New facts behind five old health ‘truths’

The key to good health is keeping an open mind – a willingness to discard the basic medical truths you hold to be self-evident when you find they’re not-so-evident after all, says Mark Beers, M.A., editor of the Merck Manual, the oldest continuously published medical reference book. It’s first edition, 104 years ago, recommended smoking tobacco to treat bronchitis and asthma!

In the past few years, recent scientific evidence has prompted experts to rethink accepted wisdom. Today’s column will discuss four widely held medical assumptions which have recently been revised.

Diastolic Is More Important Than Systolic Blood Pressure

Until a few years ago, physicians diagnosed hypertension by looking primarily at diastolic blood pressure, the lower number, which reflects pressure in the arteries as the heart relaxes between beats. A diastolic reading of 90 millimeters of mercury (mmHg) or higher signifies hypertension. Doctors paid much less attention to systolic pressure – the upper number, which measures pressure as the heart contracts – mainly because they assumed it was normal for that number to rise with age.

The standard line previously was that an appropriate systolic reading was 100 plus your age. As a result, doctors would often let systolic pressure creep progressively higher, as long as the diastolic pressure stayed low. It’s now known that this is plainly wrong.

The downplaying of systolic blood pressure was particularly unfortunate for two reasons. First, several large studies over the past decade have shown that in the middle-aged and older people, systolic pressure actually predicts the complications of hypertension better than diastolic pressure does. Second, systolic elevations are far more common than diastolic elevations, particularly in middle-aged and older people, so legions of hypertensive individuals went undiagnosed and untreated. For example, results from the Framingham Heart Study found that looking just at the diastolic pressure would identify only 22 percent of those who need antihypertensive drugs.

Fortunately, a new advisory emphasizes that systolic pressure is at least as important as diastolic. Physicians are advised to consider anything over 140 mmHg of systolic pressure or 90 mmHg of diastolic pressure as hypertension, whether or not the other number is elevated.

Eating Foods High In Calcium Causes Kidney Stones

Most kidney stones – tiny pebbles that form in the kidney and cause intense pain when they get stuck in the urinary tubes – consist of calcium plus oxalate, a substance found in nearly all fruits, vegetables, and grains. So the long-standing belief that people susceptible to stones should avoid calcium-rich foods seems sensible. But two recent Harvard studies indicate that, if anything, dietary calcium may actually reduce the risk of kidney stones.

The reason, laboratory research suggests, is that calcium in the diet blocks absorption of oxalates from food. So people with a history of kidney stones are now told to cut back on oxalate-rich foods – notably peanuts, spinach and rhubarb, and make sure they consume enough dietary calcium.

However, one of the studies found that supplemental calcium did slightly increase the risk of kidney stones. The reason, researchers suspect, is that people generally don’t take supplements with meals, thus preventing the calcium from binding with the oxalates in food. In any case, the researchers say the risk is too small to warrant telling most people who need extra calcium to avoid supplements. But people who already have a history of kidney stones and who need more calcium than foods can supply should take the supplements at mealtime.

Stress Has Nothing To Do With Ulcers

The discovery in the late 1980s that bacteria cause ulcers made the earlier blame placed on stress look absurdly naive. The bacterium, called Helicobacter pylori or H. pylori, is the major cause of ulcers; use of aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDS) is probably the second leading cause. But why do 80 percent of people who harbor H. pylori or take NSAIDS never develop ulcers? And why do at least 10 percent of ulcers develop in people with neither of those factors? A growing number of ulcer experts now look to stress for the explanation.

Considerable evidence suggests that stress plays an important role in triggering ulcers. For example, a Japanese study published in 2000 found that the rate and severity of ulcers rose in that country after an earthquake that apparently triggered strong emotional aftershocks. That finding confirms numerous previous studies that linked the onset of ulcers with specific stressful events. One recent review concluded that stress contributes to between one- to two-thirds of all ulcers.

Stress may promote ulcers in some people by stimulating excess secretion of stomach acid. That can damage the stomach lining – particularly when it’s already weakened by H. pylori infection or NSAIDs – or aggravate an existing ulcer. Stress may also weaken the body’s immune system, thereby undermining its resistance to H. pylori. Moreover, stress may slow the healing of ulcers. And it may lead people to sleep less and to smoke, drink, and take NSAIDs more – all of which may contribute to ulcers. If you have an ulcer and test positive for H. pylori, antibiotics to treat the infection are clearly warranted. But taking steps to reduce stress may speed recovery and help prevent recurrences – and it may even help other people from developing them in the first place.

Most Cases Of Impotence Are Psychological, Not Physical

Researchers used to claim that 90 percent of impotence, the inability to achieve or maintain an erection, was mental. The erectile dysfunction was usually blamed on "performance anxiety" or some other psychological problems. But better understanding of the physiology of erections has led to a reversal: Researchers now say that physical and medical problems are almost always the primary cause.

Diseases that impede blood flow – notably atherosclerosis, or clogged arteries – are the most common cause of impotence. So anything that promotes clogged arteries – including inactivity, a diet high in saturated fat (from meat and dairy products), and smoking – promotes erectile dysfunction. In addition, diseases such as diabetes that impair nerve function often cause impotence. Disorders that lower the level of the male hormone testosterone contribute to about five percent of cases. And numerous medications, including antihypertensive drugs, can inhibit erections.

Switching drugs, addressing those health problems, and adopting healthy habits can sometimes control erectile dysfunction. For example, one recent study found that exercising regularly significantly reduced complaints of impotence.

Treatment of erectile dysfunction has also changed radically. Sildenafil (Viagra) effectively treats impotence in most men by temporarilly increasing blood flow to the penis. That has greatly reduced the need for the more cumbersome awkward techniques of the past, including injections in the penis and mechanical devices. (People who take nitrates for angina should avoid Sildenafil, since the combination can make blood pressure drop dangerously low.) New inhaled drugs that start working faster than Sildenafil (which needs to be taken an hour before sex) should be available in the near future.