Introduction

"The Zone" is a 1,000,000-copy bestseller about diet. The author, Barry Sears,
PhD, recommends a caloric intake of 30% protein, 30% fat, 40% carbohydrates at
each meal and snack (3 meals and 2 snacks each day). He claims that eating this
way optimizes the insulin response and the production of "good" eicosanoids. For
more details, see

http://www.eicotech.com/home.nsf/frameset?open

In the article "The great debate: high vs. low protein diets", from the Mc
Dougall Newsletter, vol. 11 #4, July/Aug 1997, the author exposes his objections
to that diet. That article has been reprinted in the issue #34, Dec. 1997 of the
Natural Health M2M. For more information about the latter, see

http://www.rawtimes.com/m2m.html

Since the Zone diet is nearly impossible on a vegetarian or on a raw diet (even
instincto), the debate should be of interest to people eating raw food. In what
follows, I tried to respond to the substantiated claims from Mc Dougall. Many of
my comments have been plagiarized from posts of Loren Cordain and Staffan
Lindeberg on the Paleodiet list ;-) see

http://www.lsoft.com/scripts/wl.exe?SL1=PALEODIET&H=MAELSTROM.STJOHNS.EDU
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Protein and kidneys
-------------------

> Mc Dougall: "By the eighth decade of life people in affluent socieies
> commonly lose about 30 percent of their kidney function (J Gerontol 31:155,
> 1976). This loss is believed to be secondary to overwork of the kidneys caused
> by the amount of protein typically consumed on the American diet, 12% to 15%
> of protein (N Engl J Med 307:652, 1982).

I have no specific answer here, except that 30% or more calories from protein
are commonly consumed among hunter-gatherers without ill effects. In [Speth JD.
Early hominid hunting and scavenging: the role of meat as an energy source.  J
Hum Evol 1989 18:329-43],  Dr. Speth suggests that 300 g/day or roughly 50% of
one's normal total daily caloric intake would be the upper limit of protein that
could be safely consumed on a regular daily basis without impairing health.
Notice that the amount of protein on the Zone diet is well below 300 g/day, and
that in low carb diets, most of the calories are from fat, rather than from
protein.
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Protein and calcium
-------------------

> Mc Dougall: "The Nurse's Health Study recently found women who consumed 95
> grams of protein a day compared with those who consumed less than 68 grams a
> day had a 22% greater risk of forearm fractures (Am J Epidemiol 143:472,
> 1996)"

Here, I will let Staffan Lindeberg answer:

Many metabolic trials and epidemiological surveys have been performed
regarding the role of dietary protein for calcium losses. Most of them show
that an increased protein intake leads to higher urinary losses of calcium,
possibly because of an increased acidic load [29-33]. In epidemiological
surveys, dietary protein, in particular animal protein (although some
investigators do not differ between protein from meat and milk products),
has been associated with higher rates of osteoporotic fractures across
cultures [34] and among US nurses [35].
        Epidemiological studies are often biased by confounding, when a
hidden cause (like smoking) is related to a variable (like yellow fingers)
which in turn is found to be related to the disease in question (like lung
cancer). Therefore we need intervention studies for proof (although in the
case of smoking we got convinced without them). Such studies have to my
knowledge not been able to show that a change from low/moderate to high
protein intake increases the rate of kidney stones or bone loss in animals
or humans.
        In one study, rats were fed a control diet (15% soy protein plus
0.2% methionine) or a high protein diet (control plus 20% lactalbumin) for
10 months [36]. Rats which were fed the high protein diet exhibited
increases in urinary calcium but no change in bone composition.
        In another study, 99 persons who had calcium oxalate kidney stones
for the first time were randomly assigned to either a control diet or a low
animal protein, high fiber diet and followed regularly for up to 4.5 years
[37]. In the intervention group of 50 subjects, stones recurred in 12 (7.1
per 100 person-years) compared with two (1.2 per 100 person-years) in the
control group (p = 0.006), suggesting that a *low* animal protein diet
increased the risk of urinary stones.
        Furthermore, when Orwoll et al studied growing rats fed a diet low
in protein (5%) for 4, 6, and 8 wks (n = 10 animals/group) and compared
them with animals pair-fed with a protein-replete (18%) diet, skeletal
dimensions were *reduced* in the protein-deprived rats but there were no
significant differences in bone mineral content between control and
low-protein animals at 4, 6, and 8 wks [38]. Hence, they found that dietary
protein deprivation resulted in slower growth but bone mineral density was
maintained when there was a marked reduction in urinary calcium excretion.
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29. Kerstetter JE, Allen LH. Dietary protein increases urinary calcium. J
Nutr 1989; 120: 134-6.
30. Do protein and phosphorus cause calcium loss? J Nutr 1988; 118: 657-60.
31. Burtis WJ et al. Dietary hypercalciuria in patients with calcium
oxalate kidney stones. Am J Clin Nutr 1994; 60: 424-9.
32. Trinchieri A et al. The influence of diet on urinary risk factors for
stones in healthy subjects and idiopathic renal calcium stone formers. Br J
Urol 1991; 67: 230-6.
33. Breslau NA et al. Relationship of animal protein-rich diet to kidney
stone formation and calcium metabolism. J Clin Endocrinol Metab 1988; 66:
140-6.
34. Abelow BJ, Holford TR, Insogna KL. Cross-cultural association between
dietary animal protein and hip fracture: a hypothesis. Calcif Tissue Int
1992; 15: 14-8.
35. Feskanich D, Willett WC, Stampfer MJ, Colditz GA. Protein consumption
and bone fractures in women. Am J Epidemiol 1996; 143: 472-9.
36. Whiting SJ, Draper HH. Effect of chronic high protein feeding on bone
composition in the adult rat. J Nutr 1981; 111: 178-83.
37. Hiatt RA, Ettinger B, Caan B, Quesenberry CP Jr, Duncan D, Citron JT.
Randomized controlled trial of a low animal protein, high fiber diet in the
prevention of recurrent calcium oxalate kidney stones. Am J Epidemiol 1996;
144: 25-33.
38. Orwoll E; Ware M; Stribrska L; Bikle D; Sanchez T; Andon M; Li H.
Effects of dietary protein deficiency on mineral metabolism and bone
mineral density. Am J Clin Nutr 1992; 56: 314-9.
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It should be added that:
 *Green vegetables are an excellent source of calcium, much more bioavailable
than dairy. Since they contain very little calories, and grains and potatoes are
suppressed, it is possible to eat lost of vegetables and still be in the Zone.
 *Calcium is more bioavailable when grains are absent, since grains are rich in
phytic acid which strongly binds to calcium.
 *Calcium losses are apparently less when salt intake is low, and it is
obviously possible to limit salt intake on the Zone diet.
 *If dairy is limited or suppressed, then the ratio Ca/Mg is 1:1, which is
optimal.
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Impossible advice
-----------------

> Mc Dougall: "Barry Sears [...] says he eats 100 grams of protein a day [...]
> His total calorie intake is therefore 1300 calories per day. A conservative
> estimate of his actual needs would be over 2300 calories a day."

Mc Dougall concludes that, either B. Sears doesn't adhere to the proportions
30/30/40, or he eats 173 grams of protein and 77 grams of fat daily. In what
follows, we assume that the second assumption is true, i.e. that a non-calorie
restricted Zone diet consists of the proportions 30/30/40, although B. Sears
recommends to athletes to keep a ratio protein/carbohydrate of 3:4, and increase
the amount of fat in the form of monounsaturates.
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Fat and obesity
---------------
> Sears: Eating fat doesn't make you fat. We are consuming less fat than 10
> years ago and getting fatter, therefore dietary fat cannot be the culprit.

> Mc Dougall: "We are consuming the same amount (actually a little more) of fat
> now than before. But, in addition, we are consuming over 250 more calories of
> refined flours and sugars over the past 15 years [...] The reason for the
> rise in obesity is no mystery -Americans eat a high-calorie, high fat diet."

I would correct the last sentence as follows: "Americans eat a high
CARBOHYDRATE, high fat diet. High fat, low carb diets don't make you fat. The
truth is, the low-carb mailing lists are full of people who couldn't lose weight
on low fat, vegetarian diets and then achieved good results on a low carb diet.
I am not claiming that low carb diets are perfect. Many people report, after a
spectacular initial weight loss, reaching a plateau. A possible explanation is
that their endocrine functions and/or their metabolism have been damaged in such
a way that no calorie un-restricted diet could work; but low carb diets seem to
be more effective anyway.
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Carbohydrates and heart disease
-------------------------------

> Mc Dougall: "Ornish [showed] his patients on a high-carbohydrate diet had a
> 50% decrease in risk of cardiovascular deaths."

Here, no references have been supplied, but if Mc Dougall refers to "Can
lifestyle changes reverse coronary heart disease?", Lancet 1990 Jul
21;336(8708):129-133, then it should be pointed out that patients were assigned
to an experimental group (low-fat vegetarian diet, stopping smoking, stress
management training, and moderate exercise), so diet wasn't the only part of the
program.

> Mc Dougall: "WHen subjects are allowed to eat only until they are full (not
> force-fed) their cholesterol falls, their triglyceride levels don't go up
> significantly, and they lose weight (JAMA 274:1450, 1995).

A careful look at the article shows that total cholesterol indeed decreases, but
the ratio TC/HDL (total cholesterol/high-density lipoprotein) doesn't improves
(compared to the ratio on the standard American diet), but remains way too high.
The weight loss (between +2 kg and -12 kg depending on the subject) is
significant, but the study doesn't show that they would return to a normal
weight when following the diet on an extended period. In addition, weight loss
on low fat diets is usually mostly muscle mass loss, whereas high protein diets
make you lose fat body mass (in addition to an initial loss of water). It
appears, from the cited article, that a low fat diet is, in some way, an
improvement compared with the standard American diet, in my opinion low carb
diets would be generally more efficient in correcting cholesterol levels and
promoting weight loss.

> Mc Dougall: "Worldwide the lowest incidence of heart disease is found where
> people eat the lowest cholesterol diets and also have the lowest
> HDL-cholesterol levels (Lancet 2:367, 1981)"

There is no doubt that dietary cholesterol and saturated fat raise all fractions
of cholesterol, but the second factor is probably more important (Am J Clin Nutr
1981 Sep;34(9):1758-1763). Since cholesterol is found only in animal food, and
saturated fat mostly in animal food, it shouldn't be surprising that a high
cholesterol intake is correlated with a high HDL serum level. Moreover, a
correlation between a low cholesterol diet and heart disease doesn't prove
anything, since many other important factors are overlooked, like: amount of
refined sugar, global calorie intake, ratio saturated/unsaturated fat. The
effect of a low fat diet is that all fractions of cholesterol go down, but the
ratio TC/HDL (which is an independent risk factor) doesn't improve.
Remark: the Lancet article also mentions some ratios HDL/TC. Africa: 0.26-0.32,
Europe: 0.20-0.28, Asia and Surinam: 0.15-0.22.

We should mention that hunter-gatherers, despite eating on average more than 55%
of their calories from meat, have low TC and ratio TC/HDL, and low incidence of
heart disease. The main reasons are: high monounsaturated fat intake, low
carbohydrates, high protein [Metabolism 1991;40:338-43] [Clin Invest Med
1992;15:349-5] [Can J Cardiol 1995;11 (supp G):127G-31G], low ratio omega
6/omega 3, no hydrogenated oils [Am J Public Health 1994;84: 722-24] [Am J Clin
Nutr 1997;66:1006s-10], more exercise. The composition of farmed animals is
indeed rather different from the composition of wild animals.

Admittedly, people on the Zone diet usually eat ordinary meat, but it should be
pointed out that Barry Sears recommends the leanest meats, as well as fish, egg
whites and low-fat dairy. The remaining fat calories should be supplied by
monounsaturated, vegetable fat. In addition, the high protein intake (30%)
contributes to the reduction of cholesterol levels.

> Mc Dougall: "A long-term study of patients on a high-carbohydrate diet showed
> less risk of death from heart disease compared to those on the American diet
> (JAMA 173:884, 1960)."

A closer look at the article shows that "the 50 patients on the low fat diet [25
grams/day] had a caloric intake of a maximum of 1500 calories, with about 320
grams of carbohydrate and 90 grams of protein". Here, my calculation gives
25*9+320*4+90*4=1865 calories, which is not consistent with what the article
says, but nevertheless the main idea is that the patients followed a
calorie-restricted diet for 3 years, which is no doubt beneficial for their
heart disease. In addition, 90 grams (=19% by calories) is not really low
protein. And again, the reduced intake of saturated fat, and more particularly
of dairy (which is atherogenic for many reasons), certainly played a role.
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Rice and heart disease
----------------------

> Mc Dougall: "The 1993 figures [B. Sears] uses reflect the modern chinese diet,
> which is much higher in fat and cholesterol than a few years back, especially
> for those people in the cities (urban)."

It should be noted, however, that DESPITE calorie deprivation and intense
exercising, the incidence of heart disease among RURAL Chinese is not as low as
among primitive people.
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Keeping correct insulin levels.
-------------------------------

> Mc Dougall: "Protein -when eaten alone- increases insulin secretion"

Acute consumption of high levels of low fat (6.5%), lean beef protein is not
associated with a post prandial rise in insulin but rather an increase in
glucagon levels [Am J Clin Nutr 1990;52:267-72].

> Mc Dougall: "Beef fed with glucose raised insulin twice as high as glucose
> alone [...] [that] suggests synergism between glucose with aminoacid (protein)
> with respect to insulin release (Lancet 2:454, 1966). The diet fed these
> subjects met the Zone specifications [...]: 27% protein/30% fat/43%
> carbohydrates."

The truth is that it is the fat which is the real culprit here. By mixing fat
and with glucose, the blood glucose levels become less high than with glucose
alone, but the insulin response is worsened [J Clin Endocrionology and
Metabolism 1988;66:323-26]. Mixing protein with carbohydrates doesn't alter the
serum glucose nor the insulin response [Am J Clin Nutr 1990;52:267-72].

Notice moreover that Zone dieters are supposed to eat 5 meals a day. On a 2200
calorie diet, a single meal won't exceed 45 grams protein, 20 grams fat, 60
grams carbohydrates, the latter being of low glycemic index. The correct
conclusion is that, contrary to what Barry Sears says, to keep low insulin
levels it is better to eat carbohydrates and fat (even vegetable fat) at
different meals. But obviously, as far as insulin is concerned, eating a
30/30/40 diet with carbohydrates and fat at different meals is certainly better
than a high carb diet.

> Mc Dougall: "A study of adult-type diabetics, people with insulin resistance,
> and normal people found 3 weeks of a high-carbohydrate, low-fat diet and
> exercise lowered insulin levels significantly (Am J Cardiiol 69:440, 1992)."

The article says that the carbohydrates were supplied by vegeables, fruits,
legumes and whole grains -thus most of them have a low glycemic index. The total
cholesterol went down, but DESPITE a more healthy lifestyle (exercise, no
alcohol, tobacco or coffee), the ratio TC/HDL hasn't significantly improved.
Before: 226:47=4.85; after: 178:38=4.68, or 3.5% on average.
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Eicosanoids: the key?
---------------------

> Gerald Reaven of Standford says, " I find it hard to swallow that anyone
> could really believe eicosanoids are the key to all health and disease."

Indeed! Paleo-dieters will agree on that point, in particular concerning the use
of dairy. This is not to say that insulin or eicosanoids are not important, or
that Barry Sears' ideas have no value, however. Vegetarian and Zone diets can
both be healthy and unhealthy, depending on the details and on individual
variability. There is more to health than carbohydrate/protein ratio, or dietary
cholesterol or saturated fat.

The second conclusion is: don't be fooled -either way-, and check the sources by
yourself! Some arguments, with many references, may seem very convincing, but
more investigations uncover some flaws.