Are we victims of our own
Source: Harvard Men's Health Watch
Publication Date: 12/01/2006
"What a piece of work is
As usual, Shakespeare got it right. At their best, humans appear to
limitless ability to imagine and create, to innovate and build, to
achieve. As man's dreams in the 20th century became realities, he
way of life that is beyond the wildest imagination of his grandparents.
all its advantages, life in the information age presents potential
well as unparalleled opportunities. Unfortunately, some of those perils
contribute to diseases that were rare a few generations ago but
epidemic proportions today.
A scientist speculates
Writing in the August 2004 American Journal of Medicine, Dr. George P.
of the National Institutes of Health explains the potential hazards of
mismatch between human genetics and human behavior. At the core is the
stress response. It involves the brain, especially the hypothalamus,
pituitary (or "master") gland, the sympathetic nervous system, and
the adrenal glands. In response to stress, this intricate network pours
several hormones such as cortisol and other glucocorticoids, adrenaline
other sympathomimetic amines, vasopressin, and interleukin 6 and other
cytokines that mediate inflammation and immunity.
You don't have to be a scientist to know how the stress reaction feels
looks. Your heart beats faster and harder, and your blood pressure
breathing gets faster and deeper, and your pupils widen. Your muscles
and your hair may bristle a bit. Your skin becomes cool and clammy,
gets dry, and your stomach may churn with tension. You feel alert and
tense and nervous.
The changes that go on inside your body are just as impressive. Stress
activates your clotting mechanisms and turns up the immune system.
Blood sugar levels
rise, white blood cells pour into circulation, and urine production
These changes prepare humans to cope with danger. But they evolved when
dangers were predators, privation, and physical dangers. Today, most
live in a protected world of plenty. Our world has changed, but the
response has not.
In his essay, Dr. Chrousos reviews how the mismatch between our genes
lifestyle may contribute to some important contemporary diseases; a
version of his table is below.
Genes for survival, genes for disease
||Genetically determined survival responses
||Contemporary diseases that may result
||Obesity and diabetes
||Retention of salt and fluids
||High blood pressure
||Autoimmune and allergic diseases; septic shock
||Arousal and fear
||Anxiety and insomnia
||Withdrawal from danger, escape
and social isolation
|Tissue strain and injury
||Preservation of tissue integrity
||Pain and fatigue syndrome
||Promotion of clotting
||Heart attack and stroke
American Journal of Medicine 2004; 117:205.
As an endocrinologist and
geneticist, Dr. Chrousos calls for more
the survival genes that were once adaptive but are now harmful. He
knowledge will lead to preventive measures and identify targets for
development. It's a hope we all share -- but we don't have to wait for
breakthroughs in genetic engineering to correct this imbalance between
genes and our lifestyle. We should adapt to the dietary patterns and
habits that will keep our genes happy and our lives healthy and
On the run
Think about it. Our earliest ancestors depended on their physical
survival. Life itself hinged on obtaining food by hunting and
strenuous activities. Finding shelter, evading predators, and coping
whims of Mother Nature also required strength and endurance along with
Anthropologists tell us that at the dawn of humankind, in the late
era, people lived in small bands that roamed over large areas to find
shelter. Human population was sparse; scant resources, low fertility,
hostile environment limited population to a density of just one person
square mile. Society was simple, with most of the people performing
tasks. The most important task was obtaining food. Typically, it was a
of feast or famine. One to two days of virtually continuous physical
were required to obtain sustenance. These bursts of exercise were
several days of feasting and celebration -- but even during these
holidays, our ancestors were amazingly active, dancing, playing, and
up to 20 miles on foot in a single day to visit and trade with other
in all, an average day's physical activity burned up about twice as
calories as a typical American uses today.
The "all-natural" diet
Stone Age people hunted wild game, trapped fish, and gathered fruit,
seeds, and tubers. They weren't able to store food, so they ate what
when they could. The result was feast or famine; even today, the human
metabolism remains dedicated to storing calories in body fat to provide
time of need.
The Stone Age diet was high in protein but very low in fat. Meat was a
source of protein, but wild game was lean and low in fat because the
ran free and eked out a subsistence living on vegetation -- no pens,
bags, antibiotics, or hormones for them! Dairy products were unknown,
carbohydrate consumption varied, but the primitive diet was very high
and had plenty of vitamins, iron, and minerals -- except for salt,
scarce. Caloric consumption was up and down, probably averaging about
calories a day.
Change came slowly in the Stone Age. Hunting and gathering remained the
dominant way of life for about 30,000 years. But about 10,000 years
learned how to cultivate crops and domesticate animals, making life
more predictable. The population density increased, creating the need
specialized occupations and creating social hierarchies, so people
source of stress. For most folks, farming and herding required nearly
physical work as hunting and gathering, but farming produced a new way
Grains, cereals, and tubers became the main vegetable foods, and wild
replaced by dairy products and meat from farm animals. As man became
on a few crops, dietary diversity suffered and nutritional deficiency
arose. Periodic crop failures produced epidemics of malnutrition and
starvation. Stored food often spoiled, and microbes passed freely from
to humans and from person to person in the new villages and towns. New
replaced old problems, keeping the average Agricultural era lifespan at
30 years, a minimal improvement over the hunter-gatherer's life.
The industrial revolution
The agricultural way of life still prevails in much of the developing
but in the 19th century, the industrial revolution produced incredible
in the United States
and Europe. Labor-saving devices
made life much easier,
replacing physical labor with mental work. New agricultural methods
cheap and plentiful. Technology and mass production made refined
and salt -- to say nothing of tobacco and alcohol -- readily available.
brave new world was born.
The information age
Modern science has accelerated the pace of change and has spread
advances to the far corners of the globe. Life is much better (and much
today then ever before, but some good things have been lost. Exercise
dietary diversity another. We've replaced hoes with tractors, brooms
vacuums, and stairs with elevators. Fresh foods are out, refined,
foods in; that means less fiber and vitamins but more salt, sugar, fat,
calories. Freed from physical labor, people have used their heads to
science and technology to new heights, creating a society of
affluence and convenience. But progress has its price. Mental stress is
example, environmental pollution another.
Sedentary living and processed foods extract a price both in health and
dollars. Our genes retain most of the Stone Age imperatives, but life
fast lane does not. Human DNA cannot provide a substitute for the
has all but vanished from contemporary work stations. The human
still programmed to cope with the Stone Age threat of starvation, not
burden of overabundance. Evolution is too slow to have yet produced
manage today's high-calorie, high-salt, high-fat, low-fiber diet. The
no new enzymes to fight the effects of tobacco, excess alcohol, and
drugs. The nervous system remembers how to respond to the threat of a
saber-toothed tiger but has not figured out how to cope with a raging
rush-hour traffic. And as industrial pollution changes the environment,
of toxins presents new challenges to human genes and human health.
Good genes, bad genes, old genes, new
Most of us are lucky enough to have a perfectly healthy set of genes.
of us have inherited abnormal genes that cause disease. In some cases,
or two abnormal genes among the human complement of some 30,000 genes
havoc; cystic fibrosis and sickle cell anemia are examples. And in the
analysis, all cancers arise from flaws in the genes that regulate cell
Gene therapy is an experimental attempt to treat disease by introducing
genes into patients' cells. It's a tricky business. "Naked" DNA, the
genetic material, is not suitable, so scientists attach the DNA to a
device, or vector. In one approach, the DNA is attached to a chemical
such as a form of fat called a liposome. In the other, more promising,
technique, the DNA is injected into a virus, which is then allowed to
the patient's cells, carrying the new gene along with it.
Does it work? Not yet. Hundreds of gene therapy trials have been
during the past 15 years, including several dozen attempts to treat
cancer. Some partial successes have been reported -- but so have some
Scientists at the forefront of gene therapy research remain optimistic.
clinical applications are a long way off. For now, we'll have to settle
genes we have -- and that means adopting the lifestyle suited to our
genes. It's a shame to squander good genes with bad habits.
Back to the future
Molecular medicine is on the verge of making genetic engineering a
reality, but it can't possibly bring Stone Age genes up to Space Age
Since science can't reshuffle your genes, the only way for you to
nature's balance is to adopt a more natural lifestyle.
Fortunately, you can get back to basics without returning to the farm,
less the savannah. Here's how:
Eat well. Consume a variety of foods to restore nutritional diversity.
vegetable-based foods that provide essential vitamins and minerals. Eat
whole-grain products that contain the fiber you need. Avoid animal fat;
your protein from fish, poultry, beans, and legumes. Reduce your
processed foods, salt, and simple sugars. Eat smaller meals on a
schedule, balancing your caloric intake with your expenditure of
Exercise regularly. Add physical activity to your daily life by
stairs, walking instead of driving when possible, and carrying your own
parcels. Set aside 30-45 minutes nearly every day for moderate
walking, jogging, biking, swimming, dancing, gardening, and tennis are
examples. For best results, add exercises for balance, stretching
and prudent resistance training.
Control stress. Balance work and play, stimulation and relaxation,
companionship and solitude. Achieve all you can, but take time to enjoy
You don't need a spear or loincloth to get back to basics. You can
the best aspects of modern life to live naturally, enjoyably, and
It's all in your genes.
2006 by President and Fellows of Harvard