harvardâ€™s school of public health explainsvery nicely the mechanism by which protein can cause problems for bone health. it says,â€œas your body digests protein, it releases acids into the bloodstream, which the bodyneutralizes by drawing calcium from the bones. following a high-protein diet for a few weeksprobably wonâ€™t have much effect on bone strength. doing it for a long time, though,could weaken bone.â€ now weâ€™ve known for a very long time thatmeats, including fish, are acid forming in our body. scientists from columbia university,back in 1912, analyzed acid and base forming elements in food, and noted that, â€œall themeats (including fish)...show a decided excess of acid-forming elementsâ€; all the â€œmeats(including fish) show [a] decided predominance
of acid-forming elements." back in 1920, columbiaâ€™s department of chemistryalso reported that adding meat to oneâ€™s diet results in increase of calcium loss inurine, thought to be because â€œthe added meat gave to the diet as a whole an excess ofacid-forming [over base-forming mineral] elements[.]" and what have we seen from the results ofthe consumption of animal protein with regards to bones? researchers from yale universityâ€™sschool of medicine looked back across a broad array of 34 prior published studiesacross 16 countries, and they found these studies over time showed â€œa strong, positiveassociationâ€ between dietary animal protein and female bone fracture rates.
so, weâ€™ve known for some time that thisassociation exists. we know eating a diet high in animal protein results in acidity,and that our body leaches calcium from our bones to buffer the acid. one of the mechanismsbehind this phenomenon is that animal protein has a higher amount of sulfur-containing aminoacids, and the â€œsulfur-containing amino acids from animal protein lower blood phâ€. so animal proteins â€” including meat, fish,dairy, poultry or eggs â€” have higher amounts of sulfur-containing amino acids than plantfoods. as a result, when we eat diets high in animal proteins, our body produces sulfuricacid, which increases the acidity in our bodies. one of the bodyâ€™s mechanisms to neutralizethis acidity is to draw calcium from our bones
(similar, for example, to when we take antacidsthat are made with calcium to neutralize the acidity in our stomach associated with heartburn).the problem is that constantly leaching calcium from our bones can reduce bone mass, makingour bones weak and more prone to fractures and osteoporosis. moreover, the chronicallyhigher calcium excreted in our urine can also lead to the development of kidney stones. this harvard study published in the americanjournal of epidemiology followed over 80,000 women over 12 years, and found that animalprotein was associated with increased risk of forearm fracture, but no increase in riskwas observed with higher intakes of vegetable protein. it found that women who consumedthe largest amount of animal protein in the
study had a 22% higher risk of fracture. evidencesuggests that â€œhigher protein intakes in young...women have a negative impact on radialbone measurementsâ€, meaning that women who consumed higher protein diets have been foundto lose bone mineral content and bone density. so we know that our body uses base stores(including calcium from our bones) to neutralize the acidity we get from our diet. this articlefrom the journal of nutrition explains the same thing. it says, â€œdiets that are netacid producing...induce and sustain increased acidity of [our] body fluid. with increasingage, the kidneyâ€™s ability to excrete daily net acid loads declines, invoking...increasedutilization of base stores ([from our] bone [and] skeletal muscle) on a daily basis tomitigate the otherwise increasing baseline
metabolic acidosis, which results in increasedcalciuria and net losses of body calcium. those effects of net acid production and itsattendant increased body fluid acidity may contribute to...osteoporosis[.]â€ what thisis saying is the neutralizing mechanism in our bodies of taking calcium from our bonesto deal with the higher acidity caused by our diet can contribute to osteoporosis. this journal review in the european societyfor clinical nutrition and metabolism further discusses the issue, noting how problems associatedwith acidity become even worse with age. â€œthe modern western-type diet...contains excessiveanimal products, generating a state of metabolic acidosis, whose magnitude increases progressivelywith aging due to the physiological decline
in kidney function.â€ as explained in this peer-reviewed study fromthe journal of nutrition, â€œthe average american diet, which is high in protein and low infruits and vegetables, generates a large amount of acid, mainly as sulfates and phosphates.the kidneys respond to this dietary acid challenge with net acid excretion, [and] the skeletonsupplies buffer by active resorption of bone.â€ the study concludes, that, â€œoverall, theevidence leaves little doubt that excess acidity will create a reduction in total bone substance....an acid-ash diet [means] a diet that creates acid in the process of its metabolism[,]â€and this article concludes, â€œ[m]odern peoples are now eating high protein, acid-ash dietsand [are] losing their bones.â€
this study, published in the official journalof the council on renal nutrition of the national kidney foundation and the international societyof renal nutrition and metabolism, compared the net acid secretions among vegans (whoeat no animal products), lacto-ovo vegetarians (who eat no meat, but do eat dairy and eggs)and omnivores (who eat a traditional western diet of meat, dairy and eggs). the study foundthat net acid secretion was higher in both lacto-ovo vegetarians and omnivores than invegans, suggesting â€œthat higher protein intake results in more renal net acid excretionand more acidic urine.â€ in addition to increased incidents of kidney stone development, higherprotein intake was also found to be associated with "increased urinary calcium excretion."it noted, â€œhigher protein intake, especially
animal protein, was linked to an increasedrate of bone loss and increased risk of hip and forearm fractures in women.â€ the studyconcludes, â€œbecause acid-base balance has significant implications for renal and bonehealth, it is important...to introduce appropriate dietary modifications to prevent or treatthe conditions, including kidney stones, bone loss and/or [bone] fractures, and possiblyosteoporosis." so to recap, eating animal proteins increasesbody acidity, and one of the bodyâ€™s mechanisms to neutralize this acidity is to leach calciumfrom the bones. doing this for a long time can lead to loss of bone mass and weakenedbone, increased risk of fractures and osteoporosis, as well as kidney (or renal) stones. and,an easy way to avoid the increased risk of
these problems is avoiding animal protein.