High blood pressure (Hypertension); is defined as a systolic (upper) blood pressure of 140 mmHg or more and a diastolic (lower) blood pressure of 90 mmHg or more on 3 separate occasions. Hypertension increases the risk of stroke, heart attack, angina, heart failure, kidney disease, dementia (poor memory) and death (see Figure 1). Furthermore, hypertension accounts for almost 8 million deaths world-wide annually. In addition, the prevalence of hypertension increases with age for example, 1 in 10 people in their 30s will have hypertension in comparison to 1 in 2 in their 60s. However, people who take more vegetables or limit their salt intake have no increase in their blood pressure throughout their life-time.
What causes hypertension?
Ninety five percent cases of hypertension have no underlying cause and are known to have essential hypertension. The remaining 5% cases have an underlying cause for example a thyroid growth, adrenal growth etc, which in most cases is curable through surgery or medications with the resulting resolution of hypertension.
What contributes towards hypertension?
The answer to this question in a single word is ‘salt’. The common ‘table salt’ contains sodium chloride. There is robust evidence that links high salt intake to hypertension. More salt intake causes the concentration of our plasma within the blood vessels to increase. This results in more water reabsorption by the kidneys to allow dilution of the plasma volume. As the plasma volume expands (due to more water) it exerts more pressure on the blood vessels and in consequence, the blood pressure increases. Furthermore, age-related changes in the blood vessels make them more ‘stiff’ and therefore this also contributes towards hypertension.
What can I do to prevent hypertension?
The two most effective and evidence-based interventions for lowering blood pressure are sodium restriction and weight reduction. Weight reduction, particularly abdominal fat, helps in the compliance and elasticity of our blood vessels and thus helps in controlling blood pressure. In addition, sodium restriction allows less salt in the blood stream and this leads to less water reabsorption by the kidneys and helps in blood pressure control. A healthy diet, which includes generous proportion of vegetables, fruit and less salt leads to on an average 10% decrease in the systolic blood pressure. For a large number of patients, this decrease is enough to get them off blood pressure medication and minimise hypertension-mediated cardiovascular adverse effects. The UK’s Scientific Advisory Committee on Nutrition (SACN) advises in general a total salt intake of up to 4 grams per day (1.6 grams of sodium) which is equivalent to almost half a teaspoon.
What can I do to restrict my salt intake?
Quite simply, eat poultry, fish, nuts and pulses instead of red meat (see Figure 2). Also consume dairy products made of low-fat and non-fat sources. Encourage yourself to have vegetables and fruits instead of snacks and desserts. It is advisable to use polyunsaturated and monounsaturated cooking oils for example, olive oil, canola oil, corn oil, soybean oil, sunflower oil in place of butter, coconut oil or palm-kernel oil. One should limit the consumption of canned or processed food and not to have more than one meal a week in a restaurant. It is best never to skip meals and also to divide the daily intake such that one-third of the daily calories is ingested at breakfast. Moreover, regular exercise, up to 2.5 hours a week is strongly encouraged.
Figure 1: Main Complications of Hypertension
Figure 2: The Healthy Diet Pyramid.
The food at the top of the pyramid should be consumed less in comparison to the food at the base of the pyramid.