Nitrates in Food: Can They Lower Blood Pressure?
In a small study published in the New England Journal of Medicine, scientists at the Swedish School of Sport and Health Sciences found that the nitrates in certain vegetables helped to maintain blood vessel integrity and decrease blood pressure in 17 healthy, nonsmoking, young adults.
The participants each took a nitrate supplement equivalent to the amount of nitrate found in 150–250 grams of nitrate-rich vegetables for 3 days and took a placebo for 3 days. The participants diastolic blood pressure was an average of 3.7 mm Hg lower after 3 days of taking the nitrate supplements than it was after 3 days of taking the placebo.
In a separate study published in Hypertension, British researchers gave 14 healthy volunteers 2 cups of beet juice or water, which they drank within 30 minutes. Their blood pressure was checked every 15 minutes for 1 hour before they drank the juice or water and then every 15 minutes for 3 hours after drinking it. It also was checked again every hour for 6 hours and then at 24 hours after drinking the juice or water. The participants who drank the beet juice experienced a blood pressure drop an hour after drinking it. The blood pressure was at its lowest 2½–3 hours after drinking it and continued to have an effect for up to 24 hours. The blood pressure levels were at their lowest when the nitrite levels in the blood were at their highest.
Nitric oxide is a vasodilator and is important for vascular function and blood flow. Nitric oxide is crucial for vasodilation, blood pressure regulation, inhibition of endothelial inflammatory cell recruitment, and platelet aggregation. It also decreases inflammation in the body and improves glucose metabolism. Nitric oxide levels can decrease with hypertension, diabetes, or high cholesterol, as well as with endothelial cell damage. This decrease in nitric oxide can lead to the development of insulin resistance, hypertension, stroke, and atherosclerosis. Researchers also believe that a decrease in nitric oxide may play a role in the development of Parkinson’s disease.
Exercise enhances nitric oxide production and as a person ages, their vasculature creates less plasma nitrite during physical activity. Dietary nitrate supplementation is found to cause more efficient energy production during submaximal exercise.
Fruits and vegetables
It is not a new fact that a diet rich in fruits and vegetables can reduce blood pressure, which is why the Dietary Approaches to Stop Hypertension (DASH) diet calls for the consumption of four to five servings of vegetables and four to five servings of fruit each day.
Pomegranate juice seems to protect nitric oxide from oxidation and enhance its biological activity. It seems that probiotics also provide nitric oxide from nitrite and nitrate. It is possible that the nitrate content of organic vegetables is less than that of vegetables grown with the use of nitrogen-containing fertilizer. Nitrate is lost via peeling, washing, and cooking of fruits and vegetables.
Vegetables that are very high in nitrate content include:
- Red beetroot
- Rocket (rugola)
Vegetables that are high in nitrate concentration include:
- Chinese cabbage
Vegetables that contain a “middle” amount of nitrate include:
- Savoy cabbage
The following foods contain low or very low levels of nitrate:
- Broad beans
- Green bean
- Summer squash
- Sweet potatoes
You should avoid nitrates in processed meats. They are known to have negative health effects, including an increased risk of certain types of cancer and chronic obstructive pulmonary disease (COPD).
It is strongly suggested that the benefits of fruit and vegetable consumption far outweigh any perceived risk of developing cancer from ingestion of these foods. Dozens of studies have found that a high intake of fruits and vegetables helps to decrease blood pressure. It is recommended that people consume a wide variety of fruits and vegetables each day. Patients with hypertension also may find it beneficial to consume beet juice.
References and recommended readings
Bergman E. Beet juice lowers blood pressure: nitrates found in vegetables may protect blood vessels. Available at: http://www.webmd.com/hypertension-high-blood-pressure/news/20080208/beet-juice-lowers-blood-pressure. Accessed May 31, 2012.
Hord NG, Tang Y, Bryan NS. Food sources of nitrates and nitrites: the physiologic context for potential health benefits. Am J Clin Nutr [serial online]. 2009;90:1-10. Available at: http://www.ajcn.org/content/90/1/1.full. Accessed May 31, 2012.
Reif MC. Nitrates and blood pressure. Available at: http://www.netwellness.org/question.cfm/74001.htm. Accessed May 31, 2012.
Warner J. Nitrates lower blood pressure: nutrient found in spinach, other vegetables keeps blood vessels healthy. Available at: http://www.webmd.com/hypertension-high-blood-pressure/news/20061227/nitrates-lower-blood-pressure. Accessed May 31, 2012.
Contributed by Elaine Koontz, RD, LD/N
Review Date 6/12