Science journal spreads false rumors about vegan diet

An arti­cle pub­lished this week in the Pro­ceed­ings of the Nation­al Acad­e­my of Sci­ences (PNAS) claims that it would be a dis­as­ter for pub­lic health if the pop­u­la­tion of the Unit­ed States sud­den­ly went veg­an. Yet the authors are not experts on human nutri­tion or pub­lic health. Instead, they are experts on how to feed live­stock. Their con­clu­sions were not based on any actu­al stud­ies of the health of veg­an human beings. The study’s authors even freely admit that plant-based diets have sev­er­al impor­tant advan­tages:

  • Shift­ing to a plant-based diet would increase the amount of food avail­able for human beings.
  • A plant-based diet requires peo­ple to eat a greater vol­ume of food, to main­tain the same weight. [As I have explained in two of my books, this is why a veg­an diet is the key to solv­ing our epi­demics of obe­si­ty and type 2 dia­betes.]
  • The 2015 Dietary Guide­lines Advi­so­ry Com­mit­tee con­clud­ed that plant-based diets would improve health and improve long-term sus­tain­abil­i­ty of the US food sup­ply.

Nev­er­the­less, the authors of the PNAS arti­cle claimed that the plant-based diet would be defi­cient in sev­er­al impor­tant nutri­ents. Yet they did not back up this claim with any stud­ies that showed that veg­ans are real­ly like­ly to have health prob­lems as a result of nutri­ent defi­cien­cies. The authors wrote, “How­ev­er, with­out ani­mal-derived foods, domes­tic sup­plies of Ca [cal­ci­um]; arachi­don­ic, eicos­apen­taenoic, and docosa­hexaenoic fat­ty acids; and vit­a­mins A and B12 were insuf­fi­cient to meet the require­ments of the US pop­u­la­tion.” That claim is absolute­ly ridicu­lous, for the fol­low­ing rea­sons:

    • Although you do need to get some cal­ci­um from your diet, it is prac­ti­cal­ly impos­si­ble to find actu­al cas­es of peo­ple who did not get enough cal­ci­um from their food. Prob­lems with cal­ci­um bal­ance in the body usu­al­ly result from lack of vit­a­min D or from long-term con­sump­tion of high-pro­tein, high-cal­ci­um diets.
    • The Food and Nutri­tion Board of the Nation­al Acad­e­my of Sci­ences does not con­sid­er arachi­don­ic acid, eicos­apen­taenoic acid, or docosa­hexaenoic acid to be essen­tial in human nutri­tion. In oth­er words, human beings do not need to get them from their food. The only essen­tial fat­ty acids are an omega-6 fat­ty acid called linole­ic acid and an omega-3 fat­ty acid called alpha-linolenic acid. Linole­ic acid is plen­ti­ful in grains, nuts, and seeds. Alpha-linole­ic acid comes from the chloro­plas­ts in green plants and is plen­ti­ful in fresh veg­eta­bles. The require­ment for both of these essen­tial fat­ty acids is so small that it was not even dis­cov­ered until hos­pi­tal­ized patients were being fed noth­ing but fat-free intra­venous solu­tions for a long time.
    • Human beings can eas­i­ly meet their require­ments for vit­a­min A by eat­ing beta-carotene, which is plen­ti­ful in dark green, orange, or yel­low veg­eta­bles.
    • Vit­a­min B12 is the only true vit­a­min that is like­ly to be defi­cient in plant-based diets. Vit­a­min B12 is made by bac­te­ria, not by ani­mals, and can be obtained from a cheap sup­ple­ment.
    • The arti­cle also warns about dietary defi­cien­cy of vit­a­min D. Yet vit­a­min D is not a true vit­a­min. It is a hor­mone that your body can make for itself, for free, if you expose your skin to sun­shine. You don’t need to get “the sun­shine vit­a­min” from your food.

The PNAS arti­cle warns us that a shift to a veg­an diet would cause big changes to the econ­o­my. In par­tic­u­lar, it would be dis­as­trous for the live­stock indus­try. (Note that the authors of the PNAS arti­cle are aca­d­e­mics who have devot­ed their careers to serv­ing the live­stock indus­try, not to study­ing human health. This explains why they know so lit­tle about human nutri­tion and nutri­tion­al epi­demi­ol­o­gy.) A switch to a veg­an diet would also be a dis­as­ter for the phar­ma­ceu­ti­cal indus­try. Many peo­ple who shift to a low-fat, plant-based diet can stop tak­ing most or all of their pre­scrip­tion med­ica­tions. These changes would be good for pub­lic health, though bad for indus­try.

PNAS is a pres­ti­gious jour­nal. Yet like oth­er pres­ti­gious jour­nals, it occa­sion­al­ly pub­lish­es arti­cles that are full of non­sense. Like­wise, I imag­ine that PNAS prob­a­bly also rejects some good arti­cles for stu­pid rea­sons. I have worked for peer-reviewed jour­nals, and I have also sub­mit­ted arti­cles to oth­er peer-reviewed jour­nals, so I have seen the prob­lem from both sides, as I explain in this blog post. The mis­take that the edi­tors of PNAS made in this case was to fail to have this arti­cle reviewed by some­one who is a gen­uine expert in human nutri­tion and nutri­tion­al epi­demi­ol­o­gy. As a result, they end­ed up spread­ing live­stock indus­try pro­pa­gan­da.

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