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Dairy Council Digest Archives
Calcium-fortified Foods: Is There a Reason for Concern?
Are Calcium-Fortified Foods the Answer to the Calcium Crisis?
Forcertain foods and beverages, the Food and Drug Administration (FDA) hasestablished standards of identity that specify appropriate fortification levels of nutrients such as thiamin, niacin, riboflavin, folic acid, andiron in grain products; vitamins A and D in milk; and iodine in salt (13,42).Intake of fortified foods complying with these standards has contributed to nutrient intakes and reduced the risk for disease (5,13,43). For example, vitamin D fortification of cow's milk and the addition of iodine to salt have been largely responsible for the dramatic decline in rickets andgoiter, respectively, in the U.S.
Some foods are voluntarily fortified with specific nutrients such as calcium. Although voluntary food fortification can expand consumers' food choices to meet dietary recommendations for calcium, both the level of calcium fortification and the foods and beverages fortified with calcium are arbitrary. A serving of calcium-fortified foods may provide levels of calcium equivalent to that found in milk (i.e., 300mg/cup) to levels approaching daily dietary calcium recommendations (1,000mg). Also, foods fortified with calcium can be nutrient dense (e.g., yogurt) or nutrient poor (e.g., candy). The FDA cautions against random fortification of foods because of the potential for over or under fortification in consumer dietsand nutrient imbalances in the food supply (42). In addition, the FDA discourages the indiscriminate addition of nutrients to foods and the fortification of certain foods such as snack foods and candy (42).
Calcium-fortified foods and beverages treat the symptom, low calcium intake, but not the problem, which is a poor dietary pattern.
Although it is relatively easy to meet calcium recommendations if a variety of foods is consumed according to USDA/DHHS' Dietary Guidelines for Americans (44) and the USDA's Food Guide Pyramid(45), few Americans do so (16). The discrepancy between calcium intakes and recommendations has led to the marketing of an increasing number andvariety of calcium-fortified foods and beverages (17-21). In 1999, 234 foods and beverages "with added calcium" were introduced, or nearly fourtimes more than in 1995 (19). These products include calcium-fortified breakfast cereals, breads, pasta, pancake and waffle mixes, juices, juicedrinks, spreads/margarines, bottled water, candy, energy bars, soy beverages, and dairy products (e.g., yogurt, cheese) (17-22).
Calcium-fortified foods can be a reasonable option to help some people increase their low calcium intakes (13). However, opting for calcium-fortified foods, particularly at the expense of foods naturally containing calcium, is not the best way to meet calcium recommendations. Several concerns have been raised regarding the use of calcium-fortified foods and beverages (22). These concerns center on the inability of calcium-fortified foods to correct a poor dietary pattern, the risk of calcium excess, unknown calcium bioavailability, and potential negative effects of excessively high calcium diets on other nutrients such as trace minerals.
Inability to Correct a Poor Dietary Pattern. Diets low in calcium are generally low in several other nutrients and are the result of poor food choices, not the unavailability of calcium-rich foods in the food supply (46,47). Fortification of a food or beverage with a single nutrient such as calcium will not correct a poor dietary pattern. Calcium-fortified foods such as spreads/margarinesor juices are not nutritionally equivalent to calcium-rich foods such as dairy products. For example, some spreads are fortified with 100mg calcium per tablespoon (48). However, less than 3 ounces (i.e., less than half a serving) of milk can provide the same amount of calcium, along with nutrients not found in many spreads such as vitamins A and D, riboflavin,phosphorus, potassium, vitamin B12, and niacin (48). The American Academyof Pediatrics, in its recent statement on the use and misuse of fruitjuice for healthy infants and young children, cautions that calcium-fortifiedjuices provide a bioavailable source of calcium, but lack other nutrients found in cow's milk (49). Individuals using calcium-fortified foods, particularly low nutrient foods such as candy, snack foods, or water, may be misled into believing that these calcium-fortified foods are an adequate substitute for milk and other dairy foods and that they ensure a healthy diet (21).The FDA discourages fortification of low nutrient density foods because of the risk that consumers consuming such fortified products will ignore the rest of their diet, resulting in nutrient deficiencies (42).
Calcium Excess. Althoughthe percentage of U.S. adults exceeding the recommended dietary intakefor calcium is low (i.e., less than 5%) (5), this percentage may increase due to the availability of so many calcium-fortified foods and beverages, many of which are fortified at high levels (22). The window between dietary recommendations for calcium (i.e., 1,000 to 1,300mg/day) and the UL of 2,500mg is relatively small(5). It is fairly easy to exceed the UL for calcium when calcium-fortified foods are included in the diet (17,21,22). In a hypothetical case of a 25-year old male before and after a diet substituted with some calcium-fortified foods, total calcium intake increased from almost 2g/day (mostly from milk and cheese) to close to 4g/day (22). Substitution of calcium-fortifiedorange juice (300mg/ cup), calcium-fortified breakfast cereal (250mg/cup),and calcium-fortified mineral water (1,000mg/L) for their traditional counterparts doubled calcium intake (22). Thus, excess calcium intake could readily result if calcium-fortified foods are added to a diet already containing generous amounts of calcium-rich foods such as milk and cheese(7).
For certain subgroups of the population already meeting or close to meetingt heir calcium recommendation (e.g., adolescent and young adult males),this risk of calcium excess from calcium-fortified foods increases (7).
To avoid excess calcium, individuals should base their decision on whether or not to use calcium-fortified foods (or supplements) on their current dietary intake of calcium, which can be assessed by examining the Nutrition Facts labels on foods and beverages. The National Academy of Sciences, Institute of Medicine, recognizing the increase in the availability of calcium-fortified foods, states that "...it is important to maintain surveillance of the calcium-fortified productsin the market place and monitor their impact on calcium intake" (5). The effect of current intakes of calcium-fortified foods and beverages on total calcium intake of individual subgroups and the population as a whole is unknown. To be safe and effective, calcium-fortified foods should reach individuals in need, without contributing to excess calcium intakes inothers.
Compared to foods naturally containing calcium, particularly dairy foods, many calcium-fortified foods are not nutritionally equivalent and are morelikely to result in over-consumption of calcium.
Calcium Bioavailability. The bioavailability of calcium from calcium-fortified foods is another consideration. In general, calcium absorption is most efficient when consumed in doses of 500mg or less (5,50). Some well-known brands of cereal are fortified with calcium levels as high as 600 and 1,000mg/cup. A serving of these cereals with 1/2 cup of milk provides either 750 or 1,100mg of calcium. Calcium absorption from this high intake consumed at a single time islikely to be lower than multiple calcium intakes of 500mg or less.
A variety of calcium salts are used to fortify foods and beverages. Although the bioavailability of calcium from various salts is similar to that from milk (23,51), calcium bioavailability from calcium-fortified foods may differ from that expected. For example, calcium-fortified soy beverage is not comparable to cow's milk as a source of calcium, according to a recent study (52). Becauses soy beverages naturally contain very little calcium (i.e., about 10mgper serving), they are often fortified with calcium, although the amountis not regulated and levels can vary from 80 to 500mg calcium per serving(52). In a study of 16 healthy men, the calcium from soy beverage was absorbed at only 75% the efficiency of calcium from cow's milk. Sixtypercent more calcium (i.e., 500mg per serving) was needed in soy beverages for calcium absorptionto be comparable to that from cow's milk (i.e., 300mg per serving) (52).
The bioavailability of calcium in calcium-fortified foods may be influenced by the presence of inhibitors such as phytic acid in certain foods (23,53). Phytic acidcan significantly reduce calcium bioavailability in calcium-fortified breads and cereals.
Potential Negative Effects on Other Nutrients. There is some concern that fortifying foods with large quantities of calcium may adversely affect the utilization of other essential nutrients such as iron, zinc, and magnesium (5,23).However, evidence that excessively high calcium diets contribute to deficiencies of these minerals in humans, especially over the long-term and when the intake of these other nutrients is adequate, is inconclusive (23,54,55).For example, high dietary calcium intake was demonstrated to reduce zinc balance in postmenopausal women (56), but not in adolescent females (54). Additional research is needed to determine whether or not high intakes of calcium result in calcium-mineral interactions that adversely affectthe mineral status of vulnerable populations (5).
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