By Joseph E. Scherger, MD, MPH
Vice President, Primary Care, Eisenhower Medical Center; Clinical Professor, Keck School of Medicine, University of Southern California
Dr. Scherger reports no financial relationships relevant to this field of study.
SYNOPSIS: Daily one-time ingestion of inorganic nitrate from beet juice consistently lowered blood pressure in hypertensive patients by an amount comparable to single-drug therapy.
SOURCE: Kapil V, et al. Dietary nitrate provides sustained blood pressure lowering hypertensive patients. Hypertension 2015;65:320-327.
This carefully controlled, randomized trial was performed in London and compared the use of inorganic nitrates found in beet juice to placebo for controlling blood pressure in hypertensive patients. Sixty-four patients underwent a 4-week trial of drinking one 250 mL bottle of beet juice daily and 4 weeks of a placebo beet juice with the nitrate removed. There was a 2-week washout period. The sequence of juice ingestion was randomized into two groups. All patients were mildly hypertensive and had no renal impairment. Those on medication continued their therapy during the trial. Adults ages 18-85 years were included in the study.
Blood pressure was measured in three ways for each patient: once-daily home blood pressure, a 24-hour ambulatory blood pressure measurement near the end of the 4-week period, and clinic blood pressure measurements. All patients ingesting the nitrate containing beet juice had reductions in blood pressure and those on placebo did not. The blood pressure reductions were similar for all three methods. Home blood pressure dropped by 8.1 mmHg (3.8-12.4) systolic and 3.8 mmHg (0.7-6.9) diastolic. Clinic blood pressures fell by 7.7 mmHg (3.6-11) and 2.4 mmHg (0-4.9) diastolic. Ambulatory blood pressures decreased by 7.7 mmHg (3.5-11.8) systolic and 5.2 mmHg (2.7-7.7) diastolic. These reductions were sustained over 4 weeks.
Additionally, the beet juice was associated with improvements in vascular function through vasodilatation and improved endothelial function. There were no adverse side effects of ingesting the beet juice except for the change in color of the urine and feces.
It is well known that nitric oxide (NO) in the blood is a potent vasodilator. The mechanism of action of the dietary inorganic nitrate converted to NO has only recently been understood.1,2 The small intestine absorbs inorganic nitrates and blood extracts nitrates via the salivary glands of the mouth.3 The microbiome in the mouth converts the nitrate to nitrite.1,2 So much for the gastrointestinal tract being a one way street. After swallowing the saliva, the nitrite enters the circulation where it meets enzymes, nitrite reductases that convert it to NO in the circulation.4 The NO then causes vasodilation and lower blood pressure. This is a uniquely physiologic phenomenon that has defied attempts at pharmacotherapy. Organic nitrites such as nitroglycerin suffer from problems of endothelial dysfunction and tachyphylaxis.5
COMMENTARY
This study is the first to show durable blood pressure reduction from the nutritional intake of nitrates. It is an example of how nutrition has the potential to treat the most common of chronic diseases, such as hypertension.
The study indicates the use of beetroot juice. What the English call beetroot is simply beets or red beets in North America. In addition to beets, other vegetables high in nitrates include spinach, celery, rugola and other lettuce, cress, and chervil. The evidence would suggest that daily consumption of a healthy portion of these vegetables may reduce the incidence of hypertension and help treat it when it exists. Juicing vegetables would be a convenient way to ensure a consistent amount of nitrates in the daily diet.
The 12th century physician, Maimonides, stated that, “No disease that can be treated with diet should be treated with any other means.” Nutrition as therapy is underdeveloped in Western medicine. In China and other Eastern countries, the medical pharmacy is loaded with nutritional herbs, and the hospital may have a vegetable garden on site. Western physicians may look at this practice as quaint and not evidence-based through controlled trials.
Kapil and colleagues are to be commended for this carefully controlled trial of how a vegetable product used daily significantly reduces blood pressure in hypertensive patients. The role of the microbiome in this mechanism is most interesting and suggests there are many more complex nutritional therapies yet to be understood and discovered.
REFERENCES
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Larsen FJ, et al. Effects of dietary nitrate on blood pressure in healthy volunteers. N Engl J Med 2006;355:2792-2793.
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Webb AJ, et al. Acute blood pressure lowering, vasoprotective, and antiplatelet properties of dietary nitrate via bioconversion to nitratet. Hypertension 2008;51:784-790.
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Tannenbaum SR, et al. The effect of nitrate intake on nitrite formation in human saliva. Food Cosmet Toxicol 1976;14:549-552.
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Cosby K, et al. Nitrite reduction to nitric oxide by deoxyhemoglobin vasodilates the human circulation. Nat Med 2003;9:1498-1505.
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Gori T, et al. Evidence supporting abnormalities in nitric oxide synthase function induced by nitroglycerin in humans. J Am Coll Cardiol 2001;38:1096-1101.
