fibre in the modern diet
species of plants was identified, revealing
the rich diversity of fibre sources that was
consumed by the site inhabitants.
by Jeff D Leach In Australia, Aborigines are known to
Paleobiotics Lab, New Orleans, USA
have eaten some 300 different species
of fruit, 150 varieties of roots and tubers,
and a dizzying number of nuts, seeds,
and vegetables. Recent analysis of over
Are daily dietary fibre recommendations
800 of these plant foods suggest the fibre
intake was estimated between 80 to 130
too low? An evolutionary perspective
g/d – possibly more – depending on the
contribution of plants to daily energy
needs.
Modern humans are the latest in able section of your fleshy real estate. In semi-arid west Texas, a nearly
a diverse line of species within the
There are millions more lining your moist
continuous 10,000-year record of ancient
genus Homo that evolved on a nutri-
nasal passage, many more manoeuvr-
foraging reveals a plant-based diet that
tional landscape very different from
ing about your liver, heart, lungs, pan-
conservatively provided between 100
the one we find ourselves on today.
creas and trillions more have been living
to 250 g/d of dietary fibre. Analysis of
During the two and a half million years
throughout your continuous gastrointesti-
hundreds of preserved human faeces
nal tract – from mouth to anus – from the
since the first member of our genus made
(coprolites) recovered throughout the
moment you enter this world. But this is
an appearance in the fossil record,
10,000-year archaeological sequence re-
good news.
humans subsisted on an extraordinary
veal a significant diversity of plants were
The bad news is as we fill our shopping
diversity of wild plants and animals from
consumed.
carts and pantries with the latest neatly
a dynamic environment that literally
While the diversity and quantity of
boxed and wrapped goodies of industry,
changed at a glacial pace. It is only
fibre varied spatially and temporally in
we continue down a path that began
within the last 5,000 to 10,000 years that
the past, our ancestors clearly evolved
some ten thousand years ago with the
our food supply has begun to include
on a diet that included daily intake of
emergence of agriculture – an event that
domesticated plants and animals.
fibre from a huge diversity of sources
eventually, along with steel roller mills in
For more than 99 percent of human
that far exceed those recorded among
the 1880s, farm subsidies in the 1970s, and
history, our genome and its nutritional
populations in recent intervention and
the divergent interests of food sellers and
and physiological parameters were
prospective studies concerned with
public health, may be leading us on a
selected during our non-domesticated
the role of fibre in human health. These
path to one of the greatest unintended
foraging life-way conditioned, in no
modern studies invariably group people
small way, by a diet that included large
with fibre intakes hovering around 20 g/d
amounts of dietary fibre from a significant
as the ‘high fibre’ group, when in reality
diversity of sources.
these high fibre or upper quintile groups
Even though this important reality un-
are in fact low from an evolutionary per-
derlies the basic evolutionary biological
spective. Therefore, from an evolutionary
principles of modern human nutrient re-
perspective we should not be surprised
quirements, it is all but missing from policy
when analytical hair splitting of these
and research discussions on recom-
minute amounts of fibre does not yield
mended intake of dietary fibre through-
the desired protective role one might
out the world. Even more startling, much
suspect going into the study.
of our discussion on the health benefits
The potential protective role of dietary
of fibre, at least in the USA and UK, often
10,000 year old Coprolites
fibre among these modern studies may
refer to the mechanical actions of fibre
further be complicated by the lack of di-
(stool bulking, for example) and nearly
consequences in human history by
versity as much as the quantity. Accord-
ignores the critical role of dietary fibre as
tinkering with the health of our intestinal ing to data compiled by the Economic
a nutrient base of sorts for the trillions of
microbes. Current dietary advice would Research Service, United States Depart-
microbes living throughout the human
be well served by an appreciation that ment of Agriculture in 2007, 57 percent of
gut.
the average human is a complex super- all vegetables consumed by Americans
It’s safe to say that our current chronic
organism, rather than a single individual. are limited to five sources (potatoes,
low-intake of dietary fibre in the western
The archaeological and ethnographic tomatoes, leafy greens, lettuce, and on-
world (around 12 to 15g/d) – coupled
record serves as an interesting reminder ions). Unfortunately, the most consumed
with our overuse of antibiotics and the
of the magnitude of the shift in the diver- vegetable in America, the potato, is
increase in multiple antibiotic resistance
sity and quantity of fibre in human diet. often in the form of oil-soaked French
in pathogens – has started a large-scale
Along the shores of the Sea of Galilee in fries or potato chips.
genetic ‘re-engineering’ experiment on
modern-day Israel, a remarkably well- For fruit, five sources (apples, banan-
the slowly evolved and critical symbiotic
preserved collection of plant remains as, grapes, strawberries, and oranges)
relationship between humans and our
recovered from the 23,000-year-old account for 71 percent of the total
little evolutionary hitchhiking friends, with
archaeological site of Ohalo II provides intake. From an evolutionary perspec-
limited discussion of its outcome on pub-
an extraordinary window into a broad-
tive, this minimal diversity, even when
lic health.
spectrum diet that yielded a collection
coupled with the handful of whole grains
As you read this, there are millions of
of >90,000 plant remains representing
and beans/legumes consumed, trans-
tiny microbes swimming around in the
small grass seeds, cereals (emmer wheat,
lates into a striking shortfall in the physi-
fluid surrounding your eyeballs. But you
barley), acorns, almonds, raspberries,
cal and chemical diversity of fibre once
can’t see them. There are millions more
grapes, wild fig, pistachios, and various
consumed by humans and subsequently
under your fingernails, on your hands,
other fruits and berries. Owing to excel-
utilized by the hundreds of bacterial
arms, legs and just about every imagin- lent preservation, a stunning 142 different
species that inhabit the human gut. We
12 NHDmag.com May ‘08 - issue 34
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