Sorry about the link, Lex. I've attempted to summarize what I learned from both Ron and other sources here:
"Fat-rich, acidic chyme entering the duodenum triggers the release of cholecystokinin, a hormone produced in the intestinal wall that decreases gastric motility.
The acid in chyme also triggers release of secretin, another hormone. Secretin and cholecystokinin stimulate the release of pancreatic juice that contains bicarbonate, which buffers the effects of gastric acid, and digestive enzymes." --Diane S. Aschenbrenner and Samantha J. Venable,
Drug Therapy in Nursing, 2008
Digesting foods that are rich in fats and are acidifying (such as fatty meats or meats with fat--not to be confused with "acidic" foods like citrus fruits that are actually alkaline) triggers buffering secretions of alkaline bile and bicarbonate in the duodenum that raise the ph so that lipase, which requires an alkaline pH to work, can break down the fats.
Therefore, a LOW fat diet that is acidified (such as diets high in grains and low-fat dairy), does not trigger the release of as much bile and bicarbonate, so the body compensates to lower the pH of the duodenum by acquiring calcium, presumably from extracellular fluids. To maintain calcium homeostasis in whatever extracellular fluid the calcium is taken from (
http://www.mhhe.com/biosci/esp/2001_saladin/folder_structure/su/m2/s6/sum2s6_1.htm), the body then leaches calcium from the bones to restore calcium levels.
The alkaline hypothesis then says that eating alkaline foods like greens can provide an alternative buffer to the leaching of bones. My guess, however, is that this buffer may be incomplete in many people--which would explain why an alkaline diet with moderate fat may have been insufficient to stop my apparent bone loss (as evidenced by loosening teeth and diminishing jaw bone density on x-rays), but a high fat carnivorous diet succeeded. Apparently, a high fat diet allows the body's own buffering processes, which may be more efficient and effective than ingesting buffers, to kick in more fully.
The sensitivity of the trigger for release of bile and bicarbonate for different people may vary. For some, a little added buffering from ingesting greens may be sufficient to avoid problems. For others, such as people with celiac disease or gluten intolerance, and apparently me, such modest measures may be dangerously insufficient. Perhaps for you and me and Ron Hoggan, we may need to ingest higher levels of fat and acidifying foods to trigger production of the CCK and secretin?
Other potential factors are that growth hormone deficiency contributes to bone density loss (Rosén T, Johannsson G, Johansson J, Bengtsson B. 1995.
Consequences of Growth Hormone Deficiency in Adults and the Benefits and Risks of Recombinant Human Growth Hormone Treatment. Retrieved August 31, 2009, from Karger Hormone Research. Website:
http://content.karger.com/ProdukteDB/produkte.asp?Aktion=ShowAbstract&ArtikelNr=000184245&Ausgabe=241187&ProduktNr=224036), tests on Inuit people (as reported in The Paleo Diet) suggest that carnivorous-type diets result in much less calcium excreted than in the SAD.
In addition, I had these references in my files that indicate that animal protein improves calcium balance, whereas certain plant proteins, like soy protein, promote negative calcium balance:
> Herta Spencer, et al, "Do Protein and Phosphorus Cause Calcium Loss?" American Institute of Nutrition, 1988:657-660
http://jn.nutrition.org/cgi/content/abstract/118/6/657 ("a diet low in protein and phosphorus may have adverse effects on calcium balance in the elderly. Studies with adults suggest that high protein foods do not cause calcium loss.")
> Spencer, Herta, et al, Federation Proceedings, Federation of American Societies for Experimental Biology, Nov 1986, 45:12:2758-2762
> Spencer, Herta and Lois Kramer, "Further studies of the effect of a high protein diet as meat on calcium metabolism", American Journal of Clinical Nutrition, June 1983 37 (6):924-929
http://www.ajcn.org/cgi/content/abstract/37/6/924 ("These long- and short-term studies have confirmed our previous results that a high protein intake, given as meat, does not lead to hypercalciuria and does not induce calcium loss.")
> Fallon, Sally, and Mary G Enig, PhD, "Dem Bones-Do High Protein Diets Cause Bone Loss?" Price-Pottenger Nutrition Foundation Health Journal, 1996, 20:2:1-4, also posted at
http://www.westonaprice.org/mythstruths/mtbones.html> Hunt J. R., Gallagher S. K., Johnson L. K., Lykken G. I. High- versus low-meat diets: effects on zinc absorption, iron status, and calcium, copper, iron, magnesium, manganese, nitrogen, phosphorus, and zinc balance in postmenopausal women. Am. J. Clin. Nutr. 1995; 62:621-632 ("high meat consumption increases zinc retention without compromising calcium status"; note--zinc aids in the absorption of calcium into bones)
> Pannemans D.L.E., Schaafsma G., Westerterp K. R. Calcium excretion, apparent calcium absorption and calcium balance in young and elderly subjects: influence of protein intake. Br. J. Nutr. 1997; 77:721-729 ("Ca excretion in faeces (as a percentage of Ca intake) was lower during the higher protein intake")
> Barzel US. The skeleton as an ion exchange: implications for the role of acid-base imbalance in the genesis of osteoporosis. J Bone Miner Res. 1995; 10: 1431-36) ("When purified protein supplements [meaning soy - see Kaneko K, et al. Urinary calcium and calcium balance in young women affected by high protein diet of soy protein isolate and adding sulfur-containing amino acids and/or potassium.] are added to diets, calcium balance usually becomes more negative, suggesting that bone may be affected. However when increased protein is added as foods, particularly meat or dairy products, decreased calcium balance is not always seen (Hunt et al. 1995), especially in young healthy people (Pannemans et al. 1997). This is due to other components of protein-containing foods that have also been shown to alter the urinary excretion of calcium and thus potentially calcium balance. These include phosphate (Remer and Manz 1994, Spencer et al. 1988), sulfate (Remer and Manz 1994) and potassium (Sebastian et al. 1994), as well as calcium (Heaney 1993).")
I'm not sure why animal proteins and soy proteins would have opposite effects on calcium balance. Perhaps there's something about meat proteins that better triggers secretin than plant proteins?
