The U.S. Department of Health and Harvard Medical School published a report: excessive dairy and protein are one of the causes of osteoporosis. The relationship between osteoporosis and animal protein is proportional, meaning the more meat and animal protein you consume, the higher the risk of developing osteoporosis.
Excessive Protein, Increased Risk of Osteoporosis
Protein and amino acids are essential raw materials for synthesizing bone organic matter, but a high-protein diet reduces the renal tubules' reabsorption rate of calcium, increasing urinary calcium excretion. A doubling of protein intake can increase urinary calcium excretion by 50%. Excess protein intake will lead to a negative calcium balance (a state when the body's calcium absorption is less than its excretion).
As people enter old age, the decline in the function of internal organs and accelerated loss of bone calcium mean that absorbed calcium cannot compensate for excreted calcium, making the body prone to a negative calcium balance. At this point, the body must draw upon its bone calcium reserves to maintain calcium balance for normal physiological functions. Although the daily amount of bone calcium used is negligible, the continuous, slow use of bone calcium will eventually deplete it, leading to pathological changes like osteoporosis and fractures. Conversely, long-term insufficient protein intake can lead to inadequate bone matrix synthesis and slow new bone formation, also causing osteoporosis. Therefore, a moderate-protein diet is necessary.
Why does more animal protein or milk lead to faster calcium loss?
Calcium absorption is relative to phosphorus. The calcium content in cow's milk is 3-4 times higher than in breast milk. The problem is that cow's milk contains too much phosphorus, which interferes with calcium absorption. Although breast milk has less calcium, its phosphorus content is very low. In comparison, one can absorb more calcium from breast milk. Notably, many people today rely on dining out, and many processed foods, such as instant noodles, contain high levels of phosphorus, all of which affect calcium absorption rates.
Daily Protein Intake Should Be Moderate
The human body's protein requirement is approximately 0.75 grams per kilogram of body weight. For a person weighing 60 kg, 45 grams per day is sufficient. This amount can be exceeded by a single piece of meat, one egg, or a large glass of milk. Research indicates that the daily calcium requirement for the human body is about 150-200 mg, which is sufficient. The daily intake for most of the world's population is around 300-500 mg. The World Health Organization (WHO) recommends 400-500 mg, while the American Academy of Nutrition and Dietetics recommends 800 mg, and the U.S. National Institutes of Health suggests as much as 1000-1500 mg. The reason these official U.S. organizations recommend such high amounts is precisely because their population suffers from the highest rates of osteoporosis.