NEW ORLEANS — With a virtual alphabet soup of vitamin and mineral supplements available—and a constant barrage of new nutritional advice each week—it's a challenge to know what truly bolsters bone health, Neil Binkley, M.D., said at the annual meeting of the International Society for Clinical Densitometry.
General malnutrition is actually a common phenomenon in the United States, said Dr. Binkley, of the Institute on Aging at the University of Wisconsin in Madison. According to one study, 11% of patients older than 65 are undernourished. And some studies have suggested that elderly patients with fractures are more likely to be malnourished. Keeping an eye out for malnourished patients could help reduce the risk of falls and fractures, he said.
Although supplements offer an easy solution, food is still the best source of vitamins and minerals. Dr. Binkley shared the following tips:
Phosphorus
Phosphorus insufficiency is generally not a common problem, but it tends to occur in some of the more vulnerable populations. Phosphorus deficiency decreases mineralization and osteoblast function while increasing osteoclast function.
An estimated 15% of women over age 80 receive less than 70% of the U.S. recommended daily allowance (RDA) of phosphorus (1,000 mg). It has also been suggested that patients who fail to respond to calcium supplementation may, in fact, have inadequate phosphorus intake.
Vitamin D
Make sure patients are aware that not all dairy products are fortified with vitamin D. “You can't get vitamin D in food unless you happen to like liver or lots of salmon or mackerel,” Dr. Binkley said.
Vitamin D toxicity is less of a concern than it once was. Recommended levels of vitamin D range from 1,200 to 1,500 IU per day. Levels in excess of 10,000 IU per day are now believed toxic, so there is a large margin of error.
Supplements may be necessary to get enough vitamin D. Dr. Binkley noted that to get 1,000 IU vitamin D, you would need to drink half a gallon of milk or eat 40 egg yolks. Getting a little sun is also an option.
The bigger problem with ensuring that patients get enough vitamin D may be in obtaining a good assay, Dr. Binkley said. In one study, he and his colleagues used four different assays to measure patient vitamin D levels. Although the four methods agreed quite well for some patients, there were big differences among the assays for other patients.
Attempts to standardize vitamin D assays are ongoing. High-performance liquid chromatography (HPLC) appears to provide the best results. Dr. Binkley advised that if HPLC and commercial assays agree that a patient's vitamin D levels are low, they probably are.
But if commercial assays indicate a patient's levels are not low, consider HPLC. He also noted that if you give your patient very high, prescription-level doses (50,000 IU) of vitamin D, at least one of the commercial 25-hydroxy assays only detects about half of it in the blood.
Vitamin A
A family of about 25 compounds constitute vitamin A, but the active component is retinol. The RDA for vitamin A is 2,600 IU (800 mcg) per day for men and 2,300 IU (700 mcg) per day for women.
The effects of getting too much vitamin A are unclear. Generally, it's been assumed that the body has built-in safeguards to avoid vitamin A toxicity.
Yet it's theorized that excessive vitamin A will suppress osteoblast activity and stimulate bone reabsorption. In addition, epidemiologic data suggest that the consumption of more than 5,000 IU daily increases fracture risk—but clinical studies have not confirmed this association.
Dietary sources of vitamin A include liver, fish, and fortified foods such as dairy products; certain fruits and vegetables are high in carotenoids. Vitamin A supplementation is considered necessary only in special situations, and patients should be counseled never to take synthetic retinol.
Vitamin K
Low vitamin K levels have been reported in patients with osteoporotic fractures and epidemiologic data show an increased risk of hip fracture with low levels of vitamin K. But vitamin K doesn't linger in the blood for very long, so it's difficult to get an accurate measure, Dr. Binkley said.
Most of the existing data come from Japan, where a different form of vitamin K is taken from that used in the United States. The Japanese studies used 45 mg per day and showed sustained levels of bone mineral density (BMD) and vertebral fracture-prevention benefits. Adequate intake of vitamin K in the United States, however, is thought to be about 100 mcg per day. It's probably too early to recommend vitamin K supplementation, he concluded.