A randomized clinical study shows that a high intake of plants rich in nitrates reduces blood pressure in hypertensive patients. We already know about nitrates (NO3–) and nitrites (NO2–). They are added to meats to prevent the growth of pathogenic microorganisms, including the dangerous Clostridium botulinum, the causative agent of botulism.
These vegetables rich in nitrates that protect the heart and brain
But nitrates/nitrites are not just preservatives. These molecules (nitrates, in particular) are found naturally in a large number of commonly consumed vegetables. Including arugula, spinach, lettuce, beets, radishes, and bok choy. Studies suggest that a high intake of these plant-based nitrates stimulates the formation of nitric oxide (NO). It is a vasodilator gas that plays several important roles in cardiovascular health.
The mechanism involved is quite complex. After ingestion, nitrates are rapidly absorbed in the small intestine. They then accumulate in large quantities in the salivary glands. During saliva secretion, bacteria present in the mouth reduce nitrates to nitrites. These nitrites in turn are then swallowed and absorbed in the intestine. Circulating nitrites can then be reduced to nitric oxide by various enzymes. They will then provide a positive influence on various phenomena closely related to the proper functioning of the heart and blood vessels.
A study to measure exactly the benefit of foods rich in nitrates
Hypertension is the main risk factor for cardiovascular disease. In fact, a large number of studies have clearly shown that excessive blood pressure, above 130/80 mm Hg, is closely associated with a significantly increased risk of coronary heart disease and stroke. Since nitric oxide (NO) plays an important role in controlling this blood pressure, it is possible that an increase in NO caused by high dietary nitrate intake may promote vessel dilation and thus positively influence pressure.
A randomized clinical trial recently examined this question. examined the impact of a nitrate-rich diet in volunteers with hypertension or prehypertension. That is above normal, but just below the threshold of hypertension. In this study, researchers randomly separated pre- or hypertensive volunteers (mean 144/87 mm Hg) into two groups. Soit un groupe contrôle, sans modification à leurs habitudes alimentarires, et un groupe d’intervention dans lequel les participants devaient consommer chaque jour 250–300 g of legumes riches in nitrates in order to provide a contribution to the environment 350–400 mg of nitrates /day.
A very significant drop in blood pressure in 12 weeks.
After a period of 12 weeks, blood pressure was measured over a period of 24 hours and the values obtained were compared with those measured before the start of the study. The results are unequivocal. After 12 weeks on a nitrate-enriched diet, the volunteers’ blood pressure had decreased by 7 mm Hg compared to the control group.
This difference is important in terms of the impact on the risk of cardiovascular events. Studies show that every 3 mm Hg decrease in systolic pressure is associated with about an 11% reduction in the risk of stroke and a 6% reduction in the risk of heart attack. The pressure drop caused by the high consumption of nitrates is therefore very significant. The increase in the levels of nitric oxide derived from nitrates and the consequent vasodilation therefore have specific effects on blood pressure.
Red berries also lower blood pressure
It should also be noted that, in addition to nitrates, other compounds of plant origin could also stimulate NO production: for example, a recent preclinical study showed that polyphenols of the anthocyanin class present in colored fruits (small fruits such as blueberries, in particular) interacted with estrogen receptors on the surface of blood vessels to form NO and induce vasodilation. Whether due to their high content of nitrates, polyphenols or other bioactive compounds, fruits and vegetables are really essential foods to maintain good cardiovascular health.
Lundberg JO et al. Cardioprotective effects of vegetables: is nitrate the answer? Nitric Oxide 2006;15
Van der Avoort CMT et al. Increasing the intake of nitrate-rich vegetables reduces ambulatory blood pressure in middle-aged and older (pre)hypertensive adults: a 12-week randomized controlled trial. J Nutr. 2021
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