If you have a lot of stress in your life, so that your arterioles are constricting all the time, this can go one stage further. You can wind up with a permanent or fixed partial constriction of the arterioles, which will again make the blood flow slower, reducing the fall in pressure when the heart relaxes—and giving you a permanently high diastolic pressure.

People who have a lot of stress in their lives over long periods of time end up with hearts that are pumping more forcefully to push blood through the closed-down or constricted arterioles, a greater volume of blood in the system, and both high systolic and diastolic pressures.

The thing that really makes high blood pressure stay around, that sustains it and makes it chronic, is having a very particular abnormality, a very special problem with the kidneys. That's the key to most forms of hypertension.

Most people who have high blood pressure have kidneys that work just fine handling calcium, phosphorus, urea, amino acids, glucose, potassium, and most of the rest. And your doctor will likely tell you, on the basis of the tests that he runs, that your kidneys are just fine. There's only one thing wrong.

If you have hypertension, or a family history of hypertension, it probably means that you have inherited a pair of kidneys that can't handle the amount of salt that's in the foods you eat. Don't get me wrong. You may have perfectly fine kidneys in all other respects. They're just not adapted to the amount of salt in the typical Western diet.

By the time we are adults, most of us are eating ten to twelve grams of sodium chloride—salt—a day. That's a huge amount! The kidneys were designed to deal with maybe a tenth of that amount. Remember that early man grew up in Central Africa, where salt is rare and fresh food is available year round!

The quantities of salt we actually eat are a great burden on our systems. It's so destructive. As we eat more salt than the kidneys can readily excrete, over a long period of time, many years, salt builds up in the body. Now salt is so toxic that, in order for the body to tolerate it, it must be diluted in water. So the body begins to retain water as well, also in the kidneys.

When we say you're holding on to excess salt, what we really mean is that you're holding on to water as well. By the time you're an adult you may be walking around with five or ten pounds of extra water on your person, water that's only there to keep that salt diluted.

What does all this have to do with blood pressure?

Well, it turns out that pressure is a very powerful diuretic (force or substance that increases sodium excretion by the kidneys), perhaps the most powerful one of all.

When we are young and eat excess salt, our body fluids increase, and they suppress those factors that tend to cause sodium retention and enhance those factors that tend to cause sodium excretion. So we dump the salt pretty easily.

As we grow older this mechanism works less and less well, presumably because the kidneys become injured or altered in some way. Maximally suppressed sodium-retaining factors and enhanced sodium- excreting factors no longer do the job. So to stabilize the situation, and make it possible once again to excrete completely a high-sodium dietary intake, our blood pressure rises.

The body's way to get rid of more of that salt and water is to push it out through the kidneys by raising the blood pressure.

Do you realize that nearly every bit of salt you eat every day is excreted by the kidneys? If your kidneys were able to handle all that salt easily, your body wouldn't have to go to the trouble of raising your blood pressure to get rid of it. But the kidneys weren't designed to handle that much salt, so the blood pressure goes up. And that's why diuretic drugs bring the blood pressure down in some cases—they force the kidneys to excrete more salt and water, and the blood pressure drops because the diuretics are now doing the trick. I’ll let you in on a secret: eating less salt is a much simpler way of going about it.

If you have hypertension, your kidneys are probably the kind that has trouble excreting salt. Maybe you inherited this tendency. Or you injured them by eating too much salt or protein. They may get that way as a result of some kidney disease such as nephritis or Bright's disease. Or you may have simply lost one of your kidneys, perhaps in an accident or by donating it to a relative for transplantation. We used to think that anyone who didn't already show signs of having high blood pressure could safely donate a kidney to someone who needed one. But it doesn't look quite that safe anymore. We are beginning to realize that over time most everyone's kidneys become unable to cope with large amounts of salt—and that people who have only one kidney are simply hurrying that process up. Let's put it this way; if you eat the amount of salt that most of us do for long enough, your kidneys will probably lose their ability to excrete it normally. There's at least a two out of three chance that it will eventually happen. Some people just don't reach that point as fast as others. With a favorable family history and no kidney-related problems, you might not get high blood pressure until you are seventy or eighty. By that age 90% of us have it. But with kidney disease, or a family history of high blood pressure, it may happen a lot sooner. It happens to children. It happens to adolescents. It happens to young adults. It happens to most of us, sooner or later, if we eat salt.

No doubt about it, there's a close relationship between being over weight and having high blood pressure. Not everyone by any means, but most obese people have higher blood pressures than they would if they weren't obese and obese people are more likely to have hypertension (blood pressure of 140/90 or above). And this relationship between weight/obesity and blood pressure starts in childhood.

One explanation is that it takes more pressure to pump blood through that extra fatty tissue. The basal metabolic rate of people who are overweight is higher because they have more cells and more tissue that need oxygen—so their heart rates are faster, and their heat production and cardiac output are greater, than those of other people; yet their blood vessels are about the same size. Thus an increased flow through their vessels may require a higher pressure to accomplish it. Such people also have a higher level of sympathetic (emergency) nervous system hormones—the material is presented in a paper in Hypertension (1982)—and these hormones may also cause a rise in blood pressure. Probably both these reasons contribute to the relationship between obesity and high blood pressure—but, for whatever reasons, your blood pressure will sure get better when you lose those extra pounds!

There's another way of setting yourself up for high blood pressure that I'd like to mention. And, again, it has to do with the kidneys, and it's preventable.

If you take birth control pills or the estrogens that are prescribed to relieve the symptoms of menopause, you are stimulating the liver to make a substance that an enzyme (rennin) made by the kidneys works on to produce a hormone (angiotensin) that raises blood pressure. Not only that, angiotensin also reduces the flow of blood in the kidney, making it harder for you to excrete the salt you eat. You might say that taking those pills was equivalent to giving yourself the kidney factor.

Dr. Norman Hollenberg wrote the classic paper on this, in Circulation Research (1976). He studied women who were being considered as possible kidney donors, for transplants, and he found that kidney blood flow in the women who were using birth control pills was significantly lower than in those who were not. Nearly everyone who takes birth control pills will experience a rise in blood pressure if she takes them long enough. Some women will get hypertension, some of them severe hypertension, some of them malignant hypertension. But everyone will experience some rise in blood pressure. It's that simple. The relevant papers are by Dr. N. M. Kaplan, in the Annual Review of Medicine (1978), and Drs. I. R. Fisch and J. Frank, in the Journal of the American Medical Association (1977).

Millions upon millions of women started taking these pills in the late fifties and early sixties, and it took years to start seeing problems. Reducing the dose of hormone in each pill has prevented an epidemic of high blood pressure in young women. Now that was smart!

About one in a thousand people may get a blockage in the artery leading to the kidneys at some point in their lives, and that can cause high blood pressure too. The problem is very rare and can be dealt with pretty easily when it crops up. A few people have tumors of the kidney or the adrenal glands, which can also cause high blood pressure. But these problems are usually pretty obvious to the doctor taking care of you.

To sum up: ninety-five percent of people who have high blood pressure have it for one or more of five causes: salt, chronic stress, excess weight, loss of the kidneys' ability to handle salt, and time. Usually it’s all of the above.

And salt is the worst of these.

With or without hereditary disposition, salt will get you in the long run. And with or without that same hereditary factor, a salt-free diet will work wonders.

Isn't it worth it?

I've heard that the lower your blood pressures, the better off you are. Is that true? I take medicine, but my diastolic pressure doesn't get below 90. Should I take more medications, the way my doctor wants me to?

I agree with your doctor that a diastolic pressure of 80 is better than one of 90. It means you're less likely to suffer from cardiovascular disease, heart attack or stroke—and I'm all for that. So I'd like to get your diastolic pressure down below 90 too. The question is, how do we do it?

Basically, drugs don't seem to be the way to go. Dr. Norman Kaplan, the noted author and chief of the Hypertension Division at the University of Texas in Dallas, puts it this way: "The wider acceptance of a more cautious, conservative approach toward drug therapy in general seems warranted, even though it will fly in the face of current dogma and practice."

Writing in the Journal of the American Medical Association (1996), Dr. Kaplan reviewed the evidence for and against treating the 30 to 40million people in the United States who have mild hypertension with drugs. Acknowledging that hypertension "experts" and pharmaceutical advertisements have been pushing hard for "early and aggressive" drug treatment of mild hypertension, he injected a word of caution.

Because he is such a leader in the field, and a scientist whose opinion most physicians would respect, I want to share with you some of his recommendations, which are similar to my own.

After suggesting that everyone with high blood pressure should be carefully monitored, he went on to talk about people who, in addition to elevated blood pressure, have other heart disease risk factors— such as smoking, obesity, blood cholesterol greater than 200, high stress, positive family history, sedentary lifestyle, and physical deconditioning.

Dr. Kaplan suggested that these risk factors should all be attended to and that aggressive treatment of high blood pressure was warranted in the case of this group—to bring the blood pressure down by any means available.

And he concluded, "All patients, regardless of risk status, should be offered and strongly encouraged to follow non-drug therapies that are likely to help—weight reduction for the obese, moderate sodium restriction for all, and one or other relaxation techniques for those willing to use them."

Every time I go see my doctor, whether I've been taking my pills or not, my blood pressure seems to be high, and he seems to worry about it. I just can't believe it's that high all the time. I even checked it at home a few times, and it wasn't that high. It's getting where I'm worried every time I go see him. I'm afraid he's going to shake his head at me and write out another prescription.

I know exactly what you mean. A lot of my patients tell me the same thing. And I tell them not to worry so much. Round-the-clock blood pressure measurements have shown that people's blood pressure is often higher when they go to see their doctors. And in some cases the differences can be extreme. If you or your doctor wants to read the details, there are articles about this in the Journal of the American Medical Association (1982 and 1983) and the Lancet (1981). Your pressure can vary a lot just as a result of how you feel about having it measured—and who's doing the measuring. It's not uncommon, for instance, for patients to feel menacing, while nurses are more sympathetic, more "on their side." For myself, I almost always take my patients' pressure once, say, "That's not bad," or something reassuring of the sort, and then take the pressure again. And it's usually lower the second time around!

Joanne and I go back several years. She was already on a good diet, worked out at a gym, practiced TM (Transcendental Meditation)—what more was there to do?

Well, I couldn't get her to take a look at her own blood pressure. She'd even miss appointments, just so she wouldn't have to find out what her blood pressure was. She couldn't face all that worry building up inside, before I told her, "It's not so bad, 180/105," or something like that. In fact she actually stayed away a whole year at one point. She kept on taking her medicines. But she just didn't want to get her blood pressure checked.

Finally she relented. She came back and started taking her pressures at home this time—and turned the whole thing around. She's off medicines completely now. And I know that what finally solved the problem for her was her own willingness to take responsibility for her blood pressure and her body.