by Carole Jackson, Bottom Line Health
If an apple a day can keep the doctor away, what can a kiwifruit — or several — do? Well, if one of your medical issues is high blood pressure, a new study finds that eating these fuzzy tropical fruits may do you some real good.
Does that make kiwi the new fruit phenom for heart health? I called Mette Svendsen, PhD, the study’s lead researcher, who works as a registered dietician at Oslo University Hospital in Norway. She told me that she had been intrigued by an earlier study performed by her research group that found that kiwi had a promising health effect in men who smoke (a group at higher risk for hypertension) — so they decided to put the fruit to the test among nonsmokers with blood pressure issues as well. Dr. Svendsen presented the study at the American Heart Association’s annual meeting in November 2011.
QUICK KIWI CURE?
Dr. Svendsen’s research randomly assigned 118 men and women with slightly elevated blood pressure or “prehypertension” to eat three kiwis or one apple a day for eight weeks. She and her colleagues chose to study three kiwis, in particular, to try to better match the calories in one apple. Measuring the participants’ blood pressure at the beginning of the study and at the end of the study with 24-hour automatic ambulatory blood pressure monitors, researchers observed that, after the eight-week study was over, the average systolic blood pressure reading for those who ate kiwis was 3.6 mm Hg lower than for those eating apples. And the average diastolic blood pressure reading for those who ate kiwis was 1.9 mm Hg lower than for the apple-eaters.
A drop of fewer than four systolic points may not seem like a big difference, but Dr. Svendsen said that it’s large enough to be “clinically significant” — meaning that it’s enough to make a small but tangible difference in people’s cardiovascular health. And since participants didn’t change anything else in their diets — and weren’t on blood pressure medications, which is why researchers chose to study those with only mildly raised blood pressure — Dr. Svendsen told me that she feels confident that kiwis can be a frontline defense in the battle to control blood pressure. But this study is only a start, she added, so more research on the topic needs to be done to confirm kiwi’s beneficial effects on heart health.
WHAT’S THE SECRET?
Kiwis are high in potassium, which is known to be helpful in controlling blood pressure, but Dr. Svendsen told me that her team believes the potent antioxidant lutein that is found in kiwis is probably what should get the credit in this case. She explained that lutein reduces free radicals by increasing nitric oxide, which may help keep blood vessels relaxed. Compared with apples, she said, kiwis have 10 times more antioxidants.
Kiwis may be considered a somewhat exotic fruit by many Americans, but they’re actually pretty inexpensive and easy to find, even in regular supermarkets. Buy them on the firm side (they last a while when stored at room temperature), and eat them when they begin to soften just a bit. You can peel them just as you would a cucumber or carrot — or some people prefer to cut them in half and scoop out the fruit with a spoon. Dr. Svendsen said that it doesn’t matter what time of day you eat your kiwis or whether you eat them on their own, sliced in a salad or smashed into a smoothie or juicer — the results are the same.
I asked whether taking a lutein supplement could work as a stand-in for eating kiwis for those who don’t like the fruits. Dr. Svendsen said probably not — “We haven’t studied the effect of taking a supplement, but other studies on antioxidant supplements have not been promising. It seems like the fruit itself is best.”
Mette Svendsen, PhD, RD, section for preventive cardiology, department of endocrinology, obesity and preventive medicine, Oslo University Hospital, Norway.