How to avoid adult onset diabetes.

It's the fourth leading cause of death in the United States. It kills more people each year than either breast cancer or AIDS. Get it when you're middle-aged and your life could be five to ten years shorter. Or you may end up blind or on a dialysis machine.

That's the bad news. Here's the good: "At least 75 percent of the new cases of adult-onset diabetes can probably be prevented," says JoAnn Manson, an epidemiologist and endocrinologist at Harvard Medical School.

How? Weight-loss and exercise are your first defense. But researchers are also looking at whether supplements like chromium, vitamin C, or vitamin E can make a difference.

CLEARING SUGAR

Sixteen million Americans have diabetes. Half know it, half don't. And more than 600,000 others will be diagnosed with the disease this year.

Close to 95 percent of diabetics have Non-lnsulin-Dependent Diabetes Mellitus, which is also called Type II, or adult-onset. The other form, Insulin-Dependent, strikes mostly young people and is really a different disease with a different cause and different treatment. (When we use the term "diabetes" in this article, we're referring only to the adult-onset type.)

People with diabetes have a simple problem: They have trouble removing the sugar from their blood. Blood sugar, or glucose, is produced as we digest food. During and after a meal, the pancreas secretes more insulin--a hormone that enables glucose to pass into the cells, where it's stored or burned to produce energy.

But sometimes a person's insulin loses its effectiveness and has trouble clearing enough glucose out of the bloodstream. Some researchers think that obesity makes cells or the insulin receptors on cells--resistant to the hormone. But it's not really clear, because many overweight people are not insulin-resistant and many normalweight people are.

"We don't know exactly why this insulin resistance happens" says Norman Kaplan of the University of Texas Southwestern Medical Center in Dallas. "But it occurs more frequently in some families and in people who are overweight or physically inactive."

The pancreas, which thinks the problem is a lack of insulin, starts to churn out more. And, at least at first, the extra insulin forces blood sugar levels back down to normal. But there's a cost.

"If you have insulin resistance and are secreting lots of insulin to maintain your glucose levels near normal, you have a more-dangerous form of LDL ("bad") cholesterol, as well as low HDL ("good") cholesterol, high triglycerides, and higher blood pressure," says Gerald Reaven, an endocrinologist at the Stanford University School of Medicine. "In other words," he adds, "you have a whole cluster of abnormalities that increase your risk of coronary heart disease."

Eventually, the pancreas may lose the battle to supply enough insulin. If that happens, your blood glucose levels swing out of control and you have diabetes.

There's no cure. But you can control the disease...that is, you can bring blood glucose levels down with diet, weight-loss, physical activity, and sometimes medication.

"Unfortunately, by the time most people with diabetes are diagnosed, the disease has often progressed and irreparable damage may have been done," says Manson.

And that damage can lead to heart disease, stroke, kidney failure, and blindness.

PREVENTING DIABETES

Here are the two most important things you can do to prevent diabetes:

1. Shed some pounds if you're overweight, especially if you're an "apple." "There is growing evidence that people who maintain a healthy weight, or who can lose at least some of their extra fat, can substantially lower their chances of developing diabetes," says Manson.

In fact, she adds, "from 50 to 75 percent of the new cases of diabetes each year seem to be triggered by people's weighing too much" (see "Maximum Weight").

In a dozen studies that followed tens of thousands of people for years, "being overweight increased the risk of developing diabetes in men and women by more than tenfold," says Manson.

"For instance, when we monitored the health of 87,000 female nurses, we found that most of the new cases of diabetes among white women could be attributed to their extra weight."(1)

While it's not clear precisely why being overweight increases the risk of diabetes, it is clear that losing some extra weight helps.

That came through loud and clear in a new, not-yet-published study of people at high risk for diabetes (they were overweight or their parents had the disease).

"These men and women cut their risk of developing diabetes by 30 percent over a two-year period just by losing ten pounds and keeping it off," says Rena Wing, a psychologist at the University of Pittsburgh School of Medicine.

It's not just extra pounds, but where those pounds are, that may matter. Being heavy around the belly (an "apple") may be worse than being heavy in the hips and thighs (a "pear").

"There's something different about the fat that's deposited in the upper body that results in higher insulin levels," says the University of Texas's Norman Kaplan. "As a result, an 'apple' with the same weight and same amount of body fat as a 'pear' has a greater risk of developing diabetes."

But that doesn't mean that people with heavy hips are off the hook. "It's foolish to think that if you're a pear, you have no increased risk," says Reaven.

2. Exercise. "Thirty to fifty percent of the new cases of diabetes each year may be caused by too little physical activity among American adults," says Harvard's JoAnn Manson.

Exercise can cut your risk dramatically. And that's above and beyond the reduction in risk you get because the exercise helps you shed pounds.

Among nearly 6,000 men who enrolled at the University of Pennsylvania between 1928 and 1947, for example, those who spent 1,500 to 2,000 calories a week in activities like walking or sports had a 25 percent lower risk of developing diabetes during the next 14 years than those who expended fewer than 500 calories(2) (see "Getting Enough?").

And that was even true for men who were overweight or who had a family history of diabetes.

In another study, of 21,000 male physicians and 87,000 female nurses, those who exercised at least once a week had a 30 to 40 percent lower risk than those who exercised less (or not at all).(3,4)

What kind of physical activity works best? "Most important is to just start doing something regularly," says Andrea Kriska, an expert on exercise and diabetes at the University of Pittsburgh.

"It appears that the biggest difference in who gets diabetes and who doesn't is between those who are inactive and those who do some physical activity like walking, dancing, gardening, bowling, or hiking. If you don't like to run, walk. Whatever it takes to get you to do more, do it."

CHROMIUM, ANTIOXIDANTS, & DIET

Lose weight and exercise. Can anything else help prevent diabetes?

* Chromium. "A chromium supplement of about 200 micrograms (mcg) a day seems to help reduce glucose levels in those who are not getting enough chromium from their diets," says Richard Anderson, a chromium expert at the U.S. Department of Agriculture (see May 1996, p. 10). "That might help postpone the onset of diabetes," he adds.

But Anderson's studies showed only a modest reduction in blood glucose--not enough to bring levels down to normal. And none of his experiments lasted more than three months, so there's no way to tell if chromium's impact diminishes over time. What's more, there's no easy way to tell if you're deficient in chromium.

* Antioxidants. "Diabetics seem to be exposed to greater levels of free radicals in their systems," says Benjamin Caballero, who chairs the nutrition department at the Johns Hopkins School of Public Health in Baltimore. Free radicals are highly energetic molecules that can damage tissues unless they're destroyed by the body's antioxidant defenses.

"We don't know if these extra free radicals cause diabetes or result from the disease, but preliminary research suggests that antioxidants might help diabetics," he adds.

For instance, when 56 people with diabetes were given daily mega-doses of vitamin C (two grams, or 2,000 mg) for three months, they were better able to clear glucose from their blood than when they were given a (look-alike but inactive) placebo.(5)

Studies on vitamin E have been mixed: Mega-doses (900 IU a day) for three months led to a drop in blood glucose levels for 25 older Italian diabetics compared to similar people who were given a placebo, while 1,200 to 1,600 IU a day for eight to ten weeks had no effect on glucose in 16 American diabetics.(6-8)

Given the small number of studies, few researchers are willing to tell people that it's okay (or, in the case of vitamin E, safe) to take high doses of C or E to help prevent or treat diabetes.

"Some of the results certainly look encouraging," says physician Joseph Williamson of Washington University in St. Louis. "But I think we need much more detailed and careful studies before we can make any clear recommendations."

* Diet. Can what you eat--rather than how much--raise or lower your risk of diabetes? Contrary to what many people think, there is little evidence that sugar, or any food, helps promote the disease. But some foods may help prevent it.

A soon-to-be-published study by Manson and colleagues suggests that "diets high in high-fiber foods like fruits, vegetables, beans, and whole grains are associated with a lower risk of diabetes."

And even if further studies don't confirm Manson's results, that kind of diet should lower your risk of cancer, heart disease, and other health problems.

RELATED ARTICLE: Checking Out the Symptoms

Most of the symptoms of diabetes can also be due to other causes. If you have any of the following, see your physician:

* insatiable thirst or frequent urination,

* unexplained weight-loss or general fatigue,

* more infections than usual, * leg cramps or a "pins and needles" sensation in the toes and fingers,

* impotence, or

* blurred vision.

RELATED ARTICLE: Maximum Weight

A body mass index (BMI) of 25 or more raises your risk of diabetes. Your BMI is your weight (in kilograms) divided by your height (in meters) squared.

Don't panic. We've converted everything to feet, inches, and pounds. First find your height (in stocking feet). Then see the weight (with no clothes on) that corresponds to it. That's how much you'd weigh if you had a BMI of 25. And that's the weight at which your diabetes risk starts to rise. The more you weigh, the higher your risk.

(A BMI just below 25 is still not optimal. To reduce your risk of heart disease and other health problems you should weigh even less but that's another story.)

Height Weight

(lbs.)

4'8" 111 4'9" 115 4'10" 119 4'11" 124 5'0" 128 5'1" 132 5'2" 136 5'3" 141 5'4" 145 5'5" 150 5'6" 155 5'7" 159 5'8" 164 5'9" 169 5'10" 174 5'11" 179 6'0" 184 6'1" 189 6'2" 194 6'3" 200 6'4" 205 6'5" 210 6'6" 216 6'7" 221 6'8" 227 6'9" 233

RELATED ARTICLE: New Diabetes Study

The National Institutes of Health is organizing a new $150 million study to see how diabetes can be prevented by a combination of diet, exercise, and drugs. It's looking for 4,000 volunteers around the country who are 25 or older and who have trouble lowering their blood glucose (which often leads to diabetes). If you think you qualify and would like to participate, call toll-free 1-888-377-5646. You'll be tested to see if you're a good candidate.

RELATED ARTICLE: Getting Enough?

Burn 1,500 to 2,000 calories a week in physical exercise and you could lower your risk of getting diabetes by at least 25 percent. What does it take to burn that many calories? Doing any of the following (or similar) exercises seven times in a week is enough for a 150-pound man or woman.

Mixing and matching the exercises will add variety. The important thing is that you do as much as you can. And remember: Anything is better than nothing.

Exercise                                          Minutes Per Day

Sports
Swimming laps, vigorously                             20-25
Swimming laps, slowly to moderately                   25-30
Ice skating or roller skating                         25-35
Jogging or backpacking                                25-35
Aerobics, high-impact                                 25-40
Bicycling, stationary                                 25-40
Tennis                                                30-35
Bicycling, light                                      30-40
Swimming, leisurely                                   30-40
Treadmill or stair exercise, moderate                 30-40
Aerobics, low-impact                                  40-50
Skiing, downhill, light                               40-50
Calisthenics, light to moderate                       40-55
Golf                                                  40-55
Fishing                                               45-65
Ping pong                                             45-65
Water aerobics or coaching sports                     45-65
Weight lifting, light to moderate                     65-85

Leisure
Dancing, folk or square                               35-45
Playing games with children (hopscotch, etc.)         40-50
Horseback riding                                      45-65
Stretching or yoga                                    45-65
Walking (3 mph)                                       55-70
Dancing                                               65-85
Playing frisbee or bowling                            65-85
Shuffleboard                                          65-85

Around the House
Mowing the lawn                                       35-45
Gardening or walking up stairs                        40-50
Household cleaning, heavy (washing the
  car, washing windows, etc.)                         40-55
Lawnmowing (with a power mower)                       40-55
Wall or house painting                                40-55
Raking leaves                                         45-65
Walking the dog                                       55-70
Walking down stairs                                   65-85

Source: Medicine and Science in Sports and Exercise
25: 71,1993.

(1) American Journal of Epidemiology 132: 501,1990.

(2) New England Journal of Medicine 325: 147,1991.

(3) Journal of the American Medical Association 268: 63,1992.

(4) Lancet 338: 774,1991.

(5) Annals of Nutrition and Metabolism 39: 217,1995.

(6) Diabetes Care 16: 1433,1993.

(7) Diabetes Care 18: 807,1995.

(8) American Journal of Clinical Nutrition 63: 753,1996.