Vegetarian Diet Cuts Blood Pressure in Meta-Analysis

Shelley Wood

February 24, 2014

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

All the 'side effects' of a plant-based diet are desirable.

"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.

"A rapid blood-pressure–lowering effect comes from the diet change itself, probably due to the high potassium content of the diet, as well as its low content of saturated fat, which means it will reduce the 'thickness' of the blood, which in turn lowers blood pressure. The second effect comes from the fact that vegetarian diets typically elicit weight loss, and that will add to the blood-pressure reduction, albeit more gradually," Yokoyama said.

As the authors note, it is not possible to control for all factors associated with vegetarian-type diets that might influence blood pressure, including increased fiber and potassium intake, as well as lower consumption of saturated fats and sodium. Vegetarianism can also be a marker for other healthy behaviors. That said, note the authors, many of the studies controlled for lifestyle and physical activity, and the impact of vegetarian diets was consistent and "robust" across different populations despite the primary components of the diets varying from country to country and between populations.

Further studies, they add, should address what components of vegetarian diets are the key drivers of lower blood pressure, and whether public-health initiatives or clinic-based programs focused on vegetarian eating could lead to the prevention of hypertension.

The authors had no conflicts of interest.

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