Well, this current claim is heavily disputed within the RVAF community, and even I don't believe in it , but here is Cordain's latest newsletter:-
"The Paleo Diet concept lies in its ability to simply uncover apre-existing diet – a universal diet and dietary characteristicsconsumed by all humans until very recent times. The notion that omega3 fatty acids promote health (as demonstrated in the scientificliterature) is quite recent – as recent as the past 30 years. Thenotion that high protein diets may prevent disease and promote healthand well being is newer still. Further, the recognition that dietaryacid/base balance has anything to do with optimal health is barely inits infancy. Virtually, without exception, each and every one of theseso-called nutritional “discoveries” in the scientific literature aretreated cautiously, as if they were curious anomalies, rather than thepredictable and highly probable findings that they actually are – hadonly the evolutionary template been employed. In this and subsequent Paleo Diet Updates I will comment upon thelatest scientific findings which increasingly lead to the inescapableconclusion that the evolutionary basis for human nutrition representsthe grand unifying theory the discipline so sorely lacks. Recent Scientific Findings: Acid/Base Balance One of the major nutritional characteristics of ancestral human dietsthat have been almost totally ignored in both the lay and scientificliterature is acid/base balance. Pick up the latest best selling dietbook, be it a reincarnation of Dr. Atkins Diet Revolution, The SouthBeach Diet or whatever, and I can guarantee you that it will not eventouch upon this crucial concept. Briefly, let me review the basic concept. All foods upon digestionreport to the kidney as acid, base or neutral. Acid yielding foods areall cereal grains, meats, cheeses, fish and salt. The only baseyielding foods are fruits and vegetables1, 2. Fats, they typicallydisplace base yielding fruits and vegetables, they are partiallyresponsible for the net acid load in the typical western diet3, 4.There are a number of adverse health effects either partially orwholly caused by a net acid yielding diet including: osteoporosis,hypertension, stroke, calcium kidney stones, age-related musclewasting, asthma and exercise-induced asthma2-6. For more informationvisit:
http://www.thepaleodiet.com/nutritional_tools/acid.shtml. In the June issues of both the American Journal of Clinical Nutrition7and the Journal of the American College of Nutrition8, two articleswere published that reinforce the concept that net base yielding dietspromote strong bones and may prevent bone mineral loss andosteoporosis. Study #1 In the first article7, the authors report the osteoporosis preventingbenefits of high intakes of fruit and vegetables in a cross sectionalstudy of 125 girls and 132 boys between 16 and 18 years of age, 120young women between 23 and 37 years of age, and 70 men and 73 womenaged 60 to 83 years. Increasing consumption of fruits and vegetableswere associated with greater whole body bone mineral densities in theboys and girls aged 16 to 18. In the older women 60 to 83 years ofage, greater fruit intake was associated with a greater bone mineralcontent. No statistically significant associations were found in theyounger women or older men between bone mineral measurements andconsumption of vegetables alone. Strengths: This study is rigorous for two reasons. First, actualweights of fruits and vegetables were assessed using a 7 day fooddiary and secondly bone mineral data were carefully adjusted for bodysize using dual energy X-ray absorptiometry (DEXA) machines. Withoutadjustment of body size, DEXA measurements may not truly be reflectiveof bone mineral content or density. In many dietary studies foodintake 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 sectionalepidemiological study. All epidemiological studies cannot show causeand effect between diet and disease, but rather only associations.Fruit and vegetable eating is associated with enhanced bone mineralstatus, but we cannot conclude from this epidemiological study thatfruit and vegetable consumption causes greater bone mineral health. InNew York City, there are always more fire trucks at bigger fires.Hence, more fire trucks are associated with bigger fires, but morefire trucks do not cause bigger fires. Conclusions: As far as epidemiological studies go, this is a great onepointing in the direction that fruit and vegetable consumption mayimprove bone mineral status, but further, more powerful dietaryinterventions (in which fruits and vegetables are actually fed tohumans and markers of bone mineral health are measured) will berequired to make a stronger case. Study #2 In the second article8 researchers led by Bess Dawson-Hughes at TuftsUniversity in Boston conducted a dietary intervention in 40 healthymen and women over age 50. For 60 days, the subjects were put oneither a high fruit and vegetable diet (base yielding) or an acidyielding diet in which cereals replaced fruits and vegetables. Thesubjects consuming the acid yielding cereal diet experienced increasesin serum PTH (a hormone marker of increased bone breakdown), a loss ofcalcium 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 dietaryinterventions. When there are discrepancies among the various types ofexperiments, human dietary interventions represent the "trump card,"and these results prevail over the other procedures. This studyrepresents the first long term (60 day) human dietary interventiondemonstrating that an increased dietary acid load promotes changes inblood markers of bone breakdown. Weaknesses: To conclusively demonstrate beyond a shadow of a doubtthat net acid yielding diets promote bone mineral loss in humans, thissame experiment should be carried out over a longer period (1 to 2years) and actual changes in bone mineral content (as measured by dualx-ray absorptiometry [DEXA] machines) should be made, along with theblood markers of bone loss that were measured in this study. Conclusions: The study represents the most powerful experiment to dateshowing that dietary acid/base balance is crucial for long term bonemineral health in humans. Despite this evidence, the notion of dietaryacid/base balance has been completely ignored by the USDA in their MyPyramid Dietary Recommendations for the US public10 and by virtuallyall of the best selling diet books. Perhaps it is high time that theevolutionary basis for optimal human nutrition be incorporated as akey component when making public dietary recommendations. Osteoporosis is a huge health problem world wide, afflicting 1 in 3women and 1 in 10 men over the age of 55 years9. In the US 10 millionAmericans have osteoporosis, and costs are estimated at $17.9 billionannually9. Healthcare practitioners and the general public need tounderstand that there is more involved in the prevention ofosteoporosis than just calcium intake and vitamin D." Ken
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