Eat Your Heart Out

By MICHAEL D. LEMONICK

A few decades ago, taking care of your heart didn't seem all that complicated. You ate a balanced diet, didn't drink too much and got some fresh air and exercise--a round of golf, maybe. That was about it. Not that everyone, or even most people, actually lived up to these standards. But if you fell short, at least you knew what to feel guilty about.

Then we started hearing from the scientists. People who thought they were doing everything right, it turned out, were actually abusing their bodies--and in particular, their hearts. The cholesterol in steaks, cream, butter and especially those breakfast eggs was clogging arteries like sludge in a stopped-up drainpipe. Salt was poison: it drove up blood pressure and put an unhealthy strain on the ticker. Overeating and becoming overweight were a sure ticket to a coronary.

So, the thinking was, better cut out the steak, treat yourself to one egg a week (if you must), switch from butter to margarine and hide the saltshaker. Oh, and don't waste time with golf. Vigorous, pulse-pounding exercise was the only way to keep your weight within limits--and just as important, your heart properly toned. It was a spartan regimen and made folks who didn't follow it feel guiltier than ever, but it retained the virtue of being comprehensible.

Recently, however, the scientists seem to have gone mad. Hardly a week goes by without some expert somewhere issuing a new report declaring that a particular food or vitamin or activity or condition will either restore your cardiovascular health or ruin it--and as often as not, the new advice seems to contradict the old. Among the new findings:

--EGGS aren't nearly as bad for the heart as doctors used to think. Sure, they're packed with cholesterol. But scientists now know that eating cholesterol doesn't necessarily result in high levels of harmful cholesterol in the blood, where the damage is done.

--HOMOCYSTEINE, a substance found in the blood, may turn out to be as important a risk factor for heart disease as dietary cholesterol.

--SATURATED FAT, the kind found in red meat, butter and other animal products, may be a bigger threat to the heart and blood vessels than cholesterol.

--OTHER FATS--olive oil, other vegetable oils and the oil found in salmon and tuna--can actually drive down bad cholesterol and keep blood flowing freely.

--MARGARINE can be just as harmful as butter, if not worse; a process that stiffens vegetable oil into a butter-like stick also transforms it into an artery blocker. In general, the softer the margarine, the better. New butter substitutes, such as Benecol, can lower blood cholesterol.

--SALT has been considered taboo because it raises blood pressure. But it's not clear whether it's a problem for those whose pressure is normal.

--EXERCISE need not be pulse pounding to be beneficial, say experts. A little gardening or strenuous housework isn't a bad prescription for cardiovascular health.

"The impression being given," admits Dr. Irwin Rosenberg, dean of nutrition sciences at Tufts University School of Nutrition, Science and Policy, "is that nutrition science doesn't know what it's doing." But despite appearances, the medical profession has not lost its collective mind. The bewildering flood of advice that assaults us week after week simply reflects the slow, laborious gathering of knowledge that defines science in action. Like most works in progress, it moves ahead in fits and starts--and occasionally goes down a blind alley.

Yet despite all the apparent confusion, scientists actually know a lot more today about what keeps the heart humming than they did a generation ago. The first glimmerings of understanding gathered 30 years ago were accurate as far as they went--but rudimentary. Today scientists have a much deeper understanding of what foods and activities are healthful or harmful--and why. The good news is that the path to a healthier heart is now pretty clear, once you master a few key concepts.

FAT AND CHOLESTEROL

Fat has been a staple of the human diet since our remote ancestors started eating meat more than 2 million years ago. In the 1960s, however, researchers began to notice that patients who had elevated blood levels of cholesterol--a fatty substance found in meat, poultry, eggs and dairy products--also tended to suffer from heart disease. Cholesterol by-products would form thick, tough deposits, called plaques, on the inner walls of arteries, stiffening them and then starving the heart of blood and creating choke points where a clot could stop the flow entirely.

At first blush, the solution seemed pretty obvious: consume low-cholesterol foods; switch from butter to vegetable-oil-based margarine; eat fewer eggs; eat less meat. Indeed, it was the best advice at the time, based on the limited knowledge available.

As scientists learned more about how the body works, however, that prescription proved too simplistic. Some people's cholesterol levels stayed high, no matter what they ate. And a lot of heart-disease patients had normal cholesterol levels. How could this be? Only recently have some of the reasons begun to emerge. For one thing, how much cholesterol you eat doesn't necessarily determine how much ends up in your blood. The body, it turns out, also manufactures its own cholesterol. And some people's bodies are just less efficient at vacuuming up excess cholesterol than others, for reasons that are largely genetic.

So, in the next phase of research, the object became keeping cholesterol levels in the blood under control and not necessarily keeping the cholesterol out of the diet. But how to do it? Again the key seemed to be eating less red meat, cream and butter, but it was based not so much on cholesterol as on saturated fat. Reason: saturated fat increases blood cholesterol. So eggs, high in cholesterol but not in saturated fat, were taken off the forbidden list, except for those people with the most serious cholesterol problems.

To make things more complicated, researchers discovered that cholesterol travels around the body in two major forms: low-density lipoprotein (LDL), the kind that does most of the damage, and high-density lipoprotein (HDL), which actually seems to keep arteries clean. Beyond that, another class of fats, known as triglycerides, also circulates in the blood, doing more or less the same kind of damage as LDL.

Doctors then began recommending foods and activities that drive down LDL and triglycerides (eat less meat, cream and butter--one recommendation that has never changed--add olive oil and fish to the diet) and at the same time push up HDL (get more exercise and lose weight).

Then came the news that taking benign foods like vegetable and peanut oils and hydrogenating them--a process that stiffens them to make stick margarine, peanut butter and solid shortening--transforms them into substances known as trans-fatty acids, which can drive LDL and triglyceride levels through the roof. Trans-fatty acids are not technically fats, which means, astonishingly, that a food labeled FAT FREE may be bursting with stuff that can give you heart disease. The fact that stick margarine is bad doesn't mean butter is suddenly good. Says Dr. Walter Willett, head of nutrition at the Harvard School of Public Health: "I think the healthiest solution is none of the above." The recommendation to stay away from meats and animal fats, thus, hasn't been overthrown. It's simply been extended slightly to encompass a substance once thought to be relatively harmless.

How about staying away from fat entirely? Bad idea. The body needs fats, in part because vitamins like A and D must be dissolved in fat to enter the body or even move about within the body. What about the super-low-fat diets, advocated by people like Dr. Dean Ornish, director of the Preventive Medicine Research Institute in Sausalito, Calif. (see box)? They seem to work but perhaps not because they're low fat; the key may be the types of foods--beans, grains, vegetables, instead of meats and cheeses--that Ornish recommends. Indeed, Mediterranean men, who get more than 30% of their calories from fat (some three times what Ornish suggests) but who eat little saturated fat, have a very low rate of heart disease.

HDL, LDL and triglycerides aren't quite the whole story either. Over the past few years, researchers have identified yet another form of fat that could rightly be labeled Bad Cholesterol II. Called lipoprotein (a), or Lp(a), it behaves like LDL in the body. But because Lp(a) levels have more to do with your genes than your diet, they can't easily be controlled. At best, doctors think they can use Lp(a) screening to find people who should be working extra hard to reduce their other heart-attack risks.

So fat, which started out as a good thing to eat and then became a bad thing, now turns out to be a collection of very different things, some good, some bad, some absolutely neutral. It's a pattern that has been repeated for a variety of cardiovascular risk factors. It's not pretty; the tortuous progress of scientific discovery rarely is.

SALT

Researchers realized decades ago that high blood pressure is a cardiovascular danger signal. They don't understand the exact mechanism yet, but physicians think elevated pressure puts a strain on blood vessels, causing them to tear or develop weak areas where plaque can gain an easy foothold. Hypertension (to use the technical term) can also force small blood vessels to burst like an overstressed garden hose; if that happens in the brain, it's called a stroke--the other major cardiovascular killer besides heart attack.

Medication can help with the most severe cases of hypertension, but the first line of defense, physicians agree, is to cut back on a substance that has been shown over and over to keep blood pressure high: sodium, especially in the form of salt.

If cutting back on salt is good for people with hypertension, it should logically be good for everyone else too. It may be, but dueling studies released three years ago demonstrate that the case is far from airtight. Scientists writing in the British Medical Journal concluded that reducing salt intake reduces blood pressure in all people, even those who are not hypertensive. But a study published the very same week in the Journal of the American Medical Association argued that people with normal blood pressure got no significant benefit from salt reduction.

Which one was right? Probably neither, since both studies were flawed. The J.A.M.A. study included subjects who were on low-salt diets for a very short time--perhaps too short for any effect to be noticed. And the BMJ study could not effectively measure the influence of other factors that could have made a difference. Those who ate less salt may also have watched what they ate in general, for example, exercised more or been less overweight.

The truth is that the question of what ordinary people should do about salt has simply not been settled yet. That doesn't mean we should throw up our hands in despair. Even without hard scientific proof, says Dr. Theodore Kotchen of the Medical College of Wisconsin, keeping sodium levels down is probably a good idea--particularly since there is no evidence that a low-sodium diet is harmful. The one exception: people who are losing salt through heavy perspiration during exercise or hard physical work. Reducing salt intake in the middle of a heat wave can actually be dangerous to your health.

EXERCISE

Physical exertion is another area in which doctors have been sending mixed signals. As far back as 1953, studies showed that people who got more exercise had fewer heart attacks. The physiological explanation has come more slowly, but one reason is simply that the heart is a muscle; frequent workouts keep it strong.

Another factor, doctors believe, is that exercise holds down blood pressure. When the heart pumps blood more quickly through the body, vessels dilate--or widen--to accommodate the extra flow. The overall effect is to lower pressure throughout the cardiovascular system. People who get regular exercise have about a 30% lower risk of developing heart-threatening hypertension than people who don't.

Some studies have also shown that exercise raises HDL levels; that it increases the volume of plasma (blood's liquid component), thinning the blood and thus keeping dangerous clots at a minimum; and that it may boost levels of an enzyme that vacuums cholesterol and fatty acids from the blood.

None of these results is definitive, but it seems clear that however exercise works, its benefits increase if you do more of it. That's obviously true if your goal is to stay trim; exertion is fueled by calorie burning. But plenty of studies have shown it applies to staving off heart disease too, and for years the standard medical advice was to get a minimum of 20 to 30 min. of vigorous, continuous exercise at least three times each week.

Yet in the mid-1990s, the Centers for Disease Control and Prevention and the American College of Sports Medicine published a report declaring that moderate exercise was just fine--anything from washing the car for an hour to gardening for 45 min. to raking leaves to taking a leisurely stroll around the block. And it didn't even have to be all in one shot. Three short walks, for example, could substitute for one longer one. Since then, the Surgeon General, the National Institutes of Health and the President's Council on Physical Fitness and Sports have all come out with similar guidelines.

Another example of new research refining old ideas? Not this time. The change had less to do with medicine than with marketing. "Our concern," explains Russell Pate, an exercise physiologist at the University of South Carolina and lead author of the CDC report, "was that a very large percentage of the adult population was not meeting the existing standard." Reasoning that the guidelines were just too intimidating for most people and that a little exercise had to be better than none at all, Pate and his colleagues decided to lighten up the message. "The recommendations do not say," he emphasizes, "that vigorous activity was inappropriate or that the more traditional exercise prescription model was wrong."

VITAMIN E

The processes that allow the body to turn food and air into nourishment for individual cells also create by-products that amount to toxic wastes--highly reactive oxygen molecules known as free radicals that can combine with otherwise innocent substances and transform them into killers. Free radicals may be responsible in part for the genetic damage that leads to some cancers. And they also appear to be what makes LDL and triglycerides so dangerous. When a free radical combines with one of these fatty molecules, the altered cholesterol turns into a biochemical cannonball that ricochets around the bloodstream, damaging the inner walls of vessels.

Fortunately, nature has also created chemicals known as antioxidants, which can prevent dangerous oxidation from happening in the first place. Among the most powerful of these is vitamin E, which is found in vegetable oils and nuts. In 1996 a major study of postmenopausal women showed that those who eat a diet rich in vitamin E had a 62% lower than average risk of dying from heart disease.

That doesn't mean, however, that popping vitamin E pills will stave off heart disease. Previous research had reached a split decision over whether supplementary E could guard against cardiovascular problems. But the study on postmenopausal women, one of the largest yet, concluded that the vitamin was protective only when eaten in foods; in pill form, it didn't seem to do much good at all. This result could mean that the vitamin works in tandem with some other, as yet unidentified, food-borne substance.

PHYTOCHEMICALS

Adding lots of fruits and vegetables to the diet is good for the heart in all kinds of ways. It displaces meat and dairy products and thus reduces the intake of saturated fats. It puts more vitamins--not just E but also C and many of the B vitamins--into your body.

Over the past several years, however, researchers have been investigating a whole new class of plant-based substances whose role in preventing heart disease may be even more important than vitamins. Known as phytochemicals, they fall into two classes: carotenoids, found mostly in orange-colored vegetables (beta carotene is the best known of the more than 600 carotenoids); and flavonoids--some 4,000 of them, found in, among other things, onions, broccoli, red wine and tea (green, black and oolong, but not herbal).

Like vitamin E, the flavonoids and the carotenoids appear to act as antioxidants, keeping LDL and triglycerides from being oxidized by free radicals. But they do so in different ways, explains Jeffrey Blumberg, a Tufts University nutritionist: "All those free radicals come in many varieties and affect different parts of the body. So you need many different antioxidants to protect yourself at different levels."

For example, he says, vitamin E, which is fat soluble, is incorporated into the LDL or triglyceride particle, forming a last line of defense against corruption by free radicals. Water-soluble flavonoids, by contrast, can be absorbed by most cells in the body, where they can presumably take free radicals out of circulation. But so far, these are only theories. All scientists know for sure is that people who eat foods rich in these two kinds of chemicals, flavonoids and carotenoids, seem to have less heart disease--and it's not even certain that there is a cause-and-effect relationship.

As for figuring out precisely which of the thousands of phytochemicals is most important, that is decades away, if it's even a legitimate question in the first place. Just as with vitamin E--and with the studies that debunked beta-carotene supplements as cancer fighters a few years ago--it may turn out that phytochemicals work only in tandem with one another or with other chemicals found in foods. Trying to isolate the "active ingredient" might be a fool's errand. Says Dr. Ronald Krauss, a nutrition and cholesterol researcher at the Lawrence Berkeley Lab: "It's premature to interpret that research in any way other than you should eat more fruits and vegetables."

INFECTION AND INFLAMMATION

Just a couple of years ago, one of the few things scientists were pretty sure did not trigger cardiac problems was infection. They're not quite so sure anymore. Strong evidence now suggests that the immune system plays a major role in heart disease. The initial damage is done by things like high blood pressure, smoking, oxidized LDL and triglycerides, which weaken and damage the inner walls of veins and arteries. Then the immune system responds, just as it's designed to do. Instead of fixing these problems, though, the immune response makes them worse. For one thing, the body tries to repair physical tears in blood vessels as it would any other wound: blood platelets rush to the site, clump together and form a clot, a biological bandage that binds up the injury. A clot on the outside of the body--a scab, in other words--eventually falls off with no problem. But inside a vein or artery, especially one that has been narrowed with plaque deposits, a clot can get snagged, causing a heart attack.

Plaque buildup too may be an unintended by-product of immune-system action. When oxidized fatty molecules damage vessel walls, the tissues become inflamed--engorged with immune cells whose job it is to fight the invaders. Instead of vacuuming up the oxidized molecules, however, the immune cells become entangled with them; the whole mess welds itself onto the tough, sticky plaques that narrow veins and arteries. That, researchers believe, is one reason aspirin is so good at preventing second heart attacks: not only does it thin the blood and keep things flowing, it also damps down inflammation.

This same sort of blood-vessel inflammation, doctors believe, may be triggered by bacterial and viral infections. Chlamydia (which generally starts as a venereal disease) and gingivitis (an infection of the gums) have both been implicated in heart disease, and more recently so has the herpesvirus that causes cold sores. In the case of herpes, especially, it's far too early to tell whether this link is real or will evaporate under closer scrutiny.

ALCOHOL

It's known as the French paradox: people who live in France eat huge quantities of saturated fat (in the form of butter, cheese and other milk products), yet they have one of the lowest rates of cardiovascular disease in the world. One compelling explanation is that the French also drink wine, usually in moderation. Too much alcohol can destroy just about every organ in the body, the heart included. But investigators have discovered through clinical trials that people who take an occasional nip have about a 20% lower risk of heart disease than do teetotalers.

The mechanism isn't entirely clear, but alcohol may boost blood levels of HDL, the good cholesterol that cleans plaque off arterial walls. Two to four drinks a week seem optimal for men, one to three for women. Since excess alcohol consumption is the second leading cause of preventable death in the U.S., says Dr. Charles Hennekens of Harvard Medical School, "I'm opposed to a wide public health recommendation to drink alcohol. But I'm ready to consider it for a particular patient after going over his or her risks and benefits."

HOMOCYSTEINE

Victims of the rare genetic disorder known as homocystinuria usually die by age 20 from heart attack or stroke. They also have high blood levels of the amino acid homocysteine, a by-product of protein metabolism. That's highly suggestive of a cause-and-effect relationship, but after decades of investigation, the link between homocysteine and heart disease is still elusive. Says Dr. Andrew Bostom, co-director of the Cardiac Rehabilitative program at Memorial Hospital in Pawtucket, R.I.: "We have tantalizing suggestions that we might actually be dealing with a real risk factor, but we don't have smoking-gun evidence."

They do, however, have a plausible explanation for how homocysteine possibly works. If too much circulates in the blood, researchers believe, it may combine with LDL to form large molecules that are especially likely to attract the immune-system cells that help form plaques.

The good thing about homocysteine is that if it does prove to be a significant cause of heart disease, the treatment is in hand: studies have consistently shown that homocysteine can be easily controlled with B vitamins and folic acid, either in the diet or in supplements. The most recent study appeared two months ago in the New England Journal of Medicine: a government requirement that all flour, pasta and other grain products manufactured after Jan. 1, 1998, be enriched with folic acid (to stave off spinal-cord defects in newborns) has already measurably reduced homocysteine levels across the board.

New risk factors identified, old risks reassessed, varying degrees of uncertainty about every medical study ever published--it all seems so confusing, you may be tempted just to throw a steak on the grill, butter your baked potato and forget the whole thing.

But that would reflect a misunderstanding about how science works. It is not a steady march from ignorance to knowledge. It's more like a mountaineering expedition. On the way up an unscaled peak, climbers will gain some altitude on one route, then find it's a dead end. They'll spot a better one, backtrack a little and move on. The fact that they sometimes have to take a step backward for every two steps forward doesn't mean they're wasting their time. It means that inching up an uncharted mountain is tough work.

When you step back, though, and take a look at the overall picture--a long view from the upper slopes of the mountain--it turns out in hindsight that the path was clear. So it is with medical science. From the perspective of 1999, the past 40 years' worth of research points to a consistent theme: eat a balanced diet that includes lots of fruits and vegetables and fewer animal-based foods; don't smoke; and get as much exercise as you can comfortably maintain.

If it sounds as though nothing much has changed in the past three decades, that's because the basics of cardiac health--the base of the mountain--have been there all along. What has changed is doctors' understanding of why it's all true. And they're continuing to refine their knowledge so that the confusing new research emerging from the labs will one day stand on an equally firm footing. Until that happens, the best bet is to focus on those basics. Your heart will thank you for it.

--Reported by Christine Gorman and Alice Park/New York

With reporting by Christine Gorman and Alice Park/New York