For decades, researchers and doctors alike have debated the best diet for heart health. On one side is the low-fat plan, while others claim that low-carb/low-sugar is the way to go.
While those two camps continue to battle it out, when it comes to high blood pressure, one diet has endured the test of time: the Dietary Approach to Stop Hypertension, or DASH, diet. This diet focuses primarily on low-salt/low-fat foods, combined with a high intake of fruits and vegetables.
Given the success of the DASH diet, many researchers have questioned what role the high produce intake plays. More specifically, they question if it’s the high antioxidant content of these types of foods that is the key (or at least one of the keys) to its effectiveness.
This has spurred numerous studies that look at specific fruits and vegetables and their role in heart health. One such example is a study looking at the effect of kiwifruit on blood pressure, clotting factors, and angiotensin-converting enzyme (ACE) activity, an enzyme that constricts blood vessels and arteries.
Chinese Gooseberry to the Rescue
Although kiwi is also known as Chinese gooseberry, it is often associated with New Zealand. This quirky little green/yellow fruit with black seeds comes wrapped in a furry, brown, leathery skin. It is packed with carotenoids such as vitamin C, beta-carotene, lutein and zeaxanthin, which, among other health benefits, have been shown to protect your eyes as you age.
Given this antioxidant profile, Norwegian researchers wondered how a diet high in kiwi would stand up against a basic antioxidant-rich diet. To test this, they divided 100 male smokers between the ages of 44 and 74 into three groups.
The first group ate three kiwis a day, in addition to their normal diet. The second group ate an antioxidant-rich diet, as determined by a trained nutritionist. The third group ate a normal diet, with no special attention paid to antioxidant content.
All three groups were told to avoid vitamins or antioxidant supplements, as well as aspirin or medication containing aspirin. They were also asked to limit consumption of nuts, berries, pomegranates, tomatoes, tea, coffee, and in the last two groups, kiwi.
Finally, all three groups were tested for:
- Blood pressure levels
- Platelet aggregation (clotting risk)
- ACE activity (indication of vasoconstriction, or narrowing of the blood vessels)
After eight weeks, researchers found that those men in the kiwi group enjoyed a drop of 10 mmHg in systolic blood pressure (top number) and 9 mmHg is diastolic blood pressure (bottom number). The antioxidant diet group also had a 10 mmHg reduction in systolic blood pressure, but a non-significant drop in diastolic pressure.
Additionally, the number of men in the kiwi who were considered hypertensive dropped significantly. At the start of the study, 65 percent were found to have normal/high-normal blood pressure, but after eight weeks, that dropped to just 33 percent. Conversely, there were only minor changes in the antioxidant diet group.
When it came to platelet aggregation, the kiwi group enjoyed a 15 percent reduction. They also had an 11 percent reduction in ACE activity. This is particularly encouraging, as it implies that the kiwi helped to keep blood vessels dilated and unconstricted. The antioxidant diet group did not have any significant decreases in either of these areas.
While researchers were not sure what particular compounds from the kiwi were responsible for these effects, they concluded, “Kiwifruit intake may mediate anti-thrombotic effects and thus decrease the risk of cardiovascular events.”
Get to Know Kiwi
If you are not already familiar with the kiwi, you now have the perfect excuse to experiment:
- Add kiwi to oatmeal or cereal (much like you would a banana).
- Slice and add to a salad.
- Layer with strawberries and blueberries for a colorful and delicious fruit salad.
- Dice with scallions and mint for a fresh salsa topping for fish or chicken.
- Simply slice and enjoy!
 Karlsen, A et al. Kiwifruit decreases blood pressure and whole-blood platelet aggregation in male smokers. J Hum Hypertens. 2012 Jan 19. Doi: 10.1038/jhh.2011.116. [Epub ahead of print.]