Phosphorus is a vital mineral that is naturally present in numerous foods and also available as a dietary supplement. It performs a multitude of critical functions within the body. Notably, phosphorus is a fundamental component of bones, teeth, and cell membranes. It plays a key role in activating enzymes and maintaining the body’s blood pH within a healthy range. Furthermore, phosphorus is crucial for the normal functioning of nerves and muscles, including the heart, and serves as a building block for our genetic material, forming DNA, RNA, and ATP—the body’s primary energy source. [1]
The kidneys, bones, and intestines work in concert to meticulously regulate phosphorus levels in the body. When dietary phosphorus intake is insufficient or absorption is inadequate, the body initiates several mechanisms to conserve phosphorus stores and maintain normal levels. These include the kidneys excreting less phosphorus in the urine, the digestive tract increasing its efficiency in phosphorus absorption, and the bones releasing stored phosphorus into the bloodstream. [1] Conversely, if the body has sufficient phosphorus, these organs adjust their functions accordingly to maintain balance.
Recommended Daily Intake of Phosphorus
Understanding the recommended daily intake is crucial for maintaining optimal health. Health organizations have established guidelines to help individuals ensure they are getting enough phosphorus through their diet.
Recommended Dietary Allowance (RDA)
The Recommended Dietary Allowance (RDA) for phosphorus for adult men and women aged 19 years and older is 700 mg per day. This requirement remains consistent for women during pregnancy and lactation, also set at 700 mg daily. [2] This level is considered sufficient to meet the needs of nearly all healthy individuals.
Tolerable Upper Intake Level (UL)
While phosphorus is essential, excessive intake can also pose health risks. The Tolerable Upper Intake Level (UL) is defined as the maximum daily intake that is unlikely to cause adverse health effects. For phosphorus, the UL for adult men and women aged 19 to 70 years is 4,000 mg per day. For adults over 71 years of age, the UL is slightly lower at 3,000 mg daily. For pregnant and lactating women aged 14 to 50 years, the ULs are 3,500 mg and 4,000 mg per day, respectively. It is important to stay below these upper limits to avoid potential health issues associated with excessive phosphorus consumption.
Phosphorus and Its Impact on Health
Phosphorus plays a significant role in various aspects of health, and its balance in the body is crucial. Imbalances, whether deficiency or excess, can contribute to several health conditions.
Chronic Kidney Disease (CKD)
The kidneys are central to maintaining healthy phosphorus levels. In individuals with healthy kidney function, excess phosphorus is efficiently removed from the body through urine. However, Chronic Kidney Disease (CKD) impairs this function, leading to a buildup of phosphorus in the blood, a condition known as hyperphosphatemia. Studies have demonstrated that individuals with CKD often exhibit elevated phosphate levels compared to those with normal kidney function. [3] This elevation can accelerate the progression of CKD and increase the risk of cardiovascular disease, bone disorders, and mortality. [4, 5] Research suggests that patients with higher phosphate levels and more advanced CKD stages, particularly those undergoing dialysis, face a greater risk of disease progression and mortality compared to those with milder CKD forms. [6-9]
Despite these associations, it remains unclear whether lowering phosphate levels in CKD patients definitively improves long-term health outcomes. Dietary phosphorus recommendations for CKD patients vary depending on disease progression and individual blood phosphorus levels. Some guidelines advise limiting animal protein intake while increasing plant protein sources and carefully reading food labels to avoid phosphate additives. [4] Plant-based proteins like legumes, nuts, and seeds contain phytates, which can reduce phosphorus absorption. [10] Phosphate binders, medications taken with meals to reduce phosphorus absorption in the gut, are also sometimes prescribed.
Cardiovascular Disease (CVD)
Emerging research suggests a link between excess phosphorus and cardiovascular health. Some studies indicate that high phosphorus levels may promote calcification, or hardening, of heart arteries and contribute to inflammation. [11] Elevated phosphate levels have been associated with an increased risk of Cardiovascular Disease (CVD). A meta-analysis of six cohort studies involving over 120,000 healthy adults followed for up to 29 years revealed a 36% increased risk of death from CVD and all causes in participants with the highest serum phosphorus levels compared to those with the lowest levels. [12] Notably, the increased risk of all-cause mortality was primarily observed in men, not women.
Foods rich in phosphorus, such as animal proteins, often also contain other components linked to CVD, like saturated fat. This makes it challenging to isolate phosphorus as a sole risk factor for CVD. It is unclear whether phosphorus itself increases CVD risk or if high levels are indicative of other underlying risk factors. Research is ongoing to determine if dietary phosphorus restriction can prevent CVD in otherwise healthy adults. [2]
Bone Health
Maintaining the right balance of phosphorus is also critical for bone health. Elevated phosphorus levels can disrupt the delicate hormonal balance of phosphorus, calcium, and vitamin D, which are essential for regulating bone metabolism. Animal studies have indicated that high dietary phosphorus intake can negatively impact bone health. However, the evidence in humans is less conclusive, partly due to challenges in accurately estimating phosphorus intake. Most studies measure blood phosphorus levels, which may not accurately reflect total dietary phosphorus intake as the majority of phosphorus is stored in bones, and the body tightly regulates blood levels. However, research has shown that higher intakes of phosphate additives from processed foods like cola beverages and salad dressings, which are highly absorbable, are associated with adverse effects on bone metabolism. [13] These effects include increased fracture risk and reduced bone mineral density. [14] Further research is needed to fully understand the complex relationship between phosphorus intake and bone health in humans.
The Hidden Dangers of Soda Consumption
The detrimental effects of soda and sugary beverages on health are well-documented. They are recognized risk factors for diabetes, heart disease, and obesity. However, soda’s impact extends to dental health as well. The issue is not solely sugar content, which fuels bacteria in the mouth leading to tooth decay, but also the acids added to both regular and diet sodas. Most sodas contain phosphoric acid, citric acid, or both. Frequent soda consumption exposes teeth to these acids, eroding tooth enamel, the protective outer layer. This erosion makes teeth vulnerable to cavities, decay, and increased sensitivity to tooth pain as nerves become exposed. Limiting soda intake to occasional treats and opting for acid-free alternatives like seltzer water can significantly benefit dental health.
Excellent Food Sources of Phosphorus
Phosphorus is widely available in a variety of foods. Understanding the best food sources can help individuals ensure they are meeting their daily phosphorus needs through diet.
A wide array of foods naturally contain phosphorus, with particularly rich sources including dairy products, red meat, poultry, seafood, legumes, and nuts. Phosphorus from these sources is classified as organic phosphorus. Organic phosphorus is absorbed more efficiently from animal-based foods compared to plant-based foods. Plant foods like seeds, legumes, and whole grains contain phosphorus in a storage form known as phytates or phytic acid, which can hinder mineral absorption. Anti-nutrients: phytates or phytic acid The human body lacks the enzyme required to effectively break down phytic acid. As a result, phytates can bind not only to phosphorus but also to other essential minerals like iron and zinc as they pass through the digestive system. Food preparation techniques such as cooking, sprouting, and soaking can help to break down phytic acid, thereby enhancing phosphorus absorption from plant-based foods.
In contrast, inorganic phosphorus is a processed form added to foods as a preservative to enhance color, moisture, and texture. It is prevalent in fast foods, processed meats, canned and bottled beverages, and numerous other processed food items. Phosphate additives and preservatives are significant contributors to overall phosphorus intake, accounting for up to 30% of phosphorus consumption in the U.S. diet. [4] Inorganic phosphorus is highly absorbable in the gut, with an absorption rate of approximately 90%, significantly higher than the 40-60% absorption rate from natural organic phosphorus found in animal and plant foods. [15] Phosphorus is also available in supplement form for individuals who may require additional intake under medical guidance.
Here are some key food categories rich in phosphorus:
- Dairy: Milk, yogurt, cheese (especially hard cheeses like Parmesan and cheddar) are excellent sources. Dairy
- Salmon: This fatty fish is not only rich in omega-3 fatty acids but also a good source of phosphorus. Aquatic foods
- Beef: Provides a substantial amount of phosphorus, especially lean cuts.
- Poultry: Chicken and turkey are good sources, particularly dark meat.
- Pork: Similar to beef and poultry, pork contributes to phosphorus intake.
- Legumes: Lentils, beans, and chickpeas are plant-based sources of phosphorus. Legumes-pulses
- Nuts and Seeds: Almonds, walnuts, sunflower seeds, and pumpkin seeds are good sources.
- Whole Wheat Breads and Cereals: Contribute phosphorus, especially when fortified. Whole wheat breads and cereals
- Certain Vegetables: Asparagus, tomatoes, and cauliflower contain phosphorus, although in smaller amounts compared to other food groups. Vegetables
- Processed Foods: Often contain inorganic phosphorus as additives, particularly deli meats, bacon, sausage, sodas, sports drinks, and other bottled beverages. Processed foods sodas sports drinks
Recognizing Phosphorus Deficiency and Toxicity
Maintaining balanced phosphorus levels is essential. Both deficiency and toxicity can lead to health problems, although they differ significantly in their causes and prevalence.
Phosphorus Deficiency (Hypophosphatemia)
Phosphorus deficiency, or hypophosphatemia, is characterized by abnormally low blood phosphorus levels. It is important to note that blood phosphorus levels may not always reflect the total phosphorus status in the body, as the majority is stored in bones and teeth. The most common causes of phosphorus deficiency are underlying kidney problems or hyperparathyroidism, a condition involving excessive parathyroid hormone release, which leads to increased phosphorus excretion through urine. Additionally, prolonged overuse of aluminum-containing antacids can bind to phosphorus in the digestive tract, increasing the risk of deficiency.
A particularly serious form of hypophosphatemia can occur in refeeding syndrome, observed in severely malnourished individuals. Patients with conditions like cancer, advanced liver disease, alcohol abuse, or anorexia nervosa who are started on nutritional support may develop this condition. Due to their starved state, their bodies are less able to process nutrients efficiently. Sudden reintroduction of nutrition can trigger refeeding syndrome. A rapid influx of nutrients and calories causes an insulin surge, leading to rapid shifts in electrolytes and fluids in the blood. This can cause blood levels of essential electrolytes like potassium, phosphorus, and magnesium to drop precipitously. Untreated refeeding syndrome can result in severe complications, including respiratory failure, coma, cardiac arrest, and even death. This risk can be mitigated by providing intravenous electrolyte supplementation prior to initiating nutritional feedings in at-risk individuals.
Symptoms associated with phosphorus deficiency can include:
- Poor appetite
- Anemia
- Muscle weakness
- Bone pain
- Bone disease (osteomalacia in adults, rickets in children)
- Confusion
- Increased susceptibility to infections
Phosphorus Toxicity (Hyperphosphatemia)
Phosphorus toxicity, or hyperphosphatemia, resulting from excessive phosphorus intake is rare in healthy individuals because the body has efficient regulatory mechanisms to manage excess levels. It is more likely to occur with excessive supplement use, although phosphorus supplements are not commonly used, and typically do not contain high doses. [2] Hyperphosphatemia is more frequently observed in individuals with impaired kidney function, as discussed earlier.
Some individuals with hyperphosphatemia may not experience any noticeable symptoms. However, others may develop calcium deposits and hardening of soft tissues throughout the body, including the kidneys, due to disruptions in normal calcium metabolism. This calcification of soft tissues can lead to various health complications depending on the location and extent of the deposits.
Interesting Facts About Phosphorus
- Phosphorus is the second most abundant mineral in the body, surpassed only by calcium. Approximately 85% of the body’s phosphorus is stored in bones and teeth, highlighting its critical role in skeletal health.
- Inorganic phosphorus, in the form of phosphate additives, is commonly found in a wide range of processed foods, including processed meats, baked goods, sodas, iced teas, bottled coffee drinks, and flavored waters. Common phosphate additives to look for on ingredient lists include phosphoric acid, dicalcium phosphate, sodium phosphate, and trisodium phosphate. Individuals following a low-phosphorus diet should be particularly vigilant about these “hidden” sources of phosphorus by carefully scrutinizing food labels to identify and limit their intake of foods containing phosphate additives.
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References
Last reviewed March 2023
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