By Kate Kelland
LONDON, Sept 3 (Reuters) - Scientists experimenting with rats have found that de-activating certain nerves in the neck can effectively treat high blood pressure - a discovery that could be an advance in tackling one of the world's biggest silent killers.
Researchers at Britain's Bristol University found that in rats with high blood pressure, when they removed nerve links between the brain and the carotid body - a nodule about the size of a grain of rice on the side of each carotid artery - the animals' blood pressure fell and remained low.
The researchers results, published in the journal Nature Communications on Tuesday, have already led the team on to conduct a small human trial of the technique, with results expected at the end of this year.
Hypertension, or high blood pressure, is referred to by the World Health Organisation as one of the world's biggest silent killers because most people who have it can't feel or see it.
It affects around one in three people worldwide and can cause stroke, heart attacks and kidney failure.
After diagnosis, treatment of high blood pressure needs to be lifelong and many patients are able to manage their condition with anti-hypertension drugs. But experts say that for around 1 in 50 of them, medication does not help.
Julian Paton, who led this latest study at Bristol's school of physiology and pharmacology, said while scientists already knew of a link between the carotid organs and hypertension, until now they "had absolutely no idea that they contributed so massively to the generation of high blood pressure."
Tim Chico, as consultant cardiologist at the University of Sheffield who was not directly involved in the research, described the technique as "exciting and innovative" but cautioned that more work was needed to assess its effectiveness and safety before it could be considered for use in patients.
Normally, Paton explained, the carotid body acts to regulate the amount of oxygen and carbon dioxide in the blood.
It is stimulated when oxygen levels fall in the blood - such as when someone is holding their breath. This then causes a dramatic increase in breathing and blood pressure until blood oxygen levels are restored.
Having established that this response comes about through a nerve connection between the carotid body and the brain, Paton's team decided to block the nerve endings in the neck and found that it swiftly brought their blood pressure down.
Jeremy Pearson, associate medical director at the British Heart Foundation, which part-funded this latest research, said all eyes are now on the human trial aiming to find out whether the treatment might work in people with high blood pressure who don't get better with current drugs.
Tony Heagerty, a professor of medicine at Manchester University who was not involved in the study, said it was an interesting development which could "potentially avoid the use of drugs which have to be taken on a daily basis for many years." (Editing by Sonya Hepinstall)
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Research presented at a meeting last year of the American Heart Association shows that eating <a href="http://www.huffingtonpost.com/2011/11/16/kiwis-blood-pressure-apples_n_1097364.html" target="_hplink">three kiwis a day</a> is linked with decreased blood pressure. That study included 188 men and women age 55 and older, with slightly high blood pressure. They were instructed to eat three kiwis a day, or an apple a day for eight weeks. The researchers found that the people who <a href="http://www.huffingtonpost.com/2011/11/16/kiwis-blood-pressure-apples_n_1097364.html" target="_hplink">ate the kiwis</a> had lower systolic blood pressure levels than those who ate the apples. Kiwis are known to be rich in lutein, which means they have antioxidant properties. <em>Flickr photo <a href="http://www.flickr.com/photos/hulagway/5941766050/">by whologwhy</a>.</em>
Peas, Bananas And Other Potassium-Rich Foods
A 2005 study in the journal <em>Hypertension</em> found that it's possible to get the blood pressure-lowering effects from <a href="http://www.health.harvard.edu/fhg/updates/update0705c.shtml" target="_hplink">potassium-containing foods</a>, instead of just from a potassium supplement. Researchers from St. George's Medical School in London found that people who consumed potassium citrate -- which is found naturally in food -- has the same effects in <a href="http://www.health.harvard.edu/fhg/updates/update0705c.shtml" target="_hplink">decreasing blood pressure</a> in people with hypertension as those who took potassium chloride, which is only available as a supplement, Harvard Medical School reported. <em>Flickr photo <a href="http://www.flickr.com/photos/robin24/5131280208/">by robin_24</a>.</em>
<a href="http://www.mnn.com/food/healthy-eating/stories/watermelon-lowers-blood-pressure-study-finds" target="_hplink">Watermelon</a> is not just refreshing, it contains a bounty of nutrients including fiber, lycopenes, vitamin A and potassium, according to the Mother Nature Network. And, a study from Florida State University researchers shows that an amino acid found -- called <a href="http://www.mnn.com/food/healthy-eating/stories/watermelon-lowers-blood-pressure-study-finds" target="_hplink">L-citrulline/L-arginine</a> -- in watermelon could also have blood pressure-lowering effects. The researchers had nine people with prehypertension take 6 grams of the L-citrulline/L-arginine amino acid a day over a six-week period. They found that the study participants had lower blood pressure, as well as better functioning of their arteries. <em>Flickr photo <a href="http://www.flickr.com/photos/gudlyf/3657294414/">by Gudlyf</a>.</em>
Spuds may get a bad rap in the foodsphere, but a small study presented last year at a meeting of the American Chemical Society showed that the purple-hued root vegetables have <a href="http://portal.acs.org/portal/acs/corg/content?_nfpb=true&_pageLabel=PP_ARTICLEMAIN&node_id=222&content_id=CNBP_028109&use_sec=true&sec_url_var=region1&__uuid=6e3e7956-f304-482b-96f2-b644d1a2aaa5" target="_hplink">blood pressure-lowering powers</a> that are nearly as effective as oatmeal, without packing on pounds. The study included 18 people with high blood pressure. They ate six to eight <a href="http://portal.acs.org/portal/acs/corg/content?_nfpb=true&_pageLabel=PP_ARTICLEMAIN&node_id=222&content_id=CNBP_028109&use_sec=true&sec_url_var=region1&__uuid=6e3e7956-f304-482b-96f2-b644d1a2aaa5" target="_hplink">purple potatoes</a> (including the skins!) twice a day, for a month-long period. The researchers found that the study participants' systolic and diastolic blood pressure dropped at the end of the research period. (Though, it should be noted that this was just an observational study, and the potato-eaters' blood pressure was not compared to people who did not eat purple potatoes during the study.) <em>Flickr photo <a href="http://www.flickr.com/photos/taransa/5499878925/">by Taransa</a>.</em>
Eating a lot of tofu and other soy foods -- like soy nuts, miso, edamame, tempeh and soy milk -- is linked with <a href="http://www.webmd.com/hypertension-high-blood-pressure/news/20120327/soy-nutrient-may-lower-blood-pressure" target="_hplink">decreased blood pressure</a>, WebMD reported. The study, presented at the annual meeting of the American College of Cardiology, included 5,000 people whose diets were tracked over 20 years. The researchers found that the ones who <a href="http://www.webmd.com/hypertension-high-blood-pressure/news/20120327/soy-nutrient-may-lower-blood-pressure" target="_hplink">consumed the most isoflavones</a> -- found in soy, as well as peanuts and green tea -- had lower systolic blood pressure than those who consumed the fewest isoflavones, according to WebMD. <em>Flickr photo <a href="http://www.flickr.com/photos/fotoosvanrobin/5776783857/">by FotoosVanRobin</a>.</em>
Chocolate is linked with a lower BMI -- <em>and</em> it could be beneficial for people with hypertension. A 2010 review of studies in the journal <em>BMC Medicine</em> showed that <a href="http://www.biomedcentral.com/1741-7015/8/39" target="_hplink">flavanols</a>, which are found in chocolate, seemed to promote the dilation of blood vessels, which in turn can lower blood pressure. "Flavanols have been shown to increase the formation of endothelial nitric oxide, which promotes vasodilation and consequently may lower blood pressure," study researcher Dr. Karin Ried, of the University of Adelaide in Austria, said <a href="http://www.sciencedaily.com/releases/2010/06/100628075746.htm" target="_hplink">in a statement</a>. "There have, however, been conflicting results as to the real-life effects of eating chocolate. We've found that consumption can significantly, albeit modestly, reduce blood pressure for people with high blood pressure but not for people with normal blood pressure." <em>Flickr photo <a href="http://www.flickr.com/photos/sionakaren/3871516012/">by Siona Karen</a>.</em>
If you love a little heat with your food, it could be doing your <a href="http://www.sciencedirect.com/science/article/pii/S1550413110002287" target="_hplink">blood pressure</a> a favor, too. A 2010 study in the journal <em>Cell Metabolism</em> showed that <a href="http://www.sciencedirect.com/science/article/pii/S1550413110002287" target="_hplink">capsaicin</a> -- the spicy ingredient in chili peppers -- could help to lower blood pressure in rats with hypertension. However, the researchers from the Third Military Medical University in China noted that the results need to be replicated in humans. <em>Flickr photo <a href="http://www.flickr.com/photos/trostle/6114402110/">by Trostle</a>.</em>