Good and bad pro­tein habits

The Register Citizen (Torrington, CT) - - NEWS - DR. DAVID KATZ Pre­ven­tive Medicine http://david­katzmd.com/ ; founder, True Health Ini­tia­tive.

A study re­cently pub­lished in the In­ter­na­tional Jour­nal of Epi­demi­ol­ogy by re­searchers at Loma Linda Univer­sity in Cal­i­for­nia, and the Univer­sité Paris-Sa­clay, in Paris, re­ports note­wor­thy health ben­e­fit from plant pro­tein, and sig­nif­i­cant harms from an­i­mal pro­tein.

The study ex­am­ined pro­tein in­take pat­terns among over 80,000 peo­ple in the Ad­ven­tist Health Study-2, a large ob­ser­va­tional co­hort study in which peo­ple are ob­served and as­sessed over time, but not ran­dom­ized to any given in­ter­ven­tion. The high­est quin­tile of meat pro­tein in­take, as com­pared to the low­est, was as­so­ci­ated with a 60 per­cent rel­a­tive in­crease in car­dio­vas­cu­lar risk, while the high­est com­pared to low­est in­take of pro­tein from nuts and seeds was as­so­ci­ated with a 40 per­cent re­duc­tion.

The first con­sid­er­a­tion is that other di­etary fac­tors might ac­count for some, or even all, of the ef­fects at­trib­uted here to pro­tein per se. There was care­ful ad­just­ment for such fac­tors in the anal­y­sis, but such ad­just­ment can never be com­plete.

There were ob­vi­ously sys­tem­atic diet pat­tern dif­fer­ences be­tween those eat­ing a lot of meat and those eat­ing lit­tle meat but lots of nuts and seeds, and pos­si­bly other im­por­tant life­style dif­fer­ences. Some or all of these, es­pe­cially those not in­cluded in the anal­y­sis, might ac­count for some or all of the ef­fect at­trib­uted to pro­tein.

The long pre­vail­ing po­si­tion has been that an­i­mal sources of pro­tein are com­plete, and plant sources are not — with com­plete re­fer­ring to the com­ple­ment of es­sen­tial amino acids. This po­si­tion is, in fact, false. All plant foods con­tain all es­sen­tial amino acids, al­beit some at low con­cen­tra­tions. An ex­clu­sively plant-based diet pro­vides all es­sen­tial proteins for hu­man health, and the prac­tice of food com­bin­ing is not re­quired to meet the rel­e­vant thresh­old quan­ti­ties of each.

Some have ar­gued that an im­por­tant dif­fer­ence is more sul­fur-con­tain­ing amino acids in an­i­mal foods, lead­ing to the pro­duc­tion of acidic me­tab­o­lites that re­quire buffer­ing. The com­plete amino acid pro­file of an­i­mal foods, and the rel­a­tively high con­cen­tra­tion of those amino acids, may also fos­ter brisk an­abolic re­sponses (i.e., rapid tis­sue growth) which may be detri­men­tal — other than for body builders.

Other po­ten­tial ex­pla­na­tions for dif­fer­en­tial health ef­fects of plant and an­i­mal pro­tein in­clude dif­fer­ent amino acid ra­tios, and dif­fer­en­tial ef­fects on the mi­cro­biome — no­tably the pro­duc­tion of TMAO. TMAO is a me­tab­o­lite of sev­eral nu­tri­ents, no­tably choline, car­ni­tine, and lecithin, that ac­com­pany pro­tein in an­i­mal foods, and is strongly linked to car­dio­vas­cu­lar risk. There are, how­ever, com­pounds in plant foods that can also in­duce the pro­duc­tion of TMAO, and the topic is com­pli­cated.

An ex­ten­sive re­cent re­view of pro­tein sources rightly notes the near im­pos­si­bil­ity of iso­lat­ing the ef­fects of an­i­mal pro­tein, per se, from dif­fer­ences in over­all di­etary pat­tern. The same pa­per con­cludes that few of

the pro­posed mech­a­nisms of harm from an­i­mal pro­tein are well sub­stan­ti­ated, and some are not even en­tirely plau­si­ble. Far more likely, these au­thors sug­gest, is that dif­fer­ences in pro­tein are one among many fac­tors, and of un­cer­tain in­de­pen­dent sig­nif­i­cance.

Of clearer im­por­tance is dif­fer­ences in over­all nu­tri­ent pat­terns from given sources, and the dif­fer­ences in over­all di­etary pat­terns and life­style be­tween those with sig­nif­i­cant meat in­take ver­sus those with plant pre­dom­i­nant di­ets.

Stud­ies have shown re­peat­edly that a pre­dom­i­nance of plant-food pro­tein sources in the diet is as­so­ci­ated with re­duc­tions in chronic dis­ease and pre­ma­ture death as com­pared to a pre­dom­i­nance of an­i­mal food sources. En­vi­ron­men­tal

ar­gu­ments for a shift to plant pro­tein sources — no­tably beans and legumes — may be even stronger. Ar­gu­ments about meat in­take ex­tend well be­yond con­sid­er­a­tions of pro­tein con­tent or even just health ef­fects.

We will al­most cer­tainly never in­dict the “right” nu­tri­ent or can­on­ize the right one, be­cause it is the pat­tern of our di­ets and the foods we eat that most mean­ing­fully feeds our med­i­cal des­tinies. If we di­rect our fo­cus there, at last, we can re­li­ably get all of the nu­tri­ents right. But we may have to re­nounce the sat­is­fac­tion that comes with hav­ing a per­pe­tra­tor to blame.

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