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Salt of the Earth Bad on the Bones

New research shows new dangers in high-salt diets for women

TUESDAY, Nov. 13, 2001 (HealthDayNews) -- Ladies, listen up. Before you grab that bag of salty, crunchy chips and head for the couch, there's something you should know: Not only can all that sodium leave you bloated, a new study shows it also may be eating away your bones' strength.

The good news, however, is the research also shows that increasing your intake of the mineral potassium -- abundant in fruits and vegetables -- might help offset that risk.

"The impact of abundant dietary salt on skeletal health has yet to be established, but [it] is potentially detrimental through increased urinary calcium losses," reports study author Dr. Deborah Sellmeyer, director of the University of California at San Francisco/Mt. Zion Osteoporosis Center.

The study, presented last month at the 23rd Annual Meeting of the American Society for Bone and Mineral Research in Phoenix, Ariz., shows that high salt intake is linked to an increased level of urinary calcium, meaning the more salt you eat, the more calcium leaves your body. And experts say that's bad for your bones.

"The more calcium you drain from your body, the less there will be available for bones to utilize in the continual process of rebuilding new bone cells, something that takes place in the body throughout our lifetime," says New York University nutritionist Samantha Heller.

Without enough calcium, Heller says bone breaks down faster than it can rebuild, and that can lead to a weak skeleton and a better chance your bones will break.

In addition, because the body needs calcium for so many other functions, including muscle contraction, if you increase your calcium excretion, the body responds by pulling what it needs directly from the bone, says Heller.

"This further serves to weaken bone strength and contributes to the risk of fracture," she says.

Sellmeyer's research had two goals: to study the effects of a high-salt diet on both calcium retention and the development of new bone in post-menopausal women, and to examine whether the mineral potassium could counter the negative effects of such a diet.

The research began with a rotating diet. First women in the study ate low-salt meals, with no more than 1,500 milligrams of sodium daily for three weeks. They then were switched to a high-salt diet of roughly 4,000 milligrams of sodium daily for four more weeks. (One teaspoon of salt contains 2,000 milligrams of sodium.) Experts say healthy adults should eat about 1,100-3,300 milligrams of sodium per day, but most people eat 2,300 to 6,900 milligrams every day, reports the University of Illinois. (To bring this down to the dinner table even more graphically, a deluxe fast food hamburger contains 918 milligrams of sodium, says the National Agricultural Laboratory.)

In addition, during the high-salt phase of the study, the women were randomly assigned to also consume either a daily supplement containing about 1,100 milligrams of potassium or a placebo pill. Urine tests were taken after three weeks on the low-salt diet and again at the end of the study.

The result: The high-salt diet increased daily excretion of urinary calcium by 42 milligrams compared with the low-salt diet phase of the study. But when the potassium supplement was added to the high-salt diet, calcium excretion dropped to just 8 milligrams a day more than what was being lost on the low-salt diet.

Sellmeyer says at least on a preliminary basis, potassium could counteract some negative effects of a high-salt diet on bone health.

Heller, however, says, "Women should not get the idea that they can wipe away any potential damage from a high-salt diet with a potassium supplement because this is not true."

She says potassium seems to counteract only the effects of high-salt on bone health; no one's proved that it alters the negative effects of a high-salt diet on the heart, the kidneys or on blood pressure.

"It's also important for women to know that a potassium supplement should never be taken without a doctor's OK; if you want more potassium in your diet, the safest and most healthful way is with fruits and vegetables," says Heller.

If you are diagnosed with diabetes or kidney disease, or regularly use nonsteroidal anti-inflammatory drugs, diuretics, ACE inhibitors or heart medications, do not take potassium supplements or significantly increase dietary potassium without first checking with your doctor.

What To Do

For more information on sodium content in common foods click here, and for some facts on potassium, check this CNN page.

For some low-salt recipes from the American Heart Association, click here.

To find out which fruits and veggies contain the highest potassium levels, click here. And the University of Illinois has some tips and a recipe for a salt substitute.

Think you know how much salt you're getting every day? Take this quiz from the National Agricultural Library; you might be surprised at the answers. (You'll need Adobe Acrobat to read it.)

SOURCES: Interviews with Samantha Heller, M.S., R.D., department of nutrition, New York University Medical Center, Manhattan; published conference comments by Dr. Deborah Sellmeyer, assistant adjunct professor of medicine and director, University of California at San Francisco/Mt. Zion Osteoporosis Center, Calif.; Oct. 16, 2001, presentation at American Society for Bone and Mineral Research Annual Meeting, Phoenix, Ariz.
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