A randomized clinical study shows that a high intake of plants rich in nitrates lowers 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 nitrate-rich vegetables that protect the heart and the brain
But nitrates/nitrites aren’t just preservatives. These molecules (nitrates, more particularly) are found naturally in a large number of commonly consumed vegetables. Including arugula, spinach, lettuce, beetroot, radish and Chinese cabbage. 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. Following their ingestion, nitrates are rapidly absorbed in the small intestine. They then accumulate in large quantities in the salivary glands. During the secretion of saliva, nitrates are reduced to nitrites by bacteria present in the mouth. Then these nitrites are in turn 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 several phenomena closely associated with the proper functioning of the heart and blood vessels.
A study to measure exactly the benefit of nitrate-rich foods
Hypertension is the main risk factor for cardiovascular disease. A very large number of studies have indeed clearly shown that excessive blood pressure, beyond 130/80 mm Hg, is closely linked to a significant increase in the 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 a high intake of dietary nitrates can promote the dilation of the vessels and thus positively influence the pressure.
A randomized clinical study recently looked into this question. She examined the impact of a diet rich in nitrates in volunteers with hypertension or with prehypertension. That is to say above normal, but just below the threshold of hypertension. In this study, researchers randomly separated pre- or hypertensive (mean 144/87 mm Hg) volunteers into two groups. Either a control group, without modification to their eating habits, and an intervention group in which the participants had to consume 250–300 g of vegetables rich in nitrates every day in order to reach an intake of approximately 350–400 mg of nitrates /day.
A very significant drop in blood pressure in 12 weeks
After a period of 12 weeks, the 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 of a diet enriched with nitrates, the blood pressure of the volunteers had decreased by 7 mm Hg compared to that of the control group.
This difference is significant in terms of impact on the risk of cardiovascular events. Studies show that every decrease of 3 mm Hg in systolic pressure is associated with a reduction of about 11% in the risk of stroke and 6% in the risk of heart attack. The drop in pressure caused by the high consumption of nitrates is therefore highly significant. The increase in nitrate-derived nitric oxide levels and the ensuing vasodilation therefore have concrete effects on blood pressure.
Red fruits also lower blood pressure
It should also be noted that in addition to nitrates, other compounds of plant origin could also stimulate the production of NO: for example, a preclinical study recently showed that the polyphenols of the class of anthocyanins present in colored fruits (small fruits such as blueberries, in particular) interacted with estrogen receptors present on the surface of blood vessels to form NO and induce vasodilation. Whether for their high content of nitrates, polyphenols or other bioactive compounds, fruits and vegetables are truly essential foods for maintaining 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 nitrate-rich vegetable intake lowers ambulatory blood pressure in (pre)hypertensive middle-aged and older adults: a 12-Wk randomized controlled trial. J Nutr. 2021
He FJ et al. Salt reduction in England from 2003 to 2011: its relationship to blood pressure, stroke and ischaemic heart disease mortality. BMJ Open
Calfio C et al. Anthocyanins activate membrane estrogen receptors with nanomolar potencies to elicit a nongenomic vascular response via NO production. J. Am. Heart Assoc.
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