Published: Feb 24, 2014
By Todd Neale, Senior Staff Writer, MedPage Today

Vegetarians had lower blood pressure than their omnivorous counterparts, a meta-analysis showed.

Blood pressure was an average of 4.8/2.2 mm Hg lower among vegetarians in controlled trials and 6.9/4.7 mm Hg lower in cross-sectional studies (P<0.001 for all differences), according to Yoko Yokoyama, PhD, MPH, of the National Cerebral and Cardiovascular Center in Osaka, Japan, and colleagues.

The findings — reported online in JAMA Internal Medicine — suggest that “such diets could be a useful nonpharmacologic means for reducing blood pressure,” they wrote, adding that “further studies are needed to explore the relationships between specific foods and nutrients and blood pressure.”.

But it’s more important to focus on overall diet quality rather than specific aspects of diet, with the exceptions of cutting caloric intake for overweight individuals and reducing sodium intake more generally, according to Lawrence Appel, MD, director of the Welch Center for Prevention, Epidemiology, and Clinical Research at Johns Hopkins University.

“I’m not quite sure that it’s critical to find out if it’s a single nutrient or package of nutrients from a public health perspective,” Appel told MedPage Today. “This adds greater credence to the evidence on vegetarian diets.”

Although observational studies have consistently shown that eating a vegetarian diet is associated with lower rates of hypertension, only some controlled trials have demonstrated that cutting meat from the diet reduces blood pressure.

To get a better idea of the potential effect, Yokoyama and colleagues pooled results from seven controlled trials with 311 total participants and from 32 observational studies — all cross-sectional — with 21,604 total participants. For the purposes of the analysis, vegetarian diets could include fish or the rare consumption of other meat.

Significant reductions in systolic and diastolic blood pressure were seen with adherence to a vegetarian diet in both controlled and cross-sectional studies.

The reductions “are similar to those observed with commonly recommended lifestyle modifications, such as adoption of a low-sodium diet or a weight reduction of 5 kg (11 lbs), and are approximately half the magnitude of those observed with pharmaceutical therapy, such as administration of ACE inhibitors to individuals with hypertension,” the authors noted.

And according to a prior study, they added, a reduction in systolic blood pressure of 5 mm Hg would be expected to result in a 7% reduction in all-cause mortality, and a 9% and 14% reduction in mortality due to coronary heart disease and stroke, respectively.

Their analysis could not account for specific lifestyle or diet factors that might underlie the associations, but they offered some possible explanations:

• Vegetarians typically have lower body mass because the foods they eat are less dense, containing more fiber and less fat. This is not the only explanation, the authors wrote, because studies adjusting for body mass index still showed lower blood pressure in vegetarians.
• Levels of potassium, which have been inversely associated with blood pressure, are higher in vegetarian diets.
• There is some evidence that vegetarians consume less sodium and less alcohol compared with people eating other types of diets.
• Vegetarian diets often contain a lower percentage of saturated fats and a higher percentage of polyunsaturated fats.
• The blood of vegetarians may be less viscous.
• Eating more vegetable protein has been associated with lower blood pressure. 

Whatever the reasons, though, the blood pressure differences observed were meaningful from both clinical and public health perspectives, said Appel, who pointed out that themagnitude of the differences were roughly the same of those seen in the 1997 publication of the DASH study, for which he was the lead author.

“In the general population, lower blood pressure is better, whether you’re nonhypertensive or hypertensive,” Appel said. “If you are hypertensive, the vegetarian diet is one alternative among others to help control blood pressure.”

The authors noted some limitations of their analysis, including a high degree of heterogeneity among the observational studies, the small sample sizes and lack of adjustment for lifestyle factors in many of the studies, the cross-sectional design of the observational analyses, and variations in the content of the vegetarian diets between individuals and locations.

From the American Heart Association:

• 2013 AHA/ACC Guideline on Lifestyle Management to Reduce Cardiovascular Risk
• Implementing American Heart Association Pediatric and Adult Nutrition Guidelines
• Diet and Lifestyle Recommendations: Revision 2006

Primary source: JAMA Internal Medicine

Full Story

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Vegetarian Diet Cuts Blood Pressure in Meta-Analysis

Shelley Wood

February 24, 2014

Full Story from Medscape

OSAKA, JAPAN — Eating a vegetarian diet is associated with reductions in blood pressure on par with adopting the DASH (low-sodium) diet, and roughly half that of starting pharmaceutical treatment, a new meta-analysis suggests ^[1] .

“These findings establish the value of nonpharmacologic means for reducing BP,” lead author on the study, Dr Yoko Yokoyama (National Cerebral and  Cardiovascular Center, Osaka, Japan) told heart wire . “Unlike drugs, there is no cost to a diet adjustment of this type, and all the ‘side effects’ of a plant-based diet are desirable: weight loss, lower cholesterol, and better blood sugar control, among others. I would encourage physicians to prescribe plant-based diets as a matter of routine and to rely on medications only when diet changes do not do the job.”

Yokoyama et al’s meta-analysis is published February 24, 2014 in JAMA Internal Medicine. The study is the latest to examine the health impact of a vegetarian-style eating pattern on cardiovascular disease risk factors.

The authors reviewed over 250 studies addressing vegetarian diets, ultimately including seven clinical trials (six of which were randomized) and 32 observational studies that included blood-pressure findings. Diets ranged from vegan to lacto-ovo vegetarian, with one study including fish, but no meat).

The authors found that reductions in both systolic and diastolic blood pressure were significantly greater for the vegetarian diets than for the comparator (omnivorous) diets, both in the pooled clinical trials and in the pooled observational studies, although drops were greater in the observational studies.

Blood pressure reductions with vegetarian diets, compared with omnivorous diets

Study type	Systolic, mm Hg	Diastolic, mm Hg	p
Pooled clinical trials	-4.8	-2.2	<0.001
Pooled observational studies	-6.9	-4.7	<0.001

To heart wire , Yokoyama stressed that the body of evidence supporting the value of vegetarian-style diets and blood-pressure lowering is undeniable.

“This issue was examined by nearly 40 independent studies, some of which had hundreds or even thousands of participants, and the findings are strikingly consistent,” Yokoyama said. “A vegetarian diet is clearly associated with lower blood pressure. Or, put another way, a meat-based diet is associated with higher blood pressure.”

As with the DASH diet, the effect of switching to a vegetarian diet appears to be fairly rapid, and that’s likely the result of two factors.

OSAKA, JAPAN — Eating a vegetarian diet is associated with reductions in blood pressure on par with adopting the DASH (low-sodium) diet, and roughly half that of starting pharmaceutical treatment, a new meta-analysis suggests ^[1] .

“These findings establish the value of nonpharmacologic means for reducing BP,” lead author on the study, Dr Yoko Yokoyama (National Cerebral and  Cardiovascular Center, Osaka, Japan) told heart wire . “Unlike drugs, there is no cost to a diet adjustment of this type, and all the ‘side effects’ of a plant-based diet are desirable: weight loss, lower cholesterol, and better blood sugar control, among others. I would encourage physicians to prescribe plant-based diets as a matter of routine and to rely on medications only when diet changes do not do the job.”

Yokoyama et al’s meta-analysis is published February 24, 2014 in JAMA Internal Medicine. The study is the latest to examine the health impact of a vegetarian-style eating pattern on cardiovascular disease risk factors.

The authors reviewed over 250 studies addressing vegetarian diets, ultimately including seven clinical trials (six of which were randomized) and 32 observational studies that included blood-pressure findings. Diets ranged from vegan to lacto-ovo vegetarian, with one study including fish, but no meat).

The authors found that reductions in both systolic and diastolic blood pressure were significantly greater for the vegetarian diets than for the comparator (omnivorous) diets, both in the pooled clinical trials and in the pooled observational studies, although drops were greater in the observational studies.

Blood pressure reductions with vegetarian diets, compared with omnivorous diets

Study type	Systolic, mm Hg	Diastolic, mm Hg	p
Pooled clinical trials	-4.8	-2.2	<0.001
Pooled observational studies	-6.9	-4.7	<0.001

To heart wire , Yokoyama stressed that the body of evidence supporting the value of vegetarian-style diets and blood-pressure lowering is undeniable.

“This issue was examined by nearly 40 independent studies, some of which had hundreds or even thousands of participants, and the findings are strikingly consistent,” Yokoyama said. “A vegetarian diet is clearly associated with lower blood pressure. Or, put another way, a meat-based diet is associated with higher blood pressure.”

As with the DASH diet, the effect of switching to a vegetarian diet appears to be fairly rapid, and that’s likely the result of two factors.

References

1. Yokoyama Y, Nishimura K, Barnard ND, et al. Vegetarian diets and blood pressure. A meta-analysis.  JAMA Intern Med 2014; DOI:10.1001/jamainternmed.2013.14547. Abstract