What Causes Hypertension?

Hypertension, or high blood pressure, is often described as a silent killer, and affects 50 million Americans. Hypertension usually occurs without symptoms, but if your blood pressure gets really high you could develop headache, dizziness, blurred vision, ringing in the ears, or nose bleeds. Most people find out that they have high blood pressure by getting a routine blood pressure check, which can be done in any doctor's office, or which you can do more easily and cheaply by yourself at most pharmacies. If untreated (about 30% of people with high blood pressure don't know they have it) it can quietly damage your organs and set the course for other life-threatening diseases to develop, including stroke, heart disease, and kidney failure.
Hypertension happens when the body holds on to too much water, which increases the volume of blood in our heart, arteries and veins, and therefore increases the pressure against the walls of the heart and blood vessels. Sometimes the heart beats too hard and that too can increase the pressure. Either situation leads to high blood pressure, which over time causes damage to the blood vessels.
Blood pressure is measured in units of millimeters of mercury (mm Hg), which is the amount of atmospheric pressure required to support a column of mercury 1 millimeter high. Blood pressure has a number for systolic and diastolic blood pressure. Your systolic pressure, the pressure in the vessels when the heart beats, should be less than 140 mm Hg. Your diastolic pressure, the pressure in between heart beats, should be less than 90 mm Hg. Like heart disease, hypertension is a disease of modern civilization. Hypertension is a product of the way our bodies have evolved over the centuries to be able to retain water and avoid dehydration. We tend to retain salt (sodium chloride, or NaCl), because, prior to modern times, salt was relatively rare. When salt is retained in our blood vessels, it holds on to water by something called the osmotic effect, and therefore water is not excreted as much as it would be otherwise through the kidneys and into the urine.
Granted, not everyone is sensitive to salt to the same degree. However, there is no doubt that the population as a whole eats much more salt than in the past, probably at least two or three times as much, and these habits are having an adverse effect on our health, including raising blood pressure.
Since early man did not have easy access to salt, he didn't have to worry about eating too many salted potato chips and having his blood pressure go through the roof. In fact, salt retention served an important purpose to early man - it was a good thing if you were living on the savannah and wouldn't be eating or drinking for several hours. It's bad if you live in America in the 21st Century and eat fast food three times a day.
Ancient man also got more exercise, ate less food in general (not by choice), and didn't smoke, take drugs or drink alcohol. However, those tough conditions did lead to more infection; and being eaten by tigers and falling off cliffs were occupational hazards of primitive man. Luckily, these folks didn't have to also worry about their blood pressure zooming up after eating a burger and fries.
Cheeseburgers notwithstanding, our earliest need for salt developed in us a taste for salty foods, which we have never lost. In cooking, salt enhances the flavor of other foods and many cooks feel it is an essential ingredient in the kitchen. Salting your pasta water with a handful of sea salt is not going to cause high blood pressure. Most of the over salting in our system comes from pre-prepared, packaged, and many frozen foods (with the exception of flash frozen fruits and vegetables) we eat, as well as the salt found in restaurant and fast foods. Food makers put huge amounts of salt in their food for flavor enhancement, to hide the lack of other natural flavorings, and to act as a preservative. Look at any food label and you will see astronomical percentages of salt in food - often more than 25% of a serving. The best way to avoid excess sodium in food is to buy fresh, unprocessed whole foods and prepare your own meals. If you buy canned beans and vegetables, low sodium or not, you should rinse them well as this removes about 40% of the sodium.