Some references are saying that diets rich in animal proteins stimulate the release of parathyroid hormone and promote excessive elimination of calcium in the urine, which encourages bone resorption.”
One reference indicated that the federal government, intending to be on the safe side, established its minimum Recommended Dietary Allowances for protein at twice the value which it had determined as the minimum required for every person who participated in a federally sponsored experimental study. The reference pointed out that the average American routinely eats 4 times more protein than that in their daily meals. According to that, then, the average American actually consumes 8 times more protein per day than any person in the study needed to sustain good health. The link between excessive protein and calcium depletion was said to be so strong that taking supplemental calcium does NOT stem the daily calcium deficit — it is only slowed a trifle. But it went on to say that reducing protein intake to a level near the RDA had a profound positive effect. It left the body with a daily net influx of calcium, even among older women who were not taking calcium supplements. Can you provide authoritative references to evidence that confirms or refutes this?
Have you read my calcium, Recommended Dietary Allowances (RDA) and calories topics as the information about many of your questions can be found there? The RDAs are established to meet 98% of American’s needs for each nutrient and protein. Research studies are conducted every 10 years to determine the RDA for each nutrient and protein. RDAs are different in each country.
FYI once protein enters the body, all are broken down to amino acids which are absorbed thru the intestinal wall. Your body cannot tell what protein came from an animal, vegetable, or supplemental protein.
BTW, the average 20 to 60 years old adult American male eats 103 grams of protein which is 16% protein in 2585 calories per day according to the most recent survey (NHanes2013-2014) of US citizens by the government (US Department of Agriculture). Adult women ages 20 to 60 years old eat 72 grams of protein in 1901 calories or 15% of calories from protein. The RDA for protein is 63 grams for males and 50 grams for females. Therefore most American males eat 164% of their RDA for protein and American females 144%. Way too much which if not needed to build and repair lean tissue (muscles and organs) is converted to body fat and stored for the next famine.
Based on the most recent government NHANES nutrition surveys data above, Americans don’t eat 200 grams of protein per day nor do they only eat meat. Though I do agree that Americans eat too much protein.
By your sources, people would be eating over 200 grams of protein per day (RDA of protein for females of 50 grams times 4), which translates into 800 calories alone from fat-free protein food sources i.e. no meat or vegetable proteins. If this much protein from 29 ounces (200 grams of protein divided by 7 grams of protein per ounce of meat) of lean meat sources, it would equate to an additional 771 fat calories for a total of 1571 calories from lean protein sources alone.
While it is true that excess consumption of protein can lead to urinary loss of calcium due to the high phosphorus levels in meat, I don’t know specific ratios of at what point above the RDA for protein that this happens as it would be on an individual basis based on a person’s blood, muscle, and organ protein reserves as well as calcium levels in blood and bone. As your blood calcium levels drop, your body moves calcium from bone to the blood to maintain the electrolyte balance. This weakens bones and can lead to a higher risk of bone fractures.
Sorry, I cannot provide you with specific references as my nutrition knowledge accumulates from many sources (research, professional continuing education programs, and lectures), but you can do your own research by doing a PubMed (published medical research) search online. Search keywords such as calcium and protein or protein Recommended Dietary Allowances to find answers about many of your questions in the literature.