Altmed Watch

ALTMED WATCH
The latest research on complementary and alternative medicine

Too much vitamin A may increase threat of fractures

Large doses of vitamin A will likely increase the risk of fractures, according to a recent epidemiologic study. Among 2,322 subjects between the ages of 49 and 51, the risk of any kind of fracture was about 64% higher among those with serum levels above 75.6 µg/dL, when compared to those with readings in the more moderate range (62–67 µg/dL). The threat of a hip fracture in particular was almost 2.5 times greater in the high serum retinol group. And those with the highest serum levels (>103 µg/dL) faced a 700% greater risk of fractures of any kind.

Although it is difficult to determine how much dietary or supplemental vitamin A a person has to take in to reach these elevated levels—serum concentrations are determined by intake, absorption efficiency, liver function, and other factors—the researchers did find a correlation between retinol intake and fractures as well. Those who consumed more than 1.5 mg/day of preformed vitamin A (5,000 IU) were twice as likely to have a fracture, when compared to those in the lowest quintile (<0.53 mg/day). There was no association between either serum or dietary carotene—a vitamin A precursor—and fractures.

Michaelsson K, Lithell H, Vessby B, et al. Serum retinol levels and the risk of fracture. N Engl J Med. 2003; 348:287-294.

The link between tea drinking and bone mineral density

Long-term tea drinkers have denser bones, according to this large-scale epidemiologic study conducted in Taiwan. Mean total bone mineral density (BMD) was 1.150 g/cm² among men and women who didn't drink tea, compared with 1.174 g/cm² in those who had been regularly drinking tea for more than 10 years (P=0.006). (Regular tea drinkers consumed on average 414 mL/day of tea.) Similar correlations were found between tea consumption and hip and lumbar spine BMD. The researchers also found a dose-response relationship, with increasing duration of consumption correlating with increasing BMD, hinting at a possible cause/effect relationship.

When subjects' age, sex, body mass index, smoking status, alcohol use, and calcium intake were all factored into the statistical analysis, long-term tea drinking still surfaced as a contributing factor in improving BMD.

Several mechanisms of action have been proposed: Regular tea is rich in fluoride, which has been shown to slow down the osteoporotic process; it also contains flavonoids like ipiriflavone, which may improve BMD. There's also experimental data to suggest that tea extracts inhibit bone resorption. For the purposes of this study, tea consumption was defined as use of green tea (which is unfermented), oolong tea (partially unfermented), and black tea (fermented.)

Wu CH, Yang YC, Yao WJ, et al. Epidemiological evidence of increased bone density in habitual tea drinkers. Arch Intern Med. 2002;162:1001-1006.

Phytoestrogens, obesity, and type 2 diabetes

As the debate about the role of phytoestrogens in menopause management goes on, mounting evidence strongly suggests that these compounds may help control diabetes and obesity.

Both animal and human data indicate that soy protein, a source of the phytoestrogens daidzein and genistein, reduces serum insulin and insulin resistance. Other experiments suggest that flaxseed, a rich source of lignin, has similar effects. In one trial among type 2 diabetics, for instance, a high-fiber, soy protein-rich diet decreased postprandial hyperglycemia and serum triglycerides. A separate trial using soy improved glycosylated hemoglobin and lowered triglycerides.

Bhathena SJ, Velasquez MT. Beneficial role of dietary phytoestrogens in obesity and diabetes. Am J Clin Nutr. 2002;76:1191-1201.

This alternative apparently relieves osteoarthritis

S-adenosylmethionine (SAMe) is just as effective as nonsteroidal antiinflammatory drugs for relieving the pain and functional limitations brought on by osteoarthritis, according to a meta-analysis of 11 randomized clinical trials. In the review, SAMe, a physiologic compound created in the body from methionine and ATP, was given at a dose of 600 to 1,200 mg a day orally or 400 mg/day intravenously for up to 84 days.

The alternative remedy was compared to either placebo or NSAIDS like aspirin, ibuprofen, naproxen, and indomethacin. Patients on SAMe were 58% less likely to suffer adverse effects, when compared to those on NSAIDS.

Soeken KL, Lee, WL, Bausell RB, et al. Safety and efficacy of S-adenosylmethionine (SAMe) for osteoarthritis. J Fam Pract. 2002;51:425-430.

Department editor Paul L. Cerrato, MA, Managing Editor of Contemporary OB/GYN, is a guest lecturer at the Institute of Human Nutrition, Columbia University College of Physicians and Surgeons, New York, N.Y.

 

Altmed Watch. Contemporary Ob/Gyn 2003;3:118.