Bare bones: how to keep yours strong.

Pat Wootan had no idea that her bones were brittle until she broke her hip ... at the age of 62. She was at her home in Kingston, New York, when one of her two dogs suddenly ran in front of her. "I fell on my side," says Wootan. "The surgeon said he could see osteoporosis when he replaced the ball in the socket of my hip."

Wootan is now walking again, but some things aren't easy. "I can't bend, so I have to use a stick to pick things up," she explains. "I don't know how older people do it." They don't.

Only one out of three people who break a hip regain their independence. One out of four die during the year after their fracture. And nearly half of those who survive still cannot walk without aid. A broken hip is the second leading cause of admission to nursing homes.

Most people are older than 65 when they break a hip. Yet osteoporosis, the disease that leads to the fracture, starts decades earlier. So do the opportunities to prevent it.

Would you rather die or hip and end up in a nursing home? Roughly 80 percent of aged 75 or older say they'd prefer dying.

One out of six women will fracture hip during their lifetime. That's as high as the risk of breast, uterine, and ovarian cancer combined. And a man aged 50 or older is more likely to break a hip during his lifetime than to get prostate cancer.

"Osteoporosis has increased over the last ten years, and it's not just because the population is aging," says Marian T. Hannan of the Harvard Medical School and the Hebrew Rehabilitation Center for Aged in Boston. "People are fracturing more than they used to at the same age, and no one understands why."

An estimated ten million Americans now have bones that are porous enough to warrant a diagnosis of osteoporosis. Another 18 million have a bone density that isn't quite osteoporosis, but that's still low enough to raise their risk of a fracture I see "More Years, Less Bone"D. "Bone loss and hip fractures are now epidemic in people over 65, and osteoporosis has a huge impact on the public's health," says Hannan. "Up to a quarter of the people in nursing homes are there because of a hip fracture. It's an incredibly expensive and life-altering event."

Scientists aren't certain exactly why people lose bone as they age, but they do know how it happens.

"People think bone is structurally like steel, but it's actually an active organ," explains bone expert C. Conrad Johnston of the Indiana University School of Medicine. "The osteoclasts are cells that keep digging holes in the bone, while the osteoblast keep filling them back in."

But age or other factors can shift bone into negative balance, "so that you're digging more holes and not completely filling them in," says Johnston.

So far, all of the drugs that are approved for treating osteoporosis slow down the osteoclasts, he explains. "They inhibit the removal of bone, so you don't lose as much." And that can lead to a net gain in bone density.

Whether your bone density drops into what some researchers call the "fracture zone" depends in part on how much you start out with. Women have a greater risk of osteoporosis than men because they have less bone to begin with. What's more, women lose as much as 20 percent of their bone mass during the first five to seven years after menopause (see "Bones: Older and Weaker," p. 5). "Low estrogen levels are the most important cause of bone loss in women," says Johnston.

What triggers bone loss in men as they age is less clear. "We are now seeing more fractures in men," he notes. In fact, 20 percent of hip fractures occur in men.

"And when they occur, they're more devastating than when they happen to women," says Johnston. Men are twice as likely to die within the year following a fracture as women.

Women at Risk

"Osteoporosis is a silent risk factor for fracture, just as hypertension is for stroke," says Robert Lindsay, former president of the National Osteoporosis Foundation. "High-risk women should be tested to detect low bone density before fractures occur."

Who's at high risk? Any Caucasian woman aged 65 or older, according to the foundation's guidelines. (1) (It had too little data to estimate the risk of fractures in men or non-white women.) But, like recovering hip-fracture patient Pat Wootan, some younger women may also be at risk (see "Who's at Risk?").

"People who have fractured any bone after the age of 50 are at higher risk for another fracture," explains Bess Dawson-Hughes of the Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University in Boston.

That's not true if your bone is broken in a car accident or by some other massive force, she explains. "But if you simply fall and break your wrist at the age of 50, you may be a candidate for drugs that treat osteoporosis, because that kind of break may be a sign that your bones are weak."

You're also at risk if you smoke cigarettes or if your mother, father, or sibling had a fracture that wasn't caused by massive force. And weighing less than 127 pounds means a higher risk, at least in women over 50. "Thinner people have smaller bones and less padding when they hit," explains Dawson-Hughes.

That's not an excuse to gain weight--or to avoid losing weight if you need to. It's not worth getting diabetes, high blood pressure, or other health problems just to help prevent a bone fracture. But a low body weight should nudge women aged 50 or older to get a bone density test. The questions is: which kind?

"Each method predicts the risk of fractures, but I recommend DEXA," says Deborah Sellmeyer of the University of California at San Francisco.

DEXA, or DXA, stands for dual-energy X-ray absorptiometry. Unlike other tests, it can measure density in the spine, hip, and wrist, the three major sites for fracture. A DEXA scan exposes patients to only about one-hundredth of the radiation they'd get from a chest X-ray.

What's more, when the World Health Organization (WHO) defined osteoporosis, it relied on studies that used DEXA. "It's more difficult to apply the WHO guidelines with another type of bone density test," says Sellmeyer.

What To Do

"When cholesterol tests first came out, it wasn't clear what was the `normal' range and at what number you should begin treatment," says Lindsay. "The same was true for bone density tests."

That picture has changed in recent years. Now researchers know what a bone density score means, and they have more options for drug treatment (see "When Diet Isn't Enough," p. 6).

Estrogen is no longer the only option. Drugs like Fosamax usually work. And, unlike with estrogen, you don't have to worry that they may raise the risk of breast cancer. "We can tailor treatment to a woman's concerns and her risk of other problems," says Sellmeyer.

Whether or not you're at high risk, you can take steps to protect your bones at any age. Here's what experts recommend:

* Shrink your calcium deficit. The average American consumes only 600 milligrams of calcium a day. Yet the National Academy of Sciences recommends 1,000 mg for adults under age 50 and 1,200 mg for those over 50.

"Adequate calcium intake will slow the rate of bone loss and reduce the risk of fractures in most bones in older adults," says Johnston. It doesn't matter if you get your calcium from food, a supplement, or a growing number of cereals, juices, and other foods that are fortified (see "The Calcium Countdown," p. 7).

"Randomized controlled trials have shown that calcium and vitamin D can reduce the risk of fractures in older people by up to 40 percent," says Sellmeyer. (2)

But men should be especially careful not to exceed the recommended levels. Too much calcium (more than 2,000 mg a day) was linked to a higher risk of prostate cancer in some studies. It's too early to know whether other studies will confirm those results, but why take a chance?

A bonus: In a study on bone density and fractures, Dawson-Hughes and colleague Elizabeth Krall found that older people who took calcium and vitamin D supplements were also less likely to lose teeth than those who took a placebo. (3) "It's the first randomized controlled trial to show that calcium and vitamin D made a difference for tooth loss," says Dawson-Hughes.

And it's not just adults who need calcium. "It's especially important that adolescents get enough calcium to reach their genetic peak for bone mass," notes Johnston.

If that's not compelling to teenagers, other recent findings might be: Among teenage girls who participate in sports, two preliminary studies indicate that heavy-soda-drinkers are more likely to break a bone than those who drink fewer soft drinks. (4)

* Get enough vitamin D. Without sufficient vitamin D, your body can't absorb calcium efficiently. When Dawson-Hughes and her Tufts colleagues gave daily vitamin D and calcium supplements to postmenopausal Boston women from October through April, the women lost less than women who took just calcium. (5)

"And when other researchers gave vitamin D supplements or a placebo to elderly people whose blood vitamin D levels were in the lower half of the normal range, the vitamin-D-takers had half as many falls over the next year as those who got the placebo," says Dawson-Hughes. Those results suggest that the National Academy of Sciences may have aimed too low when it set its vitamin D recommendation at International Units (IU) a day for people over 70.

"There's a growing consensus that people need blood vitamin D levels in the upper half of the so-called normal range," says Dawson-Hughes. "But only two-thirds of older women who get the recommended intakes reach the upper half," probably because some women don't absorb vitamin D well or spend less time in the sun than others.

"With the current advice, we're leaving a number of women behind," she adds. To play it safe, Dawson-Hughes advises women older than 70 to get 800 IU a day of vitamin D.

* Get sufficient protein. The link between protein and bone is still fuzzy. Some scientists claim that protein harms bone because it forces the kidneys to excrete more calcium. But that's only part of the story, say others.

"The question is whether the body adjusts over the long term," says the University of California's Deborah Sellmeyer. "And no one knows the answer."

In some studies, people aged 65 or older who eat more protein are less likely to break a hip. (6,7)

"Contrary to common misconceptions, the more protein older women eat, the less their bone loss and the better their bone density," says Dawson-Hughes.

One possibility: "Protein increases calcium in the urine, but it also promotes a bone growth factor, and it's the balance between losses and gains that determines bone density," she suggests.

It's also possible that older people who eat less protein have weaker bones because they eat poorer diets. And it's conceivable that the findings in older people may not apply to others. But all things considered, the evidence so far suggests that protein protects, rather than harms, bones as they age.

"Cutting back on protein is exactly the wrong thing to do,' says Harvard Medical School's Marian T. Hannan. "That's especially true for older folks, who are facing all kinds of insults to their health. They may need the protein to recover from infections, surgery, or chronic disease."

That's not to say that you should eat more red meat. To reduce the risk of heart disease and cancer, it makes more sense to get your animal protein from chicken, fish, and low-fat milk, yogurt, or cheese.

Says Hannan: "Whether you're nine or 90, it makes sense to eat a well-balanced diet that includes calcium, protein, and plenty of fruits and vegetables."

It's also clear that protein supplements can help elderly women recover from a hip fracture. But others needn't reach for a can of Ensure.

"Women need at least the Recommended Dietary Allowance for protein to reduce their risk of fracture," says Dawson-Hughes. That's 0.4 grams for every pound you weigh, which translates into 50 grams of protein for a 120-pound woman or 60 grams for a 150-pound woman. "We don't have enough evidence to say that they should get more," she adds.

* Get enough vitamin K. Vitamin K helps blood coagulate. But in recent years, researchers have found that women who consume the least vitamin K have a higher risk of hip fractures than women who consume more. (8)

"In the Framingham Osteoporosis Study, we found that the higher the intake, the higher the bone density," says Sarah Booth of the Jean Mayer U. S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University in Boston.

Researchers aren't certain how much vitamin K is enough, but in Framingham, those at highest risk got an average of 60 micrograms a day and those at lowest risk averaged 250 micrograms a day. (9) "It would be a major accomplishment if we could get all Americans to the current recommended levels--90 micrograms a day for women and 120 micrograms for men," says Booth.

No one will know for sure if vitamin K can prevent fractures until scientists complete several trials that will test the vitamin against a placebo (see "Vitamin K on Trial," p. 8). In the meantime, it makes sense to get enough K. Dark green lettuce, spinach, collards, and other greens are some of the best sources (see "Closing in on K," p. 8).

Some multivitamins have K, but many leave it out. You might have better luck with a calcium supplement. Each Viactiv Soft Calcium Chew, for example, supplies not only 500 milligrams of calcium, but 40 micrograms (half a day's worth) of vitamin K.

Caution: if you take coumadin or other blood-thinners, check with your doctor before taking any vitamin K, because it might change the dose of drug you need to prevent blood clots.

* Avoid excess caffeine. Caffeine increases calcium losses in the urine, but only some studies have found a higher risk of fractures in people who consume large amounts (at least three cups of coffee a day). The latest studies may explain the discrepancy. Researchers found that caffeine increased bone loss only in women over 65 who have one variation of a gene involved in making vitamin D. (10)

"Until we can know an individual's genotype, we have to assume that each person has a genetic susceptibility to osteoporosis," says Linda Massey of Washington State University in Spokane. "It's prudent to recommend that anyone over 65 get adequate calcium and no more than 300 milligrams of caffeine a day." That works out to two cups of brewed coffee, four cups of brewed tea, or six cans of cola or other caffeinated soft drinks.

* Exercise to strengthen muscles and bones. "If you measure the playing arm of a pro tennis player, it has more bone than the non-playing arm," explains Indiana University's C. Conrad Johnston.

"When you exercise, the muscles pull on the bone and produce strain and a slight bending. If you increase the strain, it increases bone."

Exercise has the greatest impact when bones are still growing, but it also works in older people. "And even if we don't have a lot of 75-year-old women pumping iron, they can still walk or do other exercise that builds their muscles," says Johnston. "And muscle strength can keep people from falling."

Any exercise that's weight-bearing--that is, done standing up--builds bone. That includes walking, jogging, stair climbing, dancing, and tennis. The exceptions: "Swimming is not weight-bearing, and cycling is only partially weight-bearing," says Dawson-Hughes.

* Forestall falls. Studies have homed in on several factors that make an older person more likely to fall. For example, "beta-blockers, which lower blood pressure, can cause lightheadedness when a person stands up," explains Dawson-Hughes. Sometimes doses can be adjusted to minimize the problem.

Not surprisingly, poor vision can make someone trip and fall. "Older people may have a cataract or other visual impairment that remains a problem even after they try to correct it," says Sellmeyer.

To lower your risk, "you can fall-proof the environment," says Dawson-Hughes. "Get rid of scatter rags, remove clutter, and make sure you have good lighting on steps."

WHO'S AT RISK?

"If you're over 65 or you're female, white, postmenopausal, and have at least one other risk factor for fractures, it's worth getting a bone density test," says Tufts University's Bess Dawson-Hughes. Some risk factors you can't control; others you can. And being frail or in poor health could fall into either category. In the Study of Osteoporotic Fractures, which tracked more than 9,500 men and women for four years, the four risk factors in bold had the largest impact on who broke a hip.

Risk Factors You CAN'T CONTROL

You're at risk if you:

* fractured a bone as an adult

* have a mother, father, or sibling with a history of fractures

* are Caucasian

* are over age 65

* are a woman

* have dementia

* are frail or in poor health

Risk Factors You MAY BE ABLE TO CONTROL

You're at risk if you:

* smoke cigarettes

* have an estrogen deficiency. That means you started menopause before age 45 or are premenopausal but haven't menstruated for more than a year

* weigh less than 127 pounds

* have a chronic low calcium intake

* suffer from alcoholism

* have impaired eyesight

* suffer repeated falls

* don't get enough physical activity

* are frail or in poor health

Source: National Osteoporosis Foundation.

WHEN DIET ISN'T ENOUGH

If your T-score falls below -2.0 (or even below -1.5 if you have other risk factors), doctors start to think about medication (see "Bones: Older and Weaker," p. 5). "We don't treat on one measure alone," explains Indiana University's C. Conrad Johnston. "But if a 60-year-old woman has low bone mass and she weighs 90 pounds and her mother broke a hip, we'd consider drugs," So far, the Food and Drug Administration has approved four classes of drugs to prevent or treat osteoporosis:

* Estrogen. Low doses of estrogen (hormone replacement therapy, or HRT) reduce the risk of fractures in the spine by 50 to 80 percent and in other bones by 25 percent over five years. Researchers estimate a 50 to 75 percent drop in all fractures over ten years. Estrogen also diminishes hot flashes and other symptoms of menopause.

While researchers used to think that estrogen prevents heart disease, the picture is now muddier. "The estrogen decision has gotten tougher because the evidence that it prevents cardiovascular disease is not clear," explains the University of California's Deborah Sellmeyer.

Estrogen isn't for everyone because it also increases the risk of blood clots and breast cancer. To Sellmeyer, those risks are low, unless you've had blood clots or a family history of breast cancer.

"The extra risk of breast cancer is only 20 percent after ten or 12 years of hormone replacement therapy," she explains. "So a woman right at menopause could take it for five or ten years and then switch to another drug."

But for some women, any extra breast cancer risk is too much. Fortunately, they have other options.

* Bisphosphonates. Fosamax, Actonel, and other bisphosphonates cut the risk of a fractured hip, spine, or wrist in half. And so far, their downsides are minor.

"They're tough to absorb with food, so you have to take them with a glass of water an hour before you eat in the morning," says Sellmeyer. And in a small number of people they cause inflammation of the esophagus, "though it goes away when you stop the drug."

The only other drawback: "The first bisphosphonate, etidronate (Didronel), caused osteomalacia, which is an inability to incorporate calcium and other minerals into the bone," says Sellmeyer. But many people still take it because osteomalacia doesn't occur if you go on and off the drug every 13 weeks.

The newer bisphosphonates, alendronate (Fosamax) and risedronate (Actonel), don't seem to cause osteomalacia, she adds. Her only reservation: "They haven't been around that long--only five to eight years."

* Raloxifene. Raloxifene (Evista) is a SERM, or selective estrogen receptor modulator. It acts as an estrogen on some tissues (like bone), but as an anti-estrogen on others (like the breast), and that can increase bone density while lowering breast cancer risk.

"We've seen a 76 percent reduction in breast cancer incidence in trials of raloxifene," says Sellmeyer. "It does increase the risk of blood clots, but the risk is still very low--about one per year for every 10,000 people who take the drug."

That might be a problem for older women who are not mobile, since they're at higher risk for blood clots, she adds. Raloxifene also causes a slight (six percent) increase in hot flashes, which could be a problem during menopause.

* Calcitonin. Calcitonin is a hormone that you take by injection or nasal spray. But it may not be worth the trouble. "In recent trials, there was only a small gain in bone density and a reduction in fractures at a lower dose and none at a higher dose," says Sellmeyer.

VITAMIN K ON TRIAL

Three major studies testing vitamin K's ability to strengthen bones are about to start. If you're interested in participating and live in or near one of the study areas, call to see if you qualify.

* Boston (Tufts University). The Vitamin K Study is recruiting men and women aged 60 to 80 (the women can't be on estrogen replacement therapy). Contact Molly Damon at [phone] or [e-mail].

* Toronto (University of Toronto). The ECKO (Evaluation of the Clinical Use of Vitamin K in Postmenopausal Women with Osteopenia) study is looking for postmenopausal Caucasian women of any age. Contact Doris Yee, Emily Cooper, or Irene Ho at [phone].

* Upper Midwest (University of Wisconsin). The Effect of Vitamin K on Bone Turnover in Postmenopausal Women study is seeking women who are at least five years postmenopause (natural or surgical) and are not taking estrogen replacement therapy. Contact Judy Harke at [phone] or [e-mail].

MORE YEARS, LESS BONE

The older you are, the weaker your bones. More than
six out of every ten non-institutionalized women
between the ages of 65 and 74 have low bone mass
(light blue), and close to two out of ten have osteoporosis
(dark blue). By age 75, more than a third of all
women have osteoporosis, and by age 85 more than
half do. Rates for men are lower at every age.

[GRAPHIC OMITTED]

Source: National Osteoporosis Foundation.
BONES: OLDER AND WEAKER

The black curve shows how bone density drops as a typical
osteoporosis patient ages. When density falls below the green
line at age 50, her "T-score" is -1, which means that her bone
density is 10 to 12 percent below that of a healthy woman in
her 20s. According to the World Health Organization, a
T-score between -1 and -2.5 is called "low bone mass," or
osteopenia.

When density drops below the red line at age 70, the
woman has osteoporosis--that is, her T-score is less than
-2.5, and her bone density is 20 to 30 percent below that of a
healthy woman in her 20s.

[GRAPHIC OMITTED]

Source: National Osteoporosis Foundation.
THE CALCIUM COUNTDOWN

Getting enough calcium has never been easier, now that
companies are adding it to cereals, juices, and other healthy
foods. For a rough estimate of how much you're eating,
count 300 mg for each serving of milk, yogurt, or cheese
and 250 mg from the rest of your diet. Your daily target
depends on your age: 1,300 mg if you're 9 to 18, 1,000 mg
if you're 19 to 50, and 1,200 mg if you're over 50.

Food                                                         Calcium
                                                             (milli-
                                                             grams)

Total cereal (3/4 cup)                                         1,000

Dreyer's or Edy's Frozen Yogurt, calcium fortified (1 cup)       600
Milk, calcium fortified (1 cup)                                  500
Viactiv Soft Calcium Chews (1 chew)                              500
Yogurt, fat-free or low-fat, plain (1 cup)                   350-400
Orange Juice with calcium (1 cup)                                350
Quaker Nutrition for Women Instant Oatmeal (1 packet)            350
Milk fat-free or 1% (1 cup)                                  300-350
Swiss cheese (1 oz.)                                             270
Yogurt, low-fat, fruit flavored (8 oz.)                      250-350
Sardines canned in water, drained (2 oz.)                        220
Cheddar cheese (1 oz.)                                           210
Soy milk, enriched (1 cup)                                   200-400
Light n' Lively Twice the Calcium Cottage Cheese (1/2 cup)       200
Wheatena (1/3 cup dry)                                           200
Collard greens, frozen (1/2 cup cooked)                          180
White beans, soybeans, black-eyed peas (1 cup cooked)        160-210
Ice cream or frozen yogurt, fat-free or low-fat (1 cup)      150-300
Ricotta cheese, fat-free or light (1/4 cup)                  100-320
Aunt Jemima Pancake & Waffle Mix (3 4-inch pancakes)         100-150
Eggo Waffles (2)                                                 100
I Can't Believe It's Not Butter, Sweet Cream & Calcium
  (1 Tbs.)                                                       100
Parkay Calcium Plus (1 Tbs.)                                     100
Salmon, canned, eaten with the bones (1/4 cup)                   100
Kale, frozen (1/2 cup cooked)                                     90
Bok choy (1/2 cup cooked)                                         80
Cottage cheese, low-fat (1/2 cup)                                 70
Parmesan cheese, grated (1 Tbs.)                                  70
Black beans, chickpeas, kidneys, pintos (1 cup cooked)         50-80
Bread, white or whole wheat (2 slices)                            50
Orange (1)                                                        50
Tofu (3 oz.)                                                  40-250
Broccoli (1/2 cup cooked)                                         40
Soy milk (1 cup)                                               20-80
THE SUNSHINE VITAMIN

Vitamin D may be the sunshine vitamin, but sunscreen
blocks the ultraviolet rays that your skin
needs to make vitamin D. And north of Los Angeles
or Atlanta, the sun's UV light is too weak to make
vitamin D from late fall through early spring.

The easiest solution is to take an ordinary
multi-vitamin with 400 IU of vitamin D. If you're older
than 70, the recommended level of vitamin D is
600 IU. Only a few brands of yogurt, margarine,
and hot cereal are fortified with D.

                                                             Vitamin D
Food                                                    (International
                                                                Units)

Halibut (3 oz. cooked)                                             680
Catfish (3 oz. cooked)                                             570
Pink salmon, canned (1/4 cup)                                      400
Quaker Nutrition for Women Instant Oatmeal (1 packet)              140
Dannon Light 'n Fit Yogurt (8 oz.)                                 100
Milk, vitamin D fortified, fat-free or 1% (1 cup)                  100
Viactiv Soft Calcium Chews (1 chew)                                100
Tuna, canned (1/4 cup)                                              90
Yoplait Custard or Light Yogurt (6 oz.)                             80
Parkay Calcium Plus (1 Tbs.)                                        60
Soy milk, enriched (1 cup)                                      40-120
Breakfast cereal, fortified (3/4-1 cup)                             40
Egg, large (1)                                                      30
CLOSING IN ON K

If you love salad and other greens, you're probably
getting enough vitamin K--that means at least 90
micrograms  (mcg) a day for women and 120 mcg for men,
according to the National Academy of Sciences. The
dressing you pour on top of your salad also may have
some K (depending on the oil), but at a steeper calorie
cost. Fat-free dressings have little or no vitamin K.

If salads and green vegetables aren't regulars on
your plate, make sure that your multivitamin or calcium
supplement has some vitamin K. Labels use the old
U.S. Recommended Daily Allowance, which is 80 mcg,
so 100% of the U.S. RDA isn't quite enough.

Food                                     Vitamin K
                                      (micrograms)

Collards (1/2 cup cooked)                      370
Spinach (1/2 cup cooked)                       320
Brussels sprouts (1/2 cup cooked)              230
Romaine lettuce (1 1/2 cups)                   190
Coleslaw (1 cup)                               120
Broccoli (1/2 cup cooked)                       90
Viactiv Soft Calcium Chews (1 chew)             40
Iceberg lettuce (1 1/2 cups)                    30
Soybean oil (1 Tbs.)                            30
Canola oil (1 Tbs.)                             20
Olive oil (1 Tbs.)                               8

(1) www.nof.org/physguide.

(2) New Eng. J. Med. 337: 670, 1997.

(3) Amer. J. Med. 111: 452, 2001.

(4) Arch. Ped. Adolesc. Med. 154: 610, 2000.

(5) Ann. Intern. Med. 115: 505, 1991.

(6) J. Bone Mineral Res. 15: 2504, 2000.

(7) Amer. J. Clin. Nutr. 69: 147, 1999.

(8) Amer. J. Clin. Nutr. 69: 74, 1999.

(9) Amer. J. Clin. Nutr. 71: 1201, 2000.

(10) Amer. J. Clin. Nutr. 74: 569, 694, 2001.