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Thu, Aug-01-02, 16:17
Cutting carbohydrates risks health problems for some dieters
Copyright © 2002
United Press International
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By KATRINA WOZNICKI, United Press International
DALLAS (August 1, 2002 2:32 p.m. EDT) - The popular high-protein, low-carbohydrate diet many overweight people are using to shed pounds quickly also can increase the risk of kidney stones and bone loss, a new study revealed Thursday.
Researchers at the University of Texas Southwestern Medical Center said they have reached that conclusion after studying 10 healthy individuals who followed this diet.
"It's already been known a high-protein diet will produce high acid loads," researcher Dr. Chia-Ying Wang, a professor of internal medicine, told United Press International. The high-protein diet is widely used in this country, Wang said, and scientists wanted to confirm the dangers of this diet. Dieters will lose weight from the high-protein approach, but it is not a healthy way to shed those pounds, she said.
All 10 subjects began by eating a regular diet for two weeks. Then they were placed on a highly restrictive diet that allowed for some vegetables but no fruits and less than 20 grams of carbohydrates. Protein consumption was unrestricted. The subjects followed this diet for two weeks before starting a less-restrictive diet for the final four weeks. Everyone took daily multivitamin supplements to reduce the risk of vitamin deficiency. During the last five days of each stage of the study, participants underwent various tests to see how the various diets were affecting their bodies.
Test results showed acid load in the blood rose as much as 90 percent while subjects were on the high-protein diet - a state called ketoacidosis, which also is associated with diabetes. Levels of urinary citrate, which inhibits kidney stones, dropped by almost 25 percent. Urinary citrate readings improved slightly when subjects went on to the more moderate diet.
Researchers also reported acid excretions rose from baseline levels of 61 milli-equivalents per day to 116 during the restricted diet. These levels dropped slightly to 112 when the group resumed eating moderate levels of carbohydrates. The chronic acid excretion involved in ketosis suppresses the function of osteoblasts, cells that help form bone, increasing the risk of bone loss. The high acidic content of meat and the lack of alkaline foods such as carbohydrates in the diet increased the risk for kidney stones and bone loss, researchers reported.
Wang said, on average, people should consume half their daily calories from carbohydrates. The high-protein diet permits only 15 percent of daily calories to come from carbohydrates. Limiting carbohydrates forces the body to search for other sources of energy, one of which is fat, Wang said. Ketone bodies, which cause ketoacidosis, are formed when the body is forced to burn fat for energy.
"This type of study is unique because they put healthy people on the diet," and they still went on to develop abnormal urinary citrate levels, Liz Applegate, a professor of nutrition at the University of California at Davis, told UPI. "There's a chunk of the population that could be susceptible to kidney stones and if they're trying out this diet, it's dangerous."
Although excessive animal protein levels are linked to calcium loss, Applegate said people rarely stay on the low-carbohydrate, high-protein diet long enough to develop any potential for bone problems because too often people start to miss the foods they've been asked to cut out.
"Anybody can lose weight," Applegate added. "I can stick you on a butter diet and you'll lose weight." The key is keeping those pounds off, she said.
The U.S. Surgeon General's office in Washington and the Centers for Disease Control and Prevention in Atlanta report 61 percent - nearly two-thirds - of all Americans are either overweight or clinically obese.
The research is reported in the August issue of The American Journal of Kidney Diseases.
Copyright © 2002
United Press International
E-mail this story
By KATRINA WOZNICKI, United Press International
DALLAS (August 1, 2002 2:32 p.m. EDT) - The popular high-protein, low-carbohydrate diet many overweight people are using to shed pounds quickly also can increase the risk of kidney stones and bone loss, a new study revealed Thursday.
Researchers at the University of Texas Southwestern Medical Center said they have reached that conclusion after studying 10 healthy individuals who followed this diet.
"It's already been known a high-protein diet will produce high acid loads," researcher Dr. Chia-Ying Wang, a professor of internal medicine, told United Press International. The high-protein diet is widely used in this country, Wang said, and scientists wanted to confirm the dangers of this diet. Dieters will lose weight from the high-protein approach, but it is not a healthy way to shed those pounds, she said.
All 10 subjects began by eating a regular diet for two weeks. Then they were placed on a highly restrictive diet that allowed for some vegetables but no fruits and less than 20 grams of carbohydrates. Protein consumption was unrestricted. The subjects followed this diet for two weeks before starting a less-restrictive diet for the final four weeks. Everyone took daily multivitamin supplements to reduce the risk of vitamin deficiency. During the last five days of each stage of the study, participants underwent various tests to see how the various diets were affecting their bodies.
Test results showed acid load in the blood rose as much as 90 percent while subjects were on the high-protein diet - a state called ketoacidosis, which also is associated with diabetes. Levels of urinary citrate, which inhibits kidney stones, dropped by almost 25 percent. Urinary citrate readings improved slightly when subjects went on to the more moderate diet.
Researchers also reported acid excretions rose from baseline levels of 61 milli-equivalents per day to 116 during the restricted diet. These levels dropped slightly to 112 when the group resumed eating moderate levels of carbohydrates. The chronic acid excretion involved in ketosis suppresses the function of osteoblasts, cells that help form bone, increasing the risk of bone loss. The high acidic content of meat and the lack of alkaline foods such as carbohydrates in the diet increased the risk for kidney stones and bone loss, researchers reported.
Wang said, on average, people should consume half their daily calories from carbohydrates. The high-protein diet permits only 15 percent of daily calories to come from carbohydrates. Limiting carbohydrates forces the body to search for other sources of energy, one of which is fat, Wang said. Ketone bodies, which cause ketoacidosis, are formed when the body is forced to burn fat for energy.
"This type of study is unique because they put healthy people on the diet," and they still went on to develop abnormal urinary citrate levels, Liz Applegate, a professor of nutrition at the University of California at Davis, told UPI. "There's a chunk of the population that could be susceptible to kidney stones and if they're trying out this diet, it's dangerous."
Although excessive animal protein levels are linked to calcium loss, Applegate said people rarely stay on the low-carbohydrate, high-protein diet long enough to develop any potential for bone problems because too often people start to miss the foods they've been asked to cut out.
"Anybody can lose weight," Applegate added. "I can stick you on a butter diet and you'll lose weight." The key is keeping those pounds off, she said.
The U.S. Surgeon General's office in Washington and the Centers for Disease Control and Prevention in Atlanta report 61 percent - nearly two-thirds - of all Americans are either overweight or clinically obese.
The research is reported in the August issue of The American Journal of Kidney Diseases.