Not Just for Regularity: Eating Prunes Daily Improves Heart Health, Fights Inflammation, and Boosts Antioxidant Levels

Avoiding heart disease is at the top of many adults’ minds as they age — and with good reason, as cardiovascular disease in its various forms is the number one killer in the United States, far surpassing mortality from even cancer and car accidents. As about two-thirds of all deaths from cardiovascular disease occur in people over age 75, older adults should be aware of ways to improve or maintain heart health with age — and a simple answer may lie with the humble prune. 

Despite their notoriety for promoting regularity when you’re feeling backed up, prunes are revamping their image to be more than just a gastrointestinal stimulant. In a new study published in the Journal of Medicinal Food, researchers out of San Diego State University (SDSU) provide evidence of the additional benefits of prunes that go beyond the gut. This study finds that, after consuming just five prunes per day for six months, postmenopausal women exhibit significantly improved markers of heart health, ranging from antioxidant-boosting to inflammation-fighting to cholesterol-lowering. 

Why Our Arteries Love Estrogen

Not only do older adults already have a higher risk of dying from cardiovascular disease, but postmenopausal women specifically have an increased likelihood of developing heart-related conditions. Although menopause itself does not cause heart disease, many researchers agree that the marked decline in the hormone estrogen during and after menopause is a significant contributor to this risk. 

Estrogen is thought to positively affect the innermost layers of our arteries, which keeps blood vessels flexible, relaxed, and able to accommodate healthy blood flow. Conversely, rigid and inflexible blood vessels lead to increased blood pressure, poor blood flow to other organs, and an increased likelihood of plaque forming in arteries. Low estrogen levels have been linked to changes in lipid (fat) metabolism, abnormal cholesterol levels, increases in pro-inflammatory signaling molecules called cytokines, and oxidative stress — the accumulation of damaging compounds called reactive oxygen species (ROS).

The Inflammation-Inhibiting Power of Prunes

Hong and colleagues from SDSU speculated that prunes might be able to mitigate some of these detrimental changes that occur in postmenopausal women. Previous research in both humans and animals has found that the high levels of antioxidants and fiber in prunes reduce many risk factors for heart disease, including high cholesterol, blood pressure, and inflammation. However, studies have not yet examined the dose-dependent effects of prunes in postmenopausal women — meaning, how many prunes does one need to eat to see the benefits? 

In this study, Hong and colleagues randomized healthy, postmenopausal women aged 65 to 79 into three groups — a control group, a group eating 50 grams of prunes per day (about five prunes), and a third group consuming 100 grams of prunes (about ten prunes per day). 

After six months of habitual prune-eating, the results were conclusive — dried plums are good for the heart. The research team found that the lower-dose group consuming 50 grams per day had even better results than the higher-dose group. This could be because a daily intake of 10 prunes could add excessive amounts of sugar to the diet, which would be detrimental to inflammation and cholesterol levels.

While both treatment groups experienced significant drops in total cholesterol, only the 50-gram-per-day group saw increases in HDL (“good”) cholesterol and had marked reductions in the pro-inflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor-ɑ (TNF-ɑ). Both treatment groups also had increased antioxidant activity with reductions in markers of oxidative stress.

Inflammation within the endothelium — the single layer of cells lining blood vessels and the heart — is directly linked to atherosclerosis, the accumulation of arterial plaque that precedes cardiovascular disease. Therefore, lowering levels of inflammation, as seen by reduced IL-6 and TNF-ɑ in this study, is a valuable way to reduce heart disease risk. As one of the study authors, Mark Kern, Ph.D., RD, CSSD, states, "Reducing chronic inflammation and increasing antioxidant capacity in the body is associated with lower risk of [cardiovascular disease], along with many other diseases."

Fiber-Filled and Free Radical-Fighting

There are several bioactive components in prunes that Hong and colleagues speculate are the driving forces behind the fruits’ ability to improve inflammation and antioxidant capacity. Prunes contain plant-based compounds called polyphenols, which act as antioxidants in the body and scavenge for ROS and free radicals. Two of these polyphenols are chlorogenic acid, which is also found in coffee, apples, and artichokes, and epicatechin, found in high amounts in tea leaves and chocolate. 

Prunes also contain beneficial amounts of polysaccharides — long chains of fiber-rich carbohydrates — which can reduce ROS production directly by inhibiting a compound called xanthine oxidase. This harmful compound produces high amounts of hydrogen peroxide, a known ROS that damages the cardiovascular system. As xanthine oxidase inhibitors are used in some pharmaceutical drugs for heart disease, eating prunes may be a simpler way to block this destructive compound. 

The benefits to cholesterol and lipid levels are likely due to prunes’ fiber content, as they contain high amounts of both soluble and insoluble fiber in the forms of pectin and cellulose. (This is also why prunes help you in the bathroom.) In addition to its laxative tendencies, soluble fiber is known to lower blood cholesterol — win-win!

Lastly, abnormal liver function is another risk factor of heart disease, albeit lesser-known. The research team looked at levels of liver enzymes, which are elevated in cases of liver disease or fatty liver. High liver enzymes increase the risk of cardiovascular disease because they are tightly linked to hypertension and type 2 diabetes, which, in turn, can lead to heart disease. In this study, the 50-gram group saw the most benefit to liver health, with significant reductions in all four enzymes measured.

Five Prunes Per Day Keeps the Cardiologist Away

In this research, Hong and colleagues provide evidence that consuming just five prunes per day is sufficient to benefit a dozen or so markers and risk factors related to cardiovascular disease. Although this study was done solely with healthy postmenopausal women, the results would likely translate to other population groups at higher risk of developing heart disease.

The lower dose of 50 grams not only produced similar effects to the 100-gram group but even additionally improved many of the health parameters. This is helpful because, while eating five prunes per day sounds feasible, upwards of 10 dried plums may not be a sustainable or practical option — not to mention it may incur some potentially unwanted digestive side effects.

As Kern concludes, "Not only does this study show that prunes may be a good way to reduce inflammation and increase antioxidant capacity, it also suggests that eating prunes every day may improve cholesterol levels in postmenopausal women."

References: 

Hong MY, Kern M, Nakamichi-Lee M, Abbaspour N, Ahouraei Far A, Hooshmand S. Dried Plum Consumption Improves Total Cholesterol and Antioxidant Capacity and Reduces Inflammation in Healthy Postmenopausal Women [published online ahead of print, 2021 May 11]. J Med Food. 2021;10.1089/jmf.2020.0142. doi:10.1089/jmf.2020.0142