The Origins of the Human Diet
Deep in the milky-way lies a wispy, barely detectable, gaseous interstellar cloud which contains an 8-atom sugar called glycolaldehyde. This chemical may just be a major precursor to life on planet Earth.
Sugar molecules in the gas surrounding a young Sun-like star |
Glycolaldehyde can react with ribose, a 3-carbon sugar, to
form RNA and DNA. DNA, or deoxyribonucleic acid, is like a biological blueprint
that a living organism must follow to survive and remain functional. RNA,
or ribonucleic acid, helps carry out this blueprint's guidelines. RNA transfers
the genetic code needed for the creation of building-block-proteins from
information-storing-nuclei to the protein manufacturing segments of our body’s
cells.
Think of DNA as a blueprint or set of instructions. RNA
contains a second set of instructions for converting the blueprint into
the biological house we live in. Together, they form the basis for life on this
planet. Glycolaldehyde is one of the keys to the creation of both.
The same interstellar cloud that contains glycolaldehyde
also contains a sweet compound called ethylene glycol. It is a close relative
of sugar. This is an important actor when looking into early life on earth. In
earth’s earliest days, the atmosphere contained no oxygen. Without oxygen, life
was based on the production of energy using anaerobic processes that did not
require the presence of oxygen. These anaerobic processes, (requiring no
oxygen), allowed for the conversion of sugars as well as early forms of protein
into energy. However, another kind of process was needed for fats. This
requirement for a second process is a key concept in understanding how our
metabolisms work at their most basic level.
The first living cells were prokaryotic in nature.
Prokaryotic cells are microscopic single-celled organisms that have neither a
distinct information rich nucleus with a membrane nor any other specialized
oxygen-based sub-structures. Understandable since in earliest times there was
no oxygen present. This means that all of the living cells on the planet were
identical in their genetic structure. It also means that they primarily
metabolized sugar for energy. However, there was a very important side effect
to this process!
The oxygen that fills our atmosphere today was built up over
millions of years as a waste-product from the prokaryotic cells' anaerobic
digestion of sugar. Once there was enough oxygen to go around, prokaryotic cells
evolved into eukaryotic cells and almost all the life we see each day —
including all plants and animals, are Eukaryota. Eukaryotic cells are far more
complex and diverse than prokaryotes. They contain a nucleus, which stores a
unique genetic blueprint. Eukaryotic cells also boast their own personal
"power plants", called mitochondria. They thrive in an
oxygen rich environment. These tiny cellular substructures produce chemical
energy and they hold the key to understanding the evolution of life on earth.
They ushered in a whole new era. These complex eukaryotic cells eventually
evolved into multicellular organisms.
But how did the eukaryotic cell itself change into more
complex life forms? How did such a simple life form make the evolutionary leap
from a prokaryotic cell to a more complex eukaryotic cell to plant and animal
cells? The answer to these questions is a powerful statement about life on
earth. Eukaryotic cells evolved through teamwork.
Evidence supports the idea that eukaryotic cells are actually
the product of separate prokaryotic cells that united together in a symbiotic
union. In fact, the mitochondrion itself seems to be the
"great-great-great-great-great-great-great-great-great grandchild" of
a free-living bacterium that was engulfed by another cell. This bacterium ended
up becoming a sort of perpetual houseguest. The host cell benefitted immensely
from the chemical energy produced by the guest it was hosting (now called the
mitochondrion). The mitochondrion in turn profited from the shielded,
nutrient-rich environment surrounding it.
It is our mitochondria that produce energy by using oxygen
to burn fat. Fat is an aerobic nutrient. It forms the very foundation of
oxygen-based metabolisms. Fat cannot be used for anaerobic (non-oxygen-based)
conversion to energy.
Essential Nutrients, Nonessential Excesses and Disease
We can discuss essential nutrients in two broad categories; macronutrients and micronutrients.
You are what you eat, and you eat what you are: fats,
proteins and carbohydrates. You also must consume various other vitamins and
minerals. First we need to discuss macronutrients and then we will
look at micronutrients.
What are macronutrients? Nutrients are substances essential
for growth, metabolism, and other bodily functions. Macronutrients are
nutrients that provide our bodies with the calories and building blocks
required to make and use energy. “Macro” means large. Macronutrients are
the nutrients needed in large amounts. They tend to be complex and composed of
several substances. There are three macronutrients: fat, protein and
carbohydrate.
What are micronutrients? Micronutrients are the vitamins,
minerals, trace elements, phytochemicals, and antioxidants that are essential
for good health. Micronutrients generally get a lot of attention because they
can be packaged and bottled (for profit). However, when it comes to health and
vitality it is ultimately macronutrients that run the show.
Nutrition has become a very confusing subject for discussion
these days. What follows is basic description of the science behind what
various macronutrients do and what our basic requirements are for their
consumption. To be clear, this blog has strong reservations about the value of
manufactured foods. All foods that were not given to us by
mother-nature directly and which require significant processing should be
removed from daily life if your goal is health and longevity. This includes
manufactured so-called health foods and commercially prepared factory farmed
meats.
The category of macronutrients can be broken down into two
subsections, essential and non-essential. Essential nutrients are nutrients
that your body cannot manufacture for itself. Essential nutrients must come
from external sources. Non-essential nutrients are nutrients that can be
accessed internally or manufactured by combining a variety of other available
nutrients.
There are essential micronutrients as well. These include
the various B vitamins, vitamin C, and the fat soluble vitamins A, D, E &
K. They must be accessed externally. There are also many essential minerals,
including: Calcium, Chloride, Chromium, Cobalt (as part of Vitamin B12),
Copper, Iodine, Iron, Magnesium, Manganese, Molybdenum, Phosphorus, Potassium,
Selenium, Sodium, Zinc.
Note: There are no essential carbohydrates or sugars, all
carbohydrates eventually become sugar. Why are there no essential carbs?
Because we can make them via the synthesis of amino acids and glycerol obtained
from fat metabolism. We can also make them through de novo synthesis (also
called gluconeogenesis). Eventually, the body can adapt to a low-carbohydrate
state by producing ketones (a state called ketosis) to fuel the body/brain. We
can readily adjust to using ketones for fuel, except where excessive
carbohydrate stores are present. In that case, our bodies will
revert to running on sugar.
We do not need carbohydrates. In fact excessive intake of
carbohydrates is the cause of major diseases of affluence in the world today.
These diseases include huge increases in rates of cancer and heart disease.
Cutting excessive sugars and carbohydrates out of our diets will prevent a vast
proportion of these diseases! We know this having observed the effects of
fasting and caloric restriction.
Fasting and caloric restriction both reduce levels of
insulin, which is required for the storage of blood sugar in the form of fat.
Eating fat doesn’t make you "gain weight" directly. However, eating
excessive amounts of sugar along with that fat is what causes us to pack on
excessive and unhealthy pounds.
As well, fasting and caloric restriction reduce another
growth factor called MTOR (short for mammalian target of rapamycin), which
regulates cell growth and cell proliferation. MTOR is a protein sensing pathway
that sets a limit on the amount of protein we can eat before it starts creating
negative health effects.
Caloric Restriction
Caloric restriction, often shortened as CR, extends healthy,
average, and maximum life spans. Various studies have analysed many short lived
animals, including mice and rats, as well as animals with longer life spans
such as primates. These studies follow a variety of species through a full
lifespan in a shorter period of time than possible with humans. Studies
on humans involve less severe parameters over shorter time spans for ethical
reasons but their findings parallel those of animal studies. In published
research, this method of eating is generally called dietary restriction,
abbreviated to DR. Rodent studies conducted over the past 20 years have
reliably demonstrated up to a 40% increase in maximum life span through
life-long caloric restriction.
Appearance of Rhesus monkeys in old age (approximately 27.6 years). A and B show a typical control animal. C and D show an age-matched caloric restricted animal. |
The biological reaction to caloric restriction occurs in
most species examined to date. It likely evolved early in the history of life
on Earth as a tactic to boost the likelihood of surviving periodic famines. The
effects of such dietary restrictions are the same whether you are a mouse that
is alive for a few years or a human living for decades.
Unlike animal studies, in human studies of caloric
restriction cannot be directly credited with the same impact on life span. We
can’t directly study its effects over an entire human life span so easily and
there are serious moral implications for such research. However, it has been
shown provide numerous health benefits. These include lowered risks for most
degenerative conditions of aging as well as improved measures of health. In
recent years, more lengthy human studies of long-term and short-term calorie
restriction have systematically demonstrated these benefits. Many researchers
believe that the evidence to date shows the practice of caloric restriction
will in fact prolong the healthy human life span. There simply isn't enough
data yet to pin down the impact on an entire life span. However, it is
reasonable to deduce that the impact of caloric restriction could mean a
difference of 5-10 years of life.
The beneficial effects of caloric restriction in laboratory
animals have been known for more than 80 years, but only in the past decade has
an appreciable level of funding and attention been given to this field. There
are many ways that caloric restriction benefits health, including: increased
insulin sensitivity and decreased oxidative stress. It even positively alters
levels of the friendly bacteria in your digestive system!
There are several different ways in which caloric
restriction may work. The area that seems to get the most research is related
to a family of genes called Sirtuins. There are seven mammalian sirtuins that
we know of (SIRT1 through SIRT7). In the last decade, these sirtuin proteins
have received a lot of attention as epigenetic regulators of aging. The growing
association between ageing and neurodegeneration has led researchers to investigate
the role of sirtuins as potential targets for the development of novel
therapies to prevent or slow down the progression of Alzheimer's disease.
SIRT1, the most studied member of the sirtuin family, has
already been shown to regulate numerous neuro-protective functions, including
the antioxidant and anti-inflammatory response. It also plays a key role in the
regulation of insulin, gene transcription and the production of new
energy-producing mitochondria. There is a heavy research focus on SIRT1 gene
expression because it can be targeted by drugs and by supplements like
Resveratrol. But there is a much easier way to regulate this powerful gene
expression, and it takes us back to the beginning of today's discussion.
Simply put, SIRT1 is negatively regulated by both MTOR and
Insulin. This means that excessive protein consumption and excessive
carbohydrate consumption decrease the expression of our longevity genes. We are
complex creatures that use oxygen to create energy. This means that we are
built to burn fat, and eat fat. The sensing target for fat in our diets is a
hormone called leptin. Leptin acts as an up-regulator. It encourages the
expression of SIRT1 in a positive direction.
There are at least four solid reasons we are built to burn fat for fuel to create energy.
1. A sugar-burner can't truly use stored fat for energy generation, at least not until their excess glucose runs out. When there is enough sugar/glucose available in the blood, our bodies will use it preferentially over fat. Note here that we are using the term "preferentially". This does not mean sugar/glucose is more effective or efficient for energy production. On the contrary! Carbs have fewer calories than fat to make energy, so you are forced to eat larger volumes of them in order to have enough energy to go around.
2. When someone who is highly
dependent on carbohydrates for energy goes a few extra hours without eating,
they become very hungry. Think of it as essentially stoking metabolic fires
with kindling (energy-light sugar) and not logs of hard-wood (energy-dense
fats). Clinical studies have even shown that the body fat of even
carbohydrate-based dieters will release stored fatty acids several hours after
eating and during periods of fasting. This is yet another sign that our bodies
prefer fat as a fuel source, even if it is our own! Carbohydrate reliant eaters
are simply replacing kindling with kindling without ever using much more
efficient sources of energy.
3. A sugar-burner relies on a
short-lived source of energy. Glucose will work for you if need it, but you
can't really store very much of it in your body. Even a 150 pound person who's
fairly trim with 12% body fat has 18 pounds of animal fat on hand to be
converted into energy. Compare this to our ability to store sugar/glucose as
muscle and liver glycogen. We are limited to around 500 grams or so. This
means that sugar burners need to supply carbs from an external source, thus
stopping the burning of any body fat for energy! What a bad trade-off!
4. A sugar-burner will use up
glycogen fairly quickly, even during moderate exercise. That is not to say that
glycogen-based exercise and efforts are not of some merit. Subject to the type
of physical activity, glycogen burning can be completely necessary and
expected. But, it is valuable fuel. If instead, you're able to stay in an
oxygen-based fat-burning mode for as long as possible you are able to save
glycogen for anaerobic “all out” efforts. Glycogen stores are literally
life-saving rocket fuel for running like Hell from dangerous wild animals.
Sugar-adapted people are wasting their glycogen stores on efforts that fat
should be able to power.
Fat as a Source of Fuel: Our Evolutionary History
Looking at metabolism through the lens of evolution, we can see that fat and protein were the dominant macronutrients, (when we were lucky enough to have any food at all). Over our two and a half million years of adaptation we have sometimes not had regular access to food, especially in the form of glucose promoting carbohydrates. This would have caused our ancestors to develop effective ways to tap their own stored body fat for energy instead of relying on a steady supply of carbohydrate. Normally, our activities would not have required the level of energy that sugar can provide. After all, we were usually not in full blown flight mode (hopefully!). As a result, we have a very low levels of glycogen (for emergencies) compared to available fat rations in our bodies. Clearly it was primarily the fats and ketones, with small amounts of glucose generated internally through gluconeogenesis, that supplied us with appropriate levels of energy for healthy living. We would have had an occasional all-out-burst of required anearobic energy (because we could not consume oxygen quickly enough) running after, or away from an animal, but these moments would have been rare in a 24 hour day.
In Conclusion
Eating is our birthright. The importance of sugars, proteins, and fat in our diets dates back to the earliest days on the planet. At a molecular level, it an important part of a three cornered connection to the stars involving anaerobic (based on sugars) as well as aerobic (based on fats) energy production. We are literally built to eat properly and when we follow our natural genetic preferences we are paid back with the fruits of vitality and longevity.
An important revelation here is that, despite recent
arguments to the contrary, high fat diets have been shown, in human subjects,
to actually increase the number of mitochondria available for energy
production. This leads us to an interesting point to be covered in an upcoming
post on this blog, the influence of ketogenic diets and the progression of
cancer.