X-Message-Number: 30535
Date: Mon, 25 Feb 2008 10:16:22 -0800 (PST)
From: 
Subject: beets lower blood pressure via dietary nitrite

[This is a very good piece of work. It conclusively debunks the idea that
antioxidants are the blood pressure lowering factor in beets. Instead it
is bacteria in saliva reducing biologically inert dietary nitrate to
bioavailable nitrite which does the trick. Nitrite, and not antioxidants
is the active ingredient. The authors propose that the same explanation
is responsible for the BP lowering effect of most other fruits and
vegetables as well.]

Hypertension. 2008 Mar;51(3):784-90. Epub 2008 Feb 4.
Acute Blood Pressure Lowering, Vasoprotective, and Antiplatelet Properties
of Dietary Nitrate via Bioconversion to Nitrite.
  Webb AJ, Patel N, Loukogeorgakis S, Okorie M, Aboud Z, Misra S, Rashid R,
Miall P, Deanfield J, Benjamin N, Macallister R, Hobbs AJ, Ahluwalia A.
Clinical Pharmacology, William Harvey Research Institute, Barts & the London
School of Medicine and Dentistry, Queen Mary University of London,
Charterhouse Square, London EC1M 6BQ, UK.
  Diets rich in fruits and vegetables reduce blood pressure (BP) and the
risk of adverse cardiovascular events. However, the mechanisms of this
effect have not been elucidated. Certain vegetables possess a high nitrate
content, and we hypothesized that this might represent a source of
vasoprotective nitric oxide via bioactivation. In healthy volunteers,
approximately 3 hours after ingestion of a dietary nitrate load (beetroot
juice 500 mL), BP was substantially reduced (Delta(max) -10.4/8 mm Hg); an
effect that correlated with peak increases in plasma nitrite concentration.
The dietary nitrate load also prevented endothelial dysfunction induced by
an acute ischemic insult in the human forearm and significantly attenuated
ex vivo platelet aggregation in response to collagen and ADP. Interruption
of the enterosalivary conversion of nitrate to nitrite (facilitated by
bacterial anaerobes situated on the surface of the tongue) prevented the
rise in plasma nitrite, blocked the decrease in BP, and abolished the
inhibitory effects on platelet aggregation, confirming that these
vasoprotective effects were attributable to the activity of nitrite
converted from the ingested nitrate. These findings suggest that dietary
nitrate underlies the beneficial effects of a vegetable-rich diet and
highlights the potential of a "natural" low cost approach for the treatment
of cardiovascular disease.
PMID: 18250365

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