The Magnesium Connection

By Claudia Wallis.

Almost out of the blue, toxic shock syndrome appeared in the U.S. in the late 1970s, spreading fear among women and baffling scientists. The disease, which reached its peak in 1980, when 890 cases were reported, occurred primarily in menstruating women, though men and children could also be affected. Toxic shock could strike with appalling speed, progressing in a matter of hours from fever and dizziness to a strange, sunburn-like rash and a drop in blood pressure so severe that the victim might go into shock. For about 4% of patients, TSS proved fatal. Scientists quickly linked the disease to the use of tampons, particularly the "superabsorbent" variety, but the reasons for the tampon connection remained obscure. Last week a team of Harvard scientists finally offered an explanation.

Researchers have known for several years that TSS is caused by a toxin produced by a common and usually harmless bacterium called Staphylococcus aureus. In laboratory studies, the Harvard team, led by Infectious Disease Specialist Edward Kass, found that the bacterium produces up to 20 times as much toxin as usual in the presence of certain tampon fibers. Kass's group discovered that the fibers -- polyester foam and polyacrylate rayon -- soak up large amounts of magnesium, which is normally present in vaginal tissue and fluid. When the magnesium is removed from the bacterium's environment, the bug responds by churning out great quantities of the deadly toxin.

An important clue to the magnesium factor came from Kass's earlier research on diphtheria, which is also caused by a bacterial toxin. He recalled that when deprived of iron, the diphtheria microbe produces excessive amounts of toxin. "You comb your mind for something you can get a hold on," he says, and the diphtheria-iron connection "leaped right out." Through a trial-and- error process, Kass and his team found that magnesium played a parallel role with Staph. aureus.

The magnesium link may help explain why toxic shock typically occurs on the fourth day of a woman's period, when the menstrual flow has diminished. During the previous days, the volume of fluid is greater, and, Kass believes, there is probably enough unabsorbed magnesium present to keep toxin production in check.

Though TSS is widely feared, relatively few people are vulnerable. Doctors estimate that by age 20, 95% of the U.S. population have been exposed to Staph. aureus toxin and have developed immunity. Of the remaining 5%, some may be genetically incapable of developing immunity. These women and men may actually suffer more than one bout of TSS, which can be treated with antibiotics.

The Harvard findings have already led the manufacturers of Playtex and Tampax tampons to withdraw products containing polyacrylate rayon from the market and replace them with safer, though somewhat less absorbent versions. Procter & Gamble's Rely tampons, the only type containing polyester foam, were discontinued in 1980, after they had been linked to dozens of cases of TSS (the incidence rate promptly dropped). Kass is hopeful that his research, which was sponsored by Tambrands (the maker of Tampax), will help manufacturers in developing new tampons that are both ultra-absorbent and safe.

With reporting by John H. Kennedy/Boston