HDL cholesterol, exercise and heart disease prevention

Paul Williams is a man with guts. He could have just chilled out when he was not invited to present his probing research at a prestigious symposium given at the recent Annual Meeting of the American College of Sports Medicine in Cincinnati, Ohio. After all, the symposium, entitled 'How Much is Enough,' was supposed to explore the relationship between exercise and health, a topic about which Williams is one of the world's foremost experts.

But Williams, instead of occupying a proud place on the podium, was in a back row of the symposium hall, wearing a rumpled sports coat and clutching a carousel filled with slides portraying his life's work. Poised on the front edge of his seat like a wildcat ready to pounce on its prey, the U-Cal Berkeley scientist listened patiently as the 'big guns' of exercise research droned on, presenting two very traditional viewpoints: (1) the biggest gains in health accruing from exercise occur when people change from complete sofa spuddism to a little bit of exertion each week, and (2) running more than about 30 miles each week confers no additional health benefits, above and beyond those which come from lower mileage levels. Williams knew that both of these points were wrong, but he wasn't quite ready to react - at least not yet.

He could only wince as the final symposium presenter - the well-known 'father of aerobics,' Ken Cooper - took a somewhat terrifying tack: high levels of exercise could be associated with poor health, or more specifically, a higher risk of invasive cancer, proclaimed Cooper, who called for a wave of anti-oxidant supplements to batter down tumour cells uplifted by high-mileage exercise.

And then Williams made his move. As Cooper's final words echoed off the walls and the oxygen father beat a hasty retreat toward the exit doors, the symposium organisers seemed to try to hush debate, when Williams made a gutsy, Linford-Christie-like leap for the floor microphone, calling out that he had some data that the attendees 'might be interested in'.

Indeed we were, for Williams' numbers, cast upon the giant screen at the front of the symposium hall, countered the traditional idea that a little bit of exercise provides a huge upswing in health and that further increases in exertion furnish just tiny bits of additional protection. This conventional view is in part responsible for the official recommendation to the general public made by the United States Center for Disease Control and Prevention, which is 'to walk briskly for two miles, most days of the week' (this is comparable to telling average citizens to jog about 10 miles per week). Williams also launched a strong attack on the idea that training more than 30 miles per week offers no (or less, a la Cooper) protection from disease.

And what did we actually see on the screen? Just the numbers and findings from a decade of Williams' research, statistics which reveal the true impact of increased mileage on heart-disease risk in both male and female runners. In Williams' most recent study, he examined the running history, body-weight history, average weekly mileage, menstrual status, and hormone usage of 1837 female runners over a five-year period. The survey also assessed smoking status and dietary intake of alcohol, red meat, fish, fruit, vitamin C, vitamin E, and aspirin. Williams was also able to ascertain the study-participants' heights, weights, plasma-cholesterol and triglyceride concentrations, blood pressures, and resting heart rates from their individual doctors.


The truth about female runners
Some of Williams' findings were merely interesting: for instance, high-mileage women tended to eat less beef, lamb, and pork, compared to low-mileage females, and also took in greater quantities of fruit and vitamin E. On the other hand, there was no relationship at all between mileage and age, education, or the intake of fish, alcohol, aspirin, or vitamin C.

However, the key finding was that HDL cholesterol, the type of cholesterol which researchers feel is protective against heart disease in both men and women, rose steadily with weekly mileage, even when women ran more than 64 kilometres (40 miles) per week! This increase in HDL could not be attributed to decreased intake of red meat - or to any of the other possible HDL-controlling factors studied by Williams, including age, menstrual status, hormone-replacement therapy, usage of birth-control pills, or the intake of aspirin, alcohol, fish, or fruit.

Basically, Williams showed that each 10-mile increase in weekly running cranked up HDL cholesterol in female runners by about 3 per cent or more. For example, women who ran between 10 and 20 miles per week checked in with HDLs of about 62 mg/dl, while females averaging 20 to 30 weekly miles augmented HDL to 64. At about 35 miles per week, HDL advanced to 66, and above 40, HDL climbed to 69 mg/dl.

Small changes? Heavens, no. Researchers estimate that each 1-per cent increase in HDL can limit heart-disease risk by 3 per cent. That being true, we can say that running more than 40 weekly miles upraises HDL by 4.5 per cent in females, compared to running just 30 to 35 miles - and thus lowers heart-disease risk by almost 14 per cent (so much for the idea that going beyond 30 miles per week has little to offer). Overall, running 40 or more miles per week can reduce heart-disease risk by approximately 30 per cent, compared to running 0 to 10 weekly miles, and probably lowers mortality from cardiovascular disease by about 45 per cent, according to Williams.


Additional benefits?
Running at least 40 miles per week also significantly boosted a female's chances of having sky-high HDL concentrations (above 80mg/dl), the kind of reading which makes a heart attack as likely as an August snow storm in Torremolinos. Longer training distances also dampened systolic and diastolic blood pressure in a pretty consistent manner. To no one's surprise, adiposity, waist size, and hip size all tumbled in response to increased mileage, too.

Of course, a sceptic might argue that the higher HDL, lower blood pressures, and greater leanness in the women who ran longer distances could simply be attributed to a choice made by initially leaner women to run longer, compared to initially fatter females. Such a choice seems quite possible, since leanness is a sign of fitness and permits longer running without fatigue. Since lean women naturally tend to have higher HDL and lower blood pressure than fat women, all of the positives - greater leanness and therefore higher HDL and lower pressure - might have been present at the beginning of the study - and might have contributed to the accumulation of more miles, rather than the other way around.

Fortunately, Williams knew the subjects' weights and body-circumference statistics at the beginning of the study. Taking these into account, he was able to show that higher mileage produced leaner bodies over time (in other words, lean women didn't start out running high miles; they became lean as they ran high mileage). And when he took initial body fatness into account statistically (to prevent the potential bias mentioned above), he found that higher mileage still produced higher HDL, lower pressure, and leaner bodies.

There's been some concern that going through menopause might reduce a woman's ability to raise HDL via higher mileage. However, Williams found that both pre- and postmenopausal female runners had the same strong association between mileage and HDL. He also noted that postmenopausal oestrogen-replacement therapy had no effect on mileage's fine tendency to lift 'good' cholesterol. Unfortunately, Williams' data could not resolve the question of whether women who use oral contraceptives have the same rise in HDL in response to exercise, compared to non-oral-contraceptive users.


What about male runners?
In a separate, equally cool piece of research, Williams studied the relationship between blood fats, body composition, and mileage in 6,849 male runners, all of whom were non-smokers. In this massive group of harriers, Williams found the same relationship he had observed in women, except that he was able to extend the linkage to even higher mileage levels.

In this second study, males running about five miles per week checked in with HDL concentrations of 48.7, while men logging 15 miles moved up to 50.4. Covering 25 weekly miles sent HDL to 52.2, 35 miles meant 54.8, 45 miles produced HDLs of 57.1, 55 was linked with 59.6, and 65 miles or more skyrocketed HDL to an incredibly salubrious 61.9. Basically, each 10-mile increase in mileage added two ticks to HDL concentrations - and knocked down the risk of cardiovascular disease by around 10 per cent.

Hefty numbers of runners were involved in this research, adding strength to Williams' findings (no one can ever accuse the Berkeley scientist of stinting on the group sizes in his work). Overall, 153 men were training more than 60 miles per week, 218 ran between 50 and 59 miles, 624 covered 40 to 49 miles, over a thousand ran 30 to 39 miles, and about 2000 completed either 20 to 29 or 10 to 19 weekly miles.

Interestingly enough, Williams' data indicated that a man had to run at least 15 miles per week to raise HDL (ditto for lowering the ratio of total cholesterol to HDL and dropping total triglycerides), quite a contrast to the popular idea that 'just goin' fishin'' (or engaging in small amounts of some other equally light exertion) is enough to ameliorate heart-disease risk in a significant way.

Even cooler was Williams' penetrating analysis of the effects of mileage on the chances of having dismally low or marvellously high HDL. Basically, research has shown that having HDL concentrations below 35 mg/dl increases one's chances of having coronary-artery disease rather dramatically, while shooting HDL above 60 mg/dl provides marvellous protection from the malady. In Williams' investigation, only 16 per cent of men running about five miles per week had HDL above 60, 24 per cent of men running 25 miles per week (the typical training volume for American and British runners) had such HDL levels, 37 per cent of men running 45 miles per week enjoyed over-60 HDL, and a whopping 50 per cent of men running more than 60 miles each week attained such ultimate levels.

On the low end of things, just 1 per cent of men running 50 or more miles per week had HDL below 35, compared with 7 per cent of men running 25 weekly miles and 12 per cent of the individuals training five miles per week. As Williams calmly noted in his research write-up, 'Current exercise guidelines (which call for about 10 miles or so per week) should be revised upward'.

And that's good advice, because Williams' research blows old contentions, such as 'If you run more than 15 miles per week, you're running for reasons other than your health,' clean out of the water. Instead, there seems to be a steady, linear decrease in morbidity and mortality from heart disease as mileage advances, even beyond 30 miles per week - the previous 'threshold,' above which epidemiologists thought that no benefits accrued. In addition, moving from 30 to 40 miles per week (or from 40 to 50) seems to produce about as much benefit as shifting from zero to 10 weekly miles, contradicting the traditional view that the major gain takes place when one shifts from sedentariness to mild exercise.


What are the risks of increased mileage?
And it's nice to know that running is extremely egalitarian, producing the same upswing in HDL in both men and women. According to Williams' data, the healthful change works out to be about .2 mg/dl of HDL per mile per week. In other words, each extra five miles of weekly running pushes HDL up by about one tick, on average, diminishing heart-disease risk by 5 per cent or so. It's true that women tend to have naturally higher HDL readings than men, but these higher settings don't prevent female HDL from scooting up at about the same rate.

However, if you want to increase your mileage to lower your chances of heart maladies, bear in mind that there are risks associated with increasing mileage. One of these is an enhanced chance of musculoskeletal injury (remember, though, that mileage is not the best predictor of injury; in fact, it's well down the list, after (1) a previous history of injury and (2) the number of consecutive days of running without a day off). Still, considering that higher mileages can be linked with greater tissue damage, you should always increase your mileage gradually, without big jumps in volume. Also make sure that you're consistently strengthening your feet, ankles, shins, calves, and knees - the most injury-prone portions of your body. Walking on toes (straight-ahead, toes-in, and toes-out), walking on heels, heel raises, toe raises, marching drills performed on the toes, one-leg squats, high-bench step-ups, and one-leg hops in place can all be helpful here. If you're injured in spite of your best preventative efforts, console yourself with the thought that an occasional sore foot is far better than a plugged-up heart.

To date, no carefully conducted scientific studies support Ken Cooper's notion that running more than 40 miles per week increases the risk of cancer. However, running more miles than one's body is ready for can depress immune-system activity. It's always wise to reduce miles if the burgeoning of one's running programme leads to an increase in illness frequency.

In women, too many miles, especially coupled with too little eating, can lead to amenorrhoea and possibly osteoporosis. If menstrual regularity is compromised in conjunction with higher-mileage training, it's important to back off on the running - and stop backing away from the dining-room table. Fortunately, high-mileage running does not inevitably lead to menstrual dysfunction: in a recent study, women who covered 50 miles per week were able to maintain completely normal menstrual functioning. An important aspect of this research was that the women took one full year to increase from five weekly miles to 50, stressing the importance of gradual build-ups in volume.

And the bottom line is that running, despite its various risks, can lower your chances of developing devastating diseases such as Type-II diabetes, colon cancer, and (probably) breast cancer if you're a woman. Running also maintains body weight, limiting the incidence of diseases associated with obesity. And the especially wonderful news - for those of us who love to run - is that gradual increases in our training, even beyond 30 miles per week, tends to steadily decrease our risk of succumbing to the number-one killer in Great Britain - heart disease.

Owen Anderson