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Everything You Need to Know About Protein and Bone Health

There’s a common misconception that could be wreaking havoc on your bones… 

The misconception? That a high protein diet is bad for bone health. 

But nothing could be further from the truth! In fact, years of research show that getting plenty of protein is crucial for bone density — provided you get enough of a certain key mineral. And that increasing your protein intake can help you stay strong, healthy, and independent as you age.  

That’s why we’re taking a deep dive into the research on protein and bone health, including the truth behind the much debated “acid-ash hypothesis”. We’ll also break down exactly how much protein you need and the best places to get it. 

So let’s get started!


The Basics on Protein and Your Bones

Proteins are your body’s “building blocks”. In fact, they form the foundation of every living thing!

Yes, bone, muscle, hair, blood, tissue, immune system antibodies, and vital enzymes are all built with proteins. So without them, your body’s ability to maintain, grow, and repair tissues is compromised. But what are proteins, exactly? 

Under a microscope, proteins are made out of long chains of amino acids linked together like lego blocks. All told, there are 20 amino acids needed for metabolism and human growth. 

Eleven of these are classified as nonessential — meaning your body can produce them, so you don’t need to get them through your diet. Nine of these are classified as essential — meaning your body can’t produce them, and you have to get them through your diet! 

And when it comes to your bones, protein is especially important. Protein makes up roughly one third of your bone mass (the amount of protein your bones contain) and half of your bone volume (the amount of space protein takes up)! 

The protein in your bones is continuously broken down and built back up, as part of your bone remodeling process. And unfortunately, the protein that’s broken down isn’t reabsorbed and reused. That’s why you need a daily supply of protein to maintain your bone density. (We’ll go over the ideal amount a little later on!)  

Protein also works closely with calcium. And of course, calcium is a key mineral for bone health. So next, we’ll take a closer look at the relationship between protein and calcium. Plus, we’ll debunk the common misconception I mentioned earlier…

Calcium and Protein Work Together

You need a balance of calcium and protein for strong, healthy bones. 

Research shows these nutrients complement each other. Specifically, when you get adequate calcium in your diet, a higher protein intake benefits bone mineral density (BMD) and reduces hip fracture risk. 

Let’s break down the research:

Studies on protein intake and bone mineral density


Bone Health Benefits of Protein

So we’ve seen how protein is crucial for your bone remodeling process. We’ve also seen how a high protein diet along with adequate calcium can protect your bones! But that’s not all… 

Here are three more bone health benefits of protein:

Icon of bone structureProvides the Structural Framework for Bone

Your extracellular bone matrix is primarily made of collagen, and yes, collagen is a protein! This soft collagen matrix is like a flexible framework for bone. Calcium hardens this framework and adds strength to it. Together, collagen and calcium make your bones strong, yet flexible enough to withstand stress. 

Of course, there’s more to bones than collagen and calcium, but they’re undoubtedly two of the key ingredients! This is yet another example of how protein and calcium work together to support your bone health.

Icon of growth factor

Increases Insulin-Like Growth Factor 1 (IGF-1) Levels

We touched on IGF-1 briefly a little earlier on. If you recall, protein stimulates the production of IGF-1 — and IGF-1 boosts calcium absorption! Of course, this function favors your bones. 

But IGF-1 does much more than that. This hormone is key for bone growth. It also enhances muscle tissue and strength, which in turn, supports bone strength. Remember, your muscles and your bones are tightly intertwined… that’s why it’s called your musculoskeletal system! More on this point next.

Icon of muscle mass

Crucial for Your Muscle Mass and to Prevent Sarcopenia

Just like protein is crucial for the structure of your bones, it’s also a building block for your muscles. And just like your bones, your muscles are constantly rebuilding in response to the daily stressors of life. 

So when you don’t consume enough protein, your ability to produce new muscle and replace damaged muscle is compromised. Over time, this leads to a lower rate of muscle protein synthesis and a loss of muscle mass. 

Plus, as you age, your ability to use the protein you consume to build muscle (called your anabolic response) lessens. That’s why, older adults need to consume more protein than young adults to maintain muscle mass.

The point being, if you’re not proactive about getting enough protein as you age, it can lead to sarcopenia — a condition where your muscle mass shrinks and your muscle cells are replaced by fat. 

What does all this have to do with your bones? Well, like I mentioned in the previous bullet, your muscles and your bones are closely linked. After all, muscle contractions put stress on your bones and stimulate them to rebuild! 

So you can see how sarcopenia is bad news for bone health. In fact, sarcopenia and osteoporosis are strongly associated with each other, as well as with the frailty syndrome — a condition characterized by weakness, slowness, reduced physical activity, reduced energy, and weight loss. 

All this to say, it’s worth making sure you get enough protein every day. For your bones, your muscles, and your overall quality of life.

Debunking the Acid-Ash Hypothesis

There’s been much debate over the “acid-ash hypothesis”.  

In brief, this hypothesis suggests that high protein intake (particularly from animal sources) leads to increased acid production and bone resorption. This is attributed to high levels of sulfur-containing amino acids in animal proteins, which generate an acid load.

The idea is that the body tries to neutralize this “acid load” by recruiting calcium from bone, which leads to hypercalciuria (excess calcium in urine), bone loss, and osteoporosis. (For a more in-depth explanation of the acid-ash hypothesis — also called the alkaline diet theory — visit this page.) 

Now, this hypothesis is supported by animal and cellular studies. But not so fast! This is a perfect example of how preliminary research can be misleading. See, animal and cellular studies don’t always translate to humans, and this is one of those instances.

First off, your body is well-equipped to regulate your acid load. Your kidneys and lungs work as a team to maintain “acid-base homeostasis”. That is, a healthy balance of acid and alkaline (neutral) substances in your body. So generally, excess acid from food is easily dealt with. (Note there are exceptions to this rule, like for people with chronic kidney disease.) 

All this to say, acid production from a high-protein diet is unlikely to (even slightly!) affect this balance. 

So what gives with the studies that show high protein intake increases urinary calcium loss? Well, for starters, excess calcium in urine doesn’t necessarily come from increased bone resorption — like the acid-ash hypothesis suggests. There are several alternate mechanisms that could be at play. 

For example, higher protein intake leads to higher calcium absorption. That’s because protein stimulates the production of something called insulin-like growth factor 1 (IGF-1). In turn, IFG-1 increases the production of calcitriol — an active form of vitamin D that increases intestinal calcium absorption!

So the resulting excess calcium in urine could, in part, be due to increased calcium absorption. Of course, this theory requires more study, as the research so far has been small-scale. But an alternate mechanism (or combination of mechanisms!) seems more likely in face of the many human studies that show the benefits of a higher protein diet for bone health.

(Incidentally, this relationship between protein, IGF-1, and calcium absorption may contribute to the positive effects of high-protein with adequate calcium we saw above! More on IGF-1 coming up in the next section.) 

Still not convinced? Here’s a snapshot of studies that cast doubt on the acid-ash hypothesis:

Studies on the acid-ash hypothesis

So How Much Protein Do You Need?

Despite all the benefits of a higher protein intake discussed so far, you’ll find most official health organizations and websites recommend a modest amount. 

The current recommended daily allowance (RDA) for protein intake is 0.8 g per kg of body weight. But this RDA was set over a decade ago, and experts now believe it’s not an adequate amount. Especially for older adults…

The original RDA for protein was set with preventing a deficiency in mind. Not for promoting optimal health. And the recommendations were based on studies conducted in young, healthy adults. So the RDA fails to take into account the physiological changes that occur with aging.

Changes that occur with aging include:

  1. Sarcopenia – As discussed, you start to lose muscle mass every year as you age. The exact amount of muscle loss varies from person to person, but research suggests the average rate of muscle loss for people over 70 is 0.5-1% per year.
  2. Reduced Ability to Make Muscle – Again, as discussed, you start to develop an anabolic resistance to amino acids as you age. In simple terms, that means you become less efficient at turning the protein you consume into muscle.

So bearing these points in mind, more recent research recommends older adults consume 1-1.5 g of protein per kg of body weight. And here’s why you may want to err on the side of 1.5 g… 

In the latest double-blind randomized controlled trial (the gold standard of research!), 120 frail or close to frail adults, between the ages of 70 and 85, were assigned to one of three groups: 

  • Group one received 0.8 g of protein per kg a day
  • Group two received 1.2 g of protein per kg a day 
  • Group three received 1.5 g of protein per kg a day 

After the 12-week study period, the participants who received 1.5 g of protein per kg a day experienced the most beneficial effects (measured by muscle mass and walking speed). Notably, there were no significant differences between the 0.8 and 1.2 g of protein groups! This suggests a higher protein intake is necessary to counteract sarcopenia and frailty.  

So how much protein does 1-1.5 g equal in practical terms? 

Well, for your average 130 pound woman, 1.5 g of protein per kg would translate to about 30 grams of protein at each of your three meals during a day. (Check out the infographic below to see how to calculate your exact needs!) But there’s an important thing to note: To maximize your body’s ability to use this extra protein to produce muscle, it’s best to separate your meals by three to five hours.

But again, these are just updated guidelines. For the most accurate calculation of your protein needs, you must take your age, body weight, and activity level into consideration. That sounds complicated, but don’t worry! The visual below makes it easy for you.

How to calculate your protein needs

If you’d like to read about protein requirements in greater detail, check out this chapter on the “Recommended Dietary Allowance for Protein and Amino Acids” from the National Research Council. If you find all this information a little daunting, you can also try using this easy online protein calculator!


Top Food Sources of Protein

Calcium uses, effects - older couple making bone healthy food

What makes for a “high-quality” protein? 

Well, there are several factors to take into consideration, including the amount of protein per gram, whether it’s a complete or incomplete protein, and how it’s raised (grass fed vs. grain fed, organic vs. factory farmed, etc). 

Let’s take a closer look at how the different types of protein stack up…

Animal Protein Vs. Vegetarian Protein

Animal protein has a couple of advantages over vegetarian protein. 

First off, if you look at the amount of protein per gram, animal protein wins out. In general, vegetarian protein sources fall a short of the protein content animal sources offer so you need to eat more calories with plant proteins which can be an issue if you’re concerned about controlling body fat. 

Second, all animal protein sources are considered complete proteins. That means they provide all eight essential amino acids you need to get from your diet. On the other hand, vegetarian proteins are typically incomplete, meaning they lack one or two of essential amino acids. (Note there are a few exceptions to this rule, like quinoa and soy.)

Of course, that’s not to say you can’t fulfill your protein needs through vegetarian sources. It’s just a little trickier to do! 

If you’re a vegetarian or vegan, the key is to consume a variety of fruits, vegetables, grains, and legumes to ensure you get all the essential amino acids. For a more in-depth look at vegetarian protein, visit our “Vegetarian’s Guide to Protein and Collagen”.

It’s also worth noting that whenever possible, it’s best to choose grass-fed, wild-caught, and organic protein sources to minimize your exposure to pesticides and other chemicals. That’s because these chemicals can cause bone-damaging inflammation

Finally, as we saw a little earlier on, there’s been some debate about whether animal proteins increase acid load and urinary calcium excretion. If you recall, the theory is that animal proteins generate more sulfuric acid from sulfur-containing amino acids. But a strict vegetarian diet, with protein from grains and legumes, can deliver just as much sulfur per gram as a meat-based diet

What’s more, this theory is unsupported by science. In fact, studies published in several leading scientific journals, including The American Journal of Clinical Nutrition and Nutrition Today, discount the idea that vegetarian proteins are better for bone health than animal ones. 

Rather, research suggests the best course of action for your bones is to get a balance of both animal and vegetarian proteins! 

For example, a recent study followed 74,443 women and 35,438 men aged 50 and older for up to 32 years… and they found no evidence that higher animal protein intake increased hip fracture risk. On the contrary, plant and dairy protein were associated with significantly lower risk of hip fractures when results for both men and women were combined. 

This study shows the benefits of both animal and vegetarian proteins. And it’s only logical your body needs a balance of both. That way, you get all the essential amino acids, and the minerals and vitamins you need for strong bones!

AlgaeCal Plus provides all 13 minerals and three vitamins your bones crave in one convenient supplement. To learn more about this clinically-supported, bone-building supplement click here.

Top Animal and Vegetarian Protein Sources

Complete Protein Sources Incomplete Protein Sources** Complimentary Protein
Fish Grains Kale salad with almonds
Meat Legumes Hummus with pita
Dairy (milk, yogurt, whey) Vegetables Rice and beans
Eggs Nuts and seeds
Quinoa*
Buckwheat*
Chia and hemp seeds*
Spirulina*

*Indicates vegetable, plant-based sources

**Incomplete does not mean they’re inferior. You can create complementary proteins to provide the right balance of essential amino acids.

You can also check out our Vegetarian’s Guide to Protein and Collagen for a more in-depth look into protein for vegetarians.

Source Amount of Protein (in grams)
Sirloin Steak, 8 ounces (226 grams) 45
Can of Tuna, 6 ounces (170 grams) 40
Chicken Breast, 3.5 ounces (100 grams) 30
Whey Protein Powder, 1 scoop (32 grams) 24
Fish Fillet, 3.5 ounces (100 grams) 22
Vegetarian Sources of Protein
Tofu, ½ cup 20
Pumpkin Seeds, ¼ cup 19
Plant-Based Protein Powder, 1 scoop (32 grams) 17.78
Pulses, ½ cup 7-10
Cottage Cheese, ½ cup 12-15
Buckwheat, 3.5 ounces (100 grams) 12.6
Hard Cheese, 1 ounce (28 grams) 10
Plain Yogurt, 1 cup 8-12
Raw Almonds, ¼ cup 8
Sprouted Wheat, 3.5 ounces (100 grams) 7.5
Raw Sunflower Seeds, ¼ cup 6
1 Large Egg (57 grams) 6
Quinoa, 3.5 ounces (100 grams) 5-14 (depending on variety)

Want a printable PDF of 10 Great Sources of Protein for Healthy Bones? Click here.


Protein-Rich Recipes

Now that you’ve seen some examples of protein-rich foods, you’re probably looking for tasty ways to cook them up! 

To help inspire you, here are a few delicious protein-rich recipes from the AlgaeCal Kitchen: 

Asian slaw

Asian Chicken Slaw Salad

This fresh, colorful salad has it all! Satisfying crunch, a tangy, creamy dressing, and plenty of protein from chicken breast and pumpkin seeds. Plus, it’s quick to whip up for a healthy lunch or dinner. 

Tasty Turkey Burgers 

Turkey burgers

Turkey is an excellent source of lean protein, not to mention downright delicious! So these turkey burgers have a lot to offer. And thanks to a few clever ingredient swaps, like lettuce instead of buns, they’re an all-around healthy option.

8-Ingredient Salmon Burgers

Salmon burger

Ever struggle to get the recommended two servings of seafood a week? These super simple burgers can help! Plus, they pack in loads of calcium and protein — a combination that, as we’ve seen, is key for your bones. 


Protein and Bone Health Takeaways

Don’t shy away from protein.

Protein is a crucial component of every cell in your body. You need it to repair and build tissues, and it’s a key building block for cartilage, blood, skin, muscles, and bones. In fact, the latest expert consensus stresses the importance of protein for strong, healthy bones! 

Don’t be afraid of animal protein either. After all, the acid-ash hypothesis is unsupported by science, so including high-quality animal protein as part of a balanced diet won’t hurt your bones.   

But no matter your diet or lifestyle, there are plenty of protein options for you! Just remember to think about what you don’t want from protein too… 

Pesticides, herbicides, hormones, antibiotics, and preservatives won’t benefit you or your bones. So make sure you choose high-quality, organic, grass-fed, and wild-caught options whenever possible.

Have any recipes or tips to add more protein to your diet? Share them with us in the comments below!

Author: Monica Straith, BS

Monica is the PR and Outreach Manager and Fitness Lead at AlgaeCal. She’s an ACE Certified Personal Trainer and Nutrition Specialist, and has a B.S. and B.A. from the University of Wisconsin-Madison, where she played varsity soccer for four years. Monica pulls from her experience in athletics and health to contribute to AlgaeCal and has also been featured on myfitnesspal blog, Prevention, and Huffington Post.