- Co-Authored by Jill Parnell
Phosphorus is a mineral people rarely think about. Sure, it's important for bone health but it doesn't get nearly the same press and attention as calcium and vitamin D. That's because most of us get plenty of phosphorus in our diets from meat, milk, grains and, increasingly so, from processed food.
New population-based evidence suggests that excessive dietary phosphorus intake may lead to increased risk of cardiovascular disease and death. Where is all of this excess phosphorus in our diet coming from? Phosphate additives in processed foods, of course!
Next to calcium, phosphorus is the second most abundant mineral in our bodies, mostly stored away as a structural component of bone. In addition to its role in bone health, phosphorus is also important for metabolism of carbs and fat, kidney function and nerve transmission.
Adults 19 years and older are currently recommended to consume 700 mg per day based on the RDA (1), yet current intake levels far exceed this and have risen ~ 15% in the last 20 years (1,2). Historically, concerns related to elevated phosphorus intake have been limited to patients with kidney disease - when the kidneys are not functioning, phosphorus cannot be eliminated and blood levels rise.
The negative impact of high phosphorus levels in kidney failure patients on dialysis is well-known, namely the calcification of blood vessels leading to profound cardiovascular disease and increased mortality risk (3). But could excessive phosphorus intake potentially have the same consequences for otherwise-healthy individuals?
In a recent issue of the American Journal of Clinical Nutrition, Chang et al. (2) published data taken from NHANES indicating an increased risk of all-cause mortality when phosphorus intake rose above 1400 mg per day, double the current RDA. Similarly, high blood phosphorus levels have been linked to increased risk of cardiovascular disease and the presence of sub-clinical atherosclerosis in healthy individuals, particularly men (3).
Increasingly, experts are voicing concerns that phosphorus intakes exceeding nutrient needs are damaging our cardiovascular health (4). And they are not concerned about the phosphorus found in a glass of skim milk!
There are two distinct sources of phosphorus in the diet - organic, which is found naturally in food, and inorganic, which is present as phosphate additives.
Organic phosphorus. Food sources of organic phosphorus include sources of protein like meat, eggs, milk and legumes, as well as whole grains. Fruits and vegetables contain negligible phosphorus. Absorption of organic phosphorus, however, varies depending upon source. Approximately 40 - 60% of organic phosphorus is absorbed from animal products, whereas less than 50% is absorbed from plant source because of phytates (1).
- Low-fat dairy products: All dairy products such as milk, cheese and yogurt contain naturally-occurring phosphorus.
- Eggs: Most of the organic phosphorus found in eggs is contained within the yolk; egg whites are low in phosphorus.
- Meat: Beef, veal and pork are high in phosphorus, containing over 200 mg in a 3 oz. serving.
- Fish: The highest sources of organic phosphorus include cod, salmon and sardines.
- Legumes and beans: Legumes such as lentils and beans are very high sources of organic phosphorus, though it is poorly absorbed.
- Nuts: Almonds and peanuts are among the richest nut sources of
- Whole grains: Refined, white grains are poor sources of phosphorus as the mineral is stripped in refinement.
Inorganic phosphorus. Over 50% of processed food items on grocery store shelves have phosphate additives on the ingredient list. Why are phosphate additives so widespread? They have many uses: emulsifers, stabilizers, leavening agents, flavour enhancers and acidulants. They are also absorbed at roughly 100%, so a little bit goes a long way in terms of phosphorus intake.
Common phosphate additives include phosphoric acid, calcium phosphate and sodium phosphate. For a complete list of phosphate additives, check out the International Food Additives Council "Phosphates Use in Foods".
- Processed cheese: Imitation cheese slices and spreads are among the worst phosphate additive offenders. Di- and tri-sodium phosphate act as emulsifiers and protein stabilizers.
- Chicken products: Many chicken products (including chicken breasts!) have pyrophosphate and polyphosphate additives, which help to bind moisture and keep meat moist.
- Beverages: Phosphoric acid is an acidulant added to colas to give a tart taste. In fact, many sugar-sweetened AND sugar-free carbonated beverages and powdered drink mixes contain phosphate additives.
- Processed potatoes: Pyrophosphates are used in French fries and hash browns to prevent darkening.
- Packaged meat: Polyphosphates maintain juiciness and increase shelf life in processed meats including bacon, sausages, hams and deli meats.
- Cereals: Many dry cereals, and even some healthy ones, contain sodium and calcium phosphates to modify cereal colour. Watch out for instant hot cereals too, as phosphate additives decrease cooking time.
No Baloney's advice? No need to shy away from whole, unprocessed lean meats, dairy, legumes, nuts or whole grains... just reduce your intake of processed foods. Processed foods may offer convenience, but they also offer unhealthy amounts of many nutrients - think fat, salt and sugar, just to name a few. It appears as if we can add phosphate additives to this list as well.
This is one place where a food label will not help you - phosphorus IS NOT listed on the Nutrition Facts table - you need to go right to the ingredient list. Look for anything with "phos-" on the ingredient list to pick out the phosphate additives.
The European Food Safety Authority just reviewed phosphate additive safety at the prompting of health groups (5). Although they concluded that consistent evidence was lacking, they acknowledge that more long-term safety research is needed. Keep in mind, getting harmful food ingredients banned is a SLOW process - case in point, trans fats were introduced in vegetable shortening in 1911, we realized they were bad in the 1990s and they are finally on their way out... at least we hope they are!