Hypertension is defined as a mean resting arterial pressure of 140/90 mm Hg or higher and/or current use of antihypertensive drugs.
It is the most common public health problem in developed countries.
Often referred to as the “silent killer”, as affected individuals may be asymptomatic for many years and then suffer a fatal heart attack, it is a major risk factor for developing coronary artery disease, myocardial infarction, heart failure, stroke, and a leading cause of morbidity and mortality. However, among the risk factors for cardiovascular disease, it is the most modifiable.
It is often classified as primary or essential hypertension and secondary hypertension.
Primary hypertension, responsible for about 95 percent of cases, is probably the consequence of environmental factors, genetic factors, and their interaction. Among the environmental factors, diet plays a central role. Among the genetic factors, interest has focused on factors influencing the blood pressure response to salt intake, and several genotypes have been identified, many of which influence the renin-angiotensin-aldosterone system or renal salt handling.
Secondary hypertension is due to other diseases, usually endocrine, such as hyperthyroidism, hyperaldosteronism, and Cushing’s syndrome.
- Blood pressure levels and cardiovascular diseases
- Age-related hypertension
- Hypertension and childhood
- How to prevent hypertension
Above-optimal blood pressure levels, not yet in the hypertensive or prehypertensive range, confers an increased risk of cardiovascular disease, as shown by the fact that nearly one-third of blood pressure-related deaths from coronary heart disease are estimated to occur in non-hypertensive individuals with systolic blood pressure of 120-139 mm Hg, or diastolic blood pressure of 80-89 mm Hg. This means that the risk of cardiovascular disease increases throughout the blood pressure range, starting from 115/75 mm Hg.
|Category||Blood pressure (mm Hg)|
|Optimal||< 120||< 80|
|Normal||< 130||< 85|
|Normal Hight||130 – 139||85 – 89|
|Grade 1 hypertension||140 – 159||90 – 99|
|Grade 2 hypertension||160 – 179||100 – 109|
|Grade 3 hypertension||≥180||≥110|
|Isolated systolic hypertension||≥140||≤ 90|
Finally, pre-hypertensive individuals have a high risk, about 90%, of developing hypertension over time, although the transition is not inevitable.
The prevalence of hypertension increases with increasing age, as shown by the fact that more than half of the adult population over 60 years old is hypertensive.
Age-related risk is a function of variables such as weight gain, low physical activity, excessive use of salt, fats and saturated fatty acids, alcohol, hypercholesterolemia, and low intake of fruits and vegetables, rather than of aging per se. For example, studies of vegetarians living in industrialized countries have shown that such dietary habits are associated with a lower increase in blood pressure with increasing age, and with a markedly lower blood pressure compared to non-vegetarians.
According to a study conducted by a team of researchers from Johns Hopkins University, prevention of hypertension starts in childhood.
Furthermore, a meta-analysis on studies from diverse populations, studies published between January 1970 and July 2006, have examined the tracking of blood pressure from childhood to adulthood showing that childhood blood pressure is associated with blood pressure in later life, and that a high values in childhood are likely to help predict hypertension in adulthood.
Finally, other studies have also shown that increased blood pressure among children is related to the growing obesity epidemic.
A downward trend in blood pressure has been documented in the USA over the last two decades, and the adoption of healthy lifestyle have contributed to this trend.
Lifestyle modifications that effectively lower blood pressure are:
- reduce the intake of salt and other forms of sodium;
- follow a diet rich in fresh fruit, vegetables, complex carbohydrates and low-fat dairy products;
- increase potassium intake by consuming fruit, vegetables and legumes;
- lose body weight if overweight, or prevent weight gain among those who are thin;
- increase physical activity of low or moderate intensity;
- stop smoking;
These changes are the first line of defense in preventing high blood pressure, and need not be made one at a time: the best results are achieved when they occur simultaneously, as demonstrated by two studies in which multicomponent interventions lowered blood pressure in hypertensive and nonhypertensive individuals.
Finally, it has been demonstrated that there is also a relationship between alcohol and hypertension.
Potassium, an essential nutrient for humans, is the most abundant cation in intracellular fluids. It is therefore widely distributed in foods that come from living tissues, both animal and vegetable, but which have not undergone salting and/or drying. Cooking methods tend to lower the amount of potassium, as well.
Considering vegetables, the worst cooking method is boiling in plenty of water, for more than an hour, whereas the best is microwave cooking.
|>250 mg/100 g|
|Legumes||Dried legumes, such as chickpeas, beans, lentils, peas, and soybeans, and fresh beans.|
|Vegetables||Garlic, chard, cauliflower, cabbage, Brussels sprouts, broccoli, artichokes, cardoons, fennel, mushrooms, potatoes, tomatoes, spinach, zucchini.|
|Fruits||Avocados, apricots, bananas, fresh and dried chestnuts, watermelon, kiwi, melon, hazelnuts.|
|Dried fruits||Apricots, dates, figs, prunes, raisins, peanuts, almonds, walnuts, pine nuts, pistachios.|
|Dairy products||Milk powder (high in sodium).|
|150-250 mg/100 g|
|Fresh legumes||Green beans, broad beans, peas.|
|Vegetables||Asparagus, beets, carrots, chicory, endive, lettuce, peppers, tomatoes, leeks, radishes, celery, tomato and carrot juice, pumpkin.|
|Fruits||Pineapple, oranges, raspberries, blueberries, loquats, pears, peaches, grapefruit, grapes.|
|Meat||Meat and fish products, both fresh and preserved; the latter should be avoided because of their high sodium content.|
A high dietary potassium intake and blood pressure are inversely correlated, as demonstrated by animal studies, observational epidemiological studies, clinical trials, controlled feeding studies, such as the DASH Study and the OmniHeart trial, and meta-analysis. Furthermore, a high potassium intake also increases urinary sodium excretion.
The optimal strategy for increasing potassium intake is to consume foods naturally rich in the mineral, such as seasonal fruit and vegetables, and legumes, typical foods of the Mediterranean diet. It is therefore not difficult to reach the recommended daily intake, for the healthy population, equal to 4.7 g per day.
Sodium is the most abundant cation in extracellular fluids, of which it strongly affects the osmotic pressure values.
There are three main source of sodium.
The most intuitive source is table salt, which represents up to 20 percent of the daily intake. It is important to note the terms salt and sodium are often used interchangeably, but this is incorrect. On a weight basis, salt is 40 percent sodium and 60 percent chlorine.
A second source is salt or sodium compounds added during food preparation or processing. Between 35 to 80 percent of the daily sodium intake comes from processed foods such as:
- processed, smoked or cured meat and fish;
- meat extracts, savory snacks, soy and hot sauce;
- pre-package frozen foods;
- canned soups and legumes;
- cheeses, especially long-ripened cheeses.
There are also many sodium-based food additives, often used as preservatives and flavour enhancers.
The third source is negligible, namely, the sodium naturally present in foods, generally low in fresh foods.
A high sodium intake contributes to the increase in blood pressure and the development of hypertension. This is supported by many epidemiological, animal, and migration studies, and meta-analysis, with the final evidence coming from carefully controlled dose-response studies. Furthermore, in primitive societies, where sodium intake is very low, people rarely develop hypertension, and blood pressure does not increase with increasing age.
Therefore, a reduction in sodium intake is recommended to prevent the development of hypertension. In view of the available food supply and the high daily sodium intake, a reasonable recommendation may be to limit its intake to 2.3 g per day, equal to 5.8 g per day of salt. How can this level be achieved?
- Using as little salt as possible when preparing food.
- Avoiding adding salt at the table.
- Avoiding highly salted, processed foods.
Clinical studies have documented that a reduced sodium intake is able to lower blood pressure even the setting of antihypertensive therapy, and can facilitate hypertension control.
Some components of the diet may modify the blood pressure response to sodium. A high dietary intake of foods rich in potassium and calcium may prevent or attenuate the increase in blood pressure for a given increase in sodium intake. Conversely, some data, mainly observed in animal models, suggest that a high sucrose intake could enhance salt sensitivity of blood pressure.
Note: high sodium intakes may contribute to the development of osteoporosis by increasing renal calcium excretion, particularly if daily calcium intake is low.
Body weight, especially overweight and obesity, is a determinant of blood pressure at any age. Indeed:
- it has been estimated that the risk of developing high blood pressure is two to six times greater in overweight people than in normal weight people;
- there is a linear correlation between blood pressure and body weight or body mass index, which, if greater than 27, correlates with an increase in blood pressure;
- even when sodium intake is held constant, the correlation between change in weight and change in blood pressure is linear;
- 60 percent of hypertensive subjects are more than 20 percent overweight;
- the central distribution of body fat, as a determinant of blood pressure, with a waist circumference greater than 88 cm in women and 102 in men, is more important than the peripheral distribution of fat, both in men and women;
- weight loss, in both hypertensive and normotensive subjects, may reduce blood pressure, and the reduction occurs before, and without, achieving a desirable body weight.
Physical activity produces a drop in systolic and diastolic blood pressure. Therefore, for the primary prevention of hypertension, it is important to increase physical activity of low or moderate intensity for 30-45 minutes 3-4 times a week up to an hour most days, as recommended by the World Health Organization. Conversely, less active people are 30 to 50 percent more likely to develop hypertension than active people.
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