Are Acidic Foods Weakening Your Bones?

Does what you eat affect your bone strength? Absolutely.

When people think of bone strength, vitamin D and Calcium normally come to mind.

While these are an important part of keeping your bones healthy and strong – there’s a big scientific debate on whether you might be weakening your bones by eating too many grains and animal proteins.

For the last decade or so, a line of research has been looking at whether or not a highly acidic diet causes poor health and disease.

What does this mean? When we eat foods, they are broken down into components that may be either more acidic or alkaline (base). The foods themselves are not acidic, just the components they’re broken down into.

So does what you eat make your bones weaker? Let's take a look at the evidence.

The Biology of Bone

Acid-Base Balance

Our bodies tightly regulate the acid-base (pH) balance in our blood to stay between 7.35 and 7.45. This homeostatic balance is crucial because going above or below this range can be life-threatening.

The acidity and alkalinity of our blood are affected by several factors including environmental toxins and disruptions in the mechanisms that regulate the balance.

But one of the biggest acid-producing entities we encounter daily is food; specifically those foods with sulfur-containing amino acids.

{Amino acids are the building blocks of proteins. There are 21.}

Helping to compensate for imbalances in homeostasis are:

• The lungs, which get rid of acidic CO2 by ‘blowing it off’

• The kidneys, which expel acidic hydrogen ions via urine and reabsorb alkaline bicarbonates.

• There are several other buffering pathways as well.

Side note: Because we maintain such tight regulation of our blood pH via the above buffering pathways, urine is where we may be able to observe a higher pH. This is because the kidneys help excrete extra acid from the body.

Calcium Homeostasis

Most calcium in the body is stored in our bones and teeth; however, one percent (1%) of calcium is found in our blood and intra- and extra-cellular fluids.

This one percent is indispensable for life. It helps cells send communication signals and transport compounds across cell membranes; helps with hormone function; and is imperative to nerve transmission and regulation of heart muscle function.

Intra- and extra-cellular fluids are also tightly regulated to ensure our health.

Calcium is alkaline (a base), and we know now that both calcium and phosphate help maintain the acid-base balance in the body. So when the body senses its environment is getting too acidic, bones (and muscles!) are broken down to release calcium to help bring the body back into an acid-base balance.

Obviously, the breakdown of bone and muscle is not ideal for health.

What foods are Acidic?

Although lemons, limes, oranges, and other citrus fruits are literally acids, these do not affect our pH balance.

Rather, proteins and grains are broken down {metabolized} into acidic compounds such as sulfuric acid.

Fruits and vegetables are primarily broken down into more alkaline compounds, such as bicarbonate, which help to neutralize acid. Some vegetable proteins are slightly acidic, however, they are much less acid-producing than animal proteins.

So the hypothesis is that when we eat too much animal protein (poultry, beef, dairy, etc) and grains (bread, cereal, rice, pasta, cookies, doughnuts, tortillas, cupcakes, and similar foods) we create a more acidic environment within the body.

Because the body cannot risk a big change in pH, it immediately begins to buffer the acid by adding alkaline compounds – such as calcium from our bones and muscles.

This means that chronically eating too many acidic foods may over time leach too much calcium from the bones, potentially resulting in more bone fractures or osteoporosis.

The Verdict

Several recent meta-analyses indicate no correlation between a higher acid diet and bone mineral density or loss of muscle mass... as long as the person has adequate calcium in their diet, enough alkaline foods to help balance the acidic ones, and healthy kidney function.

This means that for the older population with poor kidney health (or even a younger adult with poor kidney function), too much animal protein and other acidic foods may impact their bone health.

For the younger population, the protection of our bone health even with a diet high in animal proteins and refined grains may be multifactorial:

• The need for more calcium as a buffer may cause our body to absorb more of this nutrient from food. Nutrition note: our body takes only the nutrients it needs from the foods we eat. This is of course assuming we are eating enough calcium-rich foods.

• Protein also contains many growth hormones, such as IGF-1, which is also important for bone formation. So this may help counter-balance the calcium-leaching effects of animal protein.

What does this mean for You?

If you have healthy kidneys and lots of veggies and fruit in your diet, you're probably good to go!

Here are some tips to help ensure you are eating the right foods - and doing the right exercises - for bone health:

1. Choose lean proteins most often and try to include some adequate-protein vegetarian days in your week. 

   • Lean animal proteins include: poultry, lean cuts of beef and lean ground beef, dairy (which doesn't necessarily have to be low fat), eggs, and fish. Vegetarian proteins include: Beans, legumes, tofu, edamame, tempeh, soy milk or other soy products, nuts, nut butters, quinoa, millet, and amaranth.

     
     

2. Reduce the amount of refined grains in your diet.

   • Focus on snacks being a combination of fruits or vegetables plus a lean protein, rather than a handful of chips, crackers, or other processed snacks. When you do eat grains, choose 100% whole grains such as high fiber/whole breads, brown rice, quinoa, millet, and other complex grains.

     
     

3. At meals, include at least 1.5 to 2 cups of vegetables.

   
   

4. Eat enough calcium-containing foods (and vitamin D!)

   • Yogurt and other dairy, fortified plant-milk, Tofu made with calcium sulfate, bone-in canned sardines or salmon, leafy greens such as spinach, kale, and turnip greens (cooking releases more calcium!), chia seeds.

   • Vitamin D promotes calcium absorption, so they work together for bone health. Vitamin D is in very few foods (Cod liver oil, trout, salmon, mushrooms grown in UV light, and eggs), so safely getting enough from sunlight exposure - without sunscreen, is important. Note that in the higher latitudes of the northern hemisphere, the sun is at an angle during wintertime that prevents the body from making vitamin D. For this reason, consider taking a vitamin D supplement during the winter months.

     
     

5. Exercise at least 30 minutes or more per day. Include 3 days per week of strength training. Weight-bearing exercises are incredibly important for your bone health.

Fruits, vegetables, nuts, seeds, legumes, and healthy oils are nature’s multivitamins, packed with the nutrients and antioxidants needed to feel, look, and perform your best. But most importantly have the micro-nutrients important for bone health. These need to be the foundation of your diet.

*It is not recommended that you start taking bicarbonate. The goal is to keep your acid-base balance by eating more fruits and vegetables and less grains and protein.

Resources:

1. Salcedo-Betancourt JD, Moe OW. The Effects of Acid on Calcium and Phosphate Metabolism. Int J Mol Sci. 2024;25(4):2081. Published 2024 Feb 8. doi:10.3390/ijms25042081

2. Dawson-Hughes B. Acid-base balance of the diet-implications for bone and muscle. Eur J Clin Nutr. 2020 Aug;74(Suppl 1):7-13. doi: 10.1038/s41430-020-0691-7. PMID: 32873951.

3. Yibing Han, Min An, Li Yang, Liuran Li, Shitao Rao, Yanzhen Cheng. Effect of Acid or Base Interventions on Bone Health: A Systematic Review, Meta-Analysis, and Meta-Regression. Advances in Nutrition. 2021: 12(4). 1540-1557.

4. Kędzia G, Woźniak M, Samborski W, Grygiel-Górniak B. Impact of Dietary Protein on Osteoporosis Development. Nutrients. 2023;15(21):4581. Published 2023 Oct 28. doi:10.3390/nu15214581

5. Frassetto L, Banerjee T, Powe N, Sebastian A. Acid Balance, Dietary Acid Load, and Bone Effects-A Controversial Subject. Nutrients. 2018;10(4):517. Published 2018 Apr 21. doi:10.3390/nu10040517

6. NIH Office of Dietary Supplements. Calcium. ODS.od.nih.gov. July 2024. Accessed 12 September 2024.

7. NIH Office of Dietary Supplements. Vitamin D. Ods.od.nih.gov. July 2024. Accessed 12 September 2024.