Abstract
Objective
To determine the prevalence of phosphorus-containing food additives in best selling processed grocery products and to compare the phosphorus content of a subset of top selling foods with and without phosphorus additives.
Design
The labels of 2394 best selling branded grocery products in northeast Ohio were reviewed for phosphorus additives. The top 5 best selling products containing phosphorus additives from each food category were matched with similar products without phosphorus additives and analyzed for phosphorus content. Four days of sample meals consisting of foods with and without phosphorus additives were created and daily phosphorus and pricing differentials were computed.
Setting
Northeast Ohio
Main outcome measures
Presence of phosphorus-containing food additives, phosphorus content
Results
44% of the best selling grocery items contained phosphorus additives. The additives were particularly common in prepared frozen foods (72%), dry food mixes (70%), packaged meat (65%), bread & baked goods (57%), soup (54%), and yogurt (51%) categories. Phosphorus additive containing foods averaged 67 mg phosphorus/100 gm more than matched non-additive containing foods (p=.03). Sample meals comprised mostly of phosphorus additive-containing foods had 736 mg more phosphorus per day compared to meals consisting of only additive-free foods. Phosphorus additive-free meals cost an average of $2.00 more per day.
Conclusion
Phosphorus additives are common in best selling processed groceries and contribute significantly to their phosphorus content. Moreover, phosphorus additive foods are less costly than phosphorus additive-free foods. As a result, persons with chronic kidney disease may purchase these popular low-cost groceries and unknowingly increase their intake of highly bioavailable phosphorus.
Keywords: Phosphorus, Food additives, Food supply, Chronic kidney disease
Introduction
An increasing body of epidemiological evidence implicates serum phosphorus and fibroblast growth factor-23 (FGF-23) as independent predictive risk factors for mortality, cardiovascular morbidity and disordered bone metabolism in persons with or without chronic kidney disease (CKD).(1–10) While mechanisms are still not fully understood, dietary phosphorus loads have been shown to increase serum phosphorus in persons with CKD and to increase FGF-23 in healthy persons and those with CKD, independent of its effects on parathyroid hormone.(11–13) As a result, persons with CKD are advised by healthcare providers to limit dietary phosphorus to 800–1000 mg/day and to avoid foods containing phosphorus additives due to their high bioavailability. (14–16)
Persons desiring to limit highly absorbable phosphorus additives must read small font food label ingredient lists to determine the presence of phosphorus additives in foods. While we have demonstrated this as an effective nutrition intervention to reduce serum phosphorus in hemodialysis patients, it may be overly restrictive as the phosphorus content of brand-specific food items is generally unknown. Food labeling regulations do not mandate reporting of phosphorus content on nutrition facts labels. (17)
Phosphorus additives have long been added to convenience and processed foods for their myriad of features including leavening, color and moisture retention, anti-caking, and flavor enhancement (18) and are classified as generally recognized as safe (GRAS) food ingredients (19). No current public data source quantifies the volume of phosphorus-containing food additives used within the United States food supply, however consumers increasingly purchase convenience, fast and processed foods due to time constraints, limited cooking skills, and learned taste preferences.(20–22) It is therefore presumed that the consumption of hidden phosphorus from additives in the United States has increased over time.
Given broad reliance on processed foods, difficulty in reading label ingredient lists and the limited availability of brand-specific phosphorus content information, we sought to determine the prevalence of phosphorus-containing food additives in best-selling grocery products and to compare the difference in phosphorus content and costs in a subset of top selling food products with and without phosphorus additives.
Methods
We obtained a dataset of grocery sales in northeast Ohio for the twelve months ending February 2010 produced by The Nielsen Company. The dataset provided regional sales data for 1.8 billion units of grocery items ($4.7 billion in sales) grouped into 125 categories. All categories were ranked by unit sales from highest to lowest. We selected the top twenty categories by unit sales, then excluded fresh produce, milk, pet food, candy, and paper products because they were minimally processed and known to not contain additives, were not food or not part of typical meals. We focused on the top 200 grocery items by unit sales for each of the remaining 15 categories, creating a dataset of 3000 items to review.
Two trained research assistants independently located each grocery item at area grocery retail stores. For each item, the Universal Product Code (UPC) on the food label was matched to the UPC in the dataset, the ingredient list searched, and the presence or absence of phosphorus-containing food additives recorded. A research coordinator compared the results to ensure uniform data collection and accuracy. When discrepancies existed, the food label was reviewed a third time to resolve the discrepancy. If an item could not be located at grocery retail stores, the manufacturer was contacted for ingredient information. It was necessary to exclude store branded items because the dataset aggregated multiple store brands into a single line item and store brands varied in presence of additives from store brand to store brand.
To explore the quantity of phosphorus contributed by phosphorus additives, the top five grocery items ranked by unit sales in each category that contained phosphorus additives were matched with similar grocery items without food additives. The matched items were chosen from the list of top selling foods identified above when possible. To illustrate, we matched Kraft Macaroni & Cheese Dinner™ with Kraft Organic Cheddar Macaroni & Cheese Dinner™. When the top 5 items included identical items in multiple package sizes (i.e. 8- and 12-ounce packaging), we chose only the top selling product and skipped to the next unique product by sales volume. If an item was discontinued or could not be located at an area grocery retail outlet, we selected the next product in the database as outlined above. The canned vegetable category was excluded from phosphorus analysis because none of the products contained phosphorus additives. The carbonated beverage category was excluded from matching because we were unable to locate similar phosphorus additive-free cola products for comparison.
Each of the top five matched items were purchased at local grocery retail outlets and, if applicable, prepared according to package instructions. When more than one cooking method was suggested, the first cooking method was used. Extra ingredients were added according to package specifications. Distilled water was used when water was required for boiling or reconstitution of dry or condensed products. When type of ingredient was not specified on the package, we used 2% milk for milk, 85% lean for ground beef, unsalted butter for butter, canola oil for oil, and soft margarine for margarine.
All food samples were weighed on a scientific grade scale and packaged in sealed containers. Samples were shipped to Medallion Laboratories, Inc., Minneapolis, MN for analysis of total phosphorus content. Medallion Laboratories ashed the samples at high temperature, digested them in acid, and used inductively coupled plasma to determine phosphorus content. One sample was analyzed for each product. Results were reported as mg phosphorus per 100 gm of product. Serving size was determined from nutrition facts labels on each product. We computed the amount of phosphorus per serving by multiplying laboratory results by measured sample weights.
Sample meals were developed using analyzed matched foods to approximate the mean calorie, protein, carbohydrate and total fat intake of adults in the 2007–2008 NHANES What We Eat in America study (Table 1).(23) Fruits, vegetables, milk and margarine were included in menus to more closely approximate “typical” meals. Meal costs were calculated using prices from sales receipts for the items analyzed and local grocery prices for any additional items.
Table 1.
Day 1 menu used to estimate phosphorus content and cost of meals with and without phosphorus additives
| Menu with Phosphorus Additives | Menu without Phosphorus Additives |
|---|---|
|
| |
| Breakfast | Breakfast |
| Cheerios, 1.5 cups | Nature's Path Organic Whole O's, 1.5 cups |
| 1% milk, 6 oz | 1% milk, 6 oz |
| Schwebels Italiano bread, 1 slice | Nickles Italian bread, 1 slice |
| Margarine, 1 teaspoon | Margarine, 1 teaspoon |
| Sunny Delight, 8 oz | Tampico citrus punch, 8 oz |
| Lunch | Lunch |
| Grilled cheese sandwich | Grilled cheese sandwich |
| Home Pride butter top wheat bread, 2 slices | Nickles split top wheat bread, 2 slices |
| Kraft Singles American cheese, 2 slices | Horizon Organic American cheese, 2 slices |
| Margarine, 1 teaspoon | Margarine, 1 teaspoon |
| Lay's cheddar and sour cream potato chips, 1 oz | Ruffles cheddar and sour cream potato chips, 1 oz |
| Celery sticks, 1 cup raw | Celery sticks, 1 cup raw |
| Apple, 1 raw | Apple, 1 raw |
| Ocean Spray cranberry juice cocktail, 12 oz | Ocean Spray cranberry juice cocktail, 12 oz |
| Dinner | Dinner |
| Hillshire Farms polska kielbasa ring, 6 oz | Johnsonville original brats links, 6 oz |
| Ore Ida golden crinkles fries, 6 oz | Cascadian Farms golden crinkle cut fries, 6 oz |
| Green beans, .5 cup cooked | Green beans, .5 cup cooked |
| Yoplait strawberry yogurt, 6 oz | Breyer strawberry yogurt, 6 oz |
| Coca-cola, 12 oz | A&W root beer, 12 oz |
Data was analyzed using JMP 9 by SAS. Data is reported as mean±SE with significance set at p<0.05.
Results
The labels of 2394 (80%) commonly purchased branded grocery products in northeast Ohio were reviewed for phosphorus additives. 606 (20%) of the food items were excluded due to inability to locate the products, items were store branded, or were discontinued. The grocery items reviewed comprised 25% of groceries (by unit volume) sold in northeast Ohio during the 52-week period included in the dataset.
Overall, phosphorus-containing food additives were present in 44% of the products reviewed. There was wide variation in the presence of phosphorus food additives between categories ranging from 72% of prepared frozen foods to 0% of canned vegetables (Figure 1). Food additives were particularly common in prepared frozen foods (72%), dry food mixes (70%), packaged meat (65%), bread & baked goods (57%), soup (54%) and yogurt (51%) categories.
Figure 1.
Prevalence of phosphorus containing food additives by food category (n=2394 total foods).
We successfully matched 56 (86%) of the 5 top-selling grocery items containing phosphorus additives in 13 categories with similar products without phosphorus additives. Foods with phosphorus additives contained an average of 67±14 mg phosphorus/100 gm more than the matched non-additive containing foods (178±27 mg/100gm and 111±15 mg/100 gm respectively; p=0.03). There was notable variation between grocery categories in the amount of extra phosphorus present in additive-containing foods, ranging from 0 mg/100 gm for frozen vegetables to 347 mg/100 gm for cheeses. In addition to cheese, cereal, packaged meats, dry food mixes, snacks, condiments and yogurt categories showed substantial differences in phosphorus content between matched additive and non-additive containing foods (Table 2).
Table 2.
Phosphorus content of foods with and without phosphorus additives. Results are shown as means and standard errors.
| Category | Number of Matched Pairs | Phosphorus mg/100 gm |
||
|---|---|---|---|---|
| Additives | No Additives | Difference | ||
| Prepared frozen foods | 2 | 86 (4) | 72 (0) | 14 (3) |
| Dry food mixes | 3 | 184 (29) | 121 (3) | 63 (31) |
| Packaged meat | 5 | 308 (73) | 190 (47) | 118 (32) |
| Bread & baked goods | 4 | 121 (18) | 103 (10) | 18 (15) |
| Soup | 5 | 23 (3) | 20 (3) | 3 (5) |
| Yogurt | 5 | 126 (23) | 77 (2) | 49 (25) |
| Frozen vegetables | 4 | 71 (2) | 71 (6) | 0 (5) |
| Juice drinks, shelf stable | 5 | 4 (2) | 0 (0) | 4 (2) |
| Cereal | 4 | 313 (62) | 176 (47) | 137 (63) |
| Ready serve foods | 5 | 80 (29) | 56 (19) | 24 (12) |
| Snacks | 5 | 202 (22) | 145 (27) | 57 (13) |
| Cheese | 4 | 753 (87) | 407 (8) | 347 (79) |
| Condiments & sauces | 5 | 99 (22) | 46 (9) | 53 (16) |
| ALL CATEGORIES | 56 | 178 (27) | 111 (15) | 67 (14) |
In sample meals, phosphorus additive foods contributed an average excess phosphorus burden of 736±91mg per day (Table 3). Phosphorus additive-free meals cost an average of $2.00±.42 more per day.
Table 3.
Phosphorus content and cost of meals with and without phosphorus additives. Results are shown as means and standard errors.
| Phosphorus, mg | Cost, $ | ||||||
|---|---|---|---|---|---|---|---|
|
|
|||||||
| Meal | Number of Meals | With additives | No additives | Difference | With additives | No additives | Difference |
| Breakfast | 4 | 540 (36) | 343 (30) | 197 (16) | 1.92 (.33) | 2.56 (.52) | −0.64 (.20) |
| Lunch | 4 | 513 (52) | 293 (20) | 221 (43) | 2.59 (.19) | 2.88 (.18) | −0.28 (.03) |
| Dinner | 4 | 735 (89) | 417 (44) | 318 (54) | 3.25 (.20) | 4.32 (.20) | −1.07 (.28) |
| ENTIRE DAY | 788 (138) | 1053 (57) | 736 (91) | 7.76(.18) | 9.76 (.46) | −2.00 (.42) | |
Discussion
We and other researchers have reported that persons may unknowingly consume excess highly bioavailable phosphorus via food additives as part of the standard American diet.(16, 17, 24–30) In this study we showed that nearly half of the best-selling grocery foods items in our region contain phosphorus additives. One-half to three-quarters of all prepared frozen foods, dry food mixes, packaged meats, breads and baked goods, soups and yogurts reviewed contained these additives (Figure 1).
Overall, the additives contributed a significant amount of phosphorus compared to additive-free foods, averaging 67 mg/100 g of additional phosphorus, but there was significant variation in extra phosphorus both within and between categories (Table 2). For instance, bread, canned vegetables and soups had minimal difference in phosphorus content between additive containing and additive-free products. This knowledge can help persons avoid phosphorus from additives and allow clinicians to focus their patient education efforts on food categories most likely to contain appreciable amounts of phosphorus additives. Understanding the magnitude of content difference is important when teaching patients how to self-dose phosphorus binders based on dietary phosphorus intake (phosphorus unit system).(31)
The cumulative effect of consuming phosphorus additives is unknown. We found that a diet comprised of multiple common processed foods with phosphorus additives contributed 736 mg/day more phosphorus (41% increase) than a diet consisting of only non-additive foods. Since these additives are highly bioavailable in the gastrointestinal tract, the impact of this excess phosphorus may be substantial. While a person with fully functioning kidneys may be able to maintain serum phosphorus within the normal range despite such a phosphorus load, persons with advanced kidney disease require dialysis and sufficient dosing of phosphorus binding medications to remove excess phosphorus (32). As a result, dialysis patients may have a particularly difficult time maintaining normal serum phosphorus levels if they consume multiple phosphorus-additive containing grocery foods. Our findings suggest reduction of additive phosphorus is an important part of phosphorus management in these patients.
Additive-containing meals were $2.00 cheaper per day than non-additive containing meals. This finding supports the potential for socioeconomic-based health disparities for developing kidney, bone and cardiovascular disease or increased morbidity and mortality as described by Gutierrez in both dialysis and non-dialysis CKD populations (33, 34). While $2.00/day may sound insignificant, average household supplemental food assistance benefits (SNAP) average only $287/month, or $4.30 per person per day.(35) Families eligible for SNAP are unlikely to afford $240 per month additional food costs to avoid phosphorus additives. ($8/day × 30 days/month).
This is the first study to survey the prevalence of phosphorus additives in commonly sold branded grocery food items and the findings have several implications for patients, healthcare providers, policy makers, manufacturers and researchers. Patients and healthcare providers should become knowledgeable about the ubiquitous use of highly bioavailable phosphorus additives in the food supply in order to enhance dietary avoidance. Reading food ingredient labels with magnifiers for ingredients containing the letters “phos” is one tested, simple educational intervention that can be employed.(17) It may be most time efficient to focus attention to ingredient labels in specific food categories with high prevalence of phosphorus additives and significantly greater phosphorus content such as dry food mixes, packaged meats, soups, yogurt, cheese and yogurt. Development of regularly updated lists of brand-specific additive-free foods may guide patients in purchasing groceries.
Policymakers should require phosphorus content as part of the standard Nutrition Facts Panel so that patients, clinicians and researchers can better assess dietary phosphorus intake in clinical and research settings. Finally, researchers should undertake studies to determine if reducing dietary phosphorus loads via food additive avoidance reduces cardiovascular risk in CKD and other populations.
There are a few important limitations to our study. First, the number of matched products analyzed within each grocery category was small due to budget limitations and inability to identify additive-free foods that closely mirrored several top selling food items. Second, we analyzed only one sample of each food item. It is not known how much variation in phosphorus content is present within individual food products, Third, this study was limited to grocery sales in northeast Ohio, representing $4.7 billion in retail grocery sales. By comparison, the U.S. Census Bureau 2010 Annual Retail Trade Report documents $521.4 billion in grocery sales.(36) However, the majority of grocery items reviewed were common, widely marketed national brands. Finally, our study included only brand name food items. Store branded foods vary in phosphorus additives content, but are generally less costly then brand name groceries. As a result, use of store branded foods may alter the results of the cost estimates we report.
Practical Application
Phosphorus-containing food items are common among the best selling grocery food items, and are particularly present in frozen meals, dry food mixes, packaged meats, breads and baked goods, soups and yogurts. The additives contributed a significant amount of phosphorus compared to additive-free foods. Modeled menus with additives contained nearly 750 mg more phosphorus per day and were less costly than phosphorus additive free meals. Because phosphorus additives are highly bioavailable, patients eating these commonly purchased foods may have difficulty maintaining serum phosphorus within the normal range. These findings suggest emphasis on label reading to avoid phosphorus additives is an appropriate strategy to manage serum phosphorus in persons with kidney disease in the absence of phosphorus content on labels.
Table 4.
Day 2 menu used to estimate phosphorus content and cost of meals with and without phosphorus additives
| Menu with Phosphorus Additives | Menu without Phosphorus Additives |
|---|---|
|
| |
| Breakfast | Breakfast |
| Sugardale bacon, 4 slices | Oscar Mayer smoked uncured bacon, 4 slices |
| Egg, 1 | Egg, 1 |
| Ore Ida hash browns country style, .5 cup cooked | Alexia hash browns, .5 cup cooked |
| Home Pride butter top wheat bread, 1 slice | Nickles split top wheat bread, 1 slice |
| Margarine, 1 teaspoon | Margarine, 1 teaspoon |
| Sunny Delight, 8 fl oz | Tampico citrus punch, 8 fl oz |
| Lunch | Lunch |
| Ball Park bun size franks, 1 | Coleman natural uncured beef hot dog, 1 |
| Kraft macaroni and cheese original, 1 cup | Kraft organic macaroni and cheese dinner, 1 cup |
| Home Pride butter top wheat bread, 1 slice | Nickles split top wheat bread, 1 slice |
| Baby carrots, 1 cup raw | Baby carrots, 1 cup raw |
| Pear, .5 cup canned | Pear, .5 cup canned |
| Gatorade orange, 20 fl oz | Propel citrus punch, 20 fl oz |
| Dinner | Dinner |
| Chicken Alfredo | Chicken Alfredo |
| Swanson premium chunk chicken breast, 4 oz | Valley Fresh chunk chicken, 4 oz |
| Ragu classic alfredo, .5 cup | Classico alfredo, .5 cup |
| Pasta, 1 cup | Pasta, 1 cup |
| Schewbels Italiano bread, 1 slice | Nickels Italian bread, 1 slice |
| Birdseye steamfresh broccoli cuts, 1 cup | Birdseye steamfresh broccoli cuts, 1 cup |
| Margarine, 1 teaspoon | Margarine, 1 teaspoon |
| Pepsi, 12 fl oz | A&W Rootbeer, 12 fl oz |
Table 5.
Day 3 menu used to estimate phosphorus content and cost of meals with and without phosphorus additives
| Menu with Phosphorus Additives | Menu without Phosphorus Additives |
|---|---|
|
| |
| Breakfast | Breakfast |
| Sugardale bacon, 4 slices | Oscar Mayer smoked uncured bacon, 4 slices |
| Cocoa Puffs cereal, 1.25 cups | Cocoa Pebbles cereal, 1.25 cups |
| 1% milk, 6 fl oz | 1% milk, 6 fl oz |
| Home Pride butter top wheat bread, 1 slice | Nickles split top wheat bread, 1 slice |
| Margarine, 1 teaspoon | Margarine, 1 teaspoon |
| Sunny Delight, 8 fl oz | Tampico citrus punch, 8 fl oz |
| Lunch | Lunch |
| Chef Boyardee spaghetti and meatballs, 2 cups | Chef Boyardee shells and meatballs, 2 cups |
| Schwebels Italiano bread, 1 slice | Nickles Italian bread, 1 slice |
| Margarine, 1 teaspoon | Margarine, 1 teaspoon |
| Canned peaches, .5 cup | Canned peaches, .5 cup |
| Pepsi, 12 fl oz | A&W Rootbeer, 12 fl oz |
| Dinner | Dinner |
| Mrs. T's potato and cheese pierogie, 113g | Contes potato, cheese and onion pierogie, 113 g |
| Schwebels Italiano bread, 1 slice | Nickels Italian bread, 1 slice |
| Birdseye Steamfresh mixed vegetables, .5 cup | Birdseye Steamfresh mixed vegetables, .5 cup |
| Margarine, 1 teaspoon | Margarine, 1 teaspoon |
| Yoplait strawberry yogurt, 6 ounces | Breyer strawberry yogurt, 6 ounces |
| Gatorade orange, 20 fl oz | Propel citrus punch, 20 fl oz |
Table 6.
Day 4 menu used to estimate phosphorus content and cost of meals with and without phosphorus additives
| Menu with Phosphorus Additives | Menu without Phosphorus Additives |
|---|---|
|
| |
| Breakfast | Breakfast |
| Sugardale bacon, 4 slices | Oscar Mayer smoked uncured bacon, 4 slices |
| Cinnamon Toast Crunch cereal, 1.5 cups | Cinnamon Chex cereal, 1.5 cups |
| 1% milk, 6 fl oz | 1% milk, 6 fl oz |
| Home Pride butter top wheat bread, 1 slice | Nickles split top wheat bread, 1 slice |
| Margarine, 1 teaspoon | Margarine, 1 teaspoon |
| Sunny Delight, 8 fl oz | Tampico citrus punch, 8 fl oz |
| Lunch | Lunch |
| Campbells tomato soup, 1 cup prepared | Valuetine tomato soup, 1 cup prepared |
| Velveeta shells and cheese, 1 cup | Kraft organic white cheddar organic shells, 1 cup |
| Baby carrots, 1 cup | Baby carrots, 1 cup |
| Coca-Cola, 12 fl oz | A&W Rootbeer, 12 fl oz |
| Dinner | Dinner |
| Broccoli, rice, cheese and chicken casserole | Broccoli, rice, cheese and chicken casserole |
| Swanson premium chunk chicken breast, 3.3 oz | Valley Fresh premium chunk chicken breast, 3.3 oz |
| Campbells cream of mushroom, 1.8 oz | Campbells cream of mushroom, 1.8 oz |
| Campbells cream of chicken soup, 1.8 oz | Health Valley Organic cream of chicken soup, 1.8 oz |
| Birdseye Steamfresh broccoli cuts, 2 oz. | Birdseye Steamfresh broccoli cuts, 2 oz. |
| Instant rice, .33 cup | Instant rice, .33 cup |
| Velveeta loaf, 2.7 ounces | Horizan Organic American single, 4 slices |
| Onion, .2 small | Onion, .2 small |
| Butter, 8 teaspoons | Butter, 8 teaspoons |
| 1% milk, 8 teaspoons | 1% milk, 8 teaspoons |
| Apple, 2 inch diameter | Apple, 2 inch diameter |
| Gatorade orange, 20 oz | Propel citrus punch, 20 oz |
Acknowledgements
We wish to extend a special thank you to Srilekha Sarathy Sayre, Julie Pencak, Michael Ivers and Marquisha Marbury for their diligence in each locating hundreds of grocery items and reading the small print ingredient lists to identify presence of phosphorus additives. Without you, this study would not have been possible.
Support This work was supported by grants MD002265 and RR024989 from the National Institutes of Health.
Footnotes
Financial Disclosure: No conflict of interest: León, Sullivan, Sehgal
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