There are 28 amino acids in nature. The human body can manufacture 19 of them. The other nine are called “essential.” We must get them from the foods we eat.

One of those “essential” aminos is methionine.

One needs methionine for many human metabolic functions including digestion, detoxification of heavy metals, and muscle metabolism. However, an excess of methionine can be toxic.

Methionine = C-5, H-11, NO, S

Methionine is a good source for sulfur. That’s the problem. Eat foods containing too much methionine, and your blood will become acidic. The sulfur converts to sulfates and weak forms of sulfuric acid. In order to neutralize the acid, in its wisdom, the body leaches calcium from bones.

“Dietary protein increases production of acid in the blood which can be neutralized by calcium mobilized from the skeleton.” {American Journal of Clinical Nutrition, 1995; 61,4}

Animal proteins contain more methionine than plant proteins. Let’s compare cow’s milk to soymilk:

Now, let’s compare 100 gram portions of tofu to meat:

(All of the meat products are lean and without skin)

Silken soft tofu: .074 grams
Hamburger: .282 grams
Hard boiled egg: .392 grams
Roast ham: .535 grams
Baked codfish: .679 grams
Swiss cheese .784 grams
Roast chicken: .801 grams

In 1988, N.A. Breslau and colleagues identified the relationship between protein-rich diets and calcium metabolism, noting that protein caused calcium loss. His work was published in the Journal of Clinical Endocrinology (1988;66:140-6).

A 1994 study published in the American Journal of Clinical Nutrition (Remer T, Am J Clin Nutr 1994;59:1356-61) found that animal proteins cause calcium to be leached from the bones and excreted in the urine.

MORE SUPPORTING EVIDENCE:

• “Osteoporosis is caused by a number of things, one of the most important being too much dietary protein.”
  {Science 1986;233, 4763}
• “Even when eating 1,400 mg of calcium daily, one can lose up to 4% of his or her bone mass each year while consuming a high-protein diet.”
  {American Journal of Clinical Nutrition 1979;32,4}
• “Increasing one’s protein intake by 100% may cause calcium loss to double.”
  {Journal of Nutrition, 1981; 111, 3}
• “The average man in the US eats 175% more protein than the recommended daily allowance and the average woman eats 144% more.”
  {Surgeon General’s Report on Nutrition and Health, 1988}

1. “Consumption of dairy products, particularly at age 20 years, were associated with an increased risk of hip fractures… metabolism of dietary protein causes increased urinary excretion of calcium.”
   {American Journal of Epidemiology 1994;139}
   

Can the problem get worse? Absolutely!

The Framingham Heart Study is the largest and most exciting heart study in the history of mankind. Some of the highlights of this exhaustive 50 year study:

In 1960, Cigarette smoking was found to increase the risk of heart disease.

In 1970, high blood pressure was found to increase the riskof stroke.

During the 1980’s, high levels of HDL cholesterol were found to reduce risk of death from heart disease.

In the 1990’s, homocysteines were identified as key factors in heart attack deaths.

Homocysteines are normal breakdown products of METHIONINE and are believed to exert a number of toxic effects in the body. The senior investigator of the Framingham heart study, William Castelli, M.D. has suggested that an elevated homocysteine level is a risk factor for heart disease. The first evidence of this was published in the American Journal of Cardiology (Glueck, 1995;75:132­6).

Two recent publications resulting from Framingham data indicate a positive correlation between cardiovascular disease mortality and blood serum levels of homocysteine.Bostom AG, et. al, Nonfasting plasma total homocysteine levels and all-cause and cardiovascular disease mortality in elderly Framingham men and women. Arch Intern Med 1999; 159:1077-1080.

Bostom A.G., et. al, Nonfasting plasma total homocysteine levels and stroke incidence in elderly persons: the Framingham Study. Ann Intern Med 131[5], 352-355, 1999.

source: http://milk.elehost.com/html/why_does_calcuim_leave_the_bon.html