Deciding which calcium form to use in producing food or supplements products depends on a variety of technical factors as well as on consumer preferences. Product development consultant Judi Quilici-Timmcke examines the markets, price points and calcium choices.
Although most people know they need dietary calcium for bone health, the actual consumption of calcium-rich foods is far too low. By some estimates, in the United States more than 90 per cent of women, 60 per cent of men, 70 per cent of infants and 66 per cent of children are calcium deficient.1 There is a substantial gap between the recommended daily calcium intake and what people actually consume. To counter this disparity, an increasing number of functional foods with added calcium are entering the market with the potential to significantly improve the statistics.
The recommended daily intake of calcium ranges from 1,000mg for adults to 1,200mg for the elderly and 1,300mg for children under age 18. According to a 1999 report by the American Academy of Pediatrics Committee on Nutrition, the appropriate mean intake for 9 to 18 year olds is between 700 and 1,000mg/day.2
When manufacturers add calcium to products, they must consider factors such as bioavailability, solubility, taste, palatability, stability and effects on the final product. They evaluate which forms of calcium are best suited for their food products and consider that some consumers prefer to get calcium in pill form. Consumers, for their part, may not be able to tolerate calcium-enriched products or foods high in calcium, yet still want to ensure that they are getting their RDA for calcium.
The objective is to market products that meet nutritional needs while also meeting the demands of consumers for such things as taste and convenience. The consumer who prioritises convenience over nutrition may choose to purchase a multiple vitamin/mineral that contains some calcium or a stand-alone calcium product, or may be swayed by a physician recommendation to choose a calcium product with magnesium and vitamin D. Other factors for making that choice may include price, bioavailability or the total number of pills they have to take per day.
The National Institute of Child Health and Human Development, part of the National Institutes of Health in Bethesda, Maryland, has demonstrated through research that calcium can prevent bone breakage and damage.2 Various studies demonstrate that bone mass can be improved with calcium levels of 500 to 1,500mg/day for prepubescent girls and adolescents.3,4 The effective dosage for postmenopausal women has been shown to be approximately 1,500 mg/day. 3
One double-blind human study provided 500mg/day calcium (in the form of calcium citrate malate, a patented formulation) or placebo to girls at the mean age of 11 years old for 18 months. The result showed a significant increase in lumbar spine and total body bone density in the calcium group compared with the placebo group.4
In addition to bone health, calcium is needed for numerous bodily functions. When calcium blood levels are low, the body draws calcium from bones to support other important functions such as nerve impulse transmission, muscle contraction and blood clotting. When calcium is not available for bone formation, it results in reduced bone density and increased bone brittleness, which can increase the risk for fractures as well as for osteoporosis.
Other nutrients such as boron, magnesium, potassium, vitamin D and zinc are also important to bone health, and some formulators have added these to calcium formulas. By doing so they are attempting to deal with a dilemma of calcium fortification: Supplementation with only pure calcium can create a mineral imbalance and stimulate leaching of magnesium, potassium and other minerals from bone, causing hypermineralisation of calcium and bone brittleness.5 New research presented by Robert Heaney, MD, at the National Osteoporosis Foundation International Symposium in Omaha, Nebraska, in March 2002, showed that healthy bones and soft tissues need calcium in concert with phosphorus if they are to grow and develop normally through a lifetime. This finding of a calcium/phosphorous co-dependence could have significant ramifications for product developers.
Calcium is a popular ingredient to add to orange juice, soymilk, breads, biscuits, cereal and popcorn. In the UK, the current trend, spurred on by the growing consumer demand for snack foods including microwave popcorn, is to add calcium and other nutrients to snack foods that can then be classified as "healthy and functional products." A new patent for fortifying low-pH, carbonated or noncarbonated beverages with calcium and vitamin D involves suspension of a water-soluble vitamin D with vegetable oil and a gum.6
Calcium in the form of lactate, gluconate, citrate, citrate malate, phosphate and carbonate also can be added to foods. Particular forms may be best suited for specific foods. Calcium citrate and calcium citrate malate have been shown to be better absorbed than other forms of calcium when added to food products and dietary supplements.7,8 Both forms have been shown in clinical research to increase bone density, and they are known to be particularly beneficial for adolescents and the elderly.4,9 Calcium citrate malate is a complex of calcium, citric acid and malic acid at a ratio of 6:2:3. It has been shown to be highly bioavailable compared to calcium carbonate.10,11,12
Although a few studies demonstrate that calcium from calcium citrate is slightly more bioavailable than calcium carbonate, or that there is no difference between the two, a meta-analysis has shown otherwise.13,14 Researchers at The University of Texas Southwestern Medical School, Center for Mineral Metabolism and Clinical Research, reviewed 15 studies with a total of 184 subjects.15 The analysis showed a significant 22 to 27 per cent higher absorption of calcium on an empty stomach or with meals from the calcium citrate form vs. the carbonate form.
Some foods that can be successfully fortified with calcium citrate are yoghurt, cheese, desserts, infant foods, cereal, single-serve juices, muffins, snacks, soymilk and some beverages.
In Israel, calcium citrate was demonstrated to be more bioavailable than calcium phosphate and calcium carbonate.16 As a result, calcium citrate has been recommended there for food enrichment as a source of calcium in juice, drink mixes, infant formulas, sports beverages, diet products and cereals.
In general, organic calcium salts, such as calcium citrate, gluconate and lactate, may be better forms than inorganic calcium salts, such as phosphate and carbonate. The reason is that organic calcium salts have a greater bioavailability, whereas phosphates appear to reduce overall calcium absorption.16 One available product has combined calcium gluconate and lactate.
An inorganic form of calcium may be chosen because it is less expensive. If this is the case, calcium carbonate has been shown to be more bioavailable than calcium phosphate.17
Calcium carbonate also has been used as a calcium source to fortify white pan breads.18 Calcium phosphate has been shown to be useful for fortifying intermediate moisture-sweetened fruit products.
While bioavailability is important, it is irrelevant if consumers won't buy products because they taste bad. Some calcium forms have a better taste and mouth feel than others. The calcium salts gluconate, lactate and tricalcium phosphate are considered tasteless, although tricalcium phosphate tends to be gritty. Calcium citrate is quite acidic and has a bitter twang and carbonate has a soapy taste.
Product developers are beginning to fortify oleaginous foods (high in fatty acids such as oleic acid) with new calcium forms such as a calcium amino acid called malic acid chelate complex. It is a newly patented complex claimed to be readily bioavailable, stable and taste good.19
Calcium In Pills
A wide variety of calcium forms are available for tablets and capsules. They include carbonate, tri-phosphate, glycinate, citrate, citrate-malate, pidolate, bisglycinocalcium, oxalate, phosphate, gluconate and hydroxyapatite.
Mass-market products often contain calcium carbonate because it is inexpensive and contains approximately 40 per cent elemental calcium, making it easier to produce larger doses in fewer capsules, which has high consumer appeal.
Although calcium carbonate is reputed to have low bioavailability, human studies have demonstrated that it can still be useful as a functional compound. One human clinical study showed that the dosage of 1,200mg/day calcium carbonate significantly reduced premenstrual symptoms.20
While carbonate may not be the most bioavailable form, the bottom line is that it is inexpensive for the mass market and provides a reasonably high concentration of calcium for those individuals who need calcium but refuse to take numerous pills.
The amount of elemental calcium in calcium phosphate is 17 per cent, calcium chloride 36 per cent, calcium citrate 21 per cent, calcium lactate 14 per cent, calcium gluconate 9 per cent, calcium citrate malate 24 per cent, bisglycinocalcium 18 per cent, hydroxyapatite 33.7 per cent, and citrate malate 24 per cent.
There is, not unexpectedly, controversy over the results of bioavailability studies of calcium forms. There has been a little research on the bioavailability of hydroxyapatite, pidolate and gluconolactate.14 The calcium form hydroxyapatite was lower in bioavailability than the other forms. The published studies performed on hydroxyapatite in the past have not pitted it against other calcium forms.
Many product developers will use half carbonate and half from another source, such as citrate or glycinate. Another option is to formulate with three or more forms of calcium, often an appealing marketing strategy to save on cost while providing a compromise in terms of bioavailability and amount of calcium per pill.
In a pill form, calcium citrate is a common calcium product used as a stand-alone in mass, health food stores, MLM markets, physicians' lines or direct sales.
Some companies seek exclusive, patented forms of minerals to make themselves unique in the marketplace. Compounds such as calcium citrate malate or bisglycinocalcium are included among patented forms. Heaney and other researchers at Creighton University in Omaha, Nebraska, investigated the use of seven sources of calcium administered to normal adult women.13 Bisglycinocalcium, a form not often used, tested better than other forms. It was absorbed approximately 1.83 times better than calcium citrate and calcium carbonate. Companies that are able to work at a higher price point may select this form. The benefit is uniqueness and increased bioavailability, but at a higher cost and increased number of pills containing the same amount of calcium as other forms.
Various gastrointestinal disorders reduce the absorption of calcium and other nutrients.21 These disorders increase the risk of nutrient deficiencies, which escalate these conditions. Product developers who formulate doctors' lines of products may consider this as a factor when selecting the form of calcium by selecting a calcium form with higher bioavailability. However, a mass-market formulator may select a calcium form positioned for the general public that is presumed to not have any health disorders.
There is concern over the lack of dietary calcium in many population groups. Many opportunities exist for companies to fortify foods with calcium that is bioavailable and palatable. With more enriched, fortified and added-calcium foods and supplements making their way to market, the statistics for calcium intake could improve in the next decade and result in reduced cases of osteoporosis and other calcium-deficiency health problems.
Judi Quilici-Timmcke, MS, is president of Q-Tech Services, a product development consultancy based in Royal Palm Beach, Florida. www.judiq.com
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