For serving size for specific foods see the Nutrient Rating Chart.
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.
Fortunately, very few nutrients are as widely available throughout our HealthyFood as phosphorus. Not only do 75 of our foods rank as excellent, very good, or good sources of this mineral, but you can also find ranked sources of phosphorus in every single one of our food groups. In fact, it would be difficult to design a HealthyFood-based diet that would meet your calorie needs yet somehow fail to provide you with the amount of phosphorus that you need.
In recent years, a good bit of controversy has unfolded about health risks involved with excessive dietary intake of phosphorus through increased consumption of soft drinks containing phosphoric acid and processed foods containing phosphate stabilizers, emulsifiers, anticaking agents, and acidity regulators. In our Summary of Food Sources and Risk of Dietary Toxicity sections, we will provide you with detailed information about this controversy. However, it is important to know that a meal plan based on whole natural foods rather than processed foods is likely to avoid excessive phosphorus risks.
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. So as a general rule, believe that you can supply your body with the phosphorus it needs to maintain a healthy pH balance by eating a balanced variety of whole, natural foods that we profile on our website.
Since only three of our HealthyFood rank as excellent sources of phosphorus (scallops, cod, and crimini mushrooms), we expect that most people will be getting their phosphorus primarily from our 28 very good and 44 good sources. That's 72 foods from which to choose, and you will find foods from every food group included in the list.
If we had to pick one food group as our top phosphorus source, it would be fish. Not only do all six of our HealthyFood fish rank in our phosphorus top 10, but each one provides at least 300 milligrams of phosphorus per serving, or about 40% of the recommended daily amount. Meats, poultry, dairy, and eggs also tend to be rich in phosphorus. Our HealthyFood in this group each contain about 100-250 milligrams of phosphorus per serving. In the U.S. as a whole, intake of these foods is relatively high, and for this reason they tend to account for a high percentage of total phosphorus intake. However, animal foods do not need to play a role in healthy phosphorus intake if you prefer to avoid them in your meal plan. The reason here is simple: numerous plant foods belonging to multiple food groups including vegetables, beans and legumes, nuts and seeds, and grains serve as good or very good sources of phosphorus.
We'd like to highlight some select plant foods that make sense to consider for optimal phosphorus nourishment. In the beans and legumes group, our list would include soybeans and lentils, with one serving of either food providing over half of the daily phosphorus requirement. In the nuts and seeds group, pumpkin seeds would be a standout, once again providing over half of the daily requirement in a single serving. Among the vegetables, green peas, broccoli, and spinach each provide about 100-150 milligrams per serving.
The phytic acid form of phosphorus found in many plant foods (and especially seeds, grains, beans, and legumes) has been a topic of widespread public discussion, centered mostly around the question of how extensively phytic acid binds together with minerals like calcium, iron, and zinc and lowers their absorption from the digestive tract up into the body. It is important to understand more about this form of phosphorus, however, than simply an assessment of its relationship to other nutrients.
Phytic acid (also referred to as inositol hexaphosphate, inositol hexakisphotphate, IP6, and phytate) is a widespread storage form for phosphorus in plants. Because appropriately timed availability of phosphorus is so essential in plant development, special enzymes called phytases have evolved to help assure proper release of phosphorus from this special storage form. While human cells do not produce phytase enzymes, bacteria living in the human digestive tract can produce them, as can many other microorganisms (including many yeasts and fungi) as well as some animals.
Recent research suggests that the amount of phosphorus we get from phytic acid in plant foods depends on the health of our intestinal bacteria. This research has started to shift some conventional thinking about phytic acid in food, which has largely dismissed phytic acid as an undigestible form of phosphorus. However, some preliminary studies have speculated that complete breakdown of phytic acid is possible in the first segment of our large intestine (called the cecum) because this segment houses an unusual number of both aerobic and anaerobic bacteria (due to higher oxygen concentrations along the lining of the cecum than in other areas of the large intestine) and that a combination of aerobic-plus-anaerobic bacterial enzyme activities may be able release all of the phosphorus groups from phytic acid. Furthermore, preliminary research findings also suggest that populations of phytic acid-digesting bacteria might be able to adapt to an individual's diet over time and increase the availability of phosphorus from this storage form of the mineral.
Much more clearly documented is the fact that fermentation of foods (for example, fermentation of soybeans into tempeh) can increase phosphorus bioavailability from phytic acid, as can the action of yeast on phytic acid-containing grains ground into flour and used in bread making. So once again, we see a pathway in which the phytic acid storage form of phosphorus in plants might also be able to serve as an important phosphorus source in human diets.
Finally, we would note that the soaking of beans, legumes, grains, and seeds has been shown to result in partial breakdown of phytic acid, and in some cases, up to 50% of phytic acid might get broken down in this way.
Taken as a whole, the research above suggests that phytic acid should not be dismissed as an unavailable form of phosphorus in plant foods, and that future research should help us understand more about this unique plant form of phosphorus. Interestingly, the degree to which phytic acid binds minerals like calcium, iron, and zinc may also be related to the action of microorganisms on phytic acid, either during food production or inside of our digestive tract. However, we will address this issue a little further in our Relationship with Other Nutrients section.
Added phosphates make up a significant portion of the total phosphorus intake in the United States. We'll discuss where these are found in the next section. For now, understand that an average United States resident may eat more than their entire daily intake requirement from added phosphorus alone, and that this amount added during food processing has doubled over the past twenty years.
|World's Healthiest Foods ranked as quality sources of|
|Mushrooms, Crimini||1 cup||15.8||86.40||12||14.0||excellent|
|Sardines||3.20 oz||188.7||444.52||64||6.1||very good|
|Soybeans||1 cup||297.6||421.40||60||3.6||very good|
|Pumpkin Seeds||0.25 cup||180.3||397.64||57||5.7||very good|
|Tuna||4 oz||147.4||377.62||54||6.6||very good|
|Salmon||4 oz||157.6||365.14||52||6.0||very good|
|Lentils||1 cup||229.7||356.40||51||4.0||very good|
|Shrimp||4 oz||134.9||347.00||50||6.6||very good|
|Turkey||4 oz||166.7||260.82||37||4.0||very good|
|Chicken||4 oz||187.1||258.55||37||3.6||very good|
|Beef||4 oz||175.0||240.40||34||3.5||very good|
|Yogurt||1 cup||149.4||232.75||33||4.0||very good|
|Tofu||4 oz||164.4||215.46||31||3.4||very good|
|Oats||0.25 cup||151.7||203.97||29||3.5||very good|
|Green Peas||1 cup||115.7||161.17||23||3.6||very good|
|Broccoli||1 cup||54.6||104.52||15||4.9||very good|
|Cow's milk||4 oz||74.4||102.48||15||3.5||very good|
|Spinach||1 cup||41.4||100.80||14||6.3||very good|
|Asparagus||1 cup||39.6||97.20||14||6.3||very good|
|Brussels Sprouts||1 cup||56.2||87.36||12||4.0||very good|
|Summer Squash||1 cup||36.0||70.20||10||5.0||very good|
|Beet Greens||1 cup||38.9||59.04||8||3.9||very good|
|Mustard Greens||1 cup||36.4||58.80||8||4.2||very good|
|Swiss Chard||1 cup||35.0||57.75||8||4.2||very good|
|Bok Choy||1 cup||20.4||49.30||7||6.2||very good|
|Fennel||1 cup||27.0||43.50||6||4.1||very good|
|Tomatoes||1 cup||32.4||43.20||6||3.4||very good|
|Turnip Greens||1 cup||28.8||41.76||6||3.7||very good|
|Cauliflower||1 cup||28.5||39.68||6||3.6||very good|
|Garbanzo Beans||1 cup||269.0||275.52||39||2.6||good|
|Navy Beans||1 cup||254.8||262.08||37||2.6||good|
|Pinto Beans||1 cup||244.5||251.37||36||2.6||good|
|Kidney Beans||1 cup||224.8||244.26||35||2.8||good|
|Black Beans||1 cup||227.0||240.80||34||2.7||good|
|Sunflower Seeds||0.25 cup||204.4||231.00||33||2.9||good|
|Sesame Seeds||0.25 cup||206.3||226.44||32||2.8||good|
|Lima Beans||1 cup||216.2||208.68||30||2.5||good|
|Dried Peas||1 cup||231.3||194.04||28||2.2||good|
|Brown Rice||1 cup||216.4||161.85||23||1.9||good|
|Sweet Potato||1 cup||180.0||108.00||15||1.5||good|
|Collard Greens||1 cup||62.7||60.80||9||2.5||good|
|Green Beans||1 cup||43.8||36.25||5||2.1||good|
|Mustard Seeds||2 tsp||20.3||33.12||5||4.2||good|
|Romaine Lettuce||2 cups||16.0||28.20||4||4.5||good|
|Bell Peppers||1 cup||28.5||23.92||3||2.2||good|
|Soy Sauce||1 TBS||10.8||23.40||3||5.6||good|
|Sea Vegetables||1 TBS||10.8||18.05||3||4.3||good|
Density>=7.6 AND DRI/DV>=10%
Density>=3.4 AND DRI/DV>=5%
Density>=1.5 AND DRI/DV>=2.5%
Phosphorus, like other minerals, is quite stable to storage, and is not destroyed or created as foods sit on the shelf. Sometimes, as we'll get to in a second, foods that are meant to be stored for long periods will have added phosphorus to help preserve them. As for whole, natural foods, you will find our recommendations for best ways to store each individual food in the How to Select and Store section found in each food's individual website profile.
As explained in a good bit of detail earlier, many plant foods store up a significant amount of phosphorus in the form of phytic acid, and there are certain preparation steps that can increase the availability of phosphorus from this food form. While these preparation steps could potentially be applied to grains, nuts, and seeds as well as beans and legumes, most studies have focused on dried beans. If dried beans are soaked overnight prior to cooking the next day, about half of their phytic acid can be broken down through this soaking process. We do not believe that this step is important for your phosphorus nourishment. At the same time, we also have not seen any research to suggest that you should avoid soaking beans.
The sprouting of beans (or grains or nuts or seeds) prior to cooking also appears to result in breakdown of phytic acid by as much as 50% or more. Of course, sprouting is a process that has an impact on many other molecules besides phytic acid, and many people report better digestion of sprouted foods. As a stage in the development of seeds into a mature plants, sprouts can also be an unusually concentrated food form for many nutrients. Once again, we do not believe that the sprouting of beans or other foods is required for good phosphorus nourishment. At the same time, we know that sprouted foods are commonly eaten and enjoyed by many people, and are well-researched with respect to their nutrient richness. As described earlier, phosphorus is a common food additive in the form of stabilizers, emulsifiers, anticaking agents, and acidity regulators. Below is a brief list of some food additive forms of this mineral.
Some foods often containing significant amounts of added phosphates include lunch meats, ham, sausages, canned fish, baked goods (including baked cookies and bars), baking mixes (like cake and pancake mix), yogurts, cheeses, and soft drinks. Frozen patties, nuggets, and strips made from breaded chicken and other meats can also contain significant amounts of these additives. In the U.S., persons relying on processed foods similar to the list of foods above may obtain over half of their daily phosphorus intake from these additives.
Soft drinks (meaning carbonated cola-type beverages) are processed beverages of special concern in terms of phosphorus because many contain added phosphoric acid in amounts of 400-600 milligrams per can or bottle. (While phosphates are classified as salts of phosphoric acid in technical chemical terms, these two terms are used interchangeably in most practical discussions of phosphorus-based food additives.) As you can see, the amount of phosphoric acid in a single soda can easily exceed over half of the daily requirement for phosphorus, and persons consuming several such sodas each day would exceed the daily requirement from the sodas alone. As described earlier, the significance of routine intake of phosphorus additives is not entirely clear in current research studies. While we would expect to see great imbalances in calcium-to-phosphorus ratio affecting bone health and the health of other body systems, research findings in this area are somewhat mixed and do not lend themselves to simple conclusions. We will talk more about this added phosphorus issue in our Risk of Dietary Toxicity section.
The risk of phosphorus deficiency in the United States is very low. In fact, dietary survey data show that average U.S. adult men eat more than twice the amount of phosphorus that they need each day. Women average 170% of the Dietary Reference Intake (DRI) level. In fact, according to the NHANES 2009-2010 data from the study, "What We Eat in America," most age and gender groups averaged higher than the phosphorus DRI. (Two groups that averaged slightly below the DRI were females 6-11 and 12-19, and we will provide more information about these groups in the next section of this article.) Given the availability of phosphorus-rich foods from every food group, and the very large number of whole, natural foods containing significant amounts of phosphorus, we just don't expect phosphorus deficiency to be a problem in balanced diets based on whole, natural foods.
The need for phosphorus can be greatest at times of greatest bone growth, as typically begins in late childhood and adolescence. Interestingly, this bone connection means that the phosphorus DRI for 9-18 year olds is higher than the DRI for adults 19 and older. This developmentally increased need for phosphorus means that teenagers might need to pay special attention to intake of this nutrient, and in particular, teenage girls, since males average greater intake of phosphorus than females across the age spectrum. NHANES study data from 2009-2010 showed that boys 6-11 years and 12-19 years averaged above the phosphorus DRI. However, this same study data showed that girls 6-11 only averaged 96% of the DRI, with girls 12-19 averaging 95%. So it is easy to see the possible challenge of meeting phosphorus needs during times of rapid bone growth. While it is true that some teenagers can be especially prone to increased intake of processed foods that are likely to contain food additive forms of phosphorus, special attention to this mineral might still be especially important for teenagers following meal plans that are based on whole, natural foods. And in addition, we continue to believe that meal plans based on whole, natural foods provide the greatest health benefits for all age groups.
Because it is such an important component in bone growth, phosphorus needs are usually greatest during the late childhood and adolescent years. (As mentioned earlier, the DRI for 9-18 year olds is 1,250 milligrams, in comparison to 700 milligrams for persons 19 and older.) Since bone growth clearly contributes to the need for increased phosphorus, period of time involving rapid bone growth can pose greater deficiency risk. And as described earlier, while average intake of phosphorus among males 6-18 years exceeded the DRI level, average intake for girls 6-18 only reaches 95-96% of the DRI. While this percentage is very close to 100%, and while intake of processed food containing added phosphates could greatly increase this percentage, we still believe that this developmental period is a time when intake of phosphorus might call for special attention, particularly in a meal plan focused on whole, natural foods. The ways that we regulate phosphorus and calcium concentrations in the body are complex, and involve the kidney, the lungs, and a number of hormones. Disease-based disruptions in any of these factors can create imbalances in acid-base balance that can have serious consequences. Special diets that manage phosphorus intake upward or downward from usual intake levels may be required in the presence of chronic health problems that involve compromise to lung or kidney function, or in the case of diagnosed hormonal problems that can affect blood calcium levels.
The relationship between calcium and phosphorus is complex and important. The same hormones and kidney compensatory measures that regulate calcium levels also tend to affect phosphorus nutrition. Also, large amounts of dietary calcium can impair absorption of dietary phosphorus.
In our Healthiest Way of Eating Plan—composed almost exclusively of HealthyFood using HealthyFood recipes—we averaged 1,326 milligrams of daily calcium and 1,716 milligrams of daily phosphorus, or a ratio slightly in favor of phosphorus at 1.3:1. However, a person eating no HealthyFood fish (which all provide about 350 milligrams of phosphorus or more per serving) and strong intake of tofu and green vegetables (averaging over 150 milligrams of dietary calcium per serving) could easily tip the balance in favor of calcium. And to add in a third comparison, the 19-70 adult male DRI requirements of 800 milligrams for calcium and 700 milligrams for phosphorus would result in a ratio of 1.1 in favor of calcium, while the 19-50 adult female requirements of 1,000 milligrams for calcium and 700 milligrams for phosphorus would result in a ratio of 1.4:1 calcium-phosphorus ratio. So as you can see, the notion of a generalized "ideal" calcium-to-phosphorus ratio does not make much sense. One thing we would say about dietary balances between calcium and phosphorus from whole, natural foods is that they seldom get extremely lop-sided in one direction or the other. While a single food—for example collard greens, with 267 milligrams of calcium per HealthyFood serving and 60 milligrams of phosphorus—could contain a ratio much greater than 2:1, it is somewhat unusual for a balanced, natural, whole foods meal plan to go much further than 2:1 or so in either direction. We have not seen a balanced, natural, whole foods diet that contained tripled the amount of calcium as phosphorus or vice-versa.
As a general recommendation, we encourage consumption of a natural, whole foods meal plan that feels best matched to your own food preferences and health needs, and to let the calcium-to-phosphorus ratio take whatever form that meal plan naturally brings along with it.
Because phytic acid is a form of phosphorus that can bind certain minerals (called divalent cations) including calcium, iron, and zinc, there has been debate over the relationship between phosphorus intake (in the form of phytic acid) and absorption of these other minerals. As described earlier, we have not seen evidence for increased risk of calcium, iron, or zinc deficiency based on intake of phytic acid from whole, natural foods in a balanced meal plan. Also, as described earlier, recent research suggests that breakdown of phytic acid routinely occurs in the large intestine due to enzymatic activity of intestinal bacteria. This research should eventually provide us with more information about absorption of other minerals that might become bound to phytic acid. Of special interest in this area is the potential relationship between phytic acid intake, calcium absorption, and bone health. We've seen several studies in this area showing no negative impact of higher phytic acid whole foods on bone calcium status even when total phosphorus intake reached the 3,000 milligram level, provided that calcium intake stayed relatively high (at approximately 2,000 milligrams). In other words, a calcium:phosphorus ratio of 0.66 from whole, natural foods was not found to compromise bone calcium status. However, we are not sure that this same welcomed finding would hold true for excessive amounts of phosphorus provided in the form of phosphate additives in a processed diet. This concern is one of the many reasons we always prefer whole foods over processed versions.
The risk of toxicity from excessive phosphorus is real, and this is one of a relatively small number of nutrients that U.S. residents frequently eat in excess of recommended amounts. The National Academy of Sciences established a Tolerable Upper Intake Limit (UL) of 4000 mg per day for adolescents and adults. The stricter recommendation for children 1-8 years and adults over 70 years of age is 3,000 milligrams, and for pregnant women the recommendation is 3,500 milligrams. As mentioned earlier, while these amounts might sound generous, it is easy to obtain 1,000 milligrams of phosphoric acid from two cans of soda pop.
The risk associated with excessive dietary phosphorus tends to show up in changes to calcium metabolism. Part of the problem is due to calcium loss, either from the bone or due to reduction in absorption from the intestine. Almost paradoxically, we also see diets too high in phosphorus leading to deposition of calcium in tissues where it doesn't belong, like arteries and kidneys. The reason we see calcium metabolism take this hit is because excessive phosphorus can disturb the tight control of electrolyte levels, leading to changes in the complex hormone balance that regulates the movement of calcium through our bodies.
Note that the problems we see with excess phosphorus intake do not show up immediately, but instead unfold over a long period of time. Parallel to diets too high in sodium or cholesterol, there is a "silent" underlying damage over time that only becomes apparent when things have gotten more severe. So it is a good idea to think about excess phosphorus intake as a potential health risk regardless of your stage of life.
In particular, however, older adults may be more susceptible to detrimental effects of excessive phosphorus. This is because kidney function, even in people without kidney disease, tends to decline with age. As mentioned earlier, this greater susceptibility translates into a UL of 3,000 milligrams for persons over 70 years of age. Also, pregnant women may want to be more careful about dietary phosphorus. This is because pregnancy increases absorption of phosphorus from foods substantially over what it is in a non-pregnant state. Once again, this extra caution translates into a pregnancy UL of 3,500 milligrams.
The good news is that it would be relatively difficult in any age group, although not impossible, to routinely exceed the UL for phosphorus from fresh, natural, unprocessed foods alone. The added phosphorus in foods—phosphates are used as preservatives and flavorings—are often where much of the excess risk comes from. Note that the World's Healthiest Foods recipes will contain almost no added phosphates of any kind. As such, we believe that the closer you stick to our whole and fresh foods cooking strategies, the less likely you'll be to push too hard on phosphorus at the expense of other minerals.
There will be some people whose diets are so high in calories that they will exceed the UL even without added phosphates. For instance, many endurance athletes will routinely eat as many as 6000 calories in a single day. The DRI document clarifies that the UL is not meant to fit this contingency, and that as long as other minerals are similarly well represented, high calorie diets do not present risk related to phosphorus intake.
In 1997, the National Academy of Sciences (NAS) released its Dietary Reference Intake (DRI) recommendations for phosphorus. All DRI recommendations came in the form of Recommended Dietary Allowances (RDAs), except for DRI recommendations involving infants under one year of age. The infant DRIs came in the form of Adequate Intake (AI) levels. The phosphorus DRIs are as follows.
The DRIs also established Tolerable Upper Intake Levels (UL) for phosphorus. These ULs are summarized below.
The Daily Value (DV) for phosphorus is 1000 mg. This is the amount that you'll see on food labels.
As our standard at HealthyFood, we chose the adult DRI of 700 milligrams of daily phosphorus intake.
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