Study: You can beat cancer with fasting


Chem­o­ther­a­py drugs work bet­ter against can­cer when com­bined with cy­cles of short, se­vere fast­ing, a study has found.

According to, re­search­ers sug­gest the fast­ing might help be­cause nor­mal cells tend to put off try­ing to di­vide when nu­tri­ents are lack­ing—but can­cer cells keep try­ing, and this pro­cess ul­ti­mately kills them.

Fast­ing, even on its own, ef­fec­tively treated a ma­jor­ity of can­cers tested in mice, in­clud­ing trans­planted can­cer tu­mors made of hu­man cells, re­search­ers said. Their stu­dy, pub­lished in the jour­nal Sci­ence Trans­la­t­ional Med­i­cine, found that five out of eight can­cer types in mice re­sponded to fast­ing alone: just as with chem­o­ther­a­py, fast­ing slowed the growth and spread of tu­mors. And with­out ex­cep­tion, “the com­bina­t­ion of fast­ing cy­cles plus chem­o­ther­a­py was ei­ther more or much more ef­fec­tive than chemo alone,” said study sen­ior au­thor Val­ter Longo of the Uni­vers­ity of South­ern Cal­i­for­nia.

Mul­ti­ple cy­cles of fast­ing com­bined with chem­o­ther­a­py cured 20 per­cent of mice with a highly ag­gres­sive type of chil­dren’s can­cer that had spread through­out the body, and 40 per­cent of mice with a more lim­it­ed spread of the same can­cer, the au­thors added. No mice sur­vived in ei­ther case if treated only with chem­o­ther­a­py.

“We don’t know wheth­er in hu­mans it’s ef­fec­tive,” said Longo, adding that it would take a clin­i­cal tri­al of sev­er­al years to find out. Re­sults from the first phase of a clin­i­cal tri­al with breast, uri­nary tract and ovar­i­an can­cer pa­tients, con­ducted at the uni­vers­ity, have been sub­mit­ted for pre­s­enta­t­ion at the next an­nu­al meet­ing of the Amer­i­can So­ci­e­ty of Can­cer On­col­o­gists. But the first phase tests only the safe­ty of a ther­a­py, in this case wheth­er pa­tients can tol­er­ate two-day fasts be­fore and af­ter chem­o­ther­a­py.

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Fast­ing is­n’t safe for eve­ry­one, Longo warned. The clin­i­cal tri­al did­n’t en­roll pa­tients who al­ready had lost more than 10 per­cent of their nor­mal weight or who had oth­er risk fac­tors, such as di­a­be­tes. Fast­ing al­so can cause a drop in blood pres­sure and headaches, which could make driv­ing and oth­er ac­ti­vi­ties dan­ger­ous for some.

In a case re­port study with self-re­ported da­ta pub­lished in the jour­nal Ag­ing in 2010, 10 can­cer pa­tients who tried fast­ing cy­cles per­ceived few­er side ef­fects from chem­o­ther­a­py.

In mice, the new study found that fast­ing cy­cles with­out chem­o­ther­a­py could slow the growth of breast can­cer as well as the can­cers mel­a­no­ma, gli­o­ma and hu­man neu­rob­las­toma. In sev­er­al cases, the fast­ing cy­cles were as ef­fec­tive as chem­o­ther­a­py, the re­search­ers said. Fast­ing al­so ex­tend­ed sur­viv­al in mice bear­ing a hu­man ovar­i­an can­cer. In the case of mel­a­no­ma, a deadly skin can­cer, the can­cer cells be­came re­sist­ant to fast­ing alone af­ter a sin­gle round, but the sin­gle cy­cle of fast­ing was as ef­fec­tive as chem­o­ther­a­ in re­duc­ing the spread of can­cer to oth­er or­gans.

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For all can­cers tested, fast­ing com­bined with chem­o­ther­a­py im­proved sur­viv­al, slowed tu­mor growth and/or lim­it­ed the spread of tu­mors, the in­ves­ti­ga­tors re­ported.

As with any po­ten­tial can­cer treat­ment, fast­ing has its lim­its, Longo stressed. The growth of large tu­mor mass­es was re­duced by mul­ti­ple fast­ing and chem­o­ther­a­py cy­cles, but can­cer-free sur­viv­al was­n’t achieved, the re­search­ers said. Longo spec­u­lat­ed that cells in­side a large tu­mor may be pro­tected some­how or that the va­ri­e­ty of muta­t­ions in a large tu­mor may make it more adapt­a­ble.

But he not­ed that in most pa­tients, on­col­o­gists have at least one chance to at­tack the can­cer be­fore it grows too large.

Longo and col­la­bo­ra­tors at the U.S. Na­t­ional In­sti­tute on Ag­ing stud­ied one type of breast can­cer in de­tail to try to un­der­stand fast­ing’s ef­fects. While nor­mal cells de­prived of nu­tri­ents en­ter a dor­mant state si­m­i­lar to hi­berna­t­ion, the re­search­ers saw that the can­cer cells tried to make new pro­teins and took oth­er steps to keep grow­ing and di­vid­ing. The re­sult, Longo said, was a “cas­cade of events” that led to the crea­t­ion of dam­ag­ing mo­le­cules called free rad­i­cals. These broke down the can­cer cells’ DNA and de­stroyed them.

“The cell is, in fact, com­mit­ting cel­lu­lar su­i­cide. What we’re see­ing is that the can­cer cell tries to com­pen­sate for the lack of all these things mis­sing in the blood af­ter fast­ing. It may be try­ing to re­place them, but it can’t,” Longo said.

The new study book­ends re­search pub­lished in the jour­nal Pro­ceed­ings of the Na­t­ional Acad­e­my of Sci­ences in 2008. In that work, Lon­go’s team showed that fast­ing pro­tected nor­mal cells against chem­o­ther­a­py, but did­n’t ad­dress the ef­fect on can­cer cells. The study al­so fo­cused only on a sin­gle can­cer and chem­o­ther­a­py drug. The new work ex­tends those re­sults by show­ing that fast­ing not only fails to pro­tect can­cer cells, but makes them more vul­ner­a­ble, Longo said. He called the ef­fect “d­if­fer­en­t stress sen­sit­iz­a­tion” to re­flect the change in vul­ner­a­bil­ity be­tween nor­mal and can­cerous cells.

Lon­go’s in­ter­est in fast­ing and can­cer grew from years of stud­ies on the ben­e­fi­cial ef­fects of fast­ing in yeast and oth­er or­gan­isms. He found 15 years ago that starved yeast cells en­ter a stress-re­sist­ant mode as they wait for bet­ter times. By con­trast, he said, the muta­t­ions in can­cer cells come at a cost, such as a loss in adapt­abil­ity to di­verse en­vi­ron­ments.

“A way to beat can­cer cells may not be to try to find drugs that kill them spe­cif­ic­ally but to con­fuse them by gen­er­at­ing ex­treme en­vi­ron­ments, such as fast­ing, that only nor­mal cells can quickly re­spond to,” Longo said.