Here is the latest on Dietary Acid/Base Balance being Crucial from Dr.
Cordain's newsletter:

"The Paleo Diet concept lies in its ability to simply uncover a
pre-existing diet – a universal diet and dietary characteristics
consumed by all humans until very recent times. The notion that omega
3 fatty acids promote health (as demonstrated in the scientific
literature) is quite recent – as recent as the past 30 years. The
notion that high protein diets may prevent disease and promote health
and well being is newer still. Further, the recognition that dietary
acid/base balance has anything to do with optimal health is barely in
its infancy. Virtually, without exception, each and every one of these
so-called nutritional “discoveries” in the scientific literature are
treated cautiously, as if they were curious anomalies, rather than the
predictable and highly probable findings that they actually are – had
only the evolutionary template been employed.

In this and subsequent Paleo Diet Updates I will comment upon the
latest scientific findings which increasingly lead to the inescapable
conclusion that the evolutionary basis for human nutrition represents
the grand unifying theory the discipline so sorely lacks.

Recent Scientific Findings: Acid/Base Balance

One of the major nutritional characteristics of ancestral human diets
that have been almost totally ignored in both the lay and scientific
literature is acid/base balance. Pick up the latest best selling diet
book, be it a reincarnation of Dr. Atkins Diet Revolution, The South
Beach Diet or whatever, and I can guarantee you that it will not even
touch upon this crucial concept.

Briefly, let me review the basic concept. All foods upon digestion
report to the kidney as acid, base or neutral. Acid yielding foods are
all cereal grains, meats, cheeses, fish and salt. The only base
yielding foods are fruits and vegetables1, 2. Fats, they typically
displace base yielding fruits and vegetables, they are partially
responsible for the net acid load in the typical western diet3, 4.
There are a number of adverse health effects either partially or
wholly caused by a net acid yielding diet including: osteoporosis,
hypertension, stroke, calcium kidney stones, age-related muscle
wasting, asthma and exercise-induced asthma2-6. For more information
visit: http://www.thepaleodiet.com/nutritional_tools/acid.shtml.

In the June issues of both the American Journal of Clinical Nutrition7
and the Journal of the American College of Nutrition8, two articles
were published that reinforce the concept that net base yielding diets
promote strong bones and may prevent bone mineral loss and
osteoporosis.

Study #1

In the first article7, the authors report the osteoporosis preventing
benefits of high intakes of fruit and vegetables in a cross sectional
study of 125 girls and 132 boys between 16 and 18 years of age, 120
young women between 23 and 37 years of age, and 70 men and 73 women
aged 60 to 83 years. Increasing consumption of fruits and vegetables
were associated with greater whole body bone mineral densities in the
boys and girls aged 16 to 18. In the older women 60 to 83 years of
age, greater fruit intake was associated with a greater bone mineral
content. No statistically significant associations were found in the
younger women or older men between bone mineral measurements and
consumption of vegetables alone.

Strengths: This study is rigorous for two reasons. First, actual
weights of fruits and vegetables were assessed using a 7 day food
diary and secondly bone mineral data were carefully adjusted for body
size using dual energy X-ray absorptiometry (DEXA) machines. Without
adjustment of body size, DEXA measurements may not truly be reflective
of bone mineral content or density. In many dietary studies food
intake is compiled not by daily diaries, but rather by 3 day recalls –
a process which is notoriously inaccurate.

Weaknesses: This experiment is classified as a cross sectional
epidemiological study. All epidemiological studies cannot show cause
and effect between diet and disease, but rather only associations.
Fruit and vegetable eating is associated with enhanced bone mineral
status, but we cannot conclude from this epidemiological study that
fruit and vegetable consumption causes greater bone mineral health. In
New York City, there are always more fire trucks at bigger fires.
Hence, more fire trucks are associated with bigger fires, but more
fire trucks do not cause bigger fires.

Conclusions: As far as epidemiological studies go, this is a great one
pointing in the direction that fruit and vegetable consumption may
improve bone mineral status, but further, more powerful dietary
interventions (in which fruits and vegetables are actually fed to
humans and markers of bone mineral health are measured) will be
required to make a stronger case.

Study #2

In the second article8 researchers led by Bess Dawson-Hughes at Tufts
University in Boston conducted a dietary intervention in 40 healthy
men and women over age 50. For 60 days, the subjects were put on
either a high fruit and vegetable diet (base yielding) or an acid
yielding diet in which cereals replaced fruits and vegetables. The
subjects consuming the acid yielding cereal diet experienced increases
in serum PTH (a hormone marker of increased bone breakdown), a loss of
calcium in the urine and increased bone breakdown.

Strengths: In order to show cause and effect between diet and disease,
scientists utilized 4 procedures: 1) epidemiological studies, 2)
tissue or in vitro studies, 3) animal studies, and 4) human dietary
interventions. When there are discrepancies among the various types of
experiments, human dietary interventions represent the "trump card,"
and these results prevail over the other procedures. This study
represents the first long term (60 day) human dietary intervention
demonstrating that an increased dietary acid load promotes changes in
blood markers of bone breakdown.

Weaknesses: To conclusively demonstrate beyond a shadow of a doubt
that net acid yielding diets promote bone mineral loss in humans, this
same experiment should be carried out over a longer period (1 to 2
years) and actual changes in bone mineral content (as measured by dual
x-ray absorptiometry [DEXA] machines) should be made, along with the
blood markers of bone loss that were measured in this study.

Conclusions: The study represents the most powerful experiment to date
showing that dietary acid/base balance is crucial for long term bone
mineral health in humans. Despite this evidence, the notion of dietary
acid/base balance has been completely ignored by the USDA in their My
Pyramid Dietary Recommendations for the US public10 and by virtually
all of the best selling diet books. Perhaps it is high time that the
evolutionary basis for optimal human nutrition be incorporated as a
key component when making public dietary recommendations.

Osteoporosis is a huge health problem world wide, afflicting 1 in 3
women and 1 in 10 men over the age of 55 years9. In the US 10 million
Americans have osteoporosis, and costs are estimated at $17.9 billion
annually9. Healthcare practitioners and the general public need to
understand that there is more involved in the prevention of
osteoporosis than just calcium intake and vitamin D."


Ken