Nuts Come in Hard Shells—for Reasons
Growing up in a low-income family in the suburbs of Detroit we had
nuts once a year. At Christmastime my father brought home a 5-pound
bag of mixed nuts all firmly encased individually in rock hard
shells. Over the next five days, with the aid of a mechanical
nutcracker and a steel pick, the six members of the McDougall family
ate almonds, Brazil nuts, cashews, hazelnuts, pecans, and walnuts.
These days, eating nuts is as convenient as unscrewing the lid of a
glass jar, and then pouring an ounce of shelled, oil-roasted, nuts
directly into your mouth. After seven chews and a swallow, in fewer
than five seconds, 120 calories of fat are gulped down. Within three
hours much of that fat is stored as metabolic dollars to be spent
during the next famine.
accurately, tree nuts) act as “storage organs of energy” for a
tree’s germ to sprout into a seedling and grow come springtime.
Seeds, legumes, and grains serve the same purposes for their parent
plants. One of the primary differences between these four organs for
the origin of life is the amount of energy stored as either fats or
carbohydrates. Nuts and seeds use mostly fats. Grains, such as
corn, rice, and wheat, store their fuel as carbohydrates. Legumes,
such as beans, peas, and lentils, also use carbohydrates for stored
technically legumes, are typically included in the nut group because
they have a similar nutrient makeup and are used in the same ways as
These storage organs are also rich in other nutrients, such as
proteins, vitamins, minerals, and many other phyto-nutrients,
important for the seedling’s growth. The high nutrient density of
these packages also has a major impact on human health when
Macronutrient Content of Plant Storage Organs
As a percent of calories. Dry
roasted, unless noted otherwise.
Population Has Lived on a Nut-based Diet
foods (five of them grains): barley, maize (corn), millet, potatoes,
rice, and wheat have fueled the caloric engines of human
civilization. The bulk of the energy in these storage organ foods
comes from carbohydrates. They contain only small amounts of fats.
Human metabolism is designed to run primarily on carbohydrates, not
fats. Proof of this begins with the recognition that the human
tongue tastes with pleasure only one source of
us to seek this goldmine of energy.
There are no pleasure sensors for fats here. The primary digestive
enzymes (amylases) in the human gut are for carbohydrates
(starches), not for fats. Finally, almost exclusively,
carbohydrates, not fats, fuel our major organs, including the blood,
liver, kidneys, and brain.
To Live on Fat
Would Mean Population Extinction
In order for populations to survive individuals must function at
peak physical and mental performance. To do less means a greater
chance of conquest by invaders, being eaten by predators, succumbing
to sicknesses, and annihilation by natural disasters. Laws of
“survival of the fittest” dictate that those who are most
productively fueled win.
Endurance athletes demonstrate the survival advantages of choosing
the right fuel. Through experience and research it has been
discovered that eating mostly carbohydrate-rich foods means the
difference between winning and losing during high-intensity exercise
performances.1-3 Research shows consuming a
low-carbohydrate regime impairs performance.4,5 In
general, three to four days of following a high-fat and/or
high-protein, low-carbohydrate diet is enough to deplete the body of
its stores of carbohydrate, resulting in a reduction in short-term
performance.6 The feeling of fatigue that
athletes experience occurs as carbohydrate reserves (glycogen
stores) in the body are depleted.2 An athlete fueled by
nuts (high in fat and low in carbohydrate) participating in an
endurance feat would be expected to perform poorly.
recently learned to choose foods that provide the most easily
assimilated carbohydrates in the quickest time; those with a high
glycemic index. The glycemic index measures the rise in blood sugar
in a person over two to three hours after eating. Higher glycemic
index foods replenish an athletes energy stores more efficiently
than those with a low value.8,9
Winners have learned to choose the same foods that have fueled all
large successful civilizations of the past—barley, corn, rice,
potatoes, pastas, and breads. They do not choose nuts and seeds,
which are deficient in carbohydrates, filled with fats, and are also
low on the glycemic index scale (between
7 and 23).10 Rice, corn, and potatoes have values over
100. The relatively low scores of legumes (30 to 40) may be one
important reason that they have rarely served as a primary food
source for large societies.
Once Ate a Nut-Based Meal
In 2002, Mary and I were invited by a couple who had attended the
McDougall (10-day live-in) Program in Santa Rosa, California to dine
with them at the very popular raw-food restaurant, Roxanne’s, in
Larkspur, California. We each had a non-alcoholic drink, an
appetizer, a soup, an entrée, and a dessert. For my main course, I
ordered the lasagna and Mary ordered the curry dish. The “cold”
uncooked lasagna was about the size of four postage stamps and was
made with raw cashew “cheese” and coconut “noodles.”11 I
prolonged my mealtime by taking small bites. My usual size forkfuls
would have left my plate empty in four bites. Halfway through dinner
my host asked me how I was enjoying my meal. In my usual not so
politically-correct manner, I responded, “Tasty, but this is barely
enough food to get me to Taco Bell.” I understand one of the reasons
for the small portion served. A full plate of Roxanne’s nutty
lasagna would have meant a thousand calories just for my entrée. I
am happy my host picked up the $500 check after the meal. Roxanne’s
restaurant is no longer open.
Of Course, Nuts
A casual review of the scientific literature might lead the reader
to conclude that eating nuts does not cause weight gain. How could
eating so many concentrated fat calories be OK for any weight loss
plan? A careful review of the methods used reveals that the trick is
to restrict the subjects’ calorie intake and/or limit the amount of
nuts they are allowed to eat to about an ounce a day.12
Still, the addition of an ounce of nuts a day should cause
some weight gain when the daily calories are otherwise unrestricted.
An ounce of nuts means an additional 150 calories daily—that’s 4500
calories a month, which could represent a monthly gain of a pound
and a half of body fat. Many reasons are given for this
unexplainable effect of little or no weight gain with added nuts:
the high satiety of nuts causes people to eat less, added nuts
displace more fattening foods (cakes and pies),
their monounsaturated and polyunsaturated fatty acids are more
readily burned off (diet-induced thermogenesis), and an increase in
fecal losses of fat due to incomplete mastication of whole nuts (nut
butters would be much more readily digested and more fattening).
Even though an
ounce of nuts a day may not cause appreciable weight gain, nuts do
not violate the laws of thermodynamics and
the evidence shows adding more than an ounce daily without other
calorie restrictions does cause weight gain.12
And excuse me! Who, when given permission, eats only one mouthful of
nuts a day?
Hurt the Bones Too
High-protein foods in Western diets, especially hard cheeses, meat,
poultry, eggs, fish, shellfish, and foods made with isolated soy
proteins, generate a large amount of acid in the body after eating
them.13 This acid must be neutralized, primarily by the
release of alkaline materials from the bones; and thus begins bone
loss and osteoporosis. 14-17
The storage organs—nuts, seeds, legumes, and grains—are rich in
nutrients, including proteins, which result in the delivery of a
small net acid load to the body. (The amount of acid caused by
animal food consumption is 6 to 10 times greater than that caused by
plant storage organs.)13 A study of people on a
Mediterranean diet supplemented with an ounce of nuts (walnuts,
hazelnuts, and almonds) daily for three months, found evidence of
adverse effects on their bones.18 There was an elevation
in their parathyroid hormone levels and a slight increase in
breakdown products of bone (deoxypyridinoline) found in the
Fortunately, most healthy plant-food-based meal plans also include
foods that are alkaline, meaning fruits and vegetables, which
neutralize the small amount of dietary acids that come from eating
nuts, seeds, legumes, and grains.11 However, this
observation should also serve as a word of caution that even a whole
foods vegetarian diet has the potential to cause problems of
over-nutrition from excess calories, fat, protein, and dietary
acids, and adding in green and yellow vegetables and fruits is
Nuts Are a
Delicacy on the McDougall Diet
We must eat, and when properly informed, we do have a choice when it
comes to the amounts of carbohydrates and fats we consume. People
are starch-eaters—meaning we thrive on a high-carbohydrate, low-fat
diet. For our best appearance and performance we must remain true to
our nature. However, most of us are also resilient. Thus, an
occasional rich food is no serious threat for otherwise trim and
healthy people—especially when this delicacy is from a whole plant
origin, such as nuts. The problems begin when occasional holiday
treats become the center of a meal plan everyday.
1) American Dietetic Association; Dietitians of Canada; American
College of Sports Medicine, Rodriguez NR, Di Marco NM, Langley S.
American College of Sports Medicine position stand. Nutrition and
athletic performance. Med Sci Sports Exerc. 2009
2) Coyle EF. Substrate utilization during exercise in active people.
Am J Clin Nutr. 1995 Apr;61(4 Suppl):968S-979S.
3) Rauch LH. The effects of carbohydrate loading on muscle glycogen
content and cycling performance. Int J Sport Nutr. 1995
4) Hawley JA. Strategies to enhance fat utilisation during
exercise. Sports Med. 1998 Apr;25(4):241-57.
5) Helge JW. Impact of a fat-rich diet on endurance in man: role of
the dietary period. Med Sci Sports Exerc. 1998
6) Maughan R. The athlete's diet: nutritional goals and dietary
strategies. Proc Nutr Soc. 2002 Feb;61(1):87-96.
7) Ivy JL. Dietary strategies to promote glycogen synthesis after
exercise. Can J Appl Physiol. 2001;26 Suppl:S236-45.
8) Hawley JA. Effect of meal frequency and timing on physical
performance. Br J Nutr. 1997 Apr;77 Suppl 1:S91-103.
9) Walton P. Glycaemic index and optimal performance. Sports
Med. 1997 Mar;23(3):164-72.
10) Foster-Powell K, Holt SH, Brand-Miller JC. International table
of glycemic index and glycemic load values: 2002. Am J Clin Nutr.
12) Natoli S,
McCoy P. A review of the evidence: nuts and body weight.
Asia Pac J
13) Remer T, Manz F. Potential renal acid load of foods and its
influence on urine pH. J Am Diet Assoc. 1995 Jul;95(7):791-7.
14) Maurer M. Neutralization of Western diet inhibits bone
resorption independently of K intake and reduces cortisol secretion
in humans. Am J Physiol Renal Physiol. 2003
15) Remer T. Influence of diet on acid-base balance. Semin
Dial. 2000 Jul-Aug;13(4):221-6.
16) Frassetto L. Diet, evolution and aging--the pathophysiologic
effects of the post-agricultural inversion of the
potassium-to-sodium and base-to-chloride ratios in the human diet.
Eur J Nutr. 2001 Oct;40(5):200-13.
17) Spence LA, Lipscomb ER, Cadogan J, Martin B, Wastney ME, Peacock
M, Weaver CM. The effect of soy protein and soy isoflavones on
calcium metabolism in postmenopausal women: a randomized crossover
study. Am J Clin Nutr. 2005 Apr;81(4):916-22.
18) Bulló M, Amigó-Correig P, Márquez-Sandoval F, Babio N,
Martínez-González MA, Estruch R, Basora J, Solà R, Salas-Salvadó J.
Mediterranean diet and high dietary acid load associated with mixed
nuts: effect on bone metabolism in elderly subjects. J Am Geriatr
Soc. 2009 Oct;57(10):1789-98.
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