Why the Right Calcium to Phosphorus Ratio is Key to Healthy Bones

Reviewed By:
Lara Pizzorno – AlgaeCal Scientific Advisory Board Member
MDiv, MA, LMT
Best-selling author of Healthy Bones Healthy You! and Your Bones; Editor of Longevity Medicine Review, and Senior Medical Editor for Integrative Medicine Advisors.

About the Advisory Board Member

Despite its wide availability in foods, calcium is one of the few nutrient deficiencies we regularly see in the United States. This also makes it one of the most commonly supplemented minerals in both food and pill form. 

And while many of us struggle to get enough calcium in our diets, it’s very common to be overloaded with phosphorus. That’s because these two minerals have an interesting inverse relationship: too much of one can deplete the other. 

This means that when our delicate balance of calcium and phosphorus is derailed, it throws off a host of biological pathways.

Now phosphorus isn’t all bad. In fact, it’s a key mineral for maintaining strong bones. Luckily, phosphorus is found in abundance in many healthy foods. But there are some sources of phosphorus that you’ll want to avoid (more on that later).

So in this article, we’ll explore:

• The important role these nutrients have in bone health
• The complex system that maintains their homeostasis
• The inverse relationship that makes things even more complicated
• How to avoid phosphorus overload

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What Is Phosphorus, And What Does It Do For Bones?

Phosphorus is one of the most abundant minerals in your body, acting as an essential structural component of cell membranes and nucleic acids, as well as many other biological processes such as energy production, cell-signaling, acid-base homeostasis, and bone mineralization [1]. 

In your bones, phosphorus works with calcium to create rigidity in the form of molecules known as hydroxyapatite crystals. Hydroxyapatite crystals strengthen the mechanical resistance of your bones, which is essential to maintaining bone health. 

While calcium and phosphorus play various roles within your body, your bones contain about 99% of your body’s calcium and 80% of your body’s phosphorus supply [2][3]. 

How Do Calcium and Phosphorus Work Together?

Calcium and Phosphorus Homeostasis

Your body is always working towards a state of homeostasis, also known as balance or equilibrium. 

Calcium and phosphorus have a highly interrelated relationship, with the delicate balance of each mineral being tightly regulated by several systems in your body. Keeping these two minerals in balance is crucial for cellular signaling, DNA structure, bone mineralization, muscle contraction, blood clotting, and neuronal excitation and involves several different organ systems and hormones [4]. 

Specifically, the organ systems involved in calcium and phosphorus homeostasis include the intestines, kidneys, and bone [5][6].

The hormones involved in the homeostasis of calcium and phosphorus include vitamin D, parathyroid hormone (PTH), calcitonin, and fibroblast growth factor (FGF23). These hormones work in concert with each other to exert their balancing effects on your intestines, kidneys, and bones. 

Should any of these organ systems or hormones become imbalanced, it can shift calcium and phosphorus homeostasis and directly impact your bone health [7].

Here is a brief review of the role each hormone plays:

Parathyroid hormone (PTH) –Your parathyroid hormone plays an important role in the balance of both calcium and phosphorus. When your serum calcium levels are low, it stimulates the release of calcium from your bones, inhibits the loss of calcium in your urine (via the kidneys), and indirectly increases your intestinal absorption of calcium in your intestines. 

PTH can also stimulate your kidneys to remove phosphate from the blood when levels are too high (or, in some cases, when there is dysfunction in the parathyroid gland). It also stimulates the release of phosphorus from your bones when serum levels are low.

Fibroblast growth factor (FGF23) – This hormone is secreted by your bone cells (osteocytes and osteoblasts) in response to increased levels of phosphorus. FGF23 targets your parathyroid to decrease the secretion of PTH and targets the kidney to increase urinary phosphorus excretion [8][9].

Vitamin D – Vitamin D is another hormone that plays a role in both calcium and phosphorus balance. In your intestine, it stimulates both calcium and phosphorus absorption to increase your serum levels of these minerals. Working with PTH, vitamin D stimulates the reabsorption of calcium and phosphorus from your kidneys (reducing the loss in your urine).  

Furthermore, since the growth of your bones depends on vitamin D, this hormone also plays a role in shuttling calcium out of your blood and back into your bones for mineralization [10].  

Calcitonin – Calcitonin is a hormone produced by your thyroid gland that primarily functions to maintain the balance of calcium in your body when your blood calcium is too high. It does this by inhibiting the breakdown of bone (the activity of osteoclasts) and decreasing the amount of calcium that your kidneys can absorb [11]. 

While calcium and phosphorus can be found throughout your body, the place where homeostasis takes place is in your blood. Therefore, because your bones store most of these minerals, they serve as a reservoir for calcium and phosphorus when your blood levels get too low. 

And your kidneys, which typically serve to remove these minerals, can either ramp up to continue to remove them from your blood, or they can slow down to enhance the amount of calcium and phosphorus that remains in circulation. 

And finally, your intestines are the site in which dietary calcium and phosphorus can be absorbed or inhibited from entering.  

Calcium and phosphorus not only work together to maintain the health of your bones, DNA, nerves, muscles, and more, but they also have an inverse relationship in your blood.

The Inverse Relationship Between Calcium and Phosphorus

Research shows that the delicate balance between calcium and phosphorus can be easily disturbed when the maintenance of these minerals is not taken seriously. 

The best example of this is The Standard American Diet (SAD), which contains an excessive load of phosphorus due to phosphate additives in processed foods, while simultaneously being low in calcium. As a result, many people in the US and other Westernized countries experience imbalances in these two minerals[12]. 

Due to the inverse relationship between calcium and phosphorus, when one of these minerals rises, the other falls. As in the example mentioned above, the stark increase in phosphorous due to the SAD without a balanced intake of calcium can lead to disharmony in calcium-phosphorus homeostasis and downstream impacts on several systems – including your bones.

The SAD affects your bones in two ways:

• It’s laden with bone-destroying refined sugars and carbohydrates. Many of these foods carry pro-inflammatory fats and chemicals that stimulate bone removing osteoclasts.

• It’s also criminally lacking in essential bone-building vitamins and minerals like calcium. High-nutrient foods like leafy greens, vegetables, whole grains, and legumes are absent from much of the SAD too.

In fact, our Bone Health Expert Lara Pizzorno calls the SAD “the perfect recipe for osteoporosis.” 

“The SAD eats your bones, in large part by causing chronic inflammation along with metabolic acidosis, an acidic pH in the body that results in calcium being withdrawn from bone to restore a more alkaline state,” she says in an excerpt from her book Healthy Bones Healthy You.

Obviously, that’s bad news for your bone density.

Under normal circumstances, your body is naturally skilled at keeping calcium and phosphorus balanced. For example, when calcium concentrations become low (or phosphorus becomes too high), your PTH will encourage the release of calcium and phosphorus from your bones and enhance the absorption of these nutrients from your intestine via the action of vitamin D [13].  

At the same time, PTH signals your kidneys to increase calcium reabsorption but instructs them to decrease phosphorus reabsorption, which keeps the two in balance. 

Interestingly, even in situations where dietary phosphorus is high, if calcium is still high, then PTH doesn’t get involved. But once phosphorus outpaces calcium, your hormonal system becomes activated [12].

While your hormonal and organ systems can do their best to maintain the balance, if this unequal proportion of calcium to phosphorus continues, it could lead to serious health issues [12]. For example, when phosphorus becomes too high, it pulls calcium out of your bones and binds with it. This can become an issue for bone health as your bones become depleted of this vital nutrient.

How to Avoid Phosphorus Overload

Diet

While it’s fine to consume healthy sources of phosphorus — such as dairy, fish, and vegetables — it’s important to avoid consuming foods that are high in phosphate additives.

Research shows too much dietary phosphorus can be a risk factor for cardiovascular and kidney diseases.[14] Unfortunately, the general population is already consuming more than enough phosphorus in processed foods and food additives! 

Phosphates (a chemical compound that contains phosphorus, often a salt) are used as preservatives in most processed foods, so make sure you read nutrition labels closely. Most often, phosphates are found in foods like sodas, sweet bakery products, cereals, crackers, pizza, cured meats, poultry, processed vegetables, egg products, candy, and chocolate. 

We’re getting so much phosphorus from phosphate additives in these processed foods that it’s increasing our risk of heart attacks, kidney disease, osteoporosis and death from virtually all causes. That’s why it’s critical to avoid consuming foods that are high in phosphate additives. It’s also important to get enough calcium to keep phosphorus levels in check.

Exercise

As you know, exercise brings many benefits to the table. It turns out a lesser known one is that it helps balance phosphorus levels. 

A study examined a nonpharmacological approach to improving phosphate control in 12 hemodialysis patients. In the study, the patients underwent an exercise program in which they pedaled a bicycle ergometer either immediately before or during dialysis. 

Each week the dialysate phosphate removal was measured. Researchers found that exercise resulted in increased dialytic removal of phosphate and could be expected in the long term to improve phosphate control. 

Granted, the sample size of this study was very small. But despite this, it’s a promising study. And a good first sign that more research should be conducted.[15]

Sleep

Growing evidence suggests that abnormally high serum phosphate levels are associated with poor sleep quality [16,17,18,19] In 2020, a multiple linear regression analysis involving 217 hemodialysis patients was conducted to determine the possible factors that influence serum phosphate levels. 

And it was found that patients who slept less than five hours per day had significantly higher serum phosphate than their counterparts who slept six hours or longer. The study confirmed that longer sleep duration was associated with a lower level of serum phosphate.

Although the findings signify that more work is needed on how sleep interventions may affect serum phosphate levels, it does give us yet another good reason to get ample shut eye.[20]

Kidney Function

‌Your kidneys play a vital role in keeping phosphorus at the proper level in your body. When your kidneys are functioning properly, they excrete 90% of your daily phosphate load. But when you have kidney problems, such as Chronic Kidney Disease (CKD), your phosphate levels can’t be regulated.

With CKD, your kidneys can’t remove the phosphorus. That means it builds up in your blood. And this excess of phosphorus can harm your body by increasing your risk of heart attack or stroke.[21] 

Moreover, kidney damage from CKD causes mineral and bone disorders. That’s because once your kidneys are damaged they can’t properly balance the hormone and mineral levels in the body. Damaged kidneys stop:

• Turning vitamin D into calcitriol, which creates an imbalance of calcium in your blood
• Removing excess phosphorus from your blood, which triggers your blood to pull calcium out of your bones — causing them to weaken

And that’s not all. When your kidneys are damaged, extra PTH gets released into your blood to move calcium from your bones in an attempt to restore your blood calcium levels. However, this response also depletes your bones of much-needed calcium.[22]

Takeaway

Phosphorus and calcium have an incredibly complex relationship that relies on a delicate balance to keep things running smoothly. When one of these nutrients gets thrown off track, it impacts the other, along with a host of biological pathways. So it’s important to maintain a proper balance of the two.

While your body will go to great lengths to create the perfect homeostasis on its own, your diet and supplement regimen play a significant role in the ratio of calcium to phosphorus in your blood. 

When this ratio is off, your hormonal system kicks in, alerting your bones, digestion, and kidneys. Ultimately, if there is disharmony in your calcium to phosphorus ratio for too long, it can cause serious issues, particularly in your bones and your kidneys.

Unfortunately, most people get too much phosphorus in their diet from processed foods and food additives. That’s why it’s so important to consume enough calcium to balance out high phosphorus intakes. It’s also critical to cut out processed foods, exercise regularly, and get enough sleep each night to help balance phosphorus levels.

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