Vegetarians on Raw-Foods Diets Have Low Bone Mass
But other measures of bone health are normal, study finds
WEDNESDAY, March 30, 2005 (HealthDay News) -- Vegetarians who eat only raw plant-derived foods have abnormally low bone mass, usually an early sign of bone-thinning diseases like osteoporosis, a new study finds.
But the researchers were surprised to learn that other measures of bone health -- such as bone turnover and vitamin D status -- were normal in the strict vegetarians.
"These people have low bone mass but low bone mass is just one aspect of their risk for fracture," said Dr. Luigi Fontana, lead author of the study, published in the current issue of the Archives of Internal Medicine.
"They had low bone mass, so clinically they are at increased risk for fracture. But some of the other markers, like bone turnover, are normal and it's possible the quality of the bone is preserved," he added.
Still, Fontana, a research instructor at Washington University in St. Louis, emphasized he would never advise people to go on a raw-foods vegetarian diet, in which people eat only plant-derived foods that have not been cooked, processed or otherwise altered.
"It's too extreme," he said.
Fontana's team studied the effects of raw plant-derived eating plans partly because there is a dearth of research on the diets and their impact. He compared the bone density and such measures as vitamin D status in 18 people who ate a raw-foods vegetarian diet for an average of 3.6 years. A control group consisted of another 18 people who ate a typical American diet. The ages of both groups ranged from 33 to 85 and none of the participants was concerned about their bone health, he said.
The vegetarians ate about 1,285 to 2,432 calories a day, with about 9.1 percent of those calories from protein, 43.2 percent from fat and 47.7 percent from carbohydrates. Their intake of calcium and vitamin D was low, 579 milligrams and 16 units, respectively, a day.
The control group ate from 1,976 to 3,537 calories a day, with about 17.9 percent of calories from protein, 32.1 percent from fat and 50 percent from carbohydrates. Their intake of calcium and vitamin D was higher -- 1,093 milligrams and 348 units, respectively, a day.
For adults, 1,000 to 1,300 milligrams of calcium a day are recommended to help prevent osteoporosis. The disease, characterized by porous bone and low bone mass, affects at least 10 million people in the United States, according to the National Osteoporosis Foundation.
An adequate intake of vitamin D for most adults below age 50 is 5 micrograms, or 200 units, according to the National Academy of Sciences. Vitamin D is also important to bone health.
The bone mineral content and bone mineral density of the vegetarians were significantly lower than the control group at all sites measured on the body -- lumbar spine, hip and neck, Fontana said.
The T-scores of the vegetarians were lower than those in the control group. A T-score compares a person's bone mineral density to the peak density of a 30-year-old healthy adult and determines the risk of fracture. A T-score between plus one and minus one is considered normal, Fontana said.
The T-scores of the vegetarians at the lumbar spine averaged minus 2.1; for the controls at the same site the score was minus 0.43.
Another expert familiar with the new study said the findings are "pretty preliminary" but, like Fontana, cautioned people not to follow the extreme raw-foods vegetarian diet.
"The numbers that concern me are that they have a low body mass index and their bone mineral content and density is on the lower end," said Lona Sandon, an assistant professor of clinical nutrition at the University of Texas Southwestern Medical Center, in Dallas, and a spokeswoman for the American Dietetic Association.
Body mass index is a ratio of height to weight and is used to assess health risks and weight status. It was just 20 in the vegetarian group, Sandon noted. The control group averaged a BMI was a little over 25. (A BMI of 18.5 to 24.9 falls within the normal range.)
"Once you get below 19.5, you are at risk of low bone mineral density long-term because you don't have enough weight-bearing to keep your bone," Sandon said.
Based on these findings, "you can't say it is OK to be on a raw-food vegetarian diet for a long period of time," she added.
To learn more about bone health, visit the National Osteoporosis Foundation.