Food Product Design: Design Elements - January 2001 - Calcium's Role

January 2001

Calcium's Role

By Suanne Klahorst
Contributing Editor

Calcium fortification has become one of the most sought- after benefits that consumers look for when reading and comparing nutritional labeling. Some of this awareness is payback for public health strategies developed by national health and nutrition organizations to address the "calcium crisis" and to raise calcium to the status of "supernutrient."

The government’s expert panel on Nutrition Monitoring classified the nation’s generally low calcium intake as an issue that warrants public health monitoring. For all ages, calcium intake is critical to bone health. However, a new awareness of calcium’s critical importance in growing children and aging adults has created a market for greater varieties of calcium-fortified foods. Up to 5% of bone calcium is reabsorbed or replaced in adults’ bones annually, a process that requires a consistent calcium source in the diet. The bones contain 98% of the body’s calcium content in the form of crystals. The remaining 2% of calcium is evenly distributed among teeth and the body’s cells. In addition to strong bones and teeth, calcium participates in important physiological functions, including muscle contraction, heartbeat and nerve function. Blood calcium, or plasma calcium, represents only 0.1% of the total calcium, however it’s precisely regulated at a level of 100 mg/L in a number of different chemical forms. The majority of the plasma calcium — 65 mg (ml)/L — is free ionized CA2+, 30 mg/L is bound to plasma proteins and 5 mg/L is in a nonionized form.

Got enough milk?
Dairy foods provide the most concentrated sources of calcium in the American diet (and the source from which the majority have traditionally obtained their daily intake). The National Academy of Science Institute of Medicine report entitled "Dietary Intakes: Calcium, Phosphorous, Magnesium, Vitamin D and Fluoride," National Academy Press, 1997, cited that in 1994, 73% of the calcium in the U.S. food supply was from milk products. Milk, yogurt, ice cream and cheese provide about 30% of the RDA per serving. While certain lowfat dairy foods such as cottage cheese, sour cream and frozen desserts contain less calcium than milk per serving, they are still considered significant sources.

Dietary and epidemiological data shows that calcium requirements are unmet in three out of four American adults. Even Americans who consume dairy foods still may not take in an adequate number of servings to meet the recommended requirements for dietary calcium.

Another issue that has affected U.S. calcium intake is lactose intolerance, which some estimate to occur at levels as high as 25% of U.S. adults. This group has been targeted as "at risk for calcium deficiency" because of its avoidance of milk. Therefore, calcium fortification of lactose-free dairy foods or dairy-food analogs would allow consumers to meet their requirement with fewer servings. One product currently addressing this is Lactaid® lowfat, lactose-free milk, marketed by McNeil Consumer Healthcare, Ft. Washington, PA. This milk, fortified with tribasic calcium phosphate, has 500 mg of calcium per serving, 200 mg more than standard milk products.

Vegetarians were another dietary group that was believed to be at risk for calcium deficiency because of their consumption of oxalate and phytate, two calcium-absorption inhibitors. However, studies of vegetarian intakes were similar to omnivores and showed that bone densities were not comprised in lacto-ovovegetarians. There is very little data available for strict vegans.

A common reason for inadequate consumption of milk among children and adults is the success of competing beverages. Studies by the USDA’s Grand Forks Human Nutrition Research Center, ND and the University of North Carolina, Chapel Hill, document the steady drop in milk consumption among adolescents over three decades. Carbonated soft drink consumption is double that of milk. But, the differences are more dramatic when particular groups of children are studied. Teenage boys reportedly consume three times more soft drinks than milk. Dairy Management Inc.™, Rosemont, IL, provided the following data on the top three beverages consumed in the United States, according to data obtained from the New York, NY-based Beverage Marketing Corporation: soft drinks at 56.5 gal. per person; beer at 22.4 gal. per person; and coffee at 22.0 gal. per person. Milk consumption has stabilized at an average of 20.0 gal. per person over the last five years.

Fortification feasibility
Absorption or bioavailability must be considered when fortifying a food with calcium. Calcium bioavailability refers to the body’s ability to absorb it, and the data varies according to the chemical form of calcium ingested and the food matrix containing the calcium. Nutritional recommendations have been developed through the research of Dr. Robert Heaney, Creighton University, Omaha, NE as well as several others. Data suggests that it is preferable to ingest calcium throughout the day rather than as a once daily supplement, and is most effectively absorbed with food. Bioavailability is a powerful selling tool in the nutritional supplement market, where the food matrix is largely dependent on the habits of the consumer. Calcium citrate malate earned its reputation largely through its favorable bioavailability data.

The absorption of calcium in foods has been documented for most high-calcium food sources. Data available at http://www.bonesummit.com/calcium.htm sourced from Connie Weaver, Ph.D., professor, Foods and Nutrition, Purdue University, West Lafayette, IN, estimates milk absorption at 32% for a total absorbed calcium of 96 mg per serving. An equal quantity of juice fortified with calcium citrate malate, a soluble form of calcium with an improved absorption of 52%, results in 156 mg of absorbed calcium. A radish, with a calcium content of only 14 mg, has the highest estimated rate of absorption at 74%, while spinach at 122 mg of calcium has the lowest absorption at 5%. If all these foods were ingested in the same meal, the bioavailability would be virtually incalculable.

Bioavailability is difficult to quantify as a standard attribute of any chemical form of calcium. Additional variables that must be considered in the calculation are the age, gender, genetics and the health of the individual consuming it. The intake of vitamin D and phosphorus must be considered as cofactors that impact absorption. Arbitrarily, the Dietary Reference Intakes (DRIs) for calcium are based on an absorption rate roughly equal to that of milk. The food industry has the extra challenge to balance this aspect of calcium fortification with other important considerations, such as solubility, compatibility with food systems and cost per serving, when choosing a chemical source of calcium for fortification.

The National Institutes of Health, the American Dietetic Association, the American Medical Association and the National Research Council all advise that the optimal calcium intake is through food consumption. The data points to food fortification rather than relying solely on dietary supplements. Research supports the theory that dairy-food consumption with calcium might prevent kidney stones. In one study, lower calcium intake resulted in more stone formation in susceptible individuals.

Mining the diet
The calcium requirement for good health varies with age, and during growth more than 1 kg of calcium is added to bones during the period from infancy to adulthood. Calcium deficiency in children has resulted in slower growth and weaker bones. Researchers report that the critical window for building strong bones is during the adolescent years of 9 to 18, however some studies show bone density increases up to age 30. Today’s calcium RDA for this age group, increased to 1,300 mg per day, reflects the need to build bone density in children. Nineteen to 50-year-olds have a RDA of 1,000 mg per day. After age 51, the calcium RDA increases again, to 1,200 mg per day, aiming to prevent osteoporosis, a disease that results in porous bones and subsequent bone fractures.

The goal of osteoporosis prevention spans an entire lifetime. Osteoporosis is the most frequent cause of fractures among elderly women, whose bone loss is accelerated when their estrogen levels decrease. The National Osteoporosis Foundation, Washington, D.C., estimates that one of two women over 50 will experience a fracture caused by osteoporosis in her lifetime. Men are also affected, but at the lower rate of one in eight.

The relationship between the calcium loss from bone and low dietary calcium is dependent on the intake of calcium beginning early in life. The National Dairy Council, Rosemont, IL, encourages consumers to view bones as a bank account where calcium "deposits" can be made to draw on later in life. As the calcium intake among children decreases due to soft-drink consumption, and the aging of America proceeds, the incidence of osteoporosis is expected to increase. Calcium retention, the bones’ ability to retain their calcium, depends on several factors in addition to dietary calcium. Exercise and a balanced diet are also factors that have been identified to contribute to calcium retention. Even prevention of small losses of bone mass each year are important because the losses are cumulative and become significant over time.

FDA-approved label claims
The Nutrition Facts panel allows calcium to appear on the nutrient list, however it is not required if it’s present in amounts less than 2% of the RDA and the following statement is added below the nutrient values: "Not a significant source of calcium." The FDA provides some suggested claims for three calcium levels that can be readily found on the supermarket shelves. Products with 10% of the RDA can have: "calcium-enriched," "calcium fortified" or "more calcium" on the label.

For cereal products containing 10% to 19% of RDA per serving, "Good Source of Calcium" is commonly used, as seen on Golden Grahams® from General Mills, Minneapolis. For products containing 20% or more of RDA, the FDA suggests "High in Calcium," which is the claim used by Kern’s® Mango Nectar, Nestle, San Francisco. "Rich in Calcium" appears on Soy Dream® by Imagine Foods, Palo Alto, CA, and "Excellent Source of Calcium," is the label choice for Nutrigrain® Bars, Kellogg’s, Battle Creek, MI. "As much Calcium as Milk" is another claim found on beverages such as Minute Maid Premium®, Coca Cola Company, Atlanta, and Florida’s Natural® from Citrus World, Lake Wales, FL.

Calcium’s nature
The RDA for calcium does not distinguish between calcium sources and there are a wide variety of calcium chemical forms to choose from. Calcium carbonate is a good source of cost-effective calcium because it contains 40% calcium — therefore less is required to meet the same level of the RDA than a source such as calcium citrate, which contains only 21% calcium. Calcium carbonate is popular in dry foods, but is insoluble and can impart off-flavors or a gritty mouthfeel to liquid products. These drawbacks are not an obstacle for cold cereals, where it is used frequently.

In baked goods, calcium might come from a variety of sources that offer not only calcium but other functional ingredients as well. Breakfast bars typically include calcium carbonate, nonfat dry milk and calcium phosphate. These are also compatible with baking pH.

For acid systems like fruit juices, the calcium must be soluble with a bland or tart acidic flavor. Tricalcium citrate and calcium lactate are frequently listed on orange juice labels. The citrate blends work well with the citrus juice flavor profile and is used alone or in combination with calcium lactate, which lends a bland flavor profile with better solubility.

Soluble selections
Calcium lactate is a very desirable calcium form for beverages and liquid products because of its high solubility. The solubility of calcium lactate is 9.3 grams per liter, while calcium citrate’s solubility is a mere 0.2 grams per liter at standard conditions of 258°C.

"Orange juice is a very forgiving product, since it is not clarified," states Ellis Hogetoorn, market development specialist, Purac America, Inc., Lincolnshire, IL. "Combinations of soluble and insoluble calcium sources are sometimes used in orange juice, since the insoluble forms of calcium can be kept in suspension more easily due to the particles in the juice. However, insoluble sources can give a slightly sandy mouthfeel and their bioavailability is not very high. For clarified juices, it is necessary to use a soluble calcium source that delivers the concentration of calcium to meet the label claim, but does not affect the taste, texture and appearance of the juice. Calcium lactate can deliver a stable form of soluble calcium that provides as much calcium as milk per serving, and can be used in both a single strength juice as well as in concentrates."

Calcium characteristics
Clarified juices present a greater challenge for calcium fortification than other products. Most fruit juices feature an acid pH range, which enhances calcium solubility. However the free calcium ions can interact with juice components. Cranberry juice, for example, is a clarified product that is susceptible to interactions with calcium resulting in color and clarity loss. To address this problem, Cranberry Juice Cocktail Plus, Ocean Spray, Middleboro MA, features the super-soluble calcium lactate and calcium gluconate combo to provide 10% of the RDA. With a solubility of 56 grams of calcium per liter at standard conditions, this combination of calcium sources provides a soluble source of the calcium level needed for the label claim. The juice also provides significant quantities of vitamins A, C and E.

Calcium with a high solubility has its own inherent problems. In grape beverages, natural pigments such as anthocyanins can experience a color shift caused by multivalent ions, such as calcium. Off-flavors can also arise with high calcium gluconate levels. Interactions with other components in beverages can cause free calcium-ion precipitation. Tannins found in tea beverages are the most likely reason that calcium-fortified teas are not common. Likewise, the tartaric acid found in Concord grape concentrate will precipitate tartaric crystals in the presence of some calcium levels. Calcium is also a catalyst for gelation when fruit pectins are present in concentrates or purees. Most juice beverages are not especially high in protein, but protein/calcium interactions need to be considered because they can result in sedimentation or a grainy texture in a protein-containing juice.

The dairy case
"It is more than a coincidence that the composition of bone and the composition of milk are similar in mineral content," explains out Eric Bastian, director research and development, Glanbia Ingredients, Monroe, WI. Bones contain two times more calcium than phosphorus (25% to 12%), and also contain important trace minerals, such as magnesium, potassium, zinc and copper — all of which are present in milk. Milk’s composition is available from the U.S. Department of Agriculture, Agricultural Research Service, 1999 USDA Nutrient Database for Standard Reference, Release 13, Nutrient Data Laboratory Home Page http://www.nal.usda.gov/fnic foodcomp.

Bastian’s literature review of dairy minerals’ role in bone health has convinced him that proper dietary ratios of minerals are important for bone development. The dietary ratios of calcium, magnesium, potassium, zinc, copper and manganese need further attention. He advocates a balanced approach to calcium consumption, which is being ignored by the current wave of calcium research and education.

Research published last year in the Journal of International Medical Research by Celotti and Bignamini concludes that magnesium is an important factor in calcium fortification and bioavailability. The development of a product to meet the needs for all these mineral nutrients can be satisfied by Glanbia’s milk mineral XTRACAL®. This dairy calcium product contains the same ratio of calcium to phosphorus as bone and milk, and also includes other trace minerals that are common to bone and milk.

Considered insoluble, much the same way as the minerals in milk exist in an insoluble colloidal dispersion stabilized by milk proteins, Asian manufacturers use milk mineral salts in milk fortification. These products require a viscous solution to prevent sedimentation, requiring the addition of gums or stabilizers. They can be solubilized in some acidic formulas.

Although popular in Asia, the U.S. standard of identity prevents the fortification of milk with milk minerals. However, designers have other options. For example, milk mineral salts containing 24% calcium, from New Zealand Milk Products, Santa Rosa, CA, can be incorporated into cookies. "Biscotti containing milk minerals have been formulated to deliver 30% of the RDA per serving," says Lee Huffman, technical services manager. Lactose-free formulations, such as milk substitutes from soy, rice or almonds, cannot use some types of dairy calcium that contain lactose. The mineral salts contain only 2.4% lactose, resulting in final products that can be considered lactose-free depending on the serving size.

For some applications, Huffman recommends the use of high-calcium milk protein, a patented compound of milk caseinate and calcium carbonate. This calcium source behaves like milk protein isolate, thereby enhancing dough handling, moisture retention and reduced spread in cookies when compared to calcium carbonate alone. It can be incorporated into a formulation that results in 30% of the RDA in one 30-gram cookie.

The combination of milk protein and calcium carbonate also eliminates grit or sediment problems inherent to calcium carbonate. In an opaque liquid beverage, like hot cocoa, it is easily suspended without gums or stabilizers, and without compromising the smooth mouthfeel and body that are characteristic of cocoa beverages. High-calcium milk protein can boost cocoa beverage protein by a factor of three and calcium to 30% of the RDA per serving. In meal-replacement beverages, the protein level can be varied depending on the desired nutrient density of the final product. Products can be sourced with standard levels of protein and calcium that allow formulators to meet a range of protein and calcium nutrition in the final product. For coffee whitener, a high calcium level is needed to reach 10% of the RDA per serving, while in a very high protein drink, 100% of the daily calcium RDA is achievable.

Another good source of dairy calcium is whey protein. It is relatively easy to incorporate whey protein into a variety of food applications since it readily replaces nonfat dry milk (NFDM) in dairy products, bakery products and confections.

"New application areas for adding calcium include fluid milk and lowfat dairy products such as yogurt, ice cream, cottage cheese and sour cream. We also have done application work in calcium-fortified cookies, pudding, cheese sauce, protein bars and meal-replacement bars," says Laurie Nelson, applications manager, Davisco Foods International, Inc., Le Sueur, MN. "Whey protein, or modified whey, not only supplies the calcium necessary to make a calcium nutrient content claim but also contains protein, lactose and phospholipids, which allows the ingredient to be used for its functional properties as well. It has excellent waterbinding, emulsification and texture modifying properties in a variety of applications."

The market sector for food with a neutral pH sometimes prefers insoluble tricalcium phosphate at a solubility of less than 0.1 gram/liter. For soymilk, the combination of calcium and isoflavones has been called the "soy synergy" for the postmenopausal market. This form works well for opaque beverages that have the viscosity or the component blend that will properly suspend the calcium and mask the gritty mouthfeel that is sometimes present with this form. Almond Breeze® non-dairy beverage, Blue Diamond, Sacramento, CA and Imagine Food’s Soy Dream also utilize this form to make their calcium contributions in the non-dairy beverage sector.

Getting the lead out
Research published by Ross et al. in the Journal of the American Medical Association (JAMA, Vol. 284 No. 11, September 20, 2000) inspired Heaney to respond with an editorial to lend perspective to the dangers of lead found in calcium supplements. (Heaney’s editorial comments, published in the same issue of JAMA, were not included in media coverage.) The research reported the testing of 22 brands of calcium supplements. Eight products had detectable levels of lead. The lead amounts were reported to the hundredth of a microgram (µg). Harmful levels of lead range from 10 µg/dL of plasma in children to 30 µg/dL in adults. Media reports on the findings failed to mention that the amount of lead in the calcium supplements was trivial.

While Heaney agreed that it was sound advice for consumers to purchase supplements that had been tested for lead, he disagreed that there was any public health concern by pointing out that servings of raisins, grapes, berries, wine and salad all contain more lead than was found in the supplements. Heaney also replied that calcium blocks intestinal lead absorption up to a factor of 10 for some levels of calcium. Heaney wrote: "all of the products tested had lead content less than both the 1992 Food and Drug Administration and the 1996 Food Chemicals Codex standards. Two thirds of the products had less lead than the more stringent California Proposition 65 standards." Concerned about the effect of media coverage on the public, Heaney argues that because of the protective effect of calcium on lead absorption, a backlash against calcium supplements caused by a lead scare "would unquestionably do far more harm, for health generally and for lead poisoning specifically, than would continued ingestion of current supplements."

In addition to wholesomeness of food ingredients, taste is the most important aspect of any mineral fortification. As long as the taste is there, the demand for the product will be there also. The supplement market recognizes this as well. Many nutraceutical companies have come out with chewable calcium in flavors like peppermint and cocoa mint raspberry to help consumers better enjoy incorporating more calcium into their diets.

Suanne Klahorst is associate director of the California Institute of Food and Agricultural Research (CIFAR) at the University of California-Davis. CIFAR serves as an informational clearing house for research programs and results related to food, nutrition, and human health at that campus. She can be contacted at [email protected].

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