As scientific research progresses, there is increasing evidence that dietary nutritional factors play a critical role in the prevention and treatment of osteoporosis. Many nutrients, such as calcium and vitamin D, play an important role in the prevention and treatment of osteoporosis and are well known to patients, but there are still some nutrients that are controversial, one of which is protein. As one of the three major thermogenic nutrients, there is no doubt about the important physiological role of protein in the body. However, studies on the role of protein in the prevention and treatment of osteoporosis have long been inconsistent: on the one hand, protein is the basic raw material for bone, and long-term deficiency is detrimental to bone health; on the other hand, some studies have shown that high protein intake increases the body’s high urinary calcium response and reduces intestinal absorption of calcium, which has a negative effect on osteoporosis. In this regard, the latter has become the focus of concern for many elderly osteoporosis patients, some of whom even go to the other extreme and strictly control the intake of protein-rich foods in their daily diet. Is such an approach scientific? Does protein have such a “killing power” in the face of osteoporosis? Should protein be the “love” or the “harm” of elderly osteoporosis patients? Protein intake and bone health Protein has been studied for its role in bone health since the 1820s, and previous studies have described its role in a dual manner. (1) Protein is the basic raw material for the organic matrix of bone, and some amino acids and peptide compounds facilitate calcium absorption. Long-term protein deficiency can lead to a decrease in plasma protein levels, resulting in insufficient protein synthesis in the bone matrix and delayed new bone formation, which is detrimental to bone health. ②High protein intake is detrimental to bone health by the following mechanisms: high protein intake can cause a high urinary calcium response; high protein intake can reduce intestinal calcium absorption; acid load hypothesis, methionine and cysteine contained in animal proteins rich in sulfur amino acids are oxidized in the liver to produce sulfuric acid, which affects blood pH (making pH acidic) and can mobilize bone calcium into the blood as a buffer, while increasing urinary calcium loss . Many recent studies have provided counter evidence against the adverse effects of protein on bone health. Some scholars believe that an increase in dietary protein can increase intestinal absorption of calcium ions, thereby inhibiting parathyroid hormone (PTH) secretion and achieving an inhibitory effect on bone resorption. It has also been suggested that the increase in urinary calcium excretion with a high-protein diet is due to increased intestinal absorption of calcium, elevated blood calcium, and subsequent increase in urinary calcium, but does not lead to a negative skeletal calcium balance.In July 2014, the European Society for Clinical Economics of Osteoporosis and Osteoarthritis (ESCEO) released a Consensus Statement on Dietary Protein and Vitamin D for the Maintenance of Musculoskeletal Health in Postmenopausal Women. The statement clearly states that, to date, there is no evidence to confirm that increased protein intake increases dietary acid load and thus promotes bone mineral loss and osteoporosis. On the contrary, more research supports the beneficial effects of protein on bone health, with two possible mechanisms. (1) It improves muscle mass and strength, and muscle mass, volume, and strength have important protective effects on bone. Certain amino acids (e.g., leucine) are activators of muscle tissue anabolism and may regulate muscle growth by regulating body protein translation, integrating signals for nutrient utilization, growth factors, and cellular energy status during cell growth, and increasing protein synthesis. ②It increases insulin-like growth factor-1 (IGF-1) levels. Some studies have reported that a high-protein diet can increase circulating levels of IGF-1 in the body. IGF-1 is a mitogenic agent for a variety of cells, including osteoblasts. IGF-1 reduces collagen degradation, increases bone deposition, promotes osteoblast differentiation and maturation, stimulates bone mineralization, and promotes bone growth. Protein intake and osteoporosis Many cross-sectional studies have attempted to find a relationship between bone mineral density (BMD) and protein intake. Darling, from Medline (January 1966-September 2007) and the Dutch Medical Abstracts database (1974-2008), enrolled subjects of comparable age, sex, vitamin D and calcium levels and found that those with higher daily protein intakes also had higher BMD. In a cross-sectional and longitudinal study of 1077 women with a mean age of 75 years, Devine et al. found that three different levels of daily dietary protein intake (<66 g, 66-87 g, and >87 g) were positively associated with BMD. Kuwabara (Kuwabara) meta-analysis of the role of protein on bone in recent years concluded that protein intake was positively associated with BMD and bone mineral content (BMC). Prevention of fractures is the most important element of osteoporosis treatment and prevention. The US National Health and Nutrition Examination Study (NHANES 1999-2002) included a total of 2006 postmenopausal women and found that dietary intake of women with low protein and high calcium (protein <46g>1200mg/d) was significantly lower than that of women with moderate protein and low calcium intake (protein 46-70g/d, calcium <400mg>70g/d, calcium >1200mg/d women) to have The risk of fracture was significantly lower (OR 0.69), so the investigators concluded that moderate calcium intake together with moderate protein is the key to reducing the risk of fracture. Appropriate protein intake in elderly patients with osteoporosis Through the previous literature review we can easily find that more and more population studies confirm the beneficial effects of protein intake in patients with osteoporosis, especially in elderly patients with osteoporosis, so how much daily protein intake is more appropriate?
The 2014 ESCEO Consensus Statement on Dietary Protein and Vitamin D for the Maintenance of Musculoskeletal Health in Postmenopausal Women, mentioned earlier, states that daily protein intake should be 1.0-1.2 g per kg of ideal body weight, and that a balanced intake of protein at three meals should be ensured, i.e., 20-25 g of high-quality protein (e.g., from dairy products) per meal. 2015 Consensus Statement on Dietary Protein and Vitamin D for the Maintenance of Musculoskeletal Health in Postmenopausal Women, published by the Chinese Society of Nutrition The Chinese Expert Consensus on Nutrition and Exercise Intervention for Muscle Weakening Syndrome formulated by the Chinese Society of Nutrition for the Elderly and others in 2015 also suggested that food protein can promote muscle protein synthesis, and the recommended protein intake for the elderly should be maintained at 1.0~1.5g per kg of ideal body weight, with a 50% ratio of high-quality protein and balanced distribution among three meals a day. Two focal points of protein intake recommendations in the above guidelines should draw our attention. One is that protein intake should be increased in the elderly. The actual protein intake of the elderly decreases with age, and studies of populations in western countries, where animal foods are the mainstay, show that 1/3 of the elderly have a protein intake of less than 0.8g per kg of ideal body weight. 50.5g; the protein energy supply ratio is 10.3%~11.8%. It can be seen that the protein intake of the elderly is still far from the nutritional target, and there is no risk of excessive protein intake. NHANES 2003-2004 showed that the unbalanced protein intake of the elderly was very common, and the protein intake at breakfast was low. The balanced distribution of protein in three meals a day is important for skeletal muscle protein synthesis and bone mass maintenance. In conclusion, protein intake plays an important role in the prevention and treatment of osteoporosis in the elderly. For ease of application, 2 examples of recipes are attached. Example 1: Elderly male, height 170 cm, weight 70 kg, body mass index (BMI) 24.2 kg/m2 (Table 1); Example 2: Elderly female, height 160 cm, weight 58 kg, BMI 22.6 kg/m2 (Table 2).