Protein and Bone Health — Muscles and Bones Work Together

• Why the old "acid-ash" myth about protein and bone is wrong
• How protein is a fundamental building block of bone
• How muscle loss and bone loss feed each other
• How much protein older adults really need
• Practical ways to get enough protein at every meal

You may have heard that high-protein diets "leach calcium from bones" because protein makes your body more acidic, and your bones release calcium to neutralize the acid. This was known as the "acid-ash hypothesis."

It sounded logical, but large studies have shown it is not true:

• A 2009 meta-analysis in the American Journal of Clinical Nutrition found no evidence that high protein intake harms bone
• The IOF published a position paper in 2018 confirming that adequate protein intake is associated with better bone health, not worse
• Studies consistently show that people who eat more protein tend to have higher bone density and fewer fractures

Protein doesn't hurt your bones. Not getting enough protein is far more harmful to bone health than getting too much.

About 50% of bone volume is made of protein, mainly a protein called collagen. Collagen forms the flexible framework of bone, like the steel rods inside reinforced concrete. Calcium and other minerals fill in around this framework, providing hardness and rigidity.

Without enough collagen, bones become brittle, like concrete without its steel rods. They may look dense on a scan, but they break more easily under stress.

Your body continuously breaks down and rebuilds bone collagen, just as it remodels the mineral component. So you need a steady supply of protein in your diet to maintain this framework.

As we age, we naturally lose both muscle mass and bone density. The two are closely linked:

• Muscles pull on bones during movement, and this mechanical stress stimulates bone to stay strong (or grow stronger)
• When muscles shrink (a condition called sarcopenia), bones receive less stimulation and weaken faster
• Weak muscles mean poor balance and greater fall risk, and falls are the number one cause of fractures in older adults
• After a fracture, reduced mobility leads to further muscle loss, creating a downward spiral

This combination of sarcopenia and osteoporosis is sometimes called "osteosarcopenia." It is one of the biggest threats to independence in older adults.

Muscle and bone decline together, and they can be strengthened together too. Enough protein together with regular exercise is the most effective approach we have.

The standard RDA for protein (0.8 g/kg/day) was set to prevent deficiency in young adults. It is now widely seen as too low for older adults, who are losing muscle and bone with age.

Expert groups now recommend:

For most healthy older adults, aiming for roughly 1.0-1.2 g per kg of body weight per day is a good target. That's about 68-82 grams for someone weighing 150 pounds (68 kg).

Spread it across the day

How you spread protein through the day matters as much as the total amount.

Research shows that muscle protein synthesis (the process of building new muscle) is best stimulated by meals containing 25-30 grams of protein each. Many older adults eat very little protein at breakfast and lunch and most of it at dinner. This pattern is less effective.

Don't save all your protein for dinner. Aim for 25-30 grams at each meal to give your muscles the best chance to rebuild throughout the day.

These foods provide high-quality protein along with other nutrients that help bones:

Animal sources

Plant sources

Breakfast ideas (25-30g protein each)

• Greek yogurt parfait: 1 cup Greek yogurt (18g) + 1/4 cup granola (3g) + 1 oz almonds (6g) = 27g
• Egg breakfast: 3 scrambled eggs (18g) + 1 oz cheese (7g) + toast = 25g
• Smoothie: 1 cup milk (8g) + 1 scoop protein powder (20g) + banana = 28g

Lunch ideas (25-30g protein each)

• Tuna salad sandwich: 3 oz tuna (20g) + whole grain bread + mixed greens = 24g
• Chicken wrap: 3 oz chicken breast (26g) + vegetables + hummus = 30g
• Bean soup: 1.5 cups lentil soup (15g) + cheese toast (10g) = 25g

Dinner ideas (25-30g protein each)

• Baked salmon: 4 oz salmon (28g) + roasted vegetables + brown rice = 32g
• Stir-fry: 3 oz chicken (26g) + tofu (5g) + vegetables + rice = 31g
• Bean chili: 1.5 cups three-bean chili (18g) + cornbread (4g) + side of Greek yogurt (8g) = 30g

Protein-rich snacks

• Cheese stick (7g) + apple
• Hard-boiled egg (6g)
• Handful of almonds (6g)
• Cottage cheese with fruit (14g)
• Glass of milk (8g)

If you have reduced appetite

Many older adults struggle to eat enough, particularly if they live alone, take medications that reduce appetite, or have dental problems. Try:

• Protein-enriched foods: Add powdered milk to soups, oatmeal, and casseroles
• Nutrient-dense snacks: Cheese, nuts, yogurt, and eggs are small but protein-rich
• Smoothies and shakes: Easier to drink than eat when appetite is low
• Eat protein first: When appetite is small, eat the protein portion of your meal before filling up on bread or salad

If you have kidney disease

If you have chronic kidney disease (CKD), higher protein intake may not be appropriate. Talk to your doctor or a registered dietitian about the right amount for your specific situation. Protein advice for people with kidney disease is quite different from general guidelines.

• Calculate your target: Multiply your weight in kg by 1.0-1.2 (or divide your weight in pounds by 2.2, then multiply by 1.0-1.2)
• Check your current intake for a typical day. Many people are surprised by how little protein they eat at breakfast and lunch
• Add a protein source to breakfast if your current morning meal is mostly carbohydrates (toast, cereal, juice)
• Keep convenient protein options stocked: canned fish, cheese sticks, Greek yogurt, hard-boiled eggs, nuts
• Combine protein with exercise. Resistance training plus enough protein is the best-proven way to preserve muscle and bone

Q. I'm vegetarian — can I get enough protein for my bones? Yes. Legumes, tofu, tempeh, eggs, dairy products, nuts, and seeds can all provide adequate protein. Eat a variety and include protein at every meal. Plant proteins can be just as effective as animal proteins when consumed in sufficient quantity.

Q. Are protein supplements (powders/shakes) okay for older adults? Yes, they can be useful, especially if appetite is low. Whey protein is well-studied and effective for muscle protein synthesis. Plant-based protein powders (pea, soy) are good alternatives. They're supplements, though. Food should be the main source when possible.

Q. Won't too much protein damage my kidneys? In people with healthy kidneys, there is no evidence that protein intakes of 1.0-1.5 g/kg/day cause kidney damage. This concern applies specifically to people who already have significant kidney disease. If you have any kidney problems, discuss protein intake with your doctor.

Q. I'm 75 and have lost my appetite. How can I get enough protein? Focus on protein-dense foods that deliver a lot of protein in small volumes: Greek yogurt, cheese, eggs, nut butters, and protein-fortified shakes. Eating smaller, more frequent meals rather than three large ones can help. If weight loss or malnutrition is a concern, ask your doctor for a referral to a registered dietitian.

• Rizzoli R, et al. Benefits and safety of dietary protein for bone health — an expert consensus paper endorsed by the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO) and by the International Osteoporosis Foundation (IOF). Osteoporos Int. 2018;29(9):1933-1948.
• Rizzoli R, et al. The role of dietary protein and vitamin D in maintaining musculoskeletal health in postmenopausal women: a consensus statement from ESCEO. Maturitas. 2014;79(1):122-132.
• Bauer J, et al. Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group. J Am Med Dir Assoc. 2013;14(8):542-559.
• Shams-White MM, et al. Dietary protein and bone health: a systematic review and meta-analysis from the National Osteoporosis Foundation. Am J Clin Nutr. 2017;105(6):1528-1543.
• Fenton TR, et al. Causal assessment of dietary acid load and bone disease: a systematic review and meta-analysis. Nutr J. 2011;10:41.
• International Osteoporosis Foundation (IOF). Protein — Nutrition Information.