Beetroot juice was associated with a 13 mmHg reduction in systolic blood pressure three hours after drinking 100 grams, while diastolic blood pressure decreased by 16.6 mmHg at the same point, according to findings published in the British Journal of Nutrition.
Higher doses of beetroot juice produced greater blood pressure reductions, reported researchers from the University of Reading.
When formulated in bread, beetroot was associated with similar reductions in blood pressure.
“Results from these studies are the first to demonstrate that acute ingestion of beetroot juice lowered blood pressure in a near dose-dependent manner in healthy normotensive individuals,” wrote the researchers, led by Professor Julie Lovegrove.
“In addition, novel bread enriched with either white or red beetroot, equivalent to 100 g beetroot juice, resulted in similar blood pressure reductions.”
The results from the bread study indicated that the active compounds in beetroot were the nitrates, and that betalains – the compounds that give beetroot its red pigment – only played a minor role, if any.
“Therefore, enriching bread with beetroot may provide a useful vehicle for the delivery of dietary nitrate and increasing vegetable consumption, with minimal impact on dietary habits,” they added.
Prof Lovegrove and her co-workers recruited 18 men with normal blood pressure to participate in their juice experiement. Men were randomly assigned to consume 0, 100, 250 or 500 grams of beetroot juice in a single-blind, cross-over trial. The men were kept in a control environment and monitored for 24 hours.
Results showed that the beetroot juice led to reductions in blood pressure, and the greater the dose the greater the reduction. Indeed, consumption of 500 grams led to systolic and diastolic blood pressure reductions of 22 mmHg and 18 mmHg, respectively, after two to three hours.
Fourteen men participated in the bread trial, during which they consumed one of three bread products: Control bread containing no beetroot, or bread enriched with red or white beetroot at a dose equivalent to 100 grams of beetroot juice.
As with the juice, the red and white beetroot-enriched bread produced systolic blood pressure reductions of 19 and 17 mmHg, respectively, and diastolic reductions of 24 and 23 mmHg, respectively.
Prof Lovegrove and her co-workers note that beetroot contains many compounds reported to offer cardiovascular benefits, including vitamins C and K, folate, fiber, and polyphenols, but they note that the nitrates are likely to be responsible for some of the effects.
“In humans, 20–25% of ingested nitrate is secreted in saliva and approximately 20% of this is converted to nitrite by commensal Gram-negative bacteria on the dorsal surface of the tongue, resulting in nitrite-rich saliva,” they explained.
“The salivary nitrite is absorbed in the stomach and enters the circulation where NO synthesis occurs by the reduction of nitrite within the blood vessel wall and erythrocytes.
“It is possible that the nitrite derived from ingested nitrate, in the present studies, provided an intravascular source of NO that resulted in vasodilation within the microcirculation to produce a decrease in peripheral resistance and therefore a reduction in blood pressure.”
Source: British Journal of Nutrition
Published online ahead of print, FirstView Articles, doi: 10.1017/S0007114512000190
“Blood pressure-lowering effects of beetroot juice and novel beetroot-enriched bread products in normotensive male subjects”
Authors: D.A. Hobbs, N. Kaffa, T.W. George, L. Methven, J.A. Lovegrove