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.

Type 2 Diabetes Keeps Fat People From Getting Even Fatter

Most peo­ple with type 2 dia­betes are at least pleas­ant­ly plump, so why do so many severe­ly obese peo­ple have no trou­ble with their blood sug­ar? I’ve known for decades that unex­plained weight loss is a com­mon sign of dia­betes. A few years ago, I began to sus­pect that type 2 dia­betes is what hap­pens when one of the body’s nat­ur­al defens­es against fur­ther weight gain gets out of con­trol. These sus­pi­cions were deep­ened when I real­ized that the drugs that are used to treat type 2 dia­betes often cause weight gain as a side effect. The drugs are dis­abling the body’s nat­ur­al resis­tance to fur­ther weight gain!

This inter­est­ing arti­cle from Endocrine Reviews argues that in type 2 dia­betes, the prob­lems with fat metab­o­lism start long before the per­son starts hav­ing abnor­mal blood sug­ar lev­els. It explains how too much fat in the body and too much fat from the diet could end up caus­ing type 2 dia­betes. It explains how eat­ing less and exer­cis­ing more could solve the under­ly­ing prob­lem.

The idea that type 2 dia­betes starts off as a prob­lem with fat metab­o­lism makes a lot of sense. It helps to explain some­thing that sci­en­tists have known since the 1930s: that you can cause insulin resis­tance in healthy vol­un­teers by feed­ing them a high-fat diet for a week. You can restore their insulin sen­si­tiv­i­ty by feed­ing them a starchy diet for a week. A switch to a low-fat, high-fiber, high-car­bo­hy­drate, pure­ly plant-based diet pro­duces a dra­mat­ic improve­ment in peo­ple with type 2 dia­betes, even before they have had a chance to lose much weight.

The tra­di­tion­al cure for type 2 dia­betes was to eat less and exer­cise more. A more sen­si­ble approach is to start off by eat­ing as much high-fiber, low-fat, plant-based food as you feel like eat­ing. This kind of diet will rapid­ly cor­rect your insulin resis­tance. As your insulin resis­tance improves, you’ll feel more like exer­cis­ing.

Of course, if you have any major health prob­lem or are tak­ing pre­scrip­tion med­ica­tions, you need to talk to a reg­is­tered dietit­ian and your pre­scriber before mak­ing any major change in diet. You may need to have your dosages adjust­ed, and you may be able to stop tak­ing some of your pre­scrip­tion med­ica­tion.

Note: I explain this top­ic in more detail in my book Thin Dia­betes, Fat Dia­betes: Pre­vent Type 1, Cure Type 2

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Pho­to by 95Berlin

Meat, But Not Sugar, Increased the Risk of Type 2 diabetes

Most of the peo­ple I talk to seem to think that they’d be health­i­er if they ate less car­bo­hy­drate. Most of them seem con­vinced that a high-car­bo­hy­drate diet makes peo­ple fat. They know that if you eat starch, it gets bro­ken down into sug­ar. They know that when sug­ar flows into your blood­stream, your pan­creas is sup­posed to release insulin to enable the sug­ar to enter your cells, where it can be burned for ener­gy. That part’s true. How­ev­er, they think that if you eat a lot of sug­ar or starch, you’ll some­how wear out your body’s abil­i­ty to make or respond to insulin and thus you’ll end up dia­bet­ic. They couldn’t be more wrong. In real­i­ty, a high-carb, low-fat diet cures the most com­mon type of dia­betes.

If eat­ing a starchy, low-fat diet made peo­ple fat and caused dia­betes, then we’d see lots of fat, dia­bet­ic peo­ple in pop­u­la­tions that eat a starchy, low-fat diet. We don’t. Instead, we see that the peo­ple of Chi­na and Japan, whose diet is based heav­i­ly on rice and veg­eta­bles, tend to be slim and remark­ably free of dia­betes and heart dis­ease. We see the same thing in oth­er pop­u­la­tions that base their diets on oth­er starchy sta­ples. For exam­ple, the indige­nous peo­ple of Peru eat a diet based heav­i­ly on pota­toes. The Tarahu­mara of Mex­i­co eat main­ly corn and beans. The peo­ple in the New Guinea High­lands eat prac­ti­cal­ly noth­ing but sweet pota­toes. The sto­ry is the same wher­ev­er we look. In real­i­ty, the pop­u­la­tions that eat low-fat, starchy, high-fiber diets are thin and healthy. The peo­ple who eat lots of fat­ty ani­mal-based foods are the ones at risk for obe­si­ty, dia­betes, and heart dis­ease.

If eat­ing a lot of sug­ar caused dia­betes, then the peo­ple who eat the most sug­ar would be more like­ly than the aver­age per­son to devel­op dia­betes. On the con­trary, a study of near­ly 40,000 women age 45 and old­er in the Unit­ed States found that the women who were eat­ing the most sug­ar were no more like­ly to get dia­betes than the ones who were eat­ing the least sug­ar [1]. The women who were most like­ly to get dia­betes were the ones who were eat­ing the most meat! [2]

Ref­er­ence List

  1. Jan­ket SJ, Man­son JE, Ses­so H, Bur­ing JE, Liu S. A prospec­tive study of sug­ar intake and risk of type 2 dia­betes in women. Dia­betes Care 2003;26:1008–1015.
  2. Song Y, Man­son JE, Bur­ing JE, Liu S. A prospec­tive study of red meat con­sump­tion and type 2 dia­betes in mid­dle-aged and elder­ly women: the women’s health study. Dia­betes Care 2004;27:2108–2115.

For more infor­ma­tion about dia­betes, see my book Thin Dia­betes, Fat Dia­betes: Pre­vent Type 1, Cure Type 2.

Thin Diabetes, Fat Diabetes: Prevent Type 1, Cure Type 2

The Glycemic Index Won’t Help You Lose Weight

Late­ly, many nutri­tion gurus have been try­ing to tell me that eat­ing a diet with a low glycemic index is the secret to los­ing weight. But if that were true, then car­rots would be more fat­ten­ing than fudge is.

Unfor­tu­nate­ly, the glycemic index is being used to steer peo­ple away from the sort of food that can real­ly help them lose weight and con­trol their blood sug­ar: unre­fined starch­es and veg­eta­bles. If you sur­vey the world’s pop­u­la­tions, you’ll find that the peo­ple who are eat­ing diets based on unre­fined starch­es and veg­eta­bles have low risks of obe­si­ty, heart dis­ease, dia­betes, and breast cancer—even though the glycemic index of their diet is high. In con­trast, the peo­ple who are eat­ing the most fat and protein—both of which tend to decrease the glycemic index of a meal—are the ones who are get­ting fat and sick.

The glycemic index was orig­i­nal­ly devel­oped to fine-tune the sys­tem of car­bo­hy­drate exchanges that peo­ple with type 1 dia­betes use to cal­cu­late how much insulin they will need to inject after a meal [1]. The glycemic index mea­sures the effect that 50 grams of carbs from any giv­en food has on your blood sug­ar. For exam­ple, if you ate 50 grams of car­bo­hy­drate from beans, your blood sug­ar wouldn’t go as high as if you ate 50 grams of car­bo­hy­drate from pota­toes instead. In oth­er words, beans have a low­er glycemic index than pota­toes do.

Like pota­toes, car­rots have a high glycemic index. How­ev­er, you’d have to eat about 4 cups of shred­ded car­rot to get 50 grams of car­bo­hy­drate. Thus, if you ate just one car­rot, it would have only a small effect on your blood sug­ar. To cor­rect for this prob­lem, some peo­ple use the glycemic load, which is the glycemic index mul­ti­plied by the total amount of car­bo­hy­drate in the food.

The glycemic index and glycemic load are of sur­pris­ing­ly lit­tle val­ue to dieters. One rea­son is that the glycemic index of any giv­en food is so hard to pre­dict. For exam­ple, you could increase the glycemic index of a pota­to by mash­ing it. Then, you could decrease the glycemic index of the mashed pota­to by adding milk and but­ter. Fats and pro­teins tend to decrease the glycemic index of a food. Although adding but­ter to a food decreas­es the food’s glycemic index, the but­ter does not make the food less fat­ten­ing!

Even if you eat a meal that has a high glycemic load, that doesn’t mean that your blood sug­ar is going to go dan­ger­ous­ly high. It all depends on your insulin sen­si­tiv­i­ty. Peo­ple who habit­u­al­ly eat a low-fat, starchy diet tend to have much small­er blood sug­ar swings than peo­ple who eat a high-fat, low-carb diet. Sci­en­tists have known that fact since the 1930s! In fact, a diet based on high-glycemic-load veg­eta­bles and unre­fined starch­es can restore the body’s insulin sen­si­tiv­i­ty, thus cur­ing type 2 dia­betes, with­in a mat­ter of weeks.

Ref­er­ence List

  1. Jenk­ins DJ, Wolever TM, Tay­lor RH et al. Glycemic index of foods: a phys­i­o­log­i­cal basis for car­bo­hy­drate exchange. Am J Clin Nutr 1981;34:362–366.

Note: For more infor­ma­tion about the con­trol of weight and blood sug­ar, see my book Thin Dia­betes, Fat Dia­betes: Pre­vent Type 1, Cure Type 2.

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Thin Diabetes, Fat Diabetes

What’s in a name? A rose by any oth­er name would smell as sweet. But when we are talk­ing about dia­betes, we should choose names that make sense. The French do. They use the term “thin dia­betes” (dia­bète mai­gre) to refer to a cat­a­stroph­ic dis­ease that results from fail­ure of the pan­creas. They use the term “fat dia­betes” (dia­bète gras) to refer to a milder, cur­able cause of high blood sug­ar. Fat dia­betes tends to occur in over­weight peo­ple, and it’s made worse by fat in the diet.

When peo­ple talk about dia­betes, they almost always mean dia­betes mel­li­tus, which is some­times called sug­ar dia­betes or just plain sug­ar. Dia­betes insipidus is an unre­lat­ed con­di­tion in which the body can’t con­serve water.

The most obvi­ous symp­tom of untreat­ed dia­betes mel­li­tus is exces­sive thirst and fre­quent uri­na­tion. The word dia­betes came from the Greek word for siphon, because water seemed to pass right through these patients. Their urine was loaded with sug­ar. Because they were los­ing calo­ries through their urine, they tend­ed to lose weight.

By the 1870s, doc­tors in France divid­ed dia­betes mel­li­tus into two cat­e­gories. Thin dia­betes was a rel­a­tive­ly rare but cat­a­stroph­ic, incur­able dis­ease that tend­ed to hap­pen in chil­dren and young adults who tend­ed to be thin to begin with. These patients rapid­ly went into a coma and died, regard­less of treat­ment. At autop­sy, it was often clear that some­thing had gone wrong with their pan­creas. In con­trast, fat dia­betes was a com­mon, rel­a­tive­ly mild con­di­tion that tend­ed to hap­pen in mid­dle-aged to elder­ly adults. It could be cured if the patient ate less and exer­cised more.

Eng­lish-speak­ing doc­tors didn’t like the terms thin dia­betes and fat dia­betes. Instead, they used the terms juve­nile dia­betes and adult-onset dia­betes. These terms are mis­lead­ing because “juve­nile” dia­betes can strike adults, and “adult-onset” dia­betes can occur in an over­weight child. After the dis­cov­ery of insulin in the 1920s, Eng­lish-speak­ing doc­tors start­ed to refer to thin dia­betes as insulin-depen­dent dia­betes mel­li­tus and fat dia­betes as non–insulin-dependent dia­betes mel­li­tus. Peo­ple with thin dia­betes would die with­out insulin ther­a­py. In con­trast, patients with fat dia­betes often respond­ed poor­ly to insulin ther­a­py.

Now that so many peo­ple with fat dia­betes are tak­ing insulin, it’s con­fus­ing to refer to their con­di­tion as non–insulin-dependent. Instead, Amer­i­can and British doc­tors now refer to thin dia­betes as type 1 dia­betes. Fat dia­betes is called type 2 dia­betes. Unfor­tu­nate­ly, these names are mean­ing­less to the lay­man.

In the 1930s, a British researcher named H.P. Himsworth found that he could induce a con­di­tion that resem­bled fat dia­betes in healthy vol­un­teers by feed­ing them a high-fat diet for only a week. After a week of eat­ing a high-fat diet, the vol­un­teers were giv­en a glu­cose tol­er­ance test. This meant that they were giv­en a dose of glu­cose in water and had their blood sug­ar mea­sured every 15 min­utes for sev­er­al hours. When the vol­un­teers had been eat­ing a fat­ty diet for a week, they got a huge spike in blood sug­ar after drink­ing the glu­cose; but when they’d been eat­ing a starchy, low-fat diet for a week, their blood sug­ar lev­els stayed low and sta­ble after they drank the glu­cose. Himsworth’s review of these exper­i­ments was pub­lished in the British Med­ical Jour­nal in 1940 [1].

When I talk to peo­ple who have fat dia­betes, they typ­i­cal­ly don’t remem­ber whether their dia­betes is type 1 or type 2. Some of them have been tak­ing insulin at least occa­sion­al­ly, so the term non–insulin-dependent makes no sense to them. Most of them have been told that they have to cut back on eat­ing car­bo­hy­drates. Unfor­tu­nate­ly, that means eat­ing lots of pro­tein and fat instead. Trag­i­cal­ly, that also means that they are injur­ing their already dam­aged kid­neys with the over­load of waste prod­ucts that come from burn­ing pro­tein for ener­gy. It also means that they are prob­a­bly mak­ing their insulin resis­tance worse, by eat­ing too much fat.

One solu­tion to this mad­ness is to start using the term fat dia­betes to refer to type 2 dia­betes. The sec­ond solu­tion is to shift the focus in the man­age­ment of type 2 dia­betes. Instead of telling patients to avoid eat­ing car­bo­hy­drates to avoid blood sug­ar spikes, shouldn’t doc­tors be teach­ing their patients to shift to a low-fat, high-car­bo­hy­drate diet to restore their nat­ur­al sen­si­tiv­i­ty to insulin? As the results of Himsworth’s stud­ies sug­gest­ed, clin­i­cal stud­ies of a high-car­bo­hy­drate, low-fat diet have shown great suc­cess in help­ing peo­ple with fat dia­betes shed pounds, con­trol their blood sug­ar, and reduce or elim­i­nate their need for pre­scrip­tion drugs [2,3].

One warn­ing: If you have dia­betes or any oth­er health prob­lem or are tak­ing pre­scrip­tion med­ica­tion, talk to a dia­betes edu­ca­tor, reg­is­tered dietit­ian, and your pre­scriber before mak­ing any major change in diet.

Ref­er­ence List

1. Himsworth HP. Insulin defi­cien­cy and insulin inef­fi­cien­cy. Br Med J 1940;1:719–722.
2. Barnard ND, Cohen J, Jenk­ins DJ et al. A low-fat veg­an diet improves glycemic con­trol and car­dio­vas­cu­lar risk fac­tors in a ran­dom­ized clin­i­cal tri­al in indi­vid­u­als with type 2 dia­betes. Dia­betes Care 2006;29:1777–1783.
3. Barnard RJ, Jung T, Inke­les SB. Diet and exer­cise in the treat­ment of NIDDM. The need for ear­ly empha­sis. Dia­betes Care 1994;17:1469–1472.

Note: You can find more infor­ma­tion about dia­betes in my book Thin Dia­betes, Fat Dia­betes: Pre­vent Type 1, Cure Type 2.

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We’ve Known Since the 1930s: Fatty Diets Cause Insulin Resistance

This graph shows the glu­cose tol­er­ance test results of a healthy per­son on a high-fat test diet as opposed to a high-carb diet. Notice that he had low­er, more sta­ble blood sug­ar lev­els after eat­ing a high-carb diet!

Low-carb gurus have been telling peo­ple that insulin resis­tance, which is the under­ly­ing cause of type 2 dia­betes, results from eat­ing too much car­bo­hy­drate. Yet sci­en­tists have known since the 1930s that the prob­lem can be pro­voked by a high-fat diet and reversed by a starchy, low-fat diet. You can read the research for your­self here.

This work was done in the 1930s. How long will it take before the low-carb gurus hear about it?

To Cure Obesity, “Eat Less Fat and More Starch”

Here’s an inter­est­ing arti­cle about the Pima Indi­ans of Ari­zona.

For about 2000 years, the Pima had been grow­ing corn, beans, and squash on irri­gat­ed land in Ari­zona. As a result, their tra­di­tion­al diet was high in starch and fiber and low in fat (~15% by calo­rie). After white set­tlers divert­ed the Pima’s irri­ga­tion water, the Pima had to fall back on the lard, sug­ar, and white flour sup­plied to them by the U.S. gov­ern­ment. After World War II, the Pima adopt­ed a diet that close­ly resem­bles the stan­dard Amer­i­can diet. It is low in fiber and gets about 40% of its calo­ries from fat. As a result, they have hor­rif­i­cal­ly high rates of obe­si­ty and type 2 dia­betes. In con­trast, their blood rel­a­tives in Mex­i­co who have kept more or less to their tra­di­tion­al diet have rel­a­tive­ly low rates of obe­si­ty and dia­betes.

Some low-carb gurus have tried to twist the Pima’s sto­ry into a jus­ti­fi­ca­tion for eat­ing less car­bo­hy­drate and more fat. In real­i­ty, it pro­vides strong encour­age­ment for peo­ple to eat more starch and fiber and a lot less fat.