The researchers found that in healthy volunteers blood pressure was reduced within just 1 hour of ingesting beetroot juice, with a peak drop occurring 3 to 4 hours after ingestion. Some degree of reduction continued to be observed until up to 24 hours after ingestion.
Researchers showed that the decrease in blood pressure was due to the chemical formation of nitrite from the dietary nitrate in the juice. The nitrate in the juice is converted in saliva, by bacteria on the tongue, into nitrite. This nitrite-containing saliva is swallowed, and in the acidic environment of the stomach is either converted into nitric oxide or re-enters the circulation as nitrite. The peak time of reduction in blood pressure correlated with the appearance and peak levels of nitrite in the circulation, an effect that was absent in a second group of volunteers who refrained from swallowing their saliva during, and for 3 hours following, beetroot ingestion.
The research reveals that it is the ingestion of dietary nitrate contained within beetroot juice - and similarly in green, leafy vegetables - which results ultimately in decreased blood pressure. Previously the protective effects of vegetable-rich diets had been attributed to their antioxidant vitamin content.
MEDICA.de; Source: Queen Mary, University of London