Humans, like other Animals, Plants and other organisms, sustain Life by metabolic processes. Metabolism is the total of all chemical processes that occur in the cells of the organism; metabolic processes imply a set of sequential chemical reactions, or pathway, which carries out some function. Each step of any metabolic pathway starts with a substrate (one or more chemicals), then effects a chemical change (either to break down the substrate molecule by catabolic reactions, or to assemble substrate molecules together into a larger molecule by anabolic reactions) in the presence of one or more catalysts. Catalysts are chemicals which speed chemical reactions without being affected by the reaction; enzymes are organic molecules which serve as catalysts which not only speed the reaction rate (of reactions that may occur only in the presence of the enzyme), but also control which of several to many possible products will be produced. For example a carbohydrate in the presence of amylase will break down to disaccharides only [and sometimes a residual polysaccharide fragment], although without the amylase will produce small polysaccharide fragments of random lengths. Simply because metabolism occurs within cells, so nutrients function within cells also. Some nutrients serve as substrates for various metabolic processes; while other nutrients serve as enzymes. Many vitamins are known to function as enzymes or co-enzymes [which apparently speed the rate of a reaction - enzyme complex in which the enzyme would speed the reaction without the co-enzyme], and some minerals are known to function as inorganic catalysts which speed the rate of the reaction - enzyme - co-enzyme complex. If that sounds confusing to you, you should be glad to know that it also confuses me, but Chemistry and I were never good friends in college.
The typical physiological response of an organism to nutrient intake (illustr 1.8, pg 1-15) is a
bell-shaped curve [illustration available]:
lethal = death
marginal = clinical deficiency
sub-optimal = marginal (sub-clinical deficiency)
optimal = Optimal
sub-optimal = marginal (sub-clinical overdose)
marginal = toxicity (clinical symptoms)
lethal = death
This graph was originally developed for agricultural plant fertilizer rates, then applied to
ecological descriptions of abundance of wild plants and animals, and now applied to human nutrient
status. Nutrient intake guidelines are based on estimates of the highest point on the curve [in
ecological applications the Optimum], but in reality there is an optimal range of acceptable
intake. In either direction from the optimal range (overdose or underdose) there is a range where
the patient will be in sub-clinical deficiency or overdose, without symptoms of deficiency or
overdose, but may exhibit impaired function. Beyond sub-clinical are the ranges where the patient
will exhibit actual symptoms of deficiency or toxicity. Extreme cases of deficiency or toxicity may
result cause death. The minimum diets [observed in Third World countries] without clinical
deficiency symptoms involve at least 800 kilocalories per day. No known populations chronically
taking in less than 800 Calories per day, including persons with severe eating disorders, are free
from nutrient deficiency symptoms. Your text suggests that it is unlikely to overdose on nutrients
without consuming supplements. While an interesting hypothesis, some overdose symptoms were known
before the development and wide-spread use of supplements. This observation (‘fact’)
clearly supports rejecting the hypothesis that ‘it is unlikely to overdose on nutrients without
consuming supplements.’ Diets limited in the range of foods consumed may lead to overdoses of
some nutrients, but clearly with sub-clinical deficiencies in several other nutrients.
Whenever I read or hear the word “adaptive”, I infer that the author/speaker is talking
about evolution or evolutionary processes, but then I am a Biologist. The context of the
reference to adaptive on page 1-17 of your text seems to support my inference, so I find it
“interesting” to look at the evolutionary time available to produce the adaptation under
discussion. Here, Brown (the author of your text) is talking about “mechanisms for managing
fluctuations… [in food supply].” I prefer to extend the concept to include any change in
food supply, not just quantity but also quality. Naturally occurring foods available to cavemen
would have exhibited seasonal cycles in relative density in essential macronutrients [carbohydrates,
lipids and protein]; and, although less is known about them, there were probably cycles in the
micronutrient densities of foods [vitamins and minerals] as well. Nutrient
density is the concentration of nutrients, measured as grams of nutrient per gram of food, or
sometimes grams of nutrient per Calorie of food.
If Humans have mechanisms for managing fluctuations in quantities of food supply, they ought also
to have similar mechanisms for fluctuations in nutrient densities. Specifically, it is well known
[among Botanists] that the carbohydrate density of plant-based foods increases during the growing
season, but begins to decline as the growing season peaks (and fruits ripen). The decline in
carbohydrate density continues until the start of the next growing season. Similarly, the lipid
density of animal-based foods increases as the carbohydrate density of plants declines in late plant
growing season, then declines through the non-growing season. There is no reason to believe that
terrestrial [land-dwelling] organisms have ever not had distinct growing seasons and dormant
seasons. The major challenges to successful invasion of the land [during the Silurian Peroid,
starting about 440 million years ago] were (1) obtaining and retaining water [and water-soluable
nutrients], and (2) dealing with climatic seasons. 440 million years has been enough time to evolve
from primitive land plants resembling green Dixon Ticonderoga© number two pencils stuck in the
ground on a mud beach to modern trees and flowers; and to evolve from primitive land animals
resembling sow bugs (a.k.a. pill bugs) and cockroaches to modern birds and mammals.
Based on fossil evidence, Humans have existed as a species [Homo sapiens]
distinct from humanoids [Homo neanderthalensis, H. erectus, H. habilis etc]
for at least 1.5 million years, or around 100,000 generations. Not only is this adequate time for
evolution to alter the adaptive mechanisms of Humans, we assume that the earliest Humans inherited
at least some of their metabolic processes from the 440 million years of evolution in land-dwelling
creatures before them. Our species originally lived in the subtropical Odavi Gorge region of east
central Africa [near the southern end of the Red Sea]. In a study involving DNA sequencing of
mitachondrial DNA from all known Human groups in all of the remote places where living Humans
can be found [from Artic Tundra to Tropical Rainforests], and assuming a mutation rate for
mitachondrial DNA, it was concluded [as a statistical construct, not a calendar date] that the
youngest woman who could have been the ancestral mother of all living Humans lived no less than
250,000 years ago, or over 15,000 generations. This should be adequate evolutionary time to alter our
mechanisms for managing fluctations in quantity and quality of food supply . However, Western
Civilization has existed for only about 6,000 years, or less than 400 generations. Western
Civilization brought us genetic modification of the food supply by agricultural breeding of animal and
plant food organisms. The oldest known agricultural breeds are wheat and cattle; this should not be
taken to be the oldest domestic breeds, but only the breeds that were sufficiently interesting to trace.
Corn is equally interesting, we just haven't yet figured out what wild species were bred to create maize
[the oldest known form of corn, resembling “baby corn” in stir-fry vegetables in size and
“Indian corn” in color, has been found in ancient buildings in Central America]. There
is some concern among scientists as to whether 400 generations is sufficient to adapt to something
as dramatic as genetic engineering [including artificial breeding], especially with a creature that
typically has fewer than 10 ‘litters’ of only one or two children each; after all, it has
taken the English Sparrow (Passer domesticus) about 100 - 200 generations [with 3+ clutches of
4+ chicks each per year, and 1 - 2 generations per year] to adapt to the different
natural habitats of North America. The English Sparrow was introduced to North American in
the mid 19th Century; they spread westward along with the settlers, and had by
the mid 20th Century become adapted to 5 different habitats not found in Europe. They are
being watched in the hopes of discovering a documented [for the first time ever] case of evolution
producing new species while Biologists are watching. The contemporary “American diet” and
artificial food supplements have existed for 20 - 100 years, which is only 2 to 6 generations. The
first McDonalds© fast-food restaurant opened in 1954
(http://www.mcdonalds.com/corp/about/mcd_history_pg1.html), launching the fast-food
phenomenon that epitomizes the American Diet. The first artificial food supplement, the artificial
sweetner saccharin© was first widely commercialized during World War I
(http://www.saccharin.org/history.html). Ten generations, or even 10's of generations, is
not evolutionary time. It is highly unlikely that we have even begun to adapt to artificial
food nor to the unbalanced nutrient densities in fast food and convenience foods.
We already know that Humans are designed for (adapted to) extracting nutrients from food. It seems
obvious that food is the ideal place to look for nutrients, and that failure to eat an adequate
diet should lead to insufficient intake of at least some nutrients. Subclinical deficiency of
one or more nutrients is called malnutrition; clincial
deficiency of one or more nutrients is called starvation.
Rhetorical question: if lipids are essential nutrients, as they are, what assessment would you
expect to be able to make (eventually) for a patient on a “fat-free” diet? [answer: they
should be in malnutrition relative to lipids, and may develop starvation relative to lipids].
How about a “low calorie” diet? [answer: malnutrition or starvation relative to
carbohydrates].
Non-rhetorical question [a question for you to think about]: When in the treatment and care of
an over-weight patient do malnutrition or starvation become medically acceptable side effects?
Malnutrition, and in extreme cases starvation, may be secondary to some disease
processes. Diarrhea, even low grade diarrhea, will cause nutrients to be transported through the
intestines too rapidly for effective absorption of nutrients. In addition, since diarrhea involves
moving fluid [water] from the mesenteric capillaries into the intestinal lumen, water soluable
nutrients can be expected to move back into the intestinal lumen with the water. Alcoholism and
some cancers are known to compromise the aborption, short-term storage and utilization [by cells]
of some nutrients. Tobacco use contributes large amounts of oxidants into the blood stream, so
reduces the effacacy of anti-oxidants such as vitamin C by chemical competition. It has been
estimated that regular tobacco use reduces the effective vitamin C in the body by up to 60%. Ulcers,
particularly bleeding ulcers, can severely compromise digestion. AIDS [not HIV positive],
and other long-term chronic illness, often lead to general malaise. Patients in general malaise
lose the desire to eat, so can become malnourished. It has also been hypothesized that there are
some [unidentified] genetic factors which cause inadequate absorption or inappropriate storage and
utilization of nutrients.
The text provides a sufficient discussion of, and examples of this for our purposes here.
The premise is that some chronic diseases are directly related to nutritional status, and that other chronic diseases may be influenced by nutritional status [either negatively, or positively].
Nutrition is not something that can be managed on a daily basis. If any meal, or full days diet,
fails to include any intake of foods containg a particular nutrient of interest, the shortfall can
be corrected by subsequent meals in the near future. More effective management of diet to provide
adequate nutrition requires accounting for nutrient intake on a monthly basis, or weekly when the
patient needs to “make up” for past dietary choices. Remember, all nutritional guidelines
are based on average daily intake, and averages can be estimated over a week or a month. The shorter
the averaging interval, the more likely the patient is to become non-compliant. Patients will
respond far better to the question: “did you have at least 2 or 3 servings of fish last
month?” than they will to “Did you have fish today?” The former will be heard as
advice; the latter, as nagging.
Dietary advice typically is intended to assure that the patient receives at least their
RDA of all nutrients, or that their diet is adequate. Recalling that
there is an optimal range of intake values, it should come as no surprise that we do not want them
to overdose on any nutrients in an effort to become adequate in other nutrients. This is what we
mean by balance. Moderation refers to
portion size. In current practice, we use moderation to assist the over-weight patient in slowing
and then reversing their weight gain, without rapid (and dangerous) weight loss. Finally, any Human
should have variety in their diet. By variety, we mean that they may
select different foods to provide particular nutrients. When a Human diet becomes monotonous,
boredom sets in, and observations of populations of people suggest that bored people assume
sub-clinical disordered eating habits. Some will chronically over-eat, while others will
“graze” leading to chronic under-eating. Neither chronic over-eating nor chronic
under-eating will produce the desired result of an adequate and balanced diet. Persons who eat
because it is a pleasant experience tend to eat more slowly [leading to more efficient digestion]
and to self-regulate portion size correctly by intuitive adaptive mechanisms. Persons who eat
because they have to eat to live, gobble down their meals rapidly, which overwhelms the natural,
intuitive adaptive self-regulating portion control mechanisms, leading to over-eating. It has been
my experience, as a disgustingly healthy person, that variety is important to making meal-time
enjoyable. Good company (such as the whole family eating together) helps also.
Food is considered, by Nutritionists, to be any substance which can provide nutrients (and limited non-nutrient material). Therefore, all foods are good. Non-foods, by extension, are substances which can provide NO nutritional benefits [or do provide toxins]. “Bad” foods in popular jargon are non-foods in Nutrition Science. The one exception is any true foods which have spoiled and become toxic!
Food Labels make interesting reading. I once saw low fat Milky Way® bars in a vending machine,
so I bought a low fat Milky Way and a normal (high fat?) Milky Way. The low fat Milky Way assured
me that it contained 20% less fat, which turned out to be a true statement. However, the low fat
Milky Way also contained 20% less candy bar, by weight in grams, so the low fat Milky Way provided
the same fat density as a high fat Milky Way. Another day, I purchased a package of Wheat Thins from
another vending machine. As I took the package out of the vending machine, I noticed that it too was
reduced fat, so again I read the label and learned to my surprise that the small envelope of crackers
contained 7 servings. The serving size was 3 crackers. I had always assumed that vending machines
sold single-serving containers. Boxes of reduced fat Wheat Thins now describe a single serving as
16 crackers. The Food Labels make interesting reading because they provide information that
can help you live a longer, and healthier life. But first, you have to learn how to read them.
We are not discussing the package labelling, which is intended to persuade you
to buy this particular item rather than some other item. The package labelling may not be as honest
as we would like. The Food Label is on the side or sometimes back of the package, in a box with a
line border. it is titled “Nutrition Facts.” Its content is regulated by the U.S. Food and
Drug Administration. It is easiest to describe by an example. I chose Girl Scout Cookies, the
Peanut Butter Sandwich, because it includes two of the ‘food groups:’ peanut butter and
cookies, but is missing the chocolate and coffee. I will simply read down the label [with comments].
Nutrition Facts
Serving Size 3 cookies (35g)
Servings Per Container about 7
[we all know that it contains only two serving; there are only 2 sleeves of cookies inside; if it
were 7 serving there would be 7 sleeves of cookies, right?]
Amount per Serving
Calories 170 Calories from Fat 60
%Daily Value*
Total Fat 6g 10%
Saturated Fat 2.5g 13%
[Roizen & Oz suggest less than 4g saturated fats, so this is OK]
Trans Fat 0g
[UL (Upper Limit) is 0g; you always want no more than 0g]
Cholesterol 0mg 0%
Sodium 120mg 5%
[try to keep your average daily total (all foods) at or below 100%]
Total Carbohydrates 24g 8%
Dietary Fiber 1g 5%
Sugars 10g
[there is no RDA for sugar]
Protein 4g
Vitamin A 0% - Vitamin C 0%
Calcium 0% - Iron 4%
*percent Daily Values are based on a 2,000 calorie diet. Your daily
values may be higher or lower depending on your calorie needs:
[this is followed by a table showing amounts of Total Fat, Sat Fat, Cholesterol, Sodium, Total
Carbohydrate & Dietary Fiber for 2,000 and 2,500 calorie diets; followed by Calories per gram for
Fat 9 - Carbohydrate 4 - Protein 4]
Ingredients: by U.S. FDA regulations, listed in order of density;
[item numbers added, emphasis (bold-face) added]
[1] Sugar,
[2] oats,
[3] peanuts,
[4] enriched Flour (wheat flour, niacin, reduced iron, thiamine
mononitrate, riboflavin, folic acid) [the stuff in parentheses is a list of ingredients in
the item],
[5] vegetable shortening (palm, partially hydrogenated soybean and/or
cottonseed oils),
contains less than 2% of:
[6] dextrose,
[7] corn syrup,
[8] corn flour,
[9] leavening (ammonium bicarbonate, sodium bicarbonate),
[10] corn syrup solids,
[11] salt,
[12] food starch-modified,
[13] corn starch,
[14] whey,
[15] natural and
[16] artificial flavor,
[17] soy lecithin
this is where we don't want to see the key ingredients Roizen & Oz recommend avoiding:
NONE of these in the first five ingredients! [listed in bold-face above]
simple sugar (anything ending in -ose or -ol, except cholesterol) [# 1
& # 6 in this cookie]
enriched, bleached or refined flour (any grain) [# 4 in this cookie]
high fructose corn syrup, or corn syrup (a.k.a. ‘sugar’) [# 7
& # 10 in this cookie]
saturated fat, trans fat (acceptable if 100% whole grain, not enriched)
[# 5 in this cookie]
partially hydrogenated… [# 5 in this cookie]
(hydrogenation converts unsaturated fats to saturated fats), see also
higher up on the label “Saturated Fats 2.5g 13%”
Contains: Wheat, soy, peanuts, milk.
[warnings for the allergic population]
Notice the “hidden” sugars (and position in list): dextrose (6), corn syrup
(7), corn syrup solids (10). Only “sugar” (in the ingredient list) counts as sugar for
the total carbohydrates and sugar higher up on the label.
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