Osteoarthritis and Cartilage 22 (2014) 1947e1948
Letter to the Editor
Food frequency questionnaire is an effective method for measuring micronutrient intake Keywords: Food frequency questionnaire Osteoarthritis Intake
Dear Editors, We read the research of Chaganti et al.1 with great interest. We believe this is a well-conducted nested caseecontrol study which provided evidence that higher level of circulating vitamin C and E did not have a protection effect against incident radiographic knee OA, and it may be even associated with an increased risk of knee OA. Such findings were quite impressive and totally overturned our conventional notions. We sincerely appreciated the tremendous effort made by the authors for presenting this extremely valuable outcome. However, there are also some worthwhile issues need to be explored. First of all, in the third paragraph of the introduction, the authors cited reference 12 to support their point of view that food frequency questionnaires (FFQ) is a method prone to misclassification of micronutrient intake and dietary vitamin C intake data shows great variability, and plasma levels may better reflect the long term vitamin C status2. However, the study conducted by Brand et al.2 is a randomized controlled trial which assessed the effect of vitamin E for symptomatic knee osteoarthritis (OA). It is basically unrelated to this point. Maybe the authors mistook reference 12 for 13, but anyway, this judgment appeared too subjective. In addition, Tangney et al.3 (reference 13) concluded that FFQ provides reasonably valid estimates for vitamin C intakes, which covered both dietary intake and supplementation. There is actually no criticism. Furthermore, the study conducted by Tangney et al.3 did not prove that plasma levels may better reflect the long term vitamin C status as the authors claimed. On the other hand, the authors expressed their negative views again on the use of FFQ to assess dietary vitamin intake, especially for vitamin C in the third and fifth paragraphs of the discussion respectively. In the third paragraph, they stated that FFQ is a method restricted by weak correlations with objective micronutrient biomarkers and misclassification of nutrient intake, especially for vitamin C. However, according to the reference paper, Dehghan et al.4 suggested that FFQ had a moderate relationship, rather than a weak correlation, with plasma vitamin C. In addition, this study is only a systematic review and meta-analysis assessing the relationship between plasma vitamin C and vitamin C intake4, which could not reach a conclusion that blood levels can better
reflect long-term circulating levels of vitamin C than assessments of dietary intake using food FFQ. This is contradictory with what the authors suggested in the fifth paragraph of the discussion. Plenty of studies adopted FFQ to measure food or nutrition intake, including lots of high quality studies5e7. As Tangney et al.3 (reference 13) suggested, FFQ was a valid and reliable method for evaluating nutrition intake if properly designed and used, but the negative attitude of the authors with respect to the use of FFQ might discourage subsequent researchers. On the other hand, Fortmann et al.8 suggested that blood levels may not fully reflect the nutritional status. Actually, the authors also admitted that blood levels may not correlate strongly with antioxidant levels in joint fluid. Furthermore, plasma levels of vitamin C and serum levels of vitamin E were only measured at the baseline, so I am afraid it is difficult to reflect the accurate circulating levels during the 30 months of follow-up. Of course, it can't be denied that blood levels may better reflect the instant levels of micronutrients. In conclusion, both dietary intake and blood level assessment have their respective advantages and disadvantages. Last but not the least, as a chronic joint disease, the authors did not mention whether the 30 month follow-up is long enough to detect the incidence of OA. Above all, we respect the contribution of the authors and we are pretty sure the results of the data analysis are accurate. Authors' contributions All authors made substantial contributions to the interpretation, drafting, and revisions and approved the final version. Conflict of interest The authors declare that they have no conflicts of interest. Acknowledgment This work was supported by Hunan Provincial Innovation Foundation for Postgraduate, the Fundamental Research Funds for the Central Universities of Central South University, the National Natural Science Foundation of China (No. 81201420, 81272034), the Provincial Science Foundation of Hunan (No. 14JJ3032), the Scientific Research Project of the Development and Reform Commission of Hunan Province ([2013]1199), the Scientific Research Project of Science and Technology Office of Hunan Province (2013SK2018), the Doctoral Scientific Fund Project of the Ministry of Education of China (20120162110036).
http://dx.doi.org/10.1016/j.joca.2014.06.039 1063-4584/© 2014 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.
1948
Letter to the Editor / Osteoarthritis and Cartilage 22 (2014) 1947e1948
References 1. Chaganti RK, Tolstykh I, Javaid MK, Neogi T, Torner J, Curtis J, et al. High plasma levels of vitamin C and E are associated with incident radiographic knee osteoarthritis. Osteoarthritis Cartilage 2014;22(2):190e6. 2. Brand C, Snaddon J, Bailey M, Cicuttini F. Vitamin E is ineffective for symptomatic relief of knee osteoarthritis: a six month double blind, randomised, placebo controlled study. Ann Rheum Dis 2001;60(10):946e9. 3. 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;134(4):927e34. 4. 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. 5. Forman JP, Stampfer MJ, Curhan GC. Diet and lifestyle risk factors associated with incident hypertension in women. JAMA 2009;302(4):401e11. 6. 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;355(19):1991e2002. J, Covas MI, Corella D, Aro s F, 7. Estruch R, Ros E, Salas-Salvado et al. Primary prevention of cardiovascular disease with a Mediterranean diet. N Engl J Med 2013;368(14):1279e90. 8. Fortmann SP, Burda BU, Senger CA, Lin JS, Whitlock EP. Vitamin and mineral supplements in the primary prevention of
cardiovascular disease and cancer: an updated systematic evidence review for the U.S. Preventive Services Task Force. Ann Intern Med 2013;159(12):824e34. C. Zeng Department of Orthopaedics, Xiangya Hospital, Central South University, #87 Xiangya Road, Changsha, Hunan Province 410008, China E-mail address: [email protected]. J. Wei Department of Epidemiology and Health Statistics, School of Public Health, Central South University, Changsha, Hunan Province 410008, China G.-h. Lei* Department of Orthopaedics, Xiangya Hospital, Central South University, #87 Xiangya Road, Changsha, Hunan Province 410008, China * Address correspondence and reprint requests to: G.-h. Lei, Department of Orthopaedics, Xiangya Hospital, Central South University, #87 Xiangya Road, Changsha, Hunan Province 410008, China. E-mail addresses: [email protected], [email protected] (G.-h. Lei).
25 June 2014
Letter to the Editor
Food frequency questionnaire is an effective method for measuring micronutrient intake Keywords: Food frequency questionnaire Osteoarthritis Intake
Dear Editors, We read the research of Chaganti et al.1 with great interest. We believe this is a well-conducted nested caseecontrol study which provided evidence that higher level of circulating vitamin C and E did not have a protection effect against incident radiographic knee OA, and it may be even associated with an increased risk of knee OA. Such findings were quite impressive and totally overturned our conventional notions. We sincerely appreciated the tremendous effort made by the authors for presenting this extremely valuable outcome. However, there are also some worthwhile issues need to be explored. First of all, in the third paragraph of the introduction, the authors cited reference 12 to support their point of view that food frequency questionnaires (FFQ) is a method prone to misclassification of micronutrient intake and dietary vitamin C intake data shows great variability, and plasma levels may better reflect the long term vitamin C status2. However, the study conducted by Brand et al.2 is a randomized controlled trial which assessed the effect of vitamin E for symptomatic knee osteoarthritis (OA). It is basically unrelated to this point. Maybe the authors mistook reference 12 for 13, but anyway, this judgment appeared too subjective. In addition, Tangney et al.3 (reference 13) concluded that FFQ provides reasonably valid estimates for vitamin C intakes, which covered both dietary intake and supplementation. There is actually no criticism. Furthermore, the study conducted by Tangney et al.3 did not prove that plasma levels may better reflect the long term vitamin C status as the authors claimed. On the other hand, the authors expressed their negative views again on the use of FFQ to assess dietary vitamin intake, especially for vitamin C in the third and fifth paragraphs of the discussion respectively. In the third paragraph, they stated that FFQ is a method restricted by weak correlations with objective micronutrient biomarkers and misclassification of nutrient intake, especially for vitamin C. However, according to the reference paper, Dehghan et al.4 suggested that FFQ had a moderate relationship, rather than a weak correlation, with plasma vitamin C. In addition, this study is only a systematic review and meta-analysis assessing the relationship between plasma vitamin C and vitamin C intake4, which could not reach a conclusion that blood levels can better
reflect long-term circulating levels of vitamin C than assessments of dietary intake using food FFQ. This is contradictory with what the authors suggested in the fifth paragraph of the discussion. Plenty of studies adopted FFQ to measure food or nutrition intake, including lots of high quality studies5e7. As Tangney et al.3 (reference 13) suggested, FFQ was a valid and reliable method for evaluating nutrition intake if properly designed and used, but the negative attitude of the authors with respect to the use of FFQ might discourage subsequent researchers. On the other hand, Fortmann et al.8 suggested that blood levels may not fully reflect the nutritional status. Actually, the authors also admitted that blood levels may not correlate strongly with antioxidant levels in joint fluid. Furthermore, plasma levels of vitamin C and serum levels of vitamin E were only measured at the baseline, so I am afraid it is difficult to reflect the accurate circulating levels during the 30 months of follow-up. Of course, it can't be denied that blood levels may better reflect the instant levels of micronutrients. In conclusion, both dietary intake and blood level assessment have their respective advantages and disadvantages. Last but not the least, as a chronic joint disease, the authors did not mention whether the 30 month follow-up is long enough to detect the incidence of OA. Above all, we respect the contribution of the authors and we are pretty sure the results of the data analysis are accurate. Authors' contributions All authors made substantial contributions to the interpretation, drafting, and revisions and approved the final version. Conflict of interest The authors declare that they have no conflicts of interest. Acknowledgment This work was supported by Hunan Provincial Innovation Foundation for Postgraduate, the Fundamental Research Funds for the Central Universities of Central South University, the National Natural Science Foundation of China (No. 81201420, 81272034), the Provincial Science Foundation of Hunan (No. 14JJ3032), the Scientific Research Project of the Development and Reform Commission of Hunan Province ([2013]1199), the Scientific Research Project of Science and Technology Office of Hunan Province (2013SK2018), the Doctoral Scientific Fund Project of the Ministry of Education of China (20120162110036).
http://dx.doi.org/10.1016/j.joca.2014.06.039 1063-4584/© 2014 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.
1948
Letter to the Editor / Osteoarthritis and Cartilage 22 (2014) 1947e1948
References 1. Chaganti RK, Tolstykh I, Javaid MK, Neogi T, Torner J, Curtis J, et al. High plasma levels of vitamin C and E are associated with incident radiographic knee osteoarthritis. Osteoarthritis Cartilage 2014;22(2):190e6. 2. Brand C, Snaddon J, Bailey M, Cicuttini F. Vitamin E is ineffective for symptomatic relief of knee osteoarthritis: a six month double blind, randomised, placebo controlled study. Ann Rheum Dis 2001;60(10):946e9. 3. 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;134(4):927e34. 4. 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. 5. Forman JP, Stampfer MJ, Curhan GC. Diet and lifestyle risk factors associated with incident hypertension in women. JAMA 2009;302(4):401e11. 6. 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;355(19):1991e2002. J, Covas MI, Corella D, Aro s F, 7. Estruch R, Ros E, Salas-Salvado et al. Primary prevention of cardiovascular disease with a Mediterranean diet. N Engl J Med 2013;368(14):1279e90. 8. Fortmann SP, Burda BU, Senger CA, Lin JS, Whitlock EP. Vitamin and mineral supplements in the primary prevention of
cardiovascular disease and cancer: an updated systematic evidence review for the U.S. Preventive Services Task Force. Ann Intern Med 2013;159(12):824e34. C. Zeng Department of Orthopaedics, Xiangya Hospital, Central South University, #87 Xiangya Road, Changsha, Hunan Province 410008, China E-mail address: [email protected]. J. Wei Department of Epidemiology and Health Statistics, School of Public Health, Central South University, Changsha, Hunan Province 410008, China G.-h. Lei* Department of Orthopaedics, Xiangya Hospital, Central South University, #87 Xiangya Road, Changsha, Hunan Province 410008, China * Address correspondence and reprint requests to: G.-h. Lei, Department of Orthopaedics, Xiangya Hospital, Central South University, #87 Xiangya Road, Changsha, Hunan Province 410008, China. E-mail addresses: [email protected], [email protected] (G.-h. Lei).
25 June 2014
