Beat Hypertension with Vegetables
Foods Rich in Nitrates May Reduce Blood Pressure
A recent study has suggested that high nitrate foods may relax blood vessel walls and lower blood pressure.
Most of us are aware of the problems posed, in the West at least, by high blood pressure. It's on the increase and is a major factor in strokes and heart disease. Diet and exercise are rightly regarded as the first line management of hypertension.
Diet is thought to be important for two reasons: firstly because of the protective effect of antioxidants and mono-unsaturated fats on blood vessel walls and secondly, because losing weight lowers blood pressure. But a study by researchers at Barts and the London School of Medicine suggests an extra dimension to the healthy diet theory.
Beetroot Juice Study
In the study, led by Professors Amrita Ahluwalia and Ben Benjamin and published in the February 2008 edition of Hypertension, two groups of healthy volunteers were given beetroot juice to drink. Beetroot, like many vegetables, is high in nitrate. 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 taking blood pressure measurements it was found the the group who had the juice plus saliva showed a significant drop in blood pressure. The non-saliva group showed no such blood pressure reduction.
Here's the interesting bit. Researchers 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.
Nitrite and Blood Pressure.
The body controls blood pressure in mainly two ways. By regulating the pumping of the heart, the force of the blood entering the arteries can be varied: less forceful pumping equals lower blood pressure. The second way is by dilating or constricting the arteries and veins. When the walls of these vessels are relaxed blood flows more easily and pressure comes down.
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 in turn derives from nitrates in food – particularly vegetables.
The Mediterranean Diet
Known to be one of the healthiest diets, those who eat it have lower blood pressures, fewer strokes and heart disease than those on some North European diets for example. This is said to be due to the antioxidants in the fruit and vegetables and the relatively high concentration of protective mono-unsaturated fats like olive oil. However, the study suggests that the nitrate rich vegetables might be a factor.
Saliva may also be important. Vegetables (especially if not over-cooked) require more chewing than processed food and this will lead to more saliva being produced and possibly more nitrite entering the digestive tract and hence a direct effect on blood pressure. Given that saliva also contains enzymes important in digestion, the old instruction to children to chew each mouthful for a minute before swallowing was clearly well founded.
This article is for information only. If you have any concerns regarding your health please consult your doctor.
Resources
Acute blood pressure lowering, vasoprotective and anti-platelet properties of dietary nitrate via bio-conversion to nitrite. A. Ahluwalia et al. Hypertension February 2008
Medicine. Eds. Souhami and Moxham. Pub. Churchill Livingstone 2002
