Phosphorus may be a lesser known mineral than the other minerals with which it is commonly grouped (like calcium or magnesium), but it is not one bit less important. Phosphorus is part of every human cell, most fluid balances throughout the body, core genetic processes (through its role as a component of RNA and DNA), and an extensive list of other processes central to our health.
Biologists who study the nature of living things typically regard the cell as the smallest functional unit of life. From single cell bacteria up through the tens of trillions of cells that make up our bodies, the structures of a cell are fairly consistent from organism to organism.
Perhaps the most defining characteristic of a cell is its outermost membrane, simply called the “cell membrane” (or sometimes the “plasma membrane”). The cell’s outer membrane acts as a mediator between its internal space and everything that takes place outside of it. From a physiological and biochemical perspective, the cell membrane consists of a “phospholipid bilayer”—two rows of molecules composed primarily of fats (lipids) and phosphorus (in a special form called “phosphate” that involves a combination of phosphorus with oxygen and hydrogen). So as you can see, phosphorus is absolutely critical for the cell’s very existence.
Phosphorus also floats around inside of every cell in a form referred to as a “phosphate anion.” This form of phosphorus is similar to the form found in the cell membrane, and it is essential for a variety of different processes occurring inside of the cell.
Finally, with a few very notable exceptions, all cells contain a nucleus, and inside of the nucleus are genetic materials including RNA and DNA that both contain phosphorus in their chemical structure. In fact, phosphorus is sometimes referred to as the “glue” that holds DNA together.
So as you can see from its role in the cell’s outer membrane, internal fluid, and genetic components, phosphorus is an essential part of the cell’s design and it is a mineral that helps enable the cell’s basic function.
Interestingly, despite its central role in cell function, most of the phosphorus in our body is not found in cell membranes, cell fluids, or genetic materials in the cell nucleus, but in our bones. At least in terms of weight, about 80-85% of this mineral is stored in bone. In fact, the main crystalline structure in bone, called hydroxyapatite, consists of phosphorus, calcium, oxygen, and hydrogen, and calcium and phosphorus are so important in formation of hydroxyapatite that it is often referred to as a “calcium phosphate” molecule. Hydroxyapatite is a key part of a bone’s structural integrity.
So without phosphorus, your bone just wouldn’t be as strong.
In addition to its role as a structural component, your dietary phosphorus can also play a couple other key roles in the complex metabolism of bone. First, dietary phosphorus can influence the production of bone by helping with phosphorylation—a chemical process by which phosphorus is linked to an amino acid—of signaling proteins that stimulate bone growth. This local hormone-like process is occurring all the time, balancing bone growth with breakdown and remodeling.
The other role is no less important, and has received much more attention of late. Dietary phosphorus is one of the key players in the hormonal process that controls calcium and bone metabolism. This hormonal process focuses on the activity of one particular hormone, called parathyroid hormone (PTH). High levels of phosphorus (as phosphate ions) in the blood increase the level of PTH. PTH then performs a number of actions all aimed at increasing calcium levels, including decreasing calcium loss in the urine, increasing calcium absorption from foods (indirectly, via activation of vitamin D), and pulling calcium from the bones.
It’s that last effect—pulling calcium from the bones—that leaves some experts concerned that excessive dietary phosphorus could lead to problems with bone metabolism over time. Current evidence suggests that in extreme situations, like the dangerously high phosphorus levels seen in advanced kidney disease, elevated phosphates in the blood can change bone metabolism for the worse. In healthy people with normal kidney function, however, we don’t have evidence to show heightened risk of this set of events.
Given the special relationship between phosphorus, calcium, hormonal function, and bone health, some observers have recommended a precise ratio of calcium-to-phosphorus intake in our everyday diet. Of course, a ratio of sorts is represented by the Dietary References Intakes (DRIs) that have been established by the National Academy of Sciences (NAS), since the adult calcium recommendations range from 800-1200 milligrams and the adult phosphorus recommendation is 700 milligrams. So we are talking about a ratio of approximately 1.1 – 1.7 in favor of calcium. However, we have yet to see research evidence to suggest that this ratio is needed for proper bone support. In fact, we have seen studies where the ratio of calcium to phosphorus also teeter-totters in favor of phosphorus without increased bone risks, except at levels where phosphorus intake exceeds calcium intake by a ratio greater than 2:1 simultaneous with calcium intake below the recommended daily amount. Taken as a whole, the research studies make it difficult for us to support any specific target ratio in dietary intake of calcium and phosphorus, and for this reason, we believe that balanced dietary intake of whole natural foods from a variety of different food groups is currently the best way to ensure a healthy ratio of these two mineral nutrients.
When we consume foods and break apart food molecules through digestion and metabolism, one of our body’s key goals is production of energy. In particular, different stages of food breakdown are designed to result in the production of a special energy carrying molecule called ATP (adenosine triphosphate). As the name of this molecule suggests, it contains three phosphorus atoms (“tri”) in the form of phosphate groups. ATP is often referred to as a “universal energy carrier” because with a few exceptions, it can be used by virtually any type of cell and it can be used in a wide variety of different ways. Our cells are always making use of ATP to perform a wide variety of metabolic processes, and when ATP is being used, it can lose one or two of its phosphate groups to become ADP (adenosine diphosphate, where the “di” stands for “two”) or AMP (adenosine monophosphate, where the “mono” stands for “one”). Most of our cells have specialized compartments, called mitochondria, in which these lower phosphate versions (AMP and ADP) can get charged back up into their highest phosphate form of ATP. As you can see, phosphorus is a mineral of central important in this energy supply process.
We have not seen research studies showing a direct relationship between ATP availability throughout the body and dietary intake of phosphorus. While we suspect that chronic severe deficiency of phosphorus could eventually compromise the availability of ATP, we know that the body would go to great lengths to try and avoid compromise in this energy carrying system, by mobilizing phosphorus stored in bone and by taking other steps. But from a practical standpoint, eating a reasonably healthy diet with a reasonable number of phosphorus-rich foods should take care of any risk in this area.
In order for us to stay healthy, different parts of our body need to maintain very specific levels of acidity. In science terms, acidity level is referred to as pH. A conventional pH scale runs from 0 – 14, where “0” is defined as the most acidic level, “14” is defined as the least acidic (or most alkaline or basic) level, and “7” is defined as neutral. Since the pH of pure water is close to 7, and since our bodies are approximately 60% water, many of the pH levels in our body fall near the “7” level. In addition, many of the enzymes in our body are designed to work at this same pH level. The pH of our blood, for example, typically ranges from 7.35-7.45. The pH of our saliva usually ranges from 6.2 – 7.4. Only in very special places—like our stomach—does the pH level get quite low. (Prior to eating, the pH level in our stomach is usually 2.5 or below.) And there is no place in our body where pH shifts to its uppermost levels. In general, a simple summary of this pH information would be that it’s extremely important for our body fluids to maintain their appropriate pH, and more often than not, appropriate pH falls somewhere near a neutral level of 7.0.
Phosphorus is one of the key nutrients our body uses to maintain proper pH. In fact, the phosphorus buffer system is one of the three major ways we balance pH in our body (the other systems being the bicarbonate and protein buffer systems). More specifically, when pH gets too low (the same as too acidic), hydrogen phosphate works to neutralize some of this acid, shifting pH back toward neutral. When pH gets too high (or too “basic”), dihydrogen phosphate works in the same way to pull pH back down toward balance. The fact that two closely-related phosphorus-containing compounds can have such opposite effects on pH doesn’t necessarily seem to make sense on the surface. Regardless, luckily this process is occurring moment by moment throughout our body.
Like the role of dietary phosphorus in support of ATP, the role of dietary phosphorus in support of acid-base balance does not appear to require any special meal planning or food selection under most ordinary circumstances. (However, circumstances like end-stage kidney disease would be a different matter and might require special steps with phosphorus-containing foods.) When the National Academy of Sciences (NAS) determined the adult Dietary Reference Intake (DRI) for phosphorus of 700 milligrams, it did not do so based on observations about problematic pH balance at nearby intake levels.