5/20/13
Despite the tremendous amount of writing about nutrition, it
doesn’t seem to be understood very deeply.
Let me first talk about ways of understanding something like
nutrition. They are the same three ways
we can understand anything complicated, and correspond to three of the many
lobes of the brain or three of man’s mental capabilities.
One way is verbal.
You can read a description of nutrition, maybe some sort of a list of
do’s and don’ts for staying healthy, or avoiding obesity, or keeping your immune
system going. If you remember them, and
understand the terms used and the grammar involved, you can say you have a
verbal understanding of some aspect of nutrition.
Another way is numerical.
You can read about the number of calories needed to keep you healthy, or
the amount of fat that is on a dish you are about to eat. You can add up the saturated fat you consumed
in a day or a month, and compare it with recommended guidelines. You can make a record of your daily weight
and figure out the trends in your weight, perhaps how much you are losing each
week on an average. If you do this, you
can say you have a numerical understanding of some aspects of nutrition.
The third way is structural, which relates to processes,
organizations, categories, and procedures.
You can’t say you have a structural understanding of nutrition because
no one does. Shockingly, scientists have
not yet figured out the details of how nutrition works in the human body.
Why on earth hasn’t research in this area been heavily
funded for the last fifty years, so now we know exactly what goes on with food
in the body? Since so much health is
related to nutrition, what is stopping scientists from simply marching through
the nutrition process and nailing down all the unknowns. Certainly it would be a lot easier to control
one’s weight if we understood just what happens when we put some combination of
ingredients into our mouths.
The bottom line is that few seem to care about this. In the United States, the Food and Drug
Administration (FDA) has the responsibility for ensuring the safety of foods
that Americans eat. Food has a wide
range of risks involved, so maybe the FDA can excuse itself from not having
sponsored enough nutrition research by saying they have lots of other things to
worry about, like salmonella in tuna fish or whatever. The National Health Service (NHS) is run by
people who know nutrition is an important factor in health, so they should be
dumping big bucks into nutrition research, except they are not. There are thousands of things that affect
health, so maybe they have an excuse as well.
The National Science Foundation (NSF) has all the billions of scientific
questions on their plate, so they can’t put too much of their money into
nutrition. And the same goes for all the
supporters of research in the US. If
there isn’t funding, there isn’t research, and there isn’t a knowledge
explosion. Too bad for all the people
who eat food.
There is no doubt that understanding nutrition will take a
lot of work. Consider what has to be
done. First of all, we are still in the
caveman era of feeding ourselves. Five
or ten thousand years ago, some people figured out putting seeds in the ground
would grow crops, everything from fruit trees to wheat, and we have been doing
this ever since. This is amazing,
considering the revolution in everything else in our lives. We don’t travel the way we did in caveman
days, we don’t live in caves, we don’t die young typically, we have ways to
kill infections instead of enduring them, and ways to deaden pain safely, we
don’t believe the sun travels around the earth as cavemen did, we don’t fear
spirits in trees and rocks, but we still plant seeds and eat the result. Hopefully somebody will soon figure out how
to replace it, but for now, we are stuck with it as a source of all our edible
ingredients.
Plants and animals are complex biologically, which means
that the basic ingredients of our food are not describable by a simple chemical
formula, but instead are a very complex amalgam of multiple chemicals, most of
them complex hydrocarbons, including various trace minerals. It is not a simple puree of these chemicals,
but there are cellular structures still present in many foods. The nutrition process has to deal with these
cells, which may be a barrier to absorbing something from inside the cell after
it is eaten. Besides the cellular
structure, much food consists of pieces of intact plant or animal, i.e.,
multiple cells bound together, which again is a challenge to the nutrition
process.
This may have been the easy part. After all, we can take some food element,
like a piece of salmon, subject it to whatever food preparation process we are
studying or including, and then examine it using all the forensic tools present
in a modern biochemical laboratory.
After a huge amount of effort, we might come up with a description of
what that piece of prepared food was structurally and chemically. This might be a count of cells of various
types present and how they were connected and bound chemically to each
other. Then we could describe each of
the cell types in terms of contents and internal structure. It would a breakthrough of sorts, as we
haven’t done this for complex plant and animal cells, even human ones. The complexity is too forbidding.
The next part is harder.
In the mouth, as we have described before, there are both physical
changes from chewing and other mouth physical actions, and chemical ones where
the saliva begins to affect the ingredients.
To find out the effect of the mouth on foods, one would have to collect chewed
food in the throat and compare it to the starting attributes of the food. This might have to be done on all of the
various types of foods.
Next is the effect of the stomach on foods. Now the
collection problem is much harder.
Perhaps some animals with identical stomachs to humans could be
used. The intestine is next. Most people have heard that there are more
microbial cells in the intestine than make up the body – of course they are one
ten-thousandth the size so the volume is small compared to the volume of a
human. However, there are many varieties
of them, and the distribution of them over the different varieties varies
between people and within one person with time, especially if food choice
changes. This bacterial mix is not
identical everywhere in the intestine, either.
These bacteria play an important role in nutrition, as they
consume some of the biochemicals in the food that reaches them, and excrete
some other biochemicals. After they have
had a chance to consume what they prefer, the lining of the intestine absorbs
some of the chemicals into the blood stream.
From there they are transported to various organs and parts of the
body. How much of what gets transported
where is another question for the nutritional researchers. The various absorbed biochemicals have to
diffuse through the capillary walls in order to get into various organs, and
then the organs’ own chemical processing factories, their cells, do their work
to produce what is needed, and perhaps what is not.
Things are easier to study when they are linear, meaning,
one effect is proportional to some input.
Linearity would mean that if you ate twice as much vitamin C in a second
trial compared to the first one, whatever cells took up vitamin C during your
initial trial would get twice as much on the second. Saturation exists, despite many writers
ignoring it. Some intestinal bacteria
which, despite your wishes to the contrary, eats up your vitamin C before it
gets to your bloodstream might not be able to deal with twice as much, so in
your first trial, the bacteria gets fed vitamin C and in the second trial, both
you and your bacteria get their fill.
This is very non-linear. The
opposite effect can happen. For example,
cell walls can change their permeability.
If some cell of your body takes in vitamin C through a pore, just
designed for it, that pore might close when the cell gets some amount of the
vitamin. So, in the first trial, you get
all you need, and the second trial, the additional amount circulates around in
the blood because no cells allow it in, and then is excreted as waste. Now, which of these two events, or many
others we could hypothesize, occur in the body?
Another gap for nutrition researchers to fill.
The question of where does saturation occur is a valid one
for all biochemicals we ingest, and saturation is only one of many
non-linearities we can imagine. Some of
them involve our bacterial companions, others just our own cells. So, if someone asks you, how much vitamin C
do I need, you need to say you don’t know.
One of the more interesting non-linearities concerns inventories. There may be places where biochemicals are
stored but not used, and the cells involve take their signature biochemical out
of the bloodstream or put it back in, depending on the level in the
bloodstream, or the presence or absence or amount of a completely different
one, perhaps one which is produced as waste of the biochemical being
stored.
With this level of complexity, scientists hack off small
parts of the problem to study, and there are many results from good scientific
exploration. But there is no comprehensive
overview that includes the whole process and gives us a structural view, to the
level of detail needed to make nutritional computations, of the entire
thing. So, we are left with some simple
approximations or estimates or guesses or hypotheses as to what is going on to
what amount. This leaves the door open
to all those who want to write about a new diet they have invented. And it leaves us in a quandary, as bad as the
one concerning taste and other attributes.
We need to ask, what would a good engineering team do in this situation…
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