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” implies 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 or oxidation, or to assemble substrate molecules together into a larger molecule or reduction) 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, although without the amylase will produce small carbohydrates 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 is a bell-shaped curve [illustration available]:
This graph was originally developed for agricultural plant fertilizer rates, then applied to ecological descriptions of abundance of wild plants and animals based on environmental factors (the ‘illustration available’ was borrowed from my Ecology class notes), and is now being 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 person 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 person will begin to exhibit actual symptoms of deficiency or toxicity [considered to be clinical meaning that licensed medical practitioners (doctors) can diagnosis the problem]. Extreme cases of deficiency or toxicity may result in death. The minimum diets [observed in Third World countries] without clinical deficiency symptoms involve at least 800 kilocalories per day. No known populations chronically [chronic means “repeating over a long period of time”] taking in less than 800 Calories per day, including persons with severe eating disorders, are free from nutrient deficiency symptoms. Brown (2008. Nutrition Now, 5th ed. ©Thompson Learning, Inc.) 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. Diets limited in the range of foods consumed may lead to overdoses of some nutrients, but clearly with sub-clinical deficiencies (or worse) 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 (Brown, 2008. Nutrition Now, 5th ed.
©Thompson Learning, Inc.)) 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 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 [those nutients required in
“large” amounts: the carbohydrates, lipids and protein]; and, although less is known about
them, there were probably cycles in the micronutrient [those required in
“small” quantities] densities of foods [vitamins and minerals] as well.
Nutrient density is the concentration of nutrients, measured as grams of
nutrient per gram 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 carbohyate density of plant-based foods
increases during the growing season, but begins to decline after the peak of the growing season (late
summer), continuing to decline until the start of the next growing season. Similarly, the lipid
density of animal-based foods increases as the carbohydrate density of plants declines late in the
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
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 animals resembling sow bugs (a.k.a.
pill bugs, or ‘rolly-polly 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 about 1.5 million years, or almost 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 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 living 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, but 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, a Native American word for corn (Zea mays) [the oldest known form of corn, teosinte (a Aztec/Puebelo word for a corn-like plant 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]; after all, it has taken the English Sparrow (Passer domesticus about 100 - 200 generations 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 [by adaptive evolution] 5 distinct “breeds” each in a different habitat 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 Human on a “fat-free” diet?
[answer: this is starvation relative to lipids.]
How about a “low calorie” diet?
[answer: this is starvation relative to carbohydrates.]
Non-rhetorical question [a question for you to think about]: When in the treatment and care of an over-weight Human do malnutrition or starvation become medically un-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 blood stream into the intestines, water soluable nutrients can be expected to move back into the intestines 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.
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 containing 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 person 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 less reliable the estimate (statistically, the variance is
higher), and longer than a month or so is too impractical (from a data collection point of view).
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, in my Universe, these substances come from living (or recently living) Plants and Animals. Therefore, all foods are good. Non-foods, by extension, are substances which can provide NO nutritional benefits [or come from un-natural sources, such as factories]. Most “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 [and therefore, had the same fat
density as a ‘high fat’ bar]. 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 [boxes of reduced fat Wheat Thins now describe
a single serving as 16 crackers]. I had always assumed that vending machines sold single-serving
containers. 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 to read them, which you will
have the opportunity to do in this course.
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,” and 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 (highlighted) with comments (not highlighted).
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
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 daily average total (all foods) at or below 100%]
Total Carbohydrates 24g 8%
Dietary Fiber 1g 5%
Sugars 10g [there is no RDA for sugar]
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]
 Sugar,  oats,  peanuts,  enriched Flour (wheat flour, niacin, reduced iron, thiamine mononitrate, riboflavin, folic acid) [the stuff in parentheses is a list of ingredients in the item],  vegetable shortening (palm, partially hydrogenated soybean and/or cottonseed oils),
contains less than 2% of:  dextrose,  corn syrup,  corn flour,  leavening (ammonium bicarbonate, sodium bicarbonate),  corn syrup solids,  salt,  food starch-modified,  corn starch,  whey,  natural and  artificial flavor,  soy lecithin
this is where we don't want to see the key ingredients Roizen & Oz recommend avoiding:
NONE of these [listed in bold-face above] in the first five ingredients!
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]
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.
TABLE OF CONTENTS
© 2004-2010 TwoOldGuys
revised: 9 Aug 2010