Osteoarthritis and Cartilage 22 (2014) 1949e1950
Letter to the Editor
Response to Letter to the Editor: “Food frequency questionnaire is an effective method for measuring micronutrient intake.” Dear Editor, We would like to thank Lei et al. for their thoughtful letter to the editor regarding our recent article on “High Plasma Levels of Vitamin C and E Are Associated with Incident Radiographic Knee Osteoarthritis.” Our paper examined the association of antioxidants with incident radiographic knee OA and did not find a protective association between high blood levels of vitamin C or E and incident knee OA. The points raised by Lei et al. are focused on the accuracy of FFQ to estimate dietary intake of the micronutrients, and we would like to respond to the points raised. First, we thank the authors for pointing out our error in citing reference 12 regarding the poor correspondence between Food Frequency Questionnaires (FFQs) estimates for dietary intake of vitamins C and E and serum levels of these micronutrients, when we intended to cite reference 13. We apologize for any confusion this editing error may have caused. However, the larger point that we were making regarding the correlation between FFQ and the measurement of blood levels of vitamin C and E remains unchanged and is supported by the study by Tangey et al., and others. There is some correlation between dietary intake of vitamin C and blood levels, but it is moderate1,2. In the study by Tangey et al.2, FFQ intake estimates account for less than 25% of the variation in serum levels of vitamin C and E in older blacks and whites, similar to what has been found in other studies3. While correlations of this magnitude provide some evidence for the validity of the FFQ-based methods, we chose to study blood levels of vitamins C and E directly rather than estimating them from dietary and supplement intake. In addition, Lei et al. also stated that several other studies4e6 utilized an FFQ to ascertain intake of various types of foods. While these are high-quality studies, FFQs were used to assess intake of DASH diet foods4, low-carbohydrate foods5, and Mediterranean diet foods6, and FFQs were not specifically used to assess vitamin C and E intake, the micronutrients studied in our paper. Lei et al. also suggest that the baseline measurements of vitamin C and E in blood may not accurately reflect serum levels 30 months later, and this point is a valid one, and a limitation that we already noted. Lei et al. also question whether 30 months follow-up is an adequate time for incident knee OA to develop. Incident radiographic knee OA by 30 months in MOST has already been used in several published studies in which the number of incident endpoints was adequate to demonstrate associations with risk factors for knee OA, including meniscal lesions7, knee malalignment8,
DOI of original article: http://dx.doi.org/10.1016/j.joca.2014.06.039.
high bone density9, leg length discrepancy10 and blood vitamin K levels11. Analyses with longer follow-up would nonetheless be of value as well. Finally, the point of Lei et al. that both dietary intake and blood level measurement of micronutrients have their respective “advantages and disadvantages” depending on the goals of a study is valid and well-taken. Again, we would like to thank Lei et al. for their comments. While we appreciate the points raised regarding the use of FFQ to estimate micronutrient intake, they do not alter the substance of our findings. Author disclosures None. Acknowledgements The MOST Study is supported by National Institutes of Health (NIH) grants from the National Institute on Aging: U01-AG19069; U01-AG-18820; U01-AG-18947; U01-AG-18832. References 1. Knutsen SF, Fraser GE, Linsted KD, Beeson WL, Shavlik DJ. Comparing biological measurements of vitamin C, folate, alpha-tocopherol and carotene with 24-hour dietary recall information in nonhispanic blacks and whites. Ann Epidemiol 2001 Aug;11(6):406e16 [Comparative Study Research Support, U.S. Gov't, P.H.S.]. 2. Tangney CC, Bienias JL, Evans DA, Morris MC. Reasonable estimates of serum vitamin E, vitamin C, and beta-cryptoxanthin are obtained with a food frequency questionnaire in older black and white adults. J Nutr 2004 Apr;134(4):927e34 [Comparative Study Research Support, U.S. Gov't, P.H.S.]. 3. Dehghan M, Akhtar-Danesh N, McMillan CR, Thabane L. Is plasma vitamin C an appropriate biomarker of vitamin C intake? A systematic review and meta-analysis. Nutr J 2007;6:41 [Meta-Analysis Review]. 4. Forman JP, Stampfer MJ, Curhan GC. Diet and lifestyle risk factors associated with incident hypertension in women. JAMA 2009 Jul 22;302(4):401e11 [Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't]. 5. Halton TL, Willett WC, Liu S, Manson JE, Albert CM, Rexrode K, et al. Low-carbohydrate-diet score and the risk of coronary heart disease in women. N Engl J Med 2006 Nov 9;355(19):
http://dx.doi.org/10.1016/j.joca.2014.08.007 1063-4584/© 2014 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.
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Letter to the Editor / Osteoarthritis and Cartilage 22 (2014) 1949e1950
1991e2002 [Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't]. Estruch R, Ros E, Salas-Salvado J, Covas MI, Corella D, Aros F, et al. Primary prevention of cardiovascular disease with a Mediterranean diet. N Engl J Med 2013 Apr 4;368(14):1279e90 [Multicenter Study Randomized Controlled Trial Research Support, Non-U.S. Gov't]. Englund M, Guermazi A, Roemer FW, Aliabadi P, Yang M, Lewis CE, et al. Meniscal tear in knees without surgery and the development of radiographic osteoarthritis among middle-aged and elderly persons: the Multicenter Osteoarthritis Study. Arthritis Rheum 2009 Mar;60(3):831e9 [Multicenter Study Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't]. Hayashi D, Englund M, Roemer FW, Niu J, Sharma L, Felson DT, et al. Knee malalignment is associated with an increased risk for incident and enlarging bone marrow lesions in the more loaded compartments: the MOST study. Osteoarthritis Cartilage 2012 Nov;20(11):1227e33 [Research Support, N.I.H., Extramural]. Nevitt MC, Zhang Y, Javaid MK, Neogi T, Curtis JR, Niu J, et al. High systemic bone mineral density increases the risk of incident knee OA and joint space narrowing, but not radiographic progression of existing knee OA: the MOST study. Ann Rheum Dis 2010 Jan;69(1):163e8 [Multicenter Study Research Support, N.I.H., Extramural]. Harvey WF, Yang M, Cooke TD, Segal NA, Lane N, Lewis CE, et al. Association of leg-length inequality with knee osteoarthritis: a cohort study. Ann Intern Med 2010 Mar 2;152(5):
287e95 [Multicenter Study Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't]. 11. Misra D, Booth SL, Tolstykh I, Felson DT, Nevitt MC, Lewis CE, et al. Vitamin K deficiency is associated with incident knee osteoarthritis. Am J Med 2013 Mar;126(3):243e8 [Multicenter Study Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S.]. R.K. Chaganti Department of Medicine, University of California, San Francisco, San Francisco, CA, USA N.E. Lane Department of Medicine, University of California at Davis Medical School, Sacramento, CA, USA M.C. Nevitt* Department of Epidemiology and Biostatistics, University of California, San Francisco, CA, USA *
Address correspondence and reprint requests to: M.C. Nevitt, Department of Epidemiology and Biostatistics, University of California, San Francisco, 185 Berry St, Ste 5700, Lobby 5, San Francisco, CA 94107, USA. Tel: 415-514 8048; Fax: 415-514-8150. E-mail address: [email protected] (M.C. Nevitt). 7 August 2014
Letter to the Editor
Response to Letter to the Editor: “Food frequency questionnaire is an effective method for measuring micronutrient intake.” Dear Editor, We would like to thank Lei et al. for their thoughtful letter to the editor regarding our recent article on “High Plasma Levels of Vitamin C and E Are Associated with Incident Radiographic Knee Osteoarthritis.” Our paper examined the association of antioxidants with incident radiographic knee OA and did not find a protective association between high blood levels of vitamin C or E and incident knee OA. The points raised by Lei et al. are focused on the accuracy of FFQ to estimate dietary intake of the micronutrients, and we would like to respond to the points raised. First, we thank the authors for pointing out our error in citing reference 12 regarding the poor correspondence between Food Frequency Questionnaires (FFQs) estimates for dietary intake of vitamins C and E and serum levels of these micronutrients, when we intended to cite reference 13. We apologize for any confusion this editing error may have caused. However, the larger point that we were making regarding the correlation between FFQ and the measurement of blood levels of vitamin C and E remains unchanged and is supported by the study by Tangey et al., and others. There is some correlation between dietary intake of vitamin C and blood levels, but it is moderate1,2. In the study by Tangey et al.2, FFQ intake estimates account for less than 25% of the variation in serum levels of vitamin C and E in older blacks and whites, similar to what has been found in other studies3. While correlations of this magnitude provide some evidence for the validity of the FFQ-based methods, we chose to study blood levels of vitamins C and E directly rather than estimating them from dietary and supplement intake. In addition, Lei et al. also stated that several other studies4e6 utilized an FFQ to ascertain intake of various types of foods. While these are high-quality studies, FFQs were used to assess intake of DASH diet foods4, low-carbohydrate foods5, and Mediterranean diet foods6, and FFQs were not specifically used to assess vitamin C and E intake, the micronutrients studied in our paper. Lei et al. also suggest that the baseline measurements of vitamin C and E in blood may not accurately reflect serum levels 30 months later, and this point is a valid one, and a limitation that we already noted. Lei et al. also question whether 30 months follow-up is an adequate time for incident knee OA to develop. Incident radiographic knee OA by 30 months in MOST has already been used in several published studies in which the number of incident endpoints was adequate to demonstrate associations with risk factors for knee OA, including meniscal lesions7, knee malalignment8,
DOI of original article: http://dx.doi.org/10.1016/j.joca.2014.06.039.
high bone density9, leg length discrepancy10 and blood vitamin K levels11. Analyses with longer follow-up would nonetheless be of value as well. Finally, the point of Lei et al. that both dietary intake and blood level measurement of micronutrients have their respective “advantages and disadvantages” depending on the goals of a study is valid and well-taken. Again, we would like to thank Lei et al. for their comments. While we appreciate the points raised regarding the use of FFQ to estimate micronutrient intake, they do not alter the substance of our findings. Author disclosures None. Acknowledgements The MOST Study is supported by National Institutes of Health (NIH) grants from the National Institute on Aging: U01-AG19069; U01-AG-18820; U01-AG-18947; U01-AG-18832. References 1. Knutsen SF, Fraser GE, Linsted KD, Beeson WL, Shavlik DJ. Comparing biological measurements of vitamin C, folate, alpha-tocopherol and carotene with 24-hour dietary recall information in nonhispanic blacks and whites. Ann Epidemiol 2001 Aug;11(6):406e16 [Comparative Study Research Support, U.S. Gov't, P.H.S.]. 2. Tangney CC, Bienias JL, Evans DA, Morris MC. Reasonable estimates of serum vitamin E, vitamin C, and beta-cryptoxanthin are obtained with a food frequency questionnaire in older black and white adults. J Nutr 2004 Apr;134(4):927e34 [Comparative Study Research Support, U.S. Gov't, P.H.S.]. 3. Dehghan M, Akhtar-Danesh N, McMillan CR, Thabane L. Is plasma vitamin C an appropriate biomarker of vitamin C intake? A systematic review and meta-analysis. Nutr J 2007;6:41 [Meta-Analysis Review]. 4. Forman JP, Stampfer MJ, Curhan GC. Diet and lifestyle risk factors associated with incident hypertension in women. JAMA 2009 Jul 22;302(4):401e11 [Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't]. 5. Halton TL, Willett WC, Liu S, Manson JE, Albert CM, Rexrode K, et al. Low-carbohydrate-diet score and the risk of coronary heart disease in women. N Engl J Med 2006 Nov 9;355(19):
http://dx.doi.org/10.1016/j.joca.2014.08.007 1063-4584/© 2014 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.
1950
6.
7.
8.
9.
10.
Letter to the Editor / Osteoarthritis and Cartilage 22 (2014) 1949e1950
1991e2002 [Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't]. Estruch R, Ros E, Salas-Salvado J, Covas MI, Corella D, Aros F, et al. Primary prevention of cardiovascular disease with a Mediterranean diet. N Engl J Med 2013 Apr 4;368(14):1279e90 [Multicenter Study Randomized Controlled Trial Research Support, Non-U.S. Gov't]. Englund M, Guermazi A, Roemer FW, Aliabadi P, Yang M, Lewis CE, et al. Meniscal tear in knees without surgery and the development of radiographic osteoarthritis among middle-aged and elderly persons: the Multicenter Osteoarthritis Study. Arthritis Rheum 2009 Mar;60(3):831e9 [Multicenter Study Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't]. Hayashi D, Englund M, Roemer FW, Niu J, Sharma L, Felson DT, et al. Knee malalignment is associated with an increased risk for incident and enlarging bone marrow lesions in the more loaded compartments: the MOST study. Osteoarthritis Cartilage 2012 Nov;20(11):1227e33 [Research Support, N.I.H., Extramural]. Nevitt MC, Zhang Y, Javaid MK, Neogi T, Curtis JR, Niu J, et al. High systemic bone mineral density increases the risk of incident knee OA and joint space narrowing, but not radiographic progression of existing knee OA: the MOST study. Ann Rheum Dis 2010 Jan;69(1):163e8 [Multicenter Study Research Support, N.I.H., Extramural]. Harvey WF, Yang M, Cooke TD, Segal NA, Lane N, Lewis CE, et al. Association of leg-length inequality with knee osteoarthritis: a cohort study. Ann Intern Med 2010 Mar 2;152(5):
287e95 [Multicenter Study Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't]. 11. Misra D, Booth SL, Tolstykh I, Felson DT, Nevitt MC, Lewis CE, et al. Vitamin K deficiency is associated with incident knee osteoarthritis. Am J Med 2013 Mar;126(3):243e8 [Multicenter Study Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S.]. R.K. Chaganti Department of Medicine, University of California, San Francisco, San Francisco, CA, USA N.E. Lane Department of Medicine, University of California at Davis Medical School, Sacramento, CA, USA M.C. Nevitt* Department of Epidemiology and Biostatistics, University of California, San Francisco, CA, USA *
Address correspondence and reprint requests to: M.C. Nevitt, Department of Epidemiology and Biostatistics, University of California, San Francisco, 185 Berry St, Ste 5700, Lobby 5, San Francisco, CA 94107, USA. Tel: 415-514 8048; Fax: 415-514-8150. E-mail address: [email protected] (M.C. Nevitt). 7 August 2014
