http://www.motherearthnews.com/eggs.aspx

What do I feed my chickens to get the most flavorful, nutritious eggs?
‹ Corrina Owen
Tulsa, Oklahoma
March 10, 2008
Basically, all you have to do is raise them as free-range poultry, so
they can choose what they want to eat.
When chickens (as well as cattle, pigs and other livestock) are allowed
to eat their natural diet, numerous studies have shown that their eggs,
milk and meat tends to be richer is several important nutrients (see
www.eatwild.com for lots of details). Tests conducted by Mother Earth
News found that, compared to the standard values reported by the USDA
for commercial eggs, hens raised on pasture produced eggs with
two-thirds more vitamin A, twice the omega-3 fatty acids, three times
more vitamin E and seven times more beta carotene. The tests also showed
that pastured eggs had one-third less cholesterol and a quarter of the
saturated fat. In addition, fresh eggs from pastured hens taste better
and provide more ³lift² in baked goods.
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The Omnivore's Dilemma: A Natural History of Four Meals by Michael Pollan
http://www.amazon.com/Omnivores-Dilemma-Natural-History-Meals/dp/01430385
83/ref=pd_bbs_1?ie=UTF8&s=books&qid=1206815576&sr=1-1

p179
The recent discovery of these secondary metabolites in plants has bought
our understanding of the biological and chemical complexity of foods to
a deeper level of refinement; history suggests we haven't gotten
anywhere near the bottom of this question, either. The first level was
reached early in the nineteenth century with the identification of the
macronutrients-protein, carbohydrate, and fat. Having isolated these
compounds, chemists thought they'd unlocked the key to human nutrition.
Yet some people (such as sailors) living on diets rich in macronutrients
nevertheless got sick. The mystery was solved when scientists discovered
the major vitamins-a second key to human nutrition. Now it's the
polyphenols in plants that we're learning play a critical role in
keeping us healthy. (And which might explain why diets heavy in
processed food fortified with vitamins still aren't as nutritious as
fresh foods.) You wonder what else is going on in these plants, what
other undiscovered qualities in them we've evolved to depend on.
In many ways the mysteries of nutrition at the eating end of the food
chain closely mirror the mysteries of fertility at the growing end: The
two realms are like wildernesses that we keep convincing ourselves our
chemistry has mapped, at least until the next level of complexity comes
into view. Curiously, Justus von Liebig, the nineteenth-century German
chemist with the spectacularly ironic surname, bears responsibility for
science's overly reductive understanding of both ends of the food chain.
It was Liebig, you'll recall, who thought he had found the chemical key
to soil fertility with the discovery of NPK, and it was the same Liebig
who thought he had found the key to human nutrition when identified the
macronutrients in food. Liebig wasn't wrong on either count, yet in both
instances he made the fatal mistake of thinking that what we knew about
nourishing plants and people was all we need to know to keep them
healthy. It's a mistake we'll probably keep repeating until we develop a
deeper respect for the complexity of food soil and, perhaps, the links
between the two.

But back to the polyphenols, which may hint at the nature of that link.
Why in the world should organically grown blackberries or corn contain
significantly more of these compounds? The authors of Davis study
haven't settled the question, but they offer two suggestive theories.
The reason plants produce these compounds in the first place is to
defend themselves against pests and diseases; the more pressure from
pathogens, the more polyphenols a plant will produce. These compounds,
then, are the products of natural selection and, more specifically, the
coevolutionary relationship between plants and the species that prey on
them. Who would have guessed that humans evolved to profit from a diet
of these plant pesticides? Or that we would invent an agriculture that
then deprived us of them? The Davis authors hypothesize that plants
being defended by man-made pesticides don't need to work as hard to make
their own polyphenol pesticides. Coddled by us and our chemicals, the
plants see no reason to invest their sources in mounting a strong
defense. (Sort of like European nations during the cold war.)
A second explanation (one that subsequent research seems to suppport)
may be that the radically simplified soils in which chemically
fertilized plants grow don't supply all the raw ingredients needed to
synthesize these compounds, leaving the plants more vulnerable to
attack, as we know conventionally grown plants tend to be. NPK might be
sufficient for plant growth yet still might not give a plant everything
it needs to manufacture ascorbic acid or lycopene or resveratrol in
quantity. As it happens, many of the polyphenols (and especially a
sublet called the flavonols) contribute to the characteristic taste of a
fruit or vegetable. Qualities we can't yet identify, in soil may
contribute qualities we've only just begun to identify in our foods and
our bodies.

Reading the Davis study I couldn't help thinking about the early
proponents of organic agriculture, people like Sir Albert Howard and J.
I. Rodale, who would have been cheered, if unsurprised, by the findings.
Both men were ridiculed for their unscientific conviction that a
reductive approach to soil fertility-the NPK mentality-would diminish
the nutritional quality of the food grown in it and, in turn, the health
of the people who lived on that food. All carrots are not created equal,
they believed; how we grow it, the soil we grow it in, what we feed that
soil all contribute qualities to a carrot, qualities that may yet escape
the explanatory net of our chemistry. Sooner or later the soil
scientists and nutritionists will catch up to Sir Howard, heed his
admonition that we begin ³treating the whole problem of health in soil,
plant, animal and man as one great subject."

p.266-269
Taking the long view of human nutrition, we evolved to eat the sort of
foods available to hunter-gatherers, most of whose genes we've inherited
and whose bodies we still (more or less) inhabit. Humans have had less
than ten thousand years‹an evolutionary blink‹to accustom our bodies to
agricultural food, and as far as our bodies are concerned, industrial
agricultural food‹a diet based largely on a small handful of staple
grains, like corn‹is still a biological novelty. Animals raised outdoors
on grass have a diet much more like that of the wild animals humans have
been eating at least since the Paleolithic era than that of the
grain-fed animals we only recently began to eat.

So it makes evolutionary sense that pastured meals, the nutritional
profile of which closely resembles that of wild game, would be better
for us. Grass-fed meat, milk, and eggs contain less total fat and less
saturated fats than the same foods from grain-fed animals. Pastured
animals also contain conjugated linoleic acid (CLA), a fatly acid dial.
some recent studies indicate may help reduce weight and prevent cancer,
and which is absent from feedlot animals. But perhaps most important,
meat, eggs, and milk from pastured animals also contain higher levels of
omega-3s, essential fatty acids created in the cells of green plants and
algae that play an indispensable role in human health, and especially in
the growth and health of neurons‹brain cells. (It's important to note
that fish contain higher levels of the most valuable omega-3s than land
animals, yet grass-fed animals do offer significant amounts of such
important omega-3s as alpha linolenic acid‹ALA.) Much research into the
role of omega-3s in the human diet remains to be done, but the
preliminary findings are suggestive: Researchers report that pregnant
women who receive supplements of omega-3s give birth to babies with
higher IQs; children with diets low in omega-3s exhibit more behavioral
and learning problems at school; and puppies eating diets high in
omega-3s prove easier to train. (All these claims come from papers
presented at a 2004 meeting of the International Society for the Study
of Fatty Acids and Lipids.)

One of the most important yet unnoticed changes to the human diet in
modern times has been in the ratio between omega-3 and omega-6, the
other essential fatty acid in our food. Omega-6 is produced in the seeds
of plants; omega-3 in the leaves. As the name indicates, both kinds of
fat are essential, but problems arise when they fall out of balance. (In
fact, there's research to suggest that the ratio of these fats in our
diet may be more important than the amounts.) Too high a ratio of
omega-6 to omega-3 can contribute to heart disease, probably because
omega-6 helps blood clot, while omega-3 helps it flow. (Omega-6 is an
inflammatory; omega-3 an anti-innammatory.) As our diet‹and the diet of
the animals we eat‹shifted from one based on green plants to one based
on grain (from grass to corn), the ratio of omega-6 to omega-3 has gone
from roughly one to one (in the diet of hunter-gatherers) to more than
ten to one. (The process of hydrogenadng oil also eliminates omega-3s.)
We may one day come to regard this shift as one of the most deleterious
dietary changes wrought by the industrialization of our food chain. It
was a change we never noticed, since the importance of omega-3s was not
recognized until the 1970s. As in the case of our imperfect knowledge of
soil, the limits of our knowledge of nutrition have obscured what the
industrialization of the food chain is doing to our health. But changes
in the composition of fats in our diet may account for many of the
diseases of civilization‹cardiac, diabetes, obesity, etc.‹that have long
been linked to modern eating habits, as well as for learning and
behavioral problems in children and depression in adults.

Research in this area promises to turn a lot of conventional nutritional
thinking on its head. It suggests, for example, that the problem with
eating red meat‹long associated with cardiovascular disease‹ may owe
less to the animal in question than to that animal's diet. (This might
explain why there are hunter-gatherer populations today who eat far more
red meat than we do without suffering the cardiovascular consequences.)
These days farmed salmon are being fed like feedlot cattle, on grain,
with the predictable result that their omega- 3 levels fall well below
those of wild fish. (Wild fish have especially high levels of omega-3
because the fat concentrates as it moves up the food chain from the
algae and phytoplankton that create it.) Conventional nutritional wisdom
holds that salmon is automatically better for us than beef, but that
judgment assumes the beef has been grain fed and the salmon krill fed;
if the steer is fattened on grass and the salmon on grain, we might
actually be better off eating the beef. (Grass-finished beef has a
two-to-one ratio of omega-6 to -3 compared to more than ten to one in
corn-fed beef.) The species of animal you eat may matter less than what
the animal you're eating has itself eaten.