Journal of the American College of Nutrition, Vol. 23, No. 4, 303-308 (2004)
Published by the American College of Nutrition
The Canadian Health Claim for Calcium, Vitamin D and Osteoporosis
Mary R. L’Abbé, PhD,
Susan J. Whiting, PhD and
David A. Hanley, MD
Bureau of Nutritional Sciences, Health Canada (M.R.L.)
College of Pharmacy and Nutrition, University of Saskatchewan (S.J.W.)
Department of Medicine, University of Calgary (D.A.H.), CANADA
Address reprint requests to: Dr. Mary L’Abbé, Director, Bureau of Nutritional Sciences, Food Directorate, Health Canada—P.L. 2203C, Banting Research Centre, Ross Ave, Ottawa, ON K1A 0L2 CANADA. E-mail: mary_l'abbe{at}hc-sc.gc.ca. Manuscript number 574 of the Bureau of Nutritional Sciences
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ABSTRACT
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To provide evidence for or against allowing a health claim for calcium in Canada, we undertook a review of the current U.S. health claim for calcium and osteoporosis, and also reviewed the scientific literature published since that health claim was first proposed and reviewed by the U.S. Food and Drug Administration in 1991 and adopted in 1993. Our objectives were 1) to determine if the science behind the claim was still valid, and if so, 2) to recommend any new wording to the claim, if warranted, prior to implementation in Canada. Based on a review of the evidence (to May 2000) related to the various claim elements, the following health claim for calcium has been established in Canada: A healthy diet with adequate calcium and vitamin D, and regular physical activity, help to achieve strong bones and may reduce the risk of osteoporosis. The compositional criteria for foods bearing this claim are that the food must provide at least 200 mg calcium per serving and that the phosphorus content (excluding that provided by phytate) must be less than the calcium content.
Key words: calcium, osteoporosis, vitamin D, health claim
Key teaching points:
•The FDA claim for calcium and osteoporosis, set in 1993, was reviewed and found to be out-of-date in terms of for whom the claim was targeted (age, race and gender).
•Vitamin D status is as much a concern as calcium status for osteoporosis prevention, therefore it was added to the claim.
•Similar rules as in the U.S. concerning application of the Canadian claim to food items were retained in the Canadian claim.
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INTRODUCTION
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Osteoporosis is a disease characterized by low bone mass and micro architectural deterioration of bone tissue, leading to increased bone fragility and a consequent increase in fracture risk. Peak bone mass is a major factor determining the risk of developing osteoporosis [1–3] and by about age 20, the human skeleton has reached 90%–95% of its peak bone mass, with the final 5%–10% of bone mineral added during the next 10 years [1]. People who have achieved a greater bone mass are less susceptible to osteoporosis [1–3]. It is estimated that one in four women and one in eight men over 50 years of age in Canada have osteoporosis [3,4]. Osteoporotic fractures are multi-factorial and may result from a variety of causes, either singly or in combination. For this reason, no single risk factor can identify all potential fracture cases. However, low calcium and vitamin D are established risk factors [3]. In a nation-wide survey, calcium intakes of Canadians were, on average, above the Adequate Intake level of 1000 mg for men 18 to 49 years, but below for women; for persons 50 years and older, intakes were well below the Adequate Intake level of 1200 mg [5]. Additionally, intake data from three provincial surveys (Nova Scotia, Quebec, Saskatchewan) also indicated that mean calcium intakes of adults 18 to 74 years of age are generally low; over these three provinces intakes ranged from 771 to 1161 and 574 to 822 mg/d (depending on age) for males and females respectively, with intakes declining with increasing age [6–8]. Vitamin D intake has not been measured in the Canadian population.
The calcium-osteoporosis claim as approved by the FDA in 1993 was: "Regular exercise and a healthy diet with enough calcium help teen and young adult white and Asian women maintain good bone health and may reduce their high risk of osteoporosis later in life" [9]. The evidence used in proposing the U.S. health claim was related to three questions, which were evaluated during the development of the claim [10]. The questions were: 1) "what is the evidence documenting the role of calcium in achieving peak bone mass;" 2) "does added calcium or high calcium intake reduce the risk of fracture or slow the rate of bone loss in younger or older subjects;" and 3) "do any of the studies show a threshold effect for the level of calcium intake associated with changes in bone mass?" Other relevant factors such as phosphorus, protein, calcium bioavailability, racial differences, age, postmenopausal age, and exercise were evaluated. To provide evidence for or against allowing a health claim for calcium in Canada, Health Canada undertook a review of the scientific literature published since that health claim was first proposed and reviewed by the U.S. Food and Drug Administration in 1991 [6] and adopted in 1993 [5]. The task, assigned to us, was to determine if the science behind that claim was still valid, and second, if the claim was still valid, to determine if any new wording to the claim was warranted, prior to implementation in Canada.
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METHODOLOGY USED IN EVALUATING THE LITERATURE
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Evidence for a calcium-osteoporosis relationship was recently examined by the Panel on Calcium and Related Nutrients of the Standing Committee on the Scientific Evaluation of Dietary Reference Intakes (DRI), of the Food And Nutrition Board, Institute of Medicine of the U.S. National Academy of Sciences, in a review carried out jointly by U.S. and Canadian scientists (hereafter referred to as the DRI Panel) [11]. We examined original studies regarding a dietary calcium-bone relationship and recorded vitamin D intakes where available (but did not assess the vitamin D-bone relationship separately) in the scientific literature for the years 1993–2000, but with emphasis on those published after the DRI report. The process for reviewing the U.S. claim and subsequently formulating one for Canada involved all three authors. Two of us (SW, DH) independently reviewed the scientific literature for Health Canada; the lead author wrote the document submitted for government approval. Additionally, in February 2000, Medline searches were conducted using the following parameters for the period 1993 to that date, restricted to English publications, using the following criteria: 1) calcium in TI (title); 2) #1 and (osteoporosis or bone); 3) #2 and trial; 4) #1 and (osteoporosis or bone and fracture); 5) #2 and meta; 6) #2 and (retrospective or cross-sectional or observational). Using these searches, additional articles not identified by the DRI Panel or external reviewers were identified, reviewed and included in this assessment. Every effort was made to ensure that all calcium clinical trials, in which a bone related outcome parameter (bone mineral density, BMD; bone mineral content, BMC; fracture) was measured, were included. However, it was not possible to ensure that all observational studies were obtained, due to the difficulty in finding such studies and the large number of potentially relevant studies that could be overlooked with conventional search parameters.
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EVALUATION OF THE EVIDENCE FOR CALCIUM AND OSTEOPOROSIS
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In the years since the FDA proposal was written, there have been a large number of intervention and cross-sectional studies published that for the most part supported the calcium and osteoporosis health claim. The DRI report for calcium also identified many studies in support of the calcium and bone health relationship. Dietary calcium is considered to be from food sources and/or supplements, and no attempt to distinguish these two sources has been made.
For children and adolescents, many randomized controlled intervention trials in which children have received supplemental calcium have been conducted since the FDA calcium and osteoporosis claim was proposed, and several have appeared subsequent to the release of the DRI report for calcium and related nutrients [12–16]. Taken together, the clinical trials have shown a modest but positive effect of increasing calcium intakes, particularly in those children with habitual intakes <1000 mg/day, on bone mineral accretion.
No controlled trials of calcium or vitamin D in young adults (19 to 50 years) were found during the literature search and few observational studies in this age group have been conducted, other than in pre- and peri-menopausal women. Observational studies, although suggestive of a benefit, were not consistent; however, a small but significant correlation coefficient between calcium intake and bone mass was found through meta-analysis of 24 of these studies [17]. Physical activity appears to be an important determinant of bone health in this age group [3]. In a number of studies conducted in this age group, physical activity was shown to be an additional important factor [18–20]. A similar conclusion about the importance of physical activity was reached in a meta analysis [21].
In both genders, after age 40, bone mass is lost from appendicular bone at a rate of 0.5% per year [22], while in women this rate increases to approximately 1% per year in the decade following menopause. A consistent feature of calcium trials in post-menopausal women has been that prevention of bone loss was greater in the first year than in subsequent years [23–26]. Considered as a whole, a large number of these studies found decreases in BMD losses, or BMD gains, with calcium supplementation when nonsupplemented intakes are below Adequate Intake levels. These findings have been confirmed in meta-analyses [27–30]. Observational studies which included men, [31] have generally indicated a positive effect of calcium on bone density for them as well.
In the elderly (those over 65 y) randomized controlled trials generally have found decreased fracture incidence [32–35], in addition to the positive changes in BMD, as is seen in younger age groups. Benefits appear to apply equally to men and women. An important consideration was that most studies provided a supplement of vitamin D along with calcium. Large observational studies have also been reported in the elderly and most support the relationship between higher intakes of calcium and increased BMD [20,36–38]. In the elderly, observational studies generally support the relationship between higher intakes of calcium and increased BMD, but were less conclusive about the benefits of calcium in reducing fracture rates.
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VITAMIN D
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Vitamin D is an important nutrient for bone health. In Canada, vitamin D fortification of milk (min 8.8–max 11.7 µg per liter) and margarine (13.25 µg per 100 grams) provides the major sources of dietary vitamin D. The other major source of vitamin D for humans is casual exposure to sunlight, however, factors such as pollution in the air, melanin of the skin, use of sunscreens and clothing to block the sun, and northern latitudes can affect the cutaneous synthesis of vitamin D [39]. The use of sunscreen is a preventative measure against skin cancer, however, its use necessitates a reliable safe and adequate source of vitamin D in the diet. There are also seasonal differences in the synthesis of vitamin D. It has been shown that the blood concentrations of 25-hydroxyvitamin D are higher in summertime than in wintertime at latitudes >40°N [40,41]. Experience during the 1960’s and early 1970’s demonstrated that a dietary source of vitamin D is necessary in Canada because of our northern latitude. Sunlight exposure during the long Canadian winter period is not adequate to prevent the occurrence of vitamin D deficiency, as evidenced by the high incidence of childhood rickets seen prior to the introduction of mandatory fortification of milk with vitamin D (for a complete review see [42]). Recent reports of apparently healthy Canadians suggest vitamin D status is less than optimal [43,44]. This is also consistent with evidence from many recent reports in which calcium and vitamin D were added together [3,32,34]. For these reasons, it is important that the linkage with vitamin D be promoted in Canada when permitting a health claim for calcium.
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HOW THE CANADIAN CLAIM WAS FORMULATED
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The Calcium-osteoporosis claim as approved by the FDA was dissected into its seven elements, each of which was evaluated. Regarding regular exercise and healthy diet, it was felt that this phrase should remain as exercise is important for bone health and calcium alone will not prevent bone loss in the absence of weight bearing exercise or other essential nutrients. The meta analysis by Kelley [29] as well as an evidence-based review by the Osteoporosis Society of Canada [3] supported maintaining the link with exercise. However, the order of these two items was reversed to read: "A healthy diet with adequate calcium ... and regular exercise ..." The second element concerned the words, "enough calcium," which implied a desirable amount. There is sufficient evidence that calcium at or near the Adequate Intake provides protection against bone loss in older adults and ensures development of peak bone mass in children and adolescents. However, the term "adequate calcium" was chosen to maintain consistency in terminology with the DRI. The third element concerned an age restriction for the claim, i.e., "teens and young adults." While most bone mass is accumulated during adolescence, there is evidence that adequate calcium during childhood can promote more bone formation [12,14,16]. Similarly, during later adult life, particularly in the elderly and during the late post menopausal years, calcium can protect against bone loss and fractures [3,24–28]. Therefore, the Canadian claim was not restricted to only teens and young adults. With respect to ethnicity, the fourth element of the FDA claim, there is evidence that white and Asian subjects have higher rates of osteoporosis than African-Americans [45]. However, all groups studied have some risk [46]. Furthermore, there is little information on risk in other ethnic groups in Canada (e.g., First Nations, East Indian). Therefore, reference to these two ethnic groups or any specific ethnic group was not justified for Canada, as it is likely that all ethnic groups have some risk and there is little information on calcium intakes and effects on bone parameters in other ethnic groups.
The fifth element of the FDA claim for calcium restricted it to women. However, both men and women are at risk for osteoporosis [3,31,33,34,46]. While men generally have lower risk, one reason for the difference is calcium intake, with Canadian males consuming more food and therefore more calcium than females at every age group beyond childhood [5–8]. The DRI Panel found no evidence of a specific gender effect in need for calcium (although there are fewer studies in men than women). Therefore, gender is not specified in the Canadian claim. Finally, the last two elements, "maintain good bone health" and "may reduce their risk of osteoporosis later in life," were reworded for clarity into two parts: one specifically directed at achieving strong bones and the second part to reducing the risk of osteoporosis. Viewing the claim as such would be consistent with the scientific evidence and with the DRI report on calcium and related nutrients [11]. There is sufficient evidence that calcium at or near levels recommended by the 1997 DRI Panel provides additional bone mass in children and adolescents, and in older adults, reduces bone loss and fractures. The terms "strong bones" and "osteoporosis" are in common usage and are used in publicity material by groups such as the Osteoporosis Society of Canada. They are appropriate for a health claim.
It was felt that the importance of vitamin D, particularly in children and the elderly, in enabling them to adequately use calcium, had to be included as part of the Canadian health claim. As summarized earlier in this review, there are several considerations in making this recommendation for Canada. The two population groups with the highest need for calcium are children and adolescents, and older adults. There is growing evidence that they also require dietary vitamin D as their needs cannot be met through sunlight exposure alone. Children in Canada may receive adequate vitamin D through fortification of milk and margarine. However, if calcium fortified food sources displaced vitamin D fortified foods, the re-emergence of rickets, similar to that seen in the 1960’s, might result. For older adults who require 10 µg/d (age 51–70) to 15 µg/d (age >70) [11], which are double and triple, respectively, the recommended intakes for younger age groups, dietary sources of vitamin D are vital. While the recommendations for vitamin D are assumed to be enough without sun exposure, recent evidence suggests this amount may not be adequate in the absence of sunlight [43].
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RESTRICTIONS ON USE OF THE CLAIM
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The U.S. Regulations restricted the use of the calcium health claim to foods with several conditions related to their phosphorus content, calcium content, and bioavailability. In addition, foods could not exceed levels of disqualifying nutrients and had to contain appropriate amounts of qualifying nutrients. In Canada, it was decided that the restriction on foods containing more phosphorus than calcium should remain except that phosphorus-containing phytate was excluded from the calculation of phosphorus content, as this phosphorus is less available to monogastics [47] and is often associated with healthy foods (i.e. high dietary fibre). The FDA health claim [9,10] requires a calcium level of 200 mg, while in Canada, a high calcium food or excellent source is 165 mg. The 1997 DRI [11] values for calcium have been harmonized between Canada and the U.S., and the new recommendations or Adequate Intakes are substantially higher than the 1990 Canadian RNI [48]. For these reasons, the 200 mg level was proposed for the Canadian calcium health claim. Bioavailability is not specifically a criterion of this health claim; however, foods fortified with calcium must still satisfy the bioavailability criterion for fortification. When the health claim regulations were established by the U.S. FDA in 1993, foods containing >400 mg were required to carry the statement, "but daily intakes exceeding 2000 mg are not likely to provide any additional benefit," as a way of limiting indiscriminate or inappropriately high fortification levels. Inclusion of this statement would not be required for Canada, as Canadian regulations do not permit indiscriminate addition of calcium to foods. Under the proposed Canadian Policy Recommendations concerning the Addition of Vitamins and Minerals to Foods [49] an upper permissible level of fortification will be established for nutrients including calcium, making this statement unnecessary.
Compositional criteria were included as part of the U.S. regulatory system so that the value of health claims would not be trivialized or compromised by their use on foods of little or no nutritional value (foods must contain at least 10% of one of five other nutrients: vitamin A, vitamin C, protein, fiber, iron) [9]. Restrictions were also placed in the U.S. on levels of fat, cholesterol, and sodium when making a health claim (disqualifying nutrients). In Canada, most of these restrictions are being dealt with in establishing the appropriate food vehicles for food fortification and do not form part of the health claim for calcium.
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SUMMARY
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Based on a review of the evidence related to the various claim elements, the following health claim is now in effect in Canada [50]:
A healthy diet with adequate calcium and vitamin D, and regular physical activity, help to achieve strong bones and may reduce the risk of osteoporosis.
The following compositional criteria are required for foods bearing this claim: the food must provide at least 200 mg calcium per serving and the phosphorus content (excluding that provided by phytate) must be less than the calcium content. The complete text and conditions for the health claim are shown in Table 1.The full review containing all references can be obtained from the Bureau of Nutritional Sciences, Health Canada.
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ACKNOWLEDGMENTS
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The authors acknowledge the assistance of Tarik Kassaye, PhD, Jennifer Boyle MSc and Yuka Suzuki, MSc for their invaluable assistance in abstracting data used in this report.
Received January 22, 2003.
Accepted January 20, 2004.
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TOP
ABSTRACT
INTRODUCTION
