part of why there is a vast amount of observational evidence suggesting that people who frequently partake of foods rich in polyphenols – including tart cherries – experience reduced risk of cardiovascular disease. And we know that a lot of other polyphenol-rich foods like cocoa and olive oil – which I have written about previously – have been shown to have a positive impact on blood pressure, likely by similar mechanisms. So even if you’re not able to load up on tart cherries (or if you’re just not into them), you can probably achieve similar effects with other fruits and vegetables.
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