Humans Are Starch Eaters

Here’s an inter­est­ing talk by Nathaniel Dominy, PhD, an Asso­ciate Pro­fes­sor of Anthro­pol­o­gy at Dart­mouth Uni­ver­si­ty. He explains the cen­tral role of diet in the amaz­ing world­wide suc­cess of the human species. If you can’t find enough to eat, you can’t do any of the oth­er things that you would need to do to help you and your chil­dren sur­vive.

He makes sev­er­al impor­tant points. One is that human beings are behav­ioral­ly “plas­tic.” He uses the term “plas­tic” in the sci­en­tif­ic sense, mean­ing that some­thing can take any shape. Our behav­ior is “plas­tic” because it can eas­i­ly be reshaped. As he point­ed out, human beings can adapt to many dif­fer­ent cli­mates because we have learned to make and wear clothes. We can also learn to eat lots of dif­fer­ent foods.

One type of food that is avail­able every­where except the Artic is starchy foods. All of the ener­gy in our diet comes from sun­light, which green plants use to make glu­cose out of car­bon diox­ide and water. Plants then store a lot of this glu­cose in the form of starch, often in their roots or tubers and in their seeds. Unfor­tu­nate­ly, starch is hard to digest. To digest it, we use amy­lase, an enzyme that con­verts the starch back to glu­cose.

Dominy sus­pects that our ances­tors’ abil­i­ty to rec­og­nize and use tuber-form­ing plants opened up a food source unknown to oth­er pri­mates. “It’s kind of a gold mine. All you have to do is dig it up.

Dominy points out that, when com­pared with oth­er pri­mates, human beings have extra copies of the gene for the starch-digest­ing enzyme amy­lase. As a result, we have a lot more amy­lase in our sali­va than goril­las or chim­panzees do. Peo­ple from soci­eties that depend heav­i­ly on starchy diets have sev­er­al more extra copies of the amy­lase gene and there­fore pro­duce a lot more amy­lase in their sali­va. In oth­er words, they have become genet­i­cal­ly more effi­cient at digest­ing starch­es. This kind of change can be seen in genet­i­cal­ly relat­ed pop­u­la­tions that have been adapt­ing to dif­fer­ent diets for only a few thou­sand years.

Although humans can and do eat prac­ti­cal­ly any­thing (we are behav­ioral­ly plas­tic), that doesn’t mean that we are well adapt­ed to a meat-based diet. As he puts it, “Anatom­i­cal­ly, we’re not adapt­ed to meat at all…. We sim­ply don’t have the adap­ta­tions that you would need to chew meat effi­cient­ly. Any­one can look at the teeth of their dog or cat and see what your teeth should look like if you’re going to eat meat. Our teeth don’t match.” Dominy con­cludes, “The fun­da­men­tal com­po­nent of the human diet is a mix of plant foods, with a large amount of starch com­ing from tubers and seeds.”

In this con­text, I’d point out that the adap­ta­tions to a meaty diet go far beyond the shape of the teeth. Even though dogs often eat a fat­ty, meaty diet, they gen­er­al­ly don’t get high cho­les­terol or ath­er­o­scle­ro­sis unless they also have a thy­roid dis­or­der that upsets their cho­les­terol metab­o­lism. In con­trast, human beings that eat a fat­ty, meaty diet are much more sus­cep­ti­ble than dogs are to high cho­les­terol and ath­er­o­scle­ro­sis. That explains why ath­er­o­scle­ro­sis is the lead­ing cause of death in the Unit­ed States but prac­ti­cal­ly nonex­is­tent in soci­eties where peo­ple eat a low-fat, plant-based diet.

Plant-Based Diet and Vitamin B2 Might Help in Managing Parkinson Disease

Back in Novem­ber 2009, I wrote a blog post about a study that sug­gest­ed that a hered­i­tary prob­lem in the metab­o­lism of riboflavin (vit­a­min B2) and the heavy con­sump­tion of red meat could both con­tribute to the cause of Parkin­son dis­ease. The researchers did blood tests for riboflavin for 31 con­sec­u­tive Parkin­son patients who entered their clin­ic. Every sin­gle one of them had abnor­mal­ly low blood lev­els of riboflavin. In com­par­i­son, only a few of the patients with oth­er neu­ro­log­ic dis­eases had low riboflavin lev­els. The Parkin­son patients also tend­ed to be heavy con­sumers of red meat. After the riboflavin defi­cien­cy was cor­rect­ed and the Parkin­son patients stopped eat­ing red meat, their motor skills improved dra­mat­i­cal­ly.

I thought that this study was impor­tant. It sug­gest­ed that cheap and gen­er­al­ly ben­e­fi­cial inter­ven­tions could pro­vide sig­nif­i­cant ben­e­fits for peo­ple with Parkin­son dis­ease. It should have been fol­lowed up with larg­er stud­ies. Keep in mind that Parkin­son dis­ease is a major cause of dis­abil­i­ty among elder­ly Amer­i­cans and ranks 14th among caus­es of death in the Unit­ed States.

Since then, I’ve seen a few stud­ies in which inves­ti­ga­tors assess riboflavin sta­tus by ask­ing peo­ple what they’ve been eat­ing, instead of doing a blood test! This is a big mis­take because the Parkin­son patients in the 2003 study had riboflavin defi­cien­cy even though they were eat­ing nor­mal amounts of riboflavin. Their bod­ies just weren’t han­dling the riboflavin effi­cient­ly. We need more research to show whether Parkin­son patients should rou­tine­ly be screened for riboflavin defi­cien­cy. Of course, if you or a loved one has Parkin­son dis­ease, you can just ask for the riboflavin lev­el to be test­ed. If a patient has a vit­a­min defi­cien­cy, it should be cor­rect­ed, shouldn’t it?

Anoth­er study, pub­lished in Jan­u­ary of 2011, found that Parkin­son patients improved when they switched to a plant-based diet. This came as no sur­prise to me because sim­ply eat­ing less pro­tein, espe­cial­ly dur­ing the day­time, can dra­mat­i­cal­ly improve the patient’s response to L-dopa, which is the drug of choice for treat­ing Parkin­son dis­ease.