Early Evidence

Already, a growing number of researchers atHarvard and elsewhere are trying to isolate theeffect on humans of beta carotene, first isolatedfrom carrots in 1910.

In 1981 and again in 1984, researchers foundthat the chemical may ward off breast cancer. Morerecent studies have pointed to the molecule'sbeneficial effect on ovarian and lung cancer.

And Micheline Mathews-Roth, an associateprofessor of medicine at the Medical School, saysthat she expects to publish a paper sometime in1991 directly linking beta carotene to theprevention of bladder cancer.

In addition, researchers have in recent monthsstumbled rather serendipitiously across a sideeffect of the chemical: its role in reducingmyocardial infarction, or heart failure.

J. Michael Gaziano, clinical fellow in medicineat the Medical School, presented the Harvardgroup's findings before an American HeartAssociation convention in Dallas last month. Thestudy was performed on 333 subjects--a subset ofthe full Physicians' Health Study--who alreadyshowed some signs of heart disease.

After six years, Gaziano and co-workers foundthat men taking a 50-milligram beta carotene pillevery other day (about 25 times the averageintake) were only half as likely as those takingplacebo pills to suffer a heart attack, an evenbetter result than the stunning 44 percentreduction achieved with aspirin.

For now, though, doctors aren't advising theirpatients to eat carrots until their stomach turnsand their skin becomes yellow. The study wasconducted on a sick population, Gaziano says, andbeta carotene's effects on healthy subjectsremains untested.

"Our message down at Dallas was primarily toresearchers," says Gaziano. "We're not at thestage where we can make recommendations...to thepublic."

Perhaps more importantly, researchers are waryof publicizing beta carotene's potential whilethousands of their subjects are still involved inthe study, either as controls or as beta carotenetakers.

"If we release more information about betacarotene, [the subjects] might start taking it,"and thus bias the study, Gaziano says. So on theadvice of the study's overseeing board, Hennekens,Gaziano and others will see no more data from thestudy until its completion, at least five yearsaway.

Scientific Theories

While they wait, however, research progressesapace on the molecule's chemical effects on humancells.

Scientists at Harvard and elsewhere haveproposed that beta carotene could hinder theoperation of low density lipoproteins (LDL), aform of cholesterol which is a prime suspect intumor growth.

Although they have no direct evidence,clinicians have seen oxidized LDL (LDL which hasabsorbed oxygen ions) devastate cells grown inpetri dishes, and they have suggested that itwould cause similar damage--perhaps even promotecancer growth--when shuttling through thecirculatory system of a human.