Food and Health Natural products help tame hypertension
Natural products help tame hypertension
Last Updated on Sunday, 06 September 2009 11:36 Written by Steve Myers Friday, 04 September 2009 11:30
A modifiable factor in heart attacks and stroke, high blood pressure is a great candidate for natural products intervention, as many nutrients and herbs have been studied for management of pre-hypertension and hypertension.
Blood pressure management is about the numbers. Normal blood pressure, the force blood exerts on vessel walls, is less than 120 mmHg systolic (heart beating) and less than 80 mmHg diastolic (heart relaxing). Pre-hypertension is 120-129/80-89 (systolic/diastolic). Stage 1 hypertension begins above 140/90, with stage 2 hypertension starting above 160/100.
The numbers get scary when you consider the death rate from high blood pressure rose 25.2 percent from 1995 to 2005, with the actual number of deaths rising 56.4 percent during that time frame, according to the American Heart Association (AHA). Add to this about one in every three Americans has high blood pressure, according to the Centers for Disease Control and Prevention (CDC), which also reported an estimated 90 percent of middle-aged adults will develop high blood pressure in the remainder of their lifetime.
Even scarier Public health officials have said as much as 20 percent of the population doesn't know they have hypertension. The confusion partially results from the fact that there are no major, recognizable symptoms of hypertension alone, although the condition can lead to greater cardiovascular problems and their associated symptoms. Even more troubling, CDC reported the cause of 90 to 95 percent of hypertension cases is not known.
The good news in all these daunting stats and facts is high blood pressure is easy to discover by a health care provider, and it is highly manageable via lifestyle and dietary changes, including dietary supplements.
Dietary strategies to blood pressure management are based on low-salt, low-fat diets proven successful in scientific research. The most popular such diet is the DASH (Dietary Approaches to Stop Hypertension) diet, which is based on National Institutes of Health (NIH) studies1 and is recommended by the AHA as well as the National Heart, Lung and Blood Institute. DASH focuses on a reduction of sodium intake while promoting an increased intake of fruits, vegetables, fish, poultry and whole grains instead of dairy and red meat.
Fruits and Vegetables
More recently, the Mediterranean diet, which also favors fruits, vegetables and healthy fats, has demonstrated benefits to hypertension management.2 Involving a cohort of 8,594 participants aged 20 to 95, the 2009 Spanish study showed an inverse link between fruit/vegetable intake and risk of hypertension amongst those with low olive oil consumption (less than 15 g/d).
That plants form the heart of anti-hypertension diets is a credit to their content of nutrients and phytochemicals, especially antioxidants. Much of the research on lowering blood-pressure risk and managing hypertension levels focuses on these plant compounds, in addition to various botanicals.
For starters, fruits and vegetables contain numerous vitamins and minerals, some of which have been linked to benefits to blood pressure. For instance, mineral intake is important to controlling blood pressure. The International Study of Macro- and Micro-nutrients and Blood Pressure (INTERMAP) found an inverse link between blood pressure and increased intakes of dietary calcium, magnesium and phosphorus.3 University of Helsinki, Finland, researchers looked at potassium, calcium and magnesium, concluding greater intakes of these minerals result in a more than 10 mm Hg fall in the population average of systolic and diastolic blood pressure.4
Intake of magnesium alone may help regulate blood pressure and has been inversely associated with incidence of hypertension.5 In fact, animal studies have shown magnesium deficiency can have a long-term negative effect on arterial thickness and stiffness, arterial pressure and incidence of hypertension.6
University of Ottawa, Ontario, scientists have reported magnesium's effect on blood pressure is via vascular tone modulation and impact on vasodilation and inflammation.7 Magnesium's benefit may be narrowly targeted, according to Korean researchers, who found oral magnesium supplementation (as magnesium oxide) had no effect on blood pressure in healthy adults who were diabetes-free, normotensive and had normal magnesium levels; however, supplementation did lower blood pressure in a subgroup of people with hypertension and normal magnesium levels.8
Despite the lack of dairy in the DASH and Mediterranean diets, calcium is still a necessary nutrient for decreasing the risk of hypertension. French researchers investigating more than 900 middle-aged men found consumption of dairy products and dietary calcium were both significantly and independently associated with low levels of systolic blood pressure.9 The key to calcium-rich dairy may be keeping fat content low, as Harvard researchers studying a cohort of 28,886 U.S. women found intakes of low-fat dairy products, calcium and vitamin D were each inversely associated with hypertension.10
A late 2008 study report from Harvard Medical School, Boston, confirmed previous research conclusions of an inverse relationship between plasma 25-hydroxyvitamin D levels and risk of incident hypertension in young women.11 Specifically, young women with low levels of vitamin D had a substantially higher risk of hypertension than women with sufficient levels of the vitamin.
Vitamin C & E
As far as vitamins go, vitamin C is known in vascular health for its roles in collagen production and vascular flexibility. On hypertension specifically, low levels of vitamin C are concurrent with increased oxidative stress in hypertensive adults, indicating an oxidative factor in the development of hypertension.12 In fact, reducing oxidative stress appears to help manage blood pressure. Japanese researchers discovered systolic blood pressure and pulse pressure were significantly reduced in elderly patients being treated for hypertension who also took ascorbic acid (600 mg/d).13 Other research confirms this complementary pairing, as 1,000 mg/d of vitamin C added to antihypertensive therapy reduced systolic blood pressure and decreased parameters of oxidative stress in a trial out of India.14
The logical progression to combining antioxidant vitamins led researchers to the study of vitamins C and E together. In a University of Pisa, Italy, trial vitamin C (1 g/d) and vitamin E (400 IU/d) given to hypertensive men for eight weeks significantly improved flow-mediated dilation (FMD) and arterial flexibility, as well as vasodilation and oxidative stress parameters.15 Similarly, University of Chile, Santiago, research found hypertensive men taking vitamins C and E for eight weeks had significantly lower systolic and diastolic blood pressure, in addition to higher serum antioxidant capacity.16
Tocotrienol isomers of vitamin E may work on their own against hypertension. According to animal research, gamma-tocotrienol administration can reduce systolic blood pressure and improve nitric oxide synthase (NOS) activity, promoting production of the vasodilator nitric oxide (NO).17
NOS synthesizes NO from L-arginine, an amino acid that has proven its own potential to reduce arterial blood pressure along with auxiliary benefits to inter-media thickness and overall endothelial function.18,19 Incidentally, vitamin-like coenzyme Q10 can protect NO from oxidative stress and was shown to reduce elevated blood pressure in a 2008 Japanese animal study.20
Given the number of micronutrients with the potential to impact blood pressure, it was only a matter of time until researchers tested multivitamin and mineral (MVM) supplements against hypertension endpoints. A Harbin Medical University, China, trial compared a low-dose MVM, a high-dose MVM, a calcium supplement and a placebo for their effects on blood pressure in obese women with increased cardiovascular disease risk, including hypertension, hyperglycemia or hyperlipemia.21 After 26 weeks of intervention, the researchers found the high-dose MVM group had significantly decreased systolic and diastolic pressure, compared to the other groups.
However, the importance of fruits, vegetables and other plants in the anti-hypertension diets is due to more than just vitamins and minerals. Flavonoids are phytochemicals with antioxidant capabilities that have been proven useful to blood pressure management. In fact, one leading researcher argued flavonoids may be more important to heart health than vitamins C and E.22
United Kingdom scientists performed a review of research on several different types of flavonoids, including those from chocolate and soy, finding some positive effects on vascular health, including blood pressure.23 However, many flavonoid classes produced insufficient data; one exception was chocolate, which significantly lowered both systolic and diastolic blood pressure, in addition to increasing FMD after acute and chronic chocolate intake. They suggested future research in this area focus on flavonones and anthocyanins.
The star of recent flavonoid research, chocolate has enjoyed positive results in various areas of heart health, including blood pressure. However, research reviewers from Athens Medical School, Greece, reported the blood pressure lowering effect of dark chocolate and flavonoid-rich cocoa is attributed to the flavonoids impact on increased NO bioavailability.24 A JAMA study supported this hypothesis, finding intake of 6.3 g/d of dark chocolate (30 mg of polyphenols) for 18 weeks by adults with untreated pre-hypertension or stage 1 hypertension led to decreased mean systolic and diastolic blood pressure, improved NO formation and increased antioxidant measures.25
Punctuating chocolate's impact on blood pressure, an Italian trial noted flavanol-rich dark chocolate decreased blood pressure in hypertensive men and improved FMD.26
Grapes are also rich in polyphenols, and grape-based products have helped vascular health and blood pressure via some of the same mechanisms as micronutrient aids. Made from grapes, wine is rich in polyphenols and may improve endothelial function and decrease blood pressure by reducing oxidative stress.27 In vitro work also suggests red wine polyphenols may prevent expression of pro-inflammatory factors, resulting in limited development of angiotensin II-induced hypertension and endothelial dysfunction.28 Animal research supported these mechanisms, indicating wine polyphenols decreased blood pressure by improving endothelium-dependent dilation and antioxidant status.29
While drinking more wine may appeal to many people, others may find a simpler method of consuming these polyphenols by way of grape seed extract (GSE) supplements, which have undergone scientific inquiry into benefits to blood pressure. University of California, Davis, researchers conducted a few studies on GSE (as MegaNatural BP, from Polyphenolics) and endothelial function an arterial blood pressure. An animal-based in vitro study found MegaNatural BP produced dose-dependent relaxation in aortic rings contacted with noradrenaline.30 The team's clinical work on the GSE showed adults with metabolic syndrome who took 150 mg/d or 300 mg/d of MegaNatural BP for one month had reductions in systolic and diastolic blood pressure.31 Their two-month follow-up study concluded pre-hypertensive subjects who received 300 mg/d of MegaNatural BP experienced a significant decrease in both systolic and diastolic blood pressure; the researchers theorized GSE polyphenols had a vasodilatory effect.32
A pair of Chinese studies on various diabetes-related endpoints in rats included results showing administration of GSE reduced systolic blood pressure.33 The researchers credited proanthocyanidins in GSE for this effect.
Pine Bark Extract
Oligomeric proanthocyanidins (OPCs) are a class of flavanols found in various botanicals, including maritime pine bark and green tea. OPCs and other flavonoids in pine bark extract have demonstrated an impact on cardiovascular health, including hypertension. In a joint study from University of Arizona, Tucson, and Westfalische Wilhelms University, Germany, men taking 200 mg/d of pine park extract (as Pycnogenol, from Horphag, supplied by Natural Health Science) had a significant decrease in systolic blood pressure, compared to placebo, but the effect on diastolic pressure failed to reach significance.34 More recently, a 2008 trial out of China examined the impact of 100 mg/d of Pycnogenol on patients with hypertension, finding the extract improved endothelial function, decreased endothelin-1 concentrations and increased NO levels in plasma.35
Another pine bark extract (as Enzogenol, from ENZO Nutraceuticals, supplied by B&D Nutritional Ingredients) underwent a 12-week pilot study by New Zealand researchers, who paired it with vitamin C and measured various cardiac parameters.36 They reported a dose of 480 mg/d of pine bark extract and 240 mg/d of vitamin C was associated with a significant reduction in systolic blood pressure.
Proanthocyanidins are closely related to fellow flavanol catechins, both of which are found in green tea. A University of Missouri, Columbia, research review discovered consumption of green tea and its epigallocatechin-3-gallate (EGCG) appears to improve endothelial function and hypertension.37 Animal research has shown similar results, with green tea extract limiting induced hypertension in rats, by addressing oxidative damage.38 Most recently, a 2009 University of Florida, Gainesville, study involved healthy adults aged 21 to 70, who took a capsule of standardized green tea (Camilla sinesis) compounds twice daily and were tested for various cardiovascular parameters.39 After three weeks, systolic and diastolic pressures were decreased by 5 mmHg and 4 mmHG, respectively; systolic pressure remained low after three months.
Still more relief from high blood pressure may come from another class of flavonoids called anthocyanins, which are the dark pigments in many richly colored fruits and vegetables.
Chokeberry (Aronia melanocarpa) anthocyanins given to adults for two months significantly lowered both systolic and diastolic blood pressure in a Polish study.40
Similarly, Japanese researchers administered anthocyanins from purple corn, purple sweet potato and red radish to hypertensive rats, finding the flavonoids decreased blood pressure and heart rate.41
Tying into the Mediterranean diet on blood pressure, pomegranates are rich in anthocyanins and tannins and may help manage blood pressure. An Israeli trial found hypertensive patients taking pomegranate juice (50 mL) for just two weeks had significantly reduced systolic blood pressure and ACE activity.42 The same research team looked at long-term intervention, finding pomegranate juice consumption by hypertensive adults over a three-year period reduced systolic blood pressure by 21 percent after just one year.43 They noted there were no further reductions at three years, but pomegranate consumption did appear to improve vascular health by decreasing carotid intima-media thickness.
Fans of the Mediterranean diet will often cite the prevalence of heart-healthy olive oil, but the leaves from the olive tree have been specifically studied for benefits to hypertension care. Olive leaf extract EFLA 943 (as Benolea, by Frutarom) showed hypotensive effects in hypertensive rats in a Cairo University, Egypt, study.44 Researchers attributed the benefit to the extract's ability to reverse adverse vascular changes. South African scientists were able to credit triterpenoids from Greek and African and olive leaf varieties to prevention of severe hypertension and atherosclerosis in experimental animals after a six-week intervention.45
Olive Leaf Extract
In 2008, German and Swiss researchers conducted two experiments on olive leaf extract in identical human twins aged 18 to 60 with borderline hypertension, in an effort to generate consistent data free from genetic differences.46 First, they gave twins either 500 mg/d of olive leaf extract for breakfast or a placebo. In the second study, they gave twins either 500 mg/d or 1,000 mg/d of olive leaf extract, or a placebo. Among those taking the highest amount of extract, systolic blood pressure fell by a significant amount, while those taking the lower amount of extract saw a five-point decline in systolic pressure, and those on placebo had a two-point increase in pressure.
Ginko Biloba
Another leaf-based supplement, Ginkgo biloba, has had decent results on blood pressure, but mixed results on other vascular health parameters. Per animal research, ginkgo extract can decrease salt-related elevation of blood pressure and support vasodilation.47 Similarly, another animal study reveals standardized ginkgo extract (as EGb 761) can suppress age-related increases in blood pressure.48 However more recent Japanese research found while ginkgo extract reduces blood pressure, it can also impair peripheral circulation and increase liver weight in aged hypertensive rats.49
A plant-based hypotensive diet, especially Mediterranean, would be lacking without garlic, which has performed consistently well against rising blood pressure. A 2008 meta-analysis from the University of Adelaide, South Australia, summed up 11 studies with evidence of a significant decrease (4.6 +/- 2.8 mmHg) in systolic blood pressure among subjects taking garlic, while those in a hypertensive subgroup had even greater reductions in both systolic and diastolic blood pressure.50 However, a subsequent meta-analysis by Hartford Hospital, Connecticut, researchers concluded garlic reduced blood pressure in subjects with elevated systolic pressure, but not those with normal systolic readings.51 Still, a clinical study has suggested garlic lowers both systolic and diastolic blood pressure.52
The mechanism behind garlic's benefit to blood pressure management is the focus of many recent studies. Some point to antioxidant actions toward improved blood pressure,53,54 while others credit garlic's allicin content for improved endothelial function.55 Still other research indicates different preparations of garlic can affect its results on hypertension. In early 2009, Russian researchers reported time-released garlic powder tablets are more effective for the treatment of mild and moderate arterial hypertension than are regular garlic supplements, possibly due to the greater bioavailability of the powdered form.56
Garlic
Other studies have focused on aged garlic extract (AGE), with one study finding both AGE and powdered garlic reversed rising blood pressure in the animals after 10 weeks of invtervention.57 Clinical research on hypercholesterolemic men revealed 7.2 g/d of AGE supplementation for six months resulted in 5.5-percent decrease in systolic blood pressure and a modest reduction in diastolic blood pressure.58 Another clinical trial showed intervention with AGE plus vitamin B1 and ginseng extract effectively lowered blood pressure in hypertensive, but not normo-tensive patients.59
Tomatoes
Tomatoes are another Mediterranean dietary staple, and their content of the carotenoid lycopene may be central to any blood pressure benefits associated with the vegetable. In fact, research out of Pennington Biomedical Research Center, Baton Rouge, LA, analyzed the phytochemical content of the DASH diet, using USDA food composition databases, and found DASH was much higher in lycopene and flavonols than control diets.60 Tomato extract itself was study by Israeli scientists, who reported the extract (as Lyc-O-Mato, from Lycored) decreased both systolic and diastolic blood pressure in grade-1 hypertensive patients.61 Specifically, 250 mg/d of Lyc-O-Mato for eight weeks decreased systolic blood pressure from 144 to 134 mmHg and diastolic blood pressure from 87.4 to 83.4 mmHg, compared to a placebo group.
Similarly, animal research has suggested fellow carotenoid astaxanthin may reduce blood pressure in hypertensive models, possibly by improving vascular elastin and arterial wall thickness, and modulating blood fluidity.62,63,64
The seasoning void in hypotensive diets that trim salt intake may well be filled by spices, which could additionally help manage blood pressure levels. The Nigella sativa seed which is often confused with black cumin, block onion and other similar black seeds is used as spice in many traditional Middle Eastern cultures and has been studied for hypotensive benefits. A study out of Shahrekord University of Medical Sciences, Iran, tested eight weeks of oral Nigella sativa (NS) seed extract supplement in patients with mild hypertension, finding doses of 100 or 200 mg/d of seed extract resulted in significant, dose-dependent reductions in both systolic an diastolic blood pressure, compared to placebo, while also improving cholesterol profiles.65
Dubbed a "silent killer," high blood pressure does not have to exact its cruel cardiovascular consequences, as numerous dietary and lifestyle modifications have proven useful in limiting development and progression of hypertension. Further, dietary ingredients, such as vitamins, minerals, fats, protein and plants, can boost these hypotensive efforts.
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