A randomized clinical trial shows that a high intake of plants rich in nitrates lowers blood pressure in hypertensive patients. We already know something about nitrates (NO3-) and nitrites (NO2-). They are added to meat 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 brain
But nitrates/nitrites are not just preservatives. These molecules (particularly nitrates) occur naturally in many commonly consumed vegetables. Including arugula, spinach, lettuce, beetroot, radish and Chinese cabbage. Studies suggest that a high intake of these plant 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 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, in turn, these nitrites are swallowed and absorbed in the gut. Circulating nitrites can then be reduced to nitric oxide by various enzymes. They will then have a positive influence on various phenomena that are closely related to the proper functioning of the heart and blood vessels.
A study to precisely measure the benefit of nitrate-rich foods
Hypertension is the main risk factor for cardiovascular disease. Indeed, a very large number of studies have clearly shown that hypertension, above 130/80 mm Hg, is closely associated with 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 may promote the dilation of blood vessels and thus positively influence the pressure.
A randomized clinical trial recently explored this question. She investigated the impact of a nitrate-rich diet in volunteers with hypertension or with prehypertension. That is, 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 of their eating habits, and an intervention group in which the participants had to consume 250-300 g of nitrate-rich vegetables every day to achieve an intake of about 350-400 mg nitrate/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 of a nitrate-enriched diet, the blood pressure of the volunteers had fallen by 7 mm Hg compared to that of the control group.
This difference is important in terms of impact on cardiovascular event risk. Studies show that each reduction in systolic pressure by 3 mm Hg is associated with a reduction of approximately 11% in the risk of stroke and 6% in the risk of heart attack. The pressure drop caused by the high consumption of nitrates is therefore very significant. The increase in nitrate concentrations of nitric oxide and the resulting vasodilation thus have concrete effects on blood pressure.
Red fruit also lowers blood pressure
It should also be noted that, in addition to nitrates, other compounds of plant origin can 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 in particular) interacted with estrogen receptors present on the surface of blood vessels to form NO and induce vasodilation. Whether for their high levels 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-week randomized controlled trial. J Nutr. 2021
He FJ et al. Salt reduction in England from 2003 to 2011: the relationship with blood pressure, stroke and death from ischemic heart disease. BMJ Open
Calfio C et al. Anthocyanins activate membrane estrogen receptors with nanomolar potencies to elicit a non-genomic vascular response via NO production. J. Am. Hart Assoc.
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