Vegetarian Diets and Blood Pressure
A 2014 meta-analysis of 7 clinical trials and 32 observational studies has found that a vegetarian diet reduces blood pressure.
Researchers from Japan recently published a meta-analysis of clinical trials and cross-sectional observational studies of a vegetarian diet and blood pressure (BP) (42). Many of these vegetarians were semi-vegetarians.
Among seven clinical trials, a vegetarian diet was found to reduce systolic and diastolic blood pressure by an average of 4.8 and 2.2 mm Hg, respectively. Among the 32 cross-sectional studies, vegetarians were found to have a lower systolic and diastolic blood pressure of 6.9 and 4.7 mm Hg respectively. These findings were statistically significant.
The authors said, “According to Whelton et al, a reduction in systolic BP of 5 mm Hg would be expected to result in a 7%, 9%, and 14% overall reduction in mortality due to all causes, coronary heart disease, and stroke, respectively….Obesity, excessive sodium intake, and excessive alcohol use are associated with increased BP and risk of hypertension; potassium intake and physical activity are associated with lower BP. In addition, intake of unsaturated fat, protein, magnesium, and dietary fiber may be associated with differences in BP.”
Interestingly, the only clinical trial that showed a vegetarian diet to increase blood pressure was the first PCRM pilot study using a vegan diet to treat type 2 diabetes (2). Diastolic blood pressure did decrease more in the control group, than the vegan group, in that study, while those on the vegan diet ended up with lower systolic blood pressure. However, two of the five subjects on the vegan diet who were on blood pressure medication discontinued their medication, while only one of four in the control group discontinued.
I have updated the Blood Pressure section of Disease Markers of Vegetarians
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References
1. Yokoyama Y, Nishimura K, Barnard ND, Takegami M, Watanabe M, Sekikawa A, Okamura T, Miyamoto Y. Vegetarian Diets and Blood Pressure: A Meta-analysis. JAMA Intern Med. 2014 Feb 24. | link
2. Nicholson AS, Sklar M, Barnard ND, Gore S, Sullivan R, Browning S. Toward improved management of NIDDM: A randomized, controlled, pilot intervention using a lowfat, vegetarian diet. Prev Med. 1999 Aug;29(2):87-91. | link
March 20th, 2014 at 8:55 pm
This meta-analysis seems biased.
1. Why the larger PCRM study (Barnard et al 2006; Barnard et al 2009) wasn’t included in the meta-analysis?
2. The largest study in the meta-analysis (and therefore the most influential on the outcome of the meta analysis) is the Ferdowsian et al study. However, this is not a randomized study and therefore shouldn’t have been included in the meta-analysis. But this is not the only flaw of this study: (1) The intervention group was under a calorie restricted diet and lost 5 kg, while the control group remained with their habitual diets and had no weight change. (2) The participants in the intervention group did not actually reduce their blood pressure. However, there was an increase in SBP in the control group, and this is the cause for the between-group difference. Since this was non-randomized trial, one cannot conclude from this trial that the vegetarian diet reduces SBP.
3. Another large study in the meta-analysis is Hakala et al. This study had 3 groups: calorie-restricted vegetarian diet, calorie-restricted mixed diet, and control. I do not have access to this study, but from the abstract, I suspect that the authors of the meta-analysis chose to compare the vegetarian diet to the control diet, and not to the mixed diet.
March 21st, 2014 at 5:50 pm
Dave,
They were looking for “interventions” not randomized trials. It might be difficult to get people to randomize to a vegan diet for any length of time.
March 21st, 2014 at 8:47 am
I have had a very interesting blood pressure journey. I used to be pre-hypertensive/early hypertensive (SBP 130’s-150’s), with a prominent white coat response, especially when measured in a public place (pharmacy, supermarket, doctor’s office). After losing a lot of weight, my BP came down to the normotensive range (120’s). Then, after going vegan and slowly eliminating processed foods while increasing intake of healthy plant-based foods known to lower blood pressure, my resting BP at the doctor’s office is consistently 90/50. This is a reduction of 40-50 mmHg. I’ve stopped measuring it at home a long time ago (before going vegan), but if it is that low in a medical environment, I can only imagine it is even lower at home. My father has resistant hypertension on three medications and still runs quite high – he is a lacto-pesco-vegetarian but 40 years older than me. I think that maintaining an optimal weight and not consuming poisons is the key to reversing hypertension, especially that variant associated with the metabolic syndrome (which I clearly had). And then consuming specific plant products that are known to further reduce BP also helps a great deal.
March 21st, 2014 at 9:42 pm
With the exception of the Ferdowsian et al study, all other studies in the meta-analysis are randomized. This study should not have been included.