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Global, regional, and national consumption levels of dietary fats and oils in 1990 and 2010: a systematic analysis including 266 country-specific nutrition surveys

BMJ 2014; 348 doi: https://doi.org/10.1136/bmj.g2272 (Published 15 April 2014) Cite this as: BMJ 2014;348:g2272

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Re: Global, regional, and national consumption levels of dietary fats and oils in 1990 and 2010: a systematic analysis including 266 country-specific nutrition surveys

We appreciate the interest from Dr. Winkler in our systematic investigation of global intakes of key dietary fats and oils by region, country, time, age, and sex.[1]

We agree with Dr. Winkler’s implications that interpretation of dietary data requires appropriate perspective, context, and recognition of strengths and limitations, as is true for any scientific research. Yet, Dr. Winkler’s concerns reflect only a partial understanding of the strengths and limitations of various nutritional assessment methods.

First, the interpretation and validity of individual-level dietary data depends on both the dietary assessment tool used (e.g., diet records, diet recalls, semi-quantitative food frequency questionnaires, tissue biomarkers), the level of assessment required (e.g., individual intake vs. population/group mean intake), and the nutrient, food, or dietary pattern of interest. In relation to these considerations, different dietary instruments have complementary pros and cons, and their validity and reliability have been extensively documented.[2 3]

Overall, both the validity and long-term reliability of foods, nutrients, and diet patterns assessed by such instruments are very reasonable, similar to other widely used measures such as blood pressure and blood cholesterol. Furthermore, when used to assess population means as in our study (rather than to assess individual intakes), these dietary instruments have even stronger validity, especially when using diet records or recalls which were the main instruments used in our analyses.

We agree with Dr. Winkler that, in contrast to measurement of specific nutrients and foods, total energy intake is poorly assessed by dietary questionnaires. Thus, few nutritional experts recommend use of dietary questionnaires to assess total energy, and total energy was not an endpoint in our investigation. On the other hand, due to correlated errors, total energy assessed by dietary instruments is very useful for energy-adjusting estimates of nutrient and food intakes to further increase their validity. Consequently, we reported intakes of these key dietary fats and oils adjusted for energy.

Renata Micha, Research Director/ Associate, PhD, Dariush Mozaffarian, Associate Professor, MD, DrPH

Departments of Epidemiology (RM, DM) and Nutrition (DM), Harvard School of Public Health, Boston, MA; Department of Food Science and Human Nutrition (RM), Agricultural University of Athens, Greece; and Division of Cardiovascular Medicine and Channing Laboratory (DM), Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA

References
1. Micha R, Khatibzadeh S, Shi P, et al. Global, regional, and national consumption levels of dietary fats and oils in 1990 and 2010: a systematic analysis including 266 country-specific nutrition surveys. BMJ (Clinical research ed) 2014;348:g2272.
2. Willett WC. Nutritional Epidemiology: Oxford University Press, 2013.
3. Gibson RS. Principles of Nutritional Assessment: Oxford University Press, 2005.

Competing interests: No competing interests

09 May 2014
Renata Micha
Research Director/ Associate
Dariush Mozaffarian, Associate Professor
Harvard School of Public Health, Boston MA, US; Agricultural University of Athens
Athens, Greece