LETTERS TO THE EDITOR
983
Reply to LF Tinker Dear Sir:
Jacques Masse Departement de Biochimie Hopital du Saint-Sacrement
References I. Masse 1. Effects of diet on serum lipids and apolipoproteins. Am J
Clin Nutr 1990;52:765(letter). 2. Wardlaw GM, Snook JT. Effect of diets high in butter, corn oil, or high-oleic acid sunflower oil on serum lipids and apolipoproteins in men. Am J C1in Nutr.1990;51:815-21. 3. Masse J. Changes in lipoproteins during weight loss. N Eng! J Med 1989;320:668 (letter). 4. Masse J. Portable cholesterol analyzers. JAMA 1990;264:1101 1990;89:836 (leiter). 5. Masse J. Clinical chemistry reference intervals for healthy elderly subjects. Am J Clin Nutr 1990;51:1115 (letter). 6. Masse J. Coffee consumption and serum lipid. Am J Med (letter) (in press). 7. Masse J. Lipid profiles after cardiac transplantation. Am J Cardiol (letter) (in press). 8. Masse J. Calculation of low-density lipoprotein cholesterol. Arch Int Med (letter) (in press). 9. DeLong OM, DeLong ER, Wood PO, Lippel K, Ritkind BM. A comparison of methods for the estimation of plasma low- and very low.density lipoprotein cholesterol: the Lipid Research Clinics Prevalence Study. JAMA 1986;256:2372-7. 10. Friedewald WT, Levy RI, Frederickson OS. Estimation oflow·density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chern 1972; 18:499-502.
Nutritional immunology in elderly people Dear Sir: I am writing to you with reference to a recently published paper by Payette et al (I). There are many problems with the data, analysis ofdata, and interpretation of the literature in this paper. It is surprising that the authors and your editorial staff seem unaware of the important data concerning vitamin E and immune function in elderly people that were published in the September issue of the journal (2). This article is not even referred to in the paper by Payette et ai, which also discusses the role of vitamin E in elderly people's immune functions-specifically of interleukin 2 (1L-2). In most journals, if very similar data are to appear, the accepted, in-press paper is shared with the authors of a forthcoming paper. Without such editorial leadership, the impression is given that the editors (and staff) do not know what' is published in their own journal. With specific regard to the paper by Payette et ai, there seem to be several grave discrepancies in the data. In Table 2, the mean daily intake (diet plus supplement) ofvitamin £ is 30 ± 76 mg and the median is 7.2 mg. Yet on p 931, the authors state that eight individuals (10% of the population) were taking megadoses of 20-80 times the Canadian recommended nutrient intake (i~.NI) of vitamin £ (which is 5-7 mg, depending on age and sex). How can the data in Table 2 be correct with eight individuals having such a wide and -high range of intakes of vitamin £? It would seem mathematically impossible to have a
median of7.2 mg unless 50% ofthe 82 participants had extremely low intakes, ie, < 7.2 mg. Because the data are so skewed and because so many variables are involved, the simple statistical analyses performed have a very great potential of resulting in incorrect conclusions. Multiple logistic regressions are required, and with this small a sample and so many variables, this may not be possible. Concerning the IL-2 activity data, because 59 of 82 subjects had IL-2 concentrations < 0.005 kU/L, any correlation with vitamin E or vitamin D concentrations would be mathematically skewed because of the high number of very low responders in this population. It is difficult to imagine that low zinc concentrations, seen in 53% of this population, were not correlated with undetectable IL-2 concentrations found in 69% of the same population. Why are probabilities rather than actual data plotted in Figure 3? What is the relationship of the SD to the actual range of intakes in the population studied? These data do not allow the reader access to the raw data used to derive this figure. It is also most surprising that the authors did not include any data related to their biochemical assays. In partiCular, did the plasma vitamin C or either serum or red blood cell folates correlate with the dietary information? Did the concentrations of nutrients in blood correlate with the immunological data? Why were these biochemical analyses mentioned in the Methods section ifthe data are not presented? The authors measured all fatty acids; what about concentrations of fat-soluble vitamins, es-
Downloaded from https://academic.oup.com/ajcn/article-abstract/53/4/983/4715125 by East Carolina University user on 15 March 2019
The letter from Tinker is an illustration of the point I tried to make when I wrote the letter (I) about the article of Wardlaw and Snook (2) and several other letters on the same subject (38). Authors and readers in the United States are generally unfamiliar with Systeme International (SI) units. The fact that the equation is corrected to be applicable with SI units does not change the eq uation, and the original article (9) did not need to be quoted again. In fact, Tinker made an error in the letter when correctly citing the equation of Friedewald et al (10) for the mg! dL units but incorrectly citing the wrong authors (9) after writing the corrected equation for use with SI units. The authors in the United States usually do their work and calculations with the conventional units and only convert their results to SI units to conform to journals' requirements. The results published are thus valid. The problem comes from the fact that the authors do not mention in their methods sections that they proceeded that way. International readers (and even readers in the United States) are not necessarily aware of this, so they can be misled to think that the uncorrected equation is also valid with SI units. Therefore, if authors want to write the uncorrected equation in their report, they should indicate that they applied it before doing the conversion to Sl units.
Quebec, GIS 4L8 Canada
983
Reply to LF Tinker Dear Sir:
Jacques Masse Departement de Biochimie Hopital du Saint-Sacrement
References I. Masse 1. Effects of diet on serum lipids and apolipoproteins. Am J
Clin Nutr 1990;52:765(letter). 2. Wardlaw GM, Snook JT. Effect of diets high in butter, corn oil, or high-oleic acid sunflower oil on serum lipids and apolipoproteins in men. Am J C1in Nutr.1990;51:815-21. 3. Masse J. Changes in lipoproteins during weight loss. N Eng! J Med 1989;320:668 (letter). 4. Masse J. Portable cholesterol analyzers. JAMA 1990;264:1101 1990;89:836 (leiter). 5. Masse J. Clinical chemistry reference intervals for healthy elderly subjects. Am J Clin Nutr 1990;51:1115 (letter). 6. Masse J. Coffee consumption and serum lipid. Am J Med (letter) (in press). 7. Masse J. Lipid profiles after cardiac transplantation. Am J Cardiol (letter) (in press). 8. Masse J. Calculation of low-density lipoprotein cholesterol. Arch Int Med (letter) (in press). 9. DeLong OM, DeLong ER, Wood PO, Lippel K, Ritkind BM. A comparison of methods for the estimation of plasma low- and very low.density lipoprotein cholesterol: the Lipid Research Clinics Prevalence Study. JAMA 1986;256:2372-7. 10. Friedewald WT, Levy RI, Frederickson OS. Estimation oflow·density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chern 1972; 18:499-502.
Nutritional immunology in elderly people Dear Sir: I am writing to you with reference to a recently published paper by Payette et al (I). There are many problems with the data, analysis ofdata, and interpretation of the literature in this paper. It is surprising that the authors and your editorial staff seem unaware of the important data concerning vitamin E and immune function in elderly people that were published in the September issue of the journal (2). This article is not even referred to in the paper by Payette et ai, which also discusses the role of vitamin E in elderly people's immune functions-specifically of interleukin 2 (1L-2). In most journals, if very similar data are to appear, the accepted, in-press paper is shared with the authors of a forthcoming paper. Without such editorial leadership, the impression is given that the editors (and staff) do not know what' is published in their own journal. With specific regard to the paper by Payette et ai, there seem to be several grave discrepancies in the data. In Table 2, the mean daily intake (diet plus supplement) ofvitamin £ is 30 ± 76 mg and the median is 7.2 mg. Yet on p 931, the authors state that eight individuals (10% of the population) were taking megadoses of 20-80 times the Canadian recommended nutrient intake (i~.NI) of vitamin £ (which is 5-7 mg, depending on age and sex). How can the data in Table 2 be correct with eight individuals having such a wide and -high range of intakes of vitamin £? It would seem mathematically impossible to have a
median of7.2 mg unless 50% ofthe 82 participants had extremely low intakes, ie, < 7.2 mg. Because the data are so skewed and because so many variables are involved, the simple statistical analyses performed have a very great potential of resulting in incorrect conclusions. Multiple logistic regressions are required, and with this small a sample and so many variables, this may not be possible. Concerning the IL-2 activity data, because 59 of 82 subjects had IL-2 concentrations < 0.005 kU/L, any correlation with vitamin E or vitamin D concentrations would be mathematically skewed because of the high number of very low responders in this population. It is difficult to imagine that low zinc concentrations, seen in 53% of this population, were not correlated with undetectable IL-2 concentrations found in 69% of the same population. Why are probabilities rather than actual data plotted in Figure 3? What is the relationship of the SD to the actual range of intakes in the population studied? These data do not allow the reader access to the raw data used to derive this figure. It is also most surprising that the authors did not include any data related to their biochemical assays. In partiCular, did the plasma vitamin C or either serum or red blood cell folates correlate with the dietary information? Did the concentrations of nutrients in blood correlate with the immunological data? Why were these biochemical analyses mentioned in the Methods section ifthe data are not presented? The authors measured all fatty acids; what about concentrations of fat-soluble vitamins, es-
Downloaded from https://academic.oup.com/ajcn/article-abstract/53/4/983/4715125 by East Carolina University user on 15 March 2019
The letter from Tinker is an illustration of the point I tried to make when I wrote the letter (I) about the article of Wardlaw and Snook (2) and several other letters on the same subject (38). Authors and readers in the United States are generally unfamiliar with Systeme International (SI) units. The fact that the equation is corrected to be applicable with SI units does not change the eq uation, and the original article (9) did not need to be quoted again. In fact, Tinker made an error in the letter when correctly citing the equation of Friedewald et al (10) for the mg! dL units but incorrectly citing the wrong authors (9) after writing the corrected equation for use with SI units. The authors in the United States usually do their work and calculations with the conventional units and only convert their results to SI units to conform to journals' requirements. The results published are thus valid. The problem comes from the fact that the authors do not mention in their methods sections that they proceeded that way. International readers (and even readers in the United States) are not necessarily aware of this, so they can be misled to think that the uncorrected equation is also valid with SI units. Therefore, if authors want to write the uncorrected equation in their report, they should indicate that they applied it before doing the conversion to Sl units.
Quebec, GIS 4L8 Canada
