Blood pressure fluctuates ordinarily for short periods each day. But if it stays up it's a major risk for heart disease, stroke, and kidney disease. High blood pressure is all the more insidious because it's a silent killer; it produces no overt symptoms, at least when it is in the initial moderate stages. Current estimates are that 40 percent of the adult population may suffer from high blood pressure. At least half that number may be undiagnosed and untreated.
What is high blood pressure? The first number refers to systolic blood pressure. While initially thought to be less important than diastolic blood pressure (which should always be less than or equal to 90), its significance is becoming better appreciated. One study showed higher incidence of memory deficits in older individuals correlated with systolic blood pressure above 140.
If we look at the issue scientifically, hypertension or high blood pressure is not in itself an illness. Somewhere along the line ingenious medical researchers developed a method for assessing the internal blood pressure of arteries in the arm and medicine now equates these rather arbitrary numbers with critical health outcomes; low blood pressure makes you feel woozy, medium blood pressure makes you feel just right and safeguards your health; and high blood pressure puts you at risk for disease.
One of the difficulties of getting a meaningful reading is that blood pressures can change drastically, even when you're at rest, especially in response to anxiety or even mild emotional stress. Hence the term "white coat syndrome" in persons whose blood pressure rises whenever they are in a doctor's office. This extreme sensitivity to environment and expectations means that a single blood pressure reading does not tell us too much in and of itself. A diagnosis of hypertension can't really be made until a series of readings are performed on different days.
Unfortunately, research shows that blood pressure medication is often instituted without adequate rechecking. If a doctor suspects "white coat syndrome," you may need to learn how to take readings at home, under "low pressure" conditions. Simple home blood pressure monitors, some that inflate automatically, facilitate blood pressure self-care. If I'm getting high readings from a patient in my office, I'll definitely get them to confirm these readings in a more relaxed setting.
There's another option if you feel that the stress of the doctor's office or clinic environment may be affecting your blood pressure readings, or if you want to confirm that several high readings are really telling you something. This is called ambulatory blood pressure monitoring, and it enables you to find out what your blood pressure is over the course of a day, as you go about your normal activities. You may discover that you do have some peaks of high blood pressure a few times a day, and you've been diagnosed with high blood pressure on the basis of those peaks, which might just happen to occur in stressful situations like your visit to the doctor's office. And the rest of the time your blood pressure is normal or low. Unfortunately, ambulatory monitoring has not been very well reimbursed by health insurance, though it probably should be, given the wild variations that can occur in a spot-check of blood pressure.
What causes high blood pressure? Well, the frustrating answer is that most cases are classified as "essential hypertension," the fancy medical term for hypertension that has no known triggers. In fact, there are a probably a complex array of causes including genetic factors, stress, sodium intake, environmental pollution, excess production of insulin, overweight and other specific nutritional factors. All these factors may operate simultaneously in a given individual or only one or two may account for that person's high blood pressure. Patients with hypertension come in all shapes and sizes: some are thin, some are overweight, some ostensibly relaxed, others nervous. Some have family histories of high blood pressure and others do not.
There are also misconceptions as to the major reasons for high blood pressure. It is commonly supposed that the most appropriate dietary intervention for lowering blood pressure is salt restriction. For many this means avoiding the salt shaker, but studies show that the sodium in one's diet comes mostly from foods that are already laden with salt. In fact, only 12-15 percent of the sodium in the diet comes from salt added at meal time. Additionally many people respond little if at all to sodium restriction. Others very clearly do. The reason for this may be differences in historical circumstances where some populations seem to acclimate to high salt intakes. This seems more likely to be the case in certain parts of Europe where salt has been used for millennia as a valuable commodity designed to help preserve food. The situation is reversed in traditional African cultures, especially in landlocked regions where gold was gladly traded for salt until the late 19th century. This may be part of the reason why African-Americans have a genetic susceptibility to salt intake.
Actually, an even more key factor in the development of high pressure may be the circulating level of insulin. In patients who suffer from carbohydrate craving associated with high cholesterol and triglycerides, particularly with features of diabetes, high blood pressure can be reduced by minimizing carbohydrate intake. Hence, subtract the salt shaker, but also basta on the pasta, and hold the Hostess Twinkies.
Does this mean that a low saturated fat has nothing to do with keeping blood pressure down? The surprising answer is that a high meat diet laden with saturated fat may indirectly contribute to insulin resistance by clogging cell receptors that determine insulin sensitivity. It is as if all those saturated fats may "glom up" the cellular machinery and initiate a vicious cycle of insulin overproduction, weight gain and subsequent carbohydrate craving which may in turn lead to high blood pressure and diabetes.
This is the so-called Syndrome X theory which predicts that carbohydrate restriction will help a certain subset of hypertensives, especially those with elevated "waist to hip ratios." (Calculate this by simply measuring the circumference of your waist and the circumference of your hips and dividing the waist circumference by the hip circumference. If the result is greater than .8 in a female, you may be prone to Syndrome X. The solution to Syndrome X is to take nutrients like fish oil, chromium and magnesium and to adopt a diet relatively low in saturated fat as well as moderate in carbohydrates.
Other nutrients that can help high blood pressure include calcium, magnesium and potassium. A recent study showed that 1200 to 1500 mg calcium daily could reduce high blood pressure associated with pregnancy in women prone to a dangerous condition called pre-eclampsia. Potassium, too, seems to play a role in lowering blood pressure, particularly in African-Americans. Magnesium has such a profound blood pressure lowering effect that patients given high doses of magnesium by IV sometimes complain of low blood pressure and temporary wooziness. It's interesting to note that a low-fat vegetarian diet is inherently high in magnesium and potassium and low in sodium. In green plants every chlorophyll molecule has a core of magnesium just has every hemoglobin molecule has a core of iron in animals, so green vegetables inherently deliver a lot of magnesium. Plant foods also have a much higher potassium to sodium ratio than animal foods (including dairy products), so vegan diets sometimes do the trick for people with high blood pressure.
Exercise, too, plays a role in lowering blood pressure. When aerobic exercise or strength training is performed, blood pressure temporarily goes up but then recedes back to normal the way your pulse rate increases with exertion, then settles back down to a slow rate. A recent study looking at African American hypertensives showed that forty minutes daily of stationary bike exercise could reverse even moderately severe high blood pressure.
Stress, also, plays a role in high blood pressure. One of the difficulties of getting a meaningful blood pressure reading is that blood pressure can change drastically, especially in response to anxiety or mild emotional stress. Hence the white coat syndrome, affecting the person whose blood pressure rises when they're actually having their blood pressure measured by a professional in a white coat. People with wide fluctuations in their blood pressure depending on their emotional state may be "hot responders," and deserve consideration for stress reduction measures such as biofeedback, yoga, and meditation. A recent study of hypertensives in Oakland, California, showed that use of daily transcendental meditation could produce significant reductions in blood pressure.
I generally reserve medications for only the most challenging patients or for those unwilling to go through the complex lifestyle adjustments that may be necessary to overcome their tendency towards high blood pressure. New medications abound but most cause side effects. Simply providing hypertensives with a quick drug fix deters them from making necessary healthy adjustments in diet, exercise and stress coping. Foregoing the drug route, at least temporarily, preserves the impetus for constructive change. Thus blood pressure can be looked at as a barometer of degenerative tendencies whose sources we can identify and eliminate.