In Defense of Food

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In Defense of Food Page 12

by Michael Pollan


  Simp­li­fi­ca­ti­on of the fo­od cha­in oc­curs at the le­vel of spe­ci­es di­ver­sity too. The as­to­un­ding va­ri­ety of fo­ods on of­fer in to­day’s su­per­mar­ket obs­cu­res the fact that the ac­tu­al num­ber of spe­ci­es in the mo­dern di­et is shrin­king. Tho­usands of plant and ani­mal va­ri­eti­es ha­ve fal­len out of com­mer­ce in the last cen­tury as in­dust­ri­al ag­ri­cul­tu­re has fo­cu­sed its at­ten­ti­ons on a small hand­ful of high-yi­el­ding (and usu­al­ly pa­ten­ted) va­ri­eti­es, with qu­ali­ti­es that su­ited them to things li­ke mec­ha­ni­cal har­ves­ting and pro­ces­sing. Half of all the broc­co­li grown com­mer­ci­al­ly in Ame­ri­ca to­day is a sing­le va­ri­ety-Ma­rat­hon-no­tab­le for its high yi­eld. The overw­hel­ming ma­j­ority of the chic­kens ra­ised for me­at in Ame­ri­ca are the sa­me hybrid, the Cor­nish cross; mo­re than 99 per­cent of the tur­keys are Bro­ad-Bre­as­ted Whi­tes.

  With the ri­se of in­dust­ri­al ag­ri­cul­tu­re, vast mo­no­cul­tu­res of a tiny gro­up of plants, most of them ce­re­al gra­ins, ha­ve rep­la­ced the di­ver­si­fi­ed farms that used to fe­ed us. A cen­tury ago, the typi­cal Iowa farm ra­ised mo­re than a do­zen dif­fe­rent plant and ani­mal spe­ci­es: cat­tle, chic­kens, corn, hogs, ap­ples, hay, oats, po­ta­to­es, cher­ri­es, whe­at, plums, gra­pes, and pe­ars. Now it ra­ises only two: corn and soy­be­ans. This simp­li­fi­ca­ti­on of the ag­ri­cul­tu­ral lands­ca­pe le­ads di­rectly to the simp­li­fi­ca­ti­on of the di­et, which is now to a re­mar­kab­le ex­tent do­mi­na­ted by-big surp­ri­se-corn and soy­be­ans. You may not think you eat a lot of corn and soy­be­ans, but you do: 75 per­cent of the ve­ge­tab­le oils in yo­ur di­et co­me from soy (rep­re­sen­ting 20 per­cent of yo­ur da­ily ca­lo­ri­es) and mo­re than half of the swe­ete­ners you con­su­me co­me from corn (rep­re­sen­ting aro­und 10 per­cent of da­ily ca­lo­ri­es).

  Why corn and soy? Be­ca­use the­se two plants are among na­tu­re’s most ef­fi­ci­ent trans­for­mers of sun­light and che­mi­cal fer­ti­li­zer in­to car­bohyd­ra­te energy (in the ca­se of corn) and fat and pro­te­in (in the ca­se of soy)-if you want to ext­ract the ma­xi­mum amo­unt of mac­ro­nut­ri­ents from the Ame­ri­can farm belt, corn and soy are the crops to plant. (It helps that the go­vern­ment pays far­mers to grow corn and soy, sub­si­di­zing every bus­hel they pro­du­ce.) Most of the corn and soy crop winds up in the fe­ed of our fo­od ani­mals (simp­lif­ying the­ir di­ets in un­he­althy ways, as we’ll see), but much of the rest go­es in­to pro­ces­sed fo­ods. The bu­si­ness mo­del of the fo­od in­dustry is or­ga­ni­zed aro­und “adding va­lue” to che­ap raw ma­te­ri­als; its ge­ni­us has be­en to fi­gu­re out how to bre­ak the­se two big se­eds down in­to the­ir che­mi­cal bu­il­ding blocks and then re­as­semb­le them in myri­ad pac­ka­ged fo­od pro­ducts. With the re­sult that to­day corn cont­ri­bu­tes 554 ca­lo­ri­es a day to Ame­ri­ca’s per ca­pi­ta fo­od supply and soy anot­her 257. Add whe­at (768 ca­lo­ri­es) and ri­ce (91) and you can see the­re isn’t a who­le lot of ro­om left in the Ame­ri­can sto­mach for any ot­her fo­ods.

  To­day the­se fo­ur crops ac­co­unt for two thirds of the ca­lo­ri­es we eat. When you con­si­der that hu­man­kind has his­to­ri­cal­ly con­su­med so­me eighty tho­usand edib­le spe­ci­es, and that three tho­usand of the­se ha­ve be­en in wi­desp­re­ad use, this rep­re­sents a ra­di­cal simp­li­fi­ca­ti­on of the hu­man di­et. Why sho­uld this con­cern us? Be­ca­use hu­mans are om­ni­vo­res, re­qu­iring so­mew­he­re bet­we­en fifty and a hund­red dif­fe­rent che­mi­cal com­po­unds and ele­ments in or­der to be he­althy. It’s hard to be­li­eve we’re get­ting everyt­hing we ne­ed from a di­et con­sis­ting lar­gely of pro­ces­sed corn, soy­be­ans, ri­ce, and whe­at.

  3) From Quality to Quantity

  Whi­le in­dust­ri­al ag­ri­cul­tu­re has ma­de tre­men­do­us stri­des in co­axing mac­ro­nut­ri­ents-ca­lo­ri­es-from the land, it is be­co­ming inc­re­asingly cle­ar that the­se ga­ins in fo­od qu­an­tity ha­ve co­me at a cost to its qu­ality. This pro­bably sho­uldn’t surp­ri­se us: Our fo­od system has long de­vo­ted its ener­gi­es to inc­re­asing yi­elds and sel­ling fo­od as che­aply as pos­sib­le. It wo­uld be too much to ho­pe tho­se go­als co­uld be ac­hi­eved wit­ho­ut sac­ri­fi­cing at le­ast so­me of the nut­ri­ti­onal qu­ality of our fo­od.

  As men­ti­oned ear­li­er, US­DA fi­gu­res show a dec­li­ne in the nut­ri­ent con­tent of the forty-three crops it has trac­ked sin­ce the 1950s. In one re­cent analy­sis, vi­ta­min C dec­li­ned by 20 per­cent, iron by 15 per­cent, ri­bof­la­vin by 38 per­cent, cal­ci­um by 16 per­cent. Go­vern­ment fi­gu­res from Eng­land tell a si­mi­lar story: dec­li­nes sin­ce the fif­ti­es of 10 per­cent or mo­re in le­vels of iron, zinc, cal­ci­um, and se­le­ni­um ac­ross a ran­ge of fo­od crops. To put this in mo­re conc­re­te terms, you now ha­ve to eat three ap­ples to get the sa­me amo­unt of iron as you wo­uld ha­ve got­ten from a sing­le 1940 ap­ple, and you’d ha­ve to eat se­ve­ral mo­re sli­ces of bre­ad to get yo­ur re­com­men­ded da­ily al­lo­wan­ce of zinc than you wo­uld ha­ve a cen­tury ago.

  The­se examp­les co­me from a 2007 re­port en­tit­led “Still No Free Lunch” writ­ten by Bri­an Hal­we­il, a re­se­arc­her for World­watch, and pub­lis­hed by the Or­ga­nic Cen­ter, a re­se­arch ins­ti­tu­te es­tab­lis­hed by the or­ga­nic fo­od in­dustry. “Ame­ri­can ag­ri­cul­tu­re’s sing­le-min­ded fo­cus on inc­re­asing yi­elds cre­ated a blind spot,” Hal­we­il wri­tes, “whe­re inc­re­men­tal ero­si­on in the nut­ri­ti­onal qu­ality of our fo­od…has lar­gely es­ca­ped the no­ti­ce of sci­en­tists, go­vern­ment, and con­su­mers.” The re­sult is the nut­ri­ti­onal equ­iva­lent of inf­la­ti­on, such that we ha­ve to eat mo­re to get the sa­me amo­unt of va­ri­o­us es­sen­ti­al nut­ri­ents. The fact that at le­ast 30 per­cent of Ame­ri­cans ha­ve a di­et de­fi­ci­ent in vi­ta­min C, vi­ta­min E, vi­ta­min A, and mag­ne­si­um su­rely owes mo­re to eating pro­ces­sed fo­ods full of empty ca­lo­ri­es than it do­es to lo­wer le­vels of nut­ri­ents in the who­le fo­ods we aren’t eating. Still, it do­esn’t help that the raw ma­te­ri­als used in the ma­nu­fac­tu­re of pro­ces­sed fo­ods ha­ve dec­li­ned in nut­ri­ti­onal qu­ality or that when we are eating who­le fo­ods, we’re get­ting subs­tan­ti­al­ly less nut­ri­ti­on per ca­lo­rie than we used to.*

  Nut­ri­ti­onal inf­la­ti­on se­ems to ha­ve two prin­ci­pal ca­uses: chan­ges in the way we grow fo­od and chan­ges in the kinds of fo­ods we grow. Hal­we­il ci­tes a con­si­de­rab­le body of re­se­arch de­monst­ra­ting that plants grown with in­dust­ri­al fer­ti­li­zers are of­ten nut­ri­ti­onal­ly in­fe­ri­or to the sa­me va­ri­eti­es grown in or­ga­nic so­ils. Why this sho­uld be so is un­cer­ta­in, but the­re are a co­up­le of hypot­he­ses. Crops grown with che­mi­cal fer­ti­li­zers grow mo­re qu­ickly, gi­ving them less ti­me and op­por­tu­nity to ac­cu­mu­la­te nut­ri­ents ot­her than the big three (nut­ri­ents in which in­dust­ri­al so­ils are apt to be de­fi­ci­ent any­way). Al­so, easy ac­cess to the ma­j­or nut­ri­ents me­ans that in­dust­ri­al crops de­ve­lop smal­ler and shal­lo­wer ro­ot systems than or­ga­ni­cal­ly grown plants; de­eply ro­oted plants ha­ve ac­cess to mo­re so­il mi­ne­rals. Bi­olo­gi­cal ac­ti­vity in the so­il al­most cer­ta­inly plays a ro­le as well; the slow de­com­po­si­ti­on of or­ga­nic mat­ter re­le­ases a wi­de ran­ge of plant nut­ri­ents, pos­sibly inc­lu­ding com­po­unds sci­en­ce hasn’t yet iden­ti­fi­ed as im­por­tant. Al­so, a bi­olo­gi­cal­ly ac­ti­ve so­il will ha­ve mo­re mycor­rhi­zae, the so­il fun­gi that li­ve in symbi­osis with plant ro­ots, sup­plying the plants with mi­ne­rals in exc­ha
n­ge for a ra­ti­on of su­gar.

  In ad­di­ti­on to the­se hig­her le­vels of mi­ne­rals, or­ga­ni­cal­ly grown crops ha­ve al­so be­en fo­und to con­ta­in mo­re phytoc­he­mi­cals-the va­ri­o­us se­con­dary com­po­unds (inclu­ding ca­ro­te­no­ids and polyp­he­nols) that plants pro­du­ce in or­der to de­fend them­sel­ves from pests and di­se­ases, many of which turn out to ha­ve im­por­tant an­ti­oxi­dant, an­ti­inf­lam­ma­tory, and ot­her be­ne­fi­ci­al ef­fects in hu­mans. Be­ca­use plants li­ving on or­ga­nic farms aren’t spra­yed with synthe­tic pes­ti­ci­des, they’re for­ced to de­fend them­sel­ves, with the re­sult that they tend to pro­du­ce bet­we­en 10 per­cent and 50 per­cent mo­re of the­se va­lu­ab­le se­con­dary com­po­unds than con­ven­ti­onal­ly grown plants.

  So­me com­bi­na­ti­on of the­se en­vi­ron­men­tal fac­tors pro­bably ac­co­unts for at le­ast part of the dec­li­ne in the nut­ri­ti­onal qu­ality of con­ven­ti­onal crops, but ge­ne­tics li­kely plays just as im­por­tant a ro­le. Very simply, we ha­ve be­en bre­eding crops for yi­eld, not nut­ri­ti­onal qu­ality, and when you bre­ed for one thing, you in­va­ri­ably sac­ri­fi­ce anot­her. Hal­we­il ci­tes se­ve­ral stu­di­es de­monst­ra­ting that when ol­der crop va­ri­eti­es are grown si­de by si­de with mo­dern cul­ti­vars, the ol­der ones typi­cal­ly ha­ve lo­wer yi­elds but subs­tan­ti­al­ly hig­her nut­ri­ent le­vels. US­DA re­se­arc­hers re­cently fo­und that bre­eding to “impro­ve” whe­at va­ri­eti­es over the past 130 ye­ars (a pe­ri­od du­ring which yi­elds of gra­in per ac­re trip­led) had re­du­ced le­vels of iron by 28 per­cent and zinc and se­le­ni­um by ro­ughly a third. Si­mi­larly, milk from mo­dern Hols­te­in cows (in which bre­eders ha­ve ma­na­ged to mo­re than trip­le da­ily yi­eld sin­ce 1950) has con­si­de­rably less but­ter­fat and ot­her nut­ri­ents than that from ol­der, less “impro­ved” va­ri­eti­es li­ke Jer­sey, Gu­ern­sey, and Brown Swiss.

  Cle­arly the ac­hi­eve­ments of in­dust­ri­al ag­ri­cul­tu­re ha­ve co­me at a cost: It can pro­du­ce a gre­at many mo­re ca­lo­ri­es per ac­re, but each of tho­se ca­lo­ri­es may supply less nut­ri­ti­on than it for­merly did. And what has hap­pe­ned on the farm has hap­pe­ned in the fo­od system as a who­le as in­dustry has pur­su­ed the sa­me ge­ne­ral stra­tegy of pro­mo­ting qu­an­tity at the ex­pen­se of qu­ality. You don’t ne­ed to spend much ti­me in an Ame­ri­can su­per­mar­ket to fi­gu­re out that this is a fo­od system or­ga­ni­zed aro­und the obj­ec­ti­ve of sel­ling lar­ge qu­an­ti­ti­es of ca­lo­ri­es as che­aply as pos­sib­le.

  Inde­ed, do­ing so has be­en of­fi­ci­al U.S. go­vern­ment po­licy sin­ce the mid-se­ven­ti­es, when a sharp spi­ke in fo­od pri­ces bro­ught pro­tes­ting ho­use­wi­ves in­to the stre­et and promp­ted the Ni­xon ad­mi­nist­ra­ti­on to adopt an am­bi­ti­o­us che­ap fo­od po­licy. Ag­ri­cul­tu­ral po­li­ci­es we­re rew­rit­ten to en­co­ura­ge far­mers to plant crops li­ke corn, soy, and whe­at fen­ce­row to fen­ce­row, and it wor­ked: Sin­ce 1980, Ame­ri­can far­mers ha­ve pro­du­ced an ave­ra­ge of 600 mo­re ca­lo­ri­es per per­son per day, the pri­ce of fo­od has fal­len, por­ti­on si­zes ha­ve bal­lo­oned, and, pre­dic­tably, we’re eating a who­le lot mo­re, at le­ast 300 mo­re ca­lo­ri­es a day than we con­su­med in 1985. What kind of ca­lo­ri­es? Ne­arly a qu­ar­ter of the­se ad­di­ti­onal ca­lo­ri­es co­me from ad­ded su­gars (and most of that in the form of high-fruc­to­se corn syrup); ro­ughly anot­her qu­ar­ter from ad­ded fat (most of it in the form of soy­be­an oil); 46 per­cent of them from gra­ins (mostly re­fi­ned); and the few ca­lo­ri­es left (8 per­cent) from fru­its and ve­ge­tab­les.* The overw­hel­ming ma­j­ority of the ca­lo­ri­es Ame­ri­cans ha­ve ad­ded to the­ir di­ets sin­ce 1985-the 93 per­cent of them in the form of su­gars, fats, and mostly re­fi­ned gra­ins-sup­ply lots of energy but very lit­tle of anyt­hing el­se.

  A di­et ba­sed on qu­an­tity rat­her than qu­ality has us­he­red a new cre­atu­re on­to the world sta­ge: the hu­man be­ing who ma­na­ges to be both over­fed and un­der­no­uris­hed, two cha­rac­te­ris­tics sel­dom fo­und in the sa­me body in the long na­tu­ral his­tory of our spe­ci­es. In most tra­di­ti­onal di­ets, when ca­lo­ri­es are ade­qu­ate, nut­ri­ent in­ta­ke will usu­al­ly be ade­qu­ate as well. In­de­ed, many tra­di­ti­onal di­ets are nut­ri­ent rich and, at le­ast com­pa­red to ours, ca­lo­rie po­or. The Wes­tern di­et has tur­ned that re­la­ti­ons­hip up­si­de down. At a he­alth cli­nic in Oak­land, Ca­li­for­nia, doc­tors re­port se­e­ing over­we­ight child­ren suf­fe­ring from old-ti­me de­fi­ci­ency di­se­ases such as ric­kets, long tho­ught to ha­ve be­en con­sig­ned to his­tory’s dust­he­ap in the de­ve­lo­ped world. But when child­ren sub­sist on fast fo­od rat­her than fresh fru­its and ve­ge­tab­les and drink mo­re so­da than milk, the old de­fi­ci­ency di­se­ases re­turn-now even in the obe­se.

  Bru­ce Ames, the re­now­ned Ber­ke­ley bi­oc­he­mist, works with kids li­ke this at Child­ren’s Hos­pi­tal and Re­se­arch Cen­ter in Oak­land. He’s con­vin­ced that our high-ca­lo­rie, low-nut­ri­ent di­et is res­pon­sib­le for many chro­nic di­se­ases, inc­lu­ding can­cer. Ames has fo­und that even subt­le mic­ro­nut­ri­ent de­fi­ci­en­ci­es-far be­low the le­vels ne­eded to pro­du­ce acu­te de­fi­ci­ency di­se­ases-can ca­use da­ma­ge to DNA that may le­ad to can­cer. Stud­ying cul­tu­red hu­man cells, he’s fo­und that “de­fi­ci­ency of vi­ta­mins C, E, B12, B6, ni­acin, fo­lic acid, iron or zinc ap­pe­ars to mi­mic ra­di­ati­on by ca­using sing­le-and do­ub­le-strand DNA bre­aks, oxi­da­ti­ve le­si­ons, or both”-pre­cur­sors to can­cer. “This has se­ri­o­us imp­li­ca­ti­ons, as half of the U.S. po­pu­la­ti­on may be de­fi­ci­ent in at le­ast one of the­se mic­ro­nut­ri­ents.” Most of the mis­sing mic­ro­nut­ri­ents are sup­pli­ed by fru­its and ve­ge­tab­les, of which only 20 per­cent of Ame­ri­can child­ren and 32 per­cent of adults eat the re­com­men­ded fi­ve da­ily ser­vings. The cel­lu­lar mec­ha­nisms Ames has iden­ti­fi­ed co­uld exp­la­in why di­ets rich in ve­ge­tab­les and fru­its se­em to of­fer so­me pro­tec­ti­on aga­inst cer­ta­in can­cers.

  Ames al­so be­li­eves, tho­ugh he hasn’t yet pro­ven it, that mic­ro­nut­ri­ent de­fi­ci­en­ci­es may cont­ri­bu­te to obe­sity. His hypot­he­sis is that a body star­ved of cri­ti­cal nut­ri­ents will ke­ep eating in the ho­pe of ob­ta­ining them. The ab­sen­ce of the­se nut­ri­ents from the di­et may “co­un­te­ract the nor­mal fe­eling of sa­ti­ety af­ter suf­fi­ci­ent ca­lo­ri­es are eaten” and that such an un­re­len­ting hun­ger “may be a bi­olo­gi­cal stra­tegy for ob­ta­ining mis­sing nut­ri­ents.” If Ames is right, then a fo­od system or­ga­ni­zed aro­und qu­an­tity rat­her than qu­ality has a dest­ruc­ti­ve fe­ed­back lo­op bu­ilt in­to it, such that the mo­re low-qu­ality fo­od one eats, the mo­re one wants to eats, in a fu­ti­le-but highly pro­fi­tab­le-qu­est for the ab­sent nut­ri­ent.

  4) From Leaves to Seeds

  It’s no ac­ci­dent that the small hand­ful of plants we’ve co­me to rely on are gra­ins (soy is a le­gu­me); the­se crops are ex­cep­ti­onal­ly ef­fi­ci­ent at trans­for­ming sun­light, fer­ti­li­zer, air, and wa­ter in­to mac­ro­nut­ri­ents-car­bohyd­ra­tes, fats, and pro­te­ins. The­se mac­ro­nut­ri­ents in turn can be pro­fi­tably con­ver­ted in­to me­at, da­iry, and pro­ces­sed fo­ods of every desc­rip­ti­on. Al­so, the fact that they co­me in the form of du­rab­le se­eds which can be sto­red for long pe­ri­ods of ti­me me­ans they can func­ti­on as com­mo­di­ti­es as well as fo­ods, ma­king the­se crops par­ti­cu­larly well adap­ted to the ne­eds of in­dust­ri­al ca­pi­ta­lism.

  The ne­eds of the hu­ma
n eater are a very dif­fe­rent mat­ter, ho­we­ver. An over­sup­ply of mac­ro­nut­ri­ents, such as we now fa­ce, it­self rep­re­sents a se­ri­o­us thre­at to our he­alth, as so­aring ra­tes of obe­sity and di­abe­tes in­di­ca­te. But, as the re­se­arch of Bru­ce Ames and ot­hers sug­gests, the un­der­sup­ply of mic­ro­nut­ri­ents may cons­ti­tu­te a thre­at just as gra­ve. Put in the most ba­sic terms, we’re eating a lot mo­re se­eds and a lot fe­wer le­aves (as do the ani­mals we de­pend on), a tec­to­nic di­etary shift the full imp­li­ca­ti­ons of which we are just now be­gin­ning to re­cog­ni­ze. To bor­row, aga­in, the nut­ri­ti­onist’s re­duc­ti­ve vo­ca­bu­lary: Le­aves pro­vi­de a host of cri­ti­cal nut­ri­ents a body can’t get from a di­et of re­fi­ned se­eds. The­re are the an­ti­oxi­dants and phytoc­he­mi­cals; the­re is the fi­ber; and then the­re are the es­sen­ti­al ome­ga-3 fatty acids fo­und in le­aves, which so­me re­se­arc­hers be­li­eve will turn out to be the most cru­ci­al mis­sing nut­ri­ent of all.

  Most pe­op­le as­so­ci­ate ome­ga-3 fatty acids with fish, but fish get them ori­gi­nal­ly from gre­en plants (spe­ci­fi­cal­ly al­gae), which is whe­re they all ori­gi­na­te.* Plant le­aves pro­du­ce the­se es­sen­ti­al fatty acids (we say they’re es­sen­ti­al be­ca­use our bo­di­es can’t pro­du­ce them on the­ir own) as part of pho­tosynt­he­sis; they oc­cupy the cell memb­ra­nes of chlo­rop­lasts, hel­ping them col­lect light. Se­eds con­ta­in mo­re of anot­her kind of es­sen­ti­al fatty acid, ome­ga-6, which ser­ves as a sto­re of energy for the de­ve­lo­ping se­ed­ling. The­se two types of pol­yun­sa­tu­ra­ted fats per­form very dif­fe­rent func­ti­ons in the plant as well as the plant eater. In desc­ri­bing the­ir res­pec­ti­ve ro­les, I’m go­ing to simp­lify the che­mistry so­mew­hat. For a mo­re comp­le­te (and fas­ci­na­ting) ac­co­unt of the bi­oc­he­mistry of the­se fats and the story of the­ir dis­co­very re­ad Su­san Al­lport’s The Qu­e­en of Fats.†

 

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