Osteoporos Int (2015) 26:835–836 DOI 10.1007/s00198-014-2868-1

LETTER

Estimation of dietary calcium intake L. A. Rasch & L. H. D. van Tuyl & M. A. E. de van der Schueren & I. E. M. Bultink & W. F. Lems

Received: 16 July 2014 / Accepted: 20 August 2014 / Published online: 30 August 2014 # International Osteoporosis Foundation and National Osteoporosis Foundation 2014

Dear Editor, With great pleasure we read the article by Macdonald et al., describing the validation of a 23-item questionnaire for estimating dietary calcium intake, the CaQ [1]. We encourage this initiative as we are in search of an easy, accurate, and feasible way to estimate the calcium intake of our patients as well. Recently, there has been a lot of attention for the possible elevated cardiovascular risks of surplus calcium supplementation on the one hand and calcium deficiency on the other hand in patients with osteoporosis. To be able to prescribe the adequate amount of calcium supplementation, a practical tool to validly estimate the dietary intake of calcium is not available to clinicians. Most dietary assessment methods are too timeconsuming for clinical practice. The gold standard of assessing dietary calcium intake is a 7-day food diary with weighed portion sizes, which is laborious for clinicians as well as for patients, and therefore not feasible in clinical practice. Food frequency questionnaires (FFQ) are far more practical; however, they still consist of many questions and thus are not feasible in clinical practice either. Macdonald et al. validated their 23-item CaQ against two “gold standards”: a 7-day food diary (n=33), which

L. A. Rasch (*) : L. H. D. van Tuyl : I. E. M. Bultink : W. F. Lems Department of Rheumatology, VU University Medical Center, Amsterdam, Netherlands e-mail: [email protected] M. A. E. de van der Schueren Department of Nutrition and Dietetics, VU University Medical Center, Amsterdam, Netherlands

is close to a real gold standard, although portion sizes were estimated rather than weighed, and a FFQ (n=72), which is similar to the CaQ except for being more elaborate. The authors conclude that their CaQ is an adequate tool to assess daily calcium intake when scoring between 700 and 1,200 mg. Although we were excited to see the work of Macdonald et al., we missed a detailed report on the number of patients that has an estimated calcium intake outside a predefined clinically relevant area. For example, if an intake of 1,000 mg would be considered normal, a difference of 250 mg between the gold standard and the questionnaire would be clinically relevant, as patients below 750 mg would benefit from supplementation. From a clinician’s perspective, it is important to know how many patients fall within the clinically relevant area, in order to judge the applicability of the CaQ for prescription of calcium supplements to patients. We recently validated a calcium intake list with only three items, which underestimated calcium intake compared to a dietary history with a clinically relevant difference of more than 250 mg in 56 % of patients [2]. Using our list to prescribe calcium supplements would mean that too many patients would be given too much calcium, possibly resulting in elevated cardiovascular risks. Currently, we are in the process of refining the list in order to improve sensitivity and specificity for use in clinical practice. We look forward to validation studies of calcium intake lists in other cohorts of osteoporosis patients to see if these lists are valid across cultures and diets and to decide on clinically relevant cutoff points for the prescription of calcium medication.

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References 1. Macdonald HM, Garland A, Burr J, Strachan A, Wood AD, Jamil NA, McLernon D, Black AJ (2014) Validation of a short

Osteoporos Int (2015) 26:835–836 questionnaire for estimating dietary calcium intakes. Osteoporos Int 25:1765–1773 2. Rasch LA, De van der Schueren MAE, Van Tuyl LHD, Bultink IEM, Lems WF (2014) Validity of a calcium intake list to estimate calcium intake in patients with osteoporosis. Austin J Nutri Food Sci 2(3):6

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