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Nitrate–rich foods

Nitrates present in foods can lower blood pressure. Nitrates are essential plant nutrients found in soil that are taken up by plants and used as their primary nitrogen source. They are a natural part of all vegetables, fruits and cereals. On the other hand, nitrite, is a chemical within the body produced by the digestion of nitrate–containig foods.

Nitrates may have a role in controlling blood pressure by maintaining the health of blood vessels. A short–term study involving 17, non–smoking and healthy young adults, observed the effects of nitrate supplement on the participants. Each person was given a daily dose of nitrate supplement that equalled the amount found in 150–250 grams of vegetables rich in nitrate (lettuce, spinach, beetroot). The study subjects were asked to take the supplement for three days, and then take a daily placebo during three different days. The results of the study concluded that although the nitrate supplement did not reduce the systolic BP, it lowered diastolic blood pressure by an average of 3.7 mm Hg.

Foods high in nitrates include Lettuce, Spinach, Cabbage, Beets, Radishes and Carrots. Nitrate can also be found in the air, water; it is also a preservative found in foods including cheese, processed meats, and fish, as well as in spirits and liqueurs.

In an earlier study, led by Professors Amrita Ahluwalia and Ben Benjamin and published in the February 2008 issue of Hypertension, two groups of healthy volunteers were given beetroot juice 500 ml (high in nitrates) to drink. The first group swallowed their saliva with the juice whereas the second group refrained from swallowing their saliva whilst drinking and for 3 hours afterwards. On measuring blood pressure, it was found that the group who had taken juice plus saliva showed a significant drop in blood pressure. The non–saliva group showed no such reduction. The study found a relationship between blood nitrite levels and lowered blood pressure in the juice plus saliva group and no rise in nitrite levels in the other group. In the first group the bacteria on the tongue converted the nitrate in the juice to nitrite which was then washed into the stomach by the saliva. In the second group, very little nitrite would have entered the stomach.

Nitric oxide is a chemical messenger produced by the walls of blood vessels and has the effect of relaxing the vessels and therefore lowering blood pressure. The body makes nitric oxide from nitrite which is derived from nitrates in food, particularly vegetables.

Dr KK Aggarwal
Editor in Chief