Diet and delu­sions about ev­i­dence

The Middletown Press (Middletown, CT) - - News - DR. DAVID KATZ Dr. David L. Katz; http://david­katzmd.com/ ; founder, True Health Ini­tia­tive.

Our peren­nial pseu­do­con­fu­sion about diet — and pseudo-con­fu­sion, it is — is fu­eled by two par­al­lel delu­sions, run­ning in op­po­site di­rec­tions. The first is that ev­ery opinion about diet changes the facts about diet; it does not. This delu­sion op­er­ates as if bias, pre­con­ceived no­tion, hav­ing the an­swer be­fore ask­ing the ques­tion, or hav­ing some­thing to sell — is fully com­men­su­rate with ex­per­tise and the weight of ev­i­dence.

The sec­ond, op­pos­ing delu­sion is that ev­ery opinion about the ev­i­dence about diet changes the stan­dard of “suf­fi­cient ev­i­dence.” It does not. This con­tention har­bors the view that any amount of ev­i­dence can be dis­missed as in­ad­e­quate or even ab­sent by those who find the mes­sage in it in­con­ve­nient.

Per­haps, then, there is a third delu­sion, too — that the two delu­sions above can co-ex­ist. They can­not. There is no way the as­ser­tion of a non-ex­pert opinion at odds with, or ab­sent any mean­ing­ful ev­i­dence can be “enough,” in a world where a vast ag­gre­ga­tion of con­sis­tent ev­i­dence can be dis­missed as in­ad­e­quate or ab­sent by those choos­ing to ig­nore it. At worst, a think­ing pop­u­la­tion is ob­li­gated to pick one of th­ese. At best, we should re­nounce both for the non­sense they are.

When con­ve­nient, ev­i­dence that would be in­ad­mis­si­ble in any other field is rou­tinely hy­per­bolized into di­etary gospel. The cur­rent fas­ci­na­tion with the ke­to­genic diet, for in­stance, es­sen­tially res­ur­rects the Atkins propo­si­tion un­der a new rubric. It is based not on a shred of ev­i­dence that the diet is sus­tain­able over time, or good for peo­ple if so. It is based en­tirely on short-term im­prove­ment in meta­bolic pro­files of obese peo­ple with and with­out type 2 diabetes. But since al­most any­thing that in­duces short-term weight loss im­proves meta­bolic pro­files in obese peo­ple — in­clud­ing co­caine use, cholera, and tu­ber­cu­lo­sis — that hardly rises to the level of rel­e­vant ev­i­dence for pop­u­la­tion­wide di­etary guid­ance.

I am not say­ing a ke­to­genic diet is akin to th­ese overtly bad ac­tors; we lack de­ci­sive ev­i­dence to know. I am sim­ply say­ing we lack the ev­i­dence re­quired to know that it is not, with a pre­pon­der­ance of re­lated ev­i­dence of­fer­ing abun­dant rea­son for con­cern. Pro­po­nents, how­ever, clearly hope we will leap, on faith in mag­i­cal reme­dies, be­fore paus­ing to look at the state of our cur­rent un­der­stand­ing.

Our big­ger prob­lem, how­ever, may be the delu­sion in the other direc­tion: that we don’t have enough, or even any, ev­i­dence to say what diet is best. Some have made ca­reers prin­ci­pally by mar­ket­ing this con­tention. It is false.

The camp ped­dling the view that “there is no ev­i­dence” over­looks the con­sid­er­able ran­dom­ized trial ev­i­dence sup­port­ing the ba­sic theme of an op­ti­mal diet. But RCTs are not nec­es­sar­ily the pri­mary ar­gu­ment for a given di­etary pat­tern. Much of the ev­i­dence about diet is writ­ten in the fate of pop­u­la­tions of us, over life­times and gen­er­a­tions, as it is for all other species.

The as­ser­tion that the only al­ter­na­tive to ab­so­lute cer­tainty about ev­ery de­tail is ab­ject ig­no­rance of all fun­da­men­tals is ab­surd in gen­eral, as it is for diet specif­i­cally. Were it true, we would know noth­ing about any­thing. There is no science, not chem­istry, not physics, not en­gi­neer­ing —where our knowl­edge is re­motely like per­fect. Yet, it is good enough to send peo­ple to the moon and space­craft to other plan­ets; to split atoms; to image ev­ery nook and cranny of a liv­ing body; to trans­plant or­gans; and to beam messages such as this one through cy­berspace. The pre­vail­ing al­ter­na­tive to know­ing ev­ery­thing is know­ing some­thing; and at times if not of­ten, know­ing enough.

Delu­sions can be be­nign or ma­lig­nant; those re­gard­ing nu­tri­tion are most cer­tainly the lat­ter. While the pseudo-de­bates over pseudo-con­tro­ver­sies rage, and the fol­lies of his­tory end­lessly re­peat, diet has de­volved into the lead­ing cause of pre­ma­ture death and chronic dis­ease in the United States. The real rea­sons for the car­nage, un­der the cover of pseu­do­con­fu­sion, hide in plain sight.

When you hear “there is no ev­i­dence,” look for yourself. If you read­ily find yourself up to your neck in ci­ta­tions, you need not be qual­i­fied in re­search method­ol­ogy to know the claim of “no ev­i­dence” is false. Delu­sions about diet and ev­i­dence pre­vail, and both diet and health are the poorer for it.

My ad­vice is sim­ply to chew the rel­e­vant claims a bit more care­fully be­fore you swal­low them.

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