Vitamins A and D Improve Bone Health in Children and Adults
Philadelphia PA, 19 June 2003

Research Presented at ENDO 2003, the 85th Annual Meeting of The Endocrine Society

New research highlights the important role that vitamins A and D play in bone health and identifies a common and previously under-appreciated relationship in postmenopausal women.

Two of the new studies found that vitamin D deficiency is much more frequent among African American children and adults than previously thought, while a third finds that high and low levels of vitamin A can increase hip fractures in older women. A fourth study discovered a relationship between hypercalciuria—a condition that causes loss of calcium through urine—and bone fractures in postmenopausal women.

All four studies will be presented during ENDO 2003, the 85th Annual Meeting of The Endocrine Society, beginning June 20 at the Pennsylvania Convention Center in Philadelphia, PA.

Vitamin D

During adolescent years, nutritional problems such as vitamin D deficiency can have a negative impact on bone density. In adults, low levels of vitamin D can be responsible for low dietary calcium absorption as well as hyperparathyroidism—a condition that occurs when the parathyroid gland, which is located in the neck, produces too much parathyroid hormone. When this happens, there is too much calcium in the patient's blood. Hyperparathyroidism can cause fatigue, disorientation, and depression, and can also lead to bone loss and kidney stones.

Two new studies reveal that vitamin D deficiency is widespread among African American adolescents and women. In one study, researchers measured vitamin D levels in more than two hundred adolescents. Eighteen percent of the subjects tested positive for vitamin D deficiency, which was equal in boys and girls, but more prevalent in African Americans and during the winter months. Researchers also discovered a correlation between lifestyle variables and vitamin D deficiency.

"Adolescents who took vitamins as well as calcium supplements and exercised regularly were less likely to suffer from vitamin D deficiency," explains Dr. Catherine Gordon, an endocrinologist at Children's Hospital in Boston. "Our findings suggest that vitamin D deficiency is common among adolescents. It is critical that we find ways to help adolescents maintain healthy levels of vitamin D to avoid skeletal problems as they age."

In a second study on vitamin D, researchers found an extremely high—nearly 65 percent—prevalence rate of vitamin D deficiency among obese African Americans, particularly in African American women. In the study, researchers compared the levels of vitamin D deficiency in overweight African American and Caucasian subjects. Many of the subjects with vitamin D deficiency were also found to suffer from secondary hyperparathyroidism as a result of their low levels of vitamin D.

"We already know that dark skin pigment and increased body weight put people at higher risk for developing vitamin D deficiency," notes Dr. Shamik Parikh, a clinical investigator at the National Institute of Child Health and Human Development. "Our findings suggest that obese African Americans, especially women, should be regularly screened for vitamin D deficiency."

Vitamin A

Recent studies have shown that high intake of vitamin A can be associated with lower bone density and increased risk of fracture. The new research has generally focused on populations with high intake of vitamin A.

Investigators at Columbia University's College of Physicians and Surgeons in New York City sought to determine whether high and low levels of vitamin A placed postmenopausal women at an increased risk for hip fractures. The doctors used the United States government's NHANES I survey, which began in the 1970s. NHANES I has information now from a 22-year follow-up of nearly three thousand women. One hundred and seventy nine women in the study experienced hip fractures during the study and follow-up. Researchers divided these women into five groups, or quintiles, based on their vitamin A levels.

"Women with the highest vitamin A levels and lowest vitamin A levels were both twice as likely to experience a hip fracture when compared with women who had average levels of vitamin A," said Dr. Alexander Opotowsky, the lead investigator in the study. "This is the first time that a study has demonstrated increased hip fractures at both ends of the vitamin A concentration curve."

The investigators note that these new results may prompt the medical community to reassess recent calls to decrease vitamin A supplementation among general populations. Dr. Opotowsky explains that for some people, vitamin A supplementations may increase fracture risk, but for people with low vitamin A levels, supplementation may be a benefit.

"Our analysis suggests that small amounts of vitamin A may not influence overall hip fracture rates. However, without knowing the vitamin A status of an individual, eliminating vitamin A supplements could actually increase the number of vitamin A deficient individuals, which would put them at further risk not only for hip fractures, but also for other health risks associated with low vitamin A," explains Dr. Opotowsky.

Hypercalciuria

Hypercalciuria is a condition where a person loses calcium through their urine. Studies have shown that vertebral fractures are more common among people with hypercalciuria. However, until now, the percentage of people with hypercalciuria who suffer from fractures has not been known.

Researchers in Italy studied about 13,000 men and women over a 10-year period and found 46 males and about 1,200 females with hypercalciuria. Through x-rays of the hypercalciuric men and women, researchers found that 85 percent of males and 21 percent of females with hypercalciuria experienced fractures.

"About 3.7 percent of women in the general public experience fractures," said Dr. Maurizio Bevilacqua, a researcher at Luigi Sacco-Polo University Hospital in Milano, Italy. "According to our findings, this number increases to about 21 percent in postmenopausal women with hypercalciuria. Testing for hypercalciuria, which is a simple and inexpensive exam, could identify postmenopausal women who are at risk for vertebral fractures."

About The Endocrine Society

The Endocrine Society is the world's oldest, largest, and most active organization devoted to research on hormones, and the clinical practice of endocrinology. Endocrinologists are specially trained doctors who diagnose, treat and conduct basic and clinical research on complex hormonal disorders such as diabetes, thyroid disease, osteoporosis, obesity, hypertension, cholesterol and reproductive disorders. Today, The Endocrine Society's membership consists of over 10,000 scientists, physicians, educators, nurses and students, in more than 80 countries. Together, these members represent all basic, applied, and clinical interests in endocrinology. The Endocrine Society is based in Bethesda, MD.

Source

Endocrine Society (www.endo-society.org).