By Kevin Klatt
A few weeks ago, I had the pleasure of reading Allyson West and Marie Caudill’s Research and Practice Innovations paper in the Journal of the Academy of Nutrition and Dietetics, entitled “Applied Choline-Omics: Lessons from Human Metabolic Studies for the Integration of Genomics Research into Nutrition Practice” (1). The publication elegantly describes how integrating metabolomic, transcriptomic and genetic/epigenetic approaches into traditional controlled feeding studies can help refine the Dietary Reference Intakes, and elucidate the mechanisms by which choline and folate contribute to overall health.
Referencing the Nutrition Research Priorities established by the American Society for Nutrition (ASN) in 2013 (2), we can clearly see that the approaches described by West and Caudill fall in line with ASN’s thinking on how to advance the field of nutritional sciences. The Nutrition Research Priorities report specifically highlights furthering our understanding of nutrition and health by pursuing –omics research to understand individual responses to nutrients. For me, it was encouraging to see these kinds of advanced techniques and their clinical applications representing the field of research in a major clinical nutrition journal.
Fast-forwarding to this past week, I found myself staring at headlines inflaming the conversation around the newest low-carbohydrate/low-fat research, published in the reputable Annals of Internal Medicine (3). The publication is a randomized trial that ultimately concludes “the low-carbohydrate diet was more effective for weight loss and cardiovascular risk factor reduction than the low-fat diet”. Being in such a high profile journal and funded by the NIH, one would expect this publication to add some significant perspective to our understanding of energy balance and disease progression, two areas also highlighted in the 2013 Nutrition Research Priorities report. Unfortunately, upon reading the paper, one is quickly underwhelmed by the lackluster weight loss over 12 months, the poor accuracy of the dietary recall data, the lack of any information about diet quality, the use of imprecise measurement techniques, and the authors’ failure to discuss alternative conclusion, beyond just the low-carbohydrate component of the diet. I have specifically detailed the limitations of this trial elsewhere.
As I finished reading the study, West and Caudill’s ‘Choline-omics’ paper came to mind, and I couldn’t help but feel frustrated: why are we still funding these overly reductionist paradigms of low-carb vs low-fat, when much more integrative and informative approaches are being taken? To quote the 2013 Nutrition Research Priorities report on the topic of energy balance:
“A systems approach is preferable because the standard experimental approach of varying one factor at a time has accomplished little to address the population-wide problem of energy imbalance.”
Yet here we are, still trying (and failing) to vary only one factor, and publishing it in a premier journal for physicians. Is this how we want to represent nutrition research?
I further sat and thought about this trial: even at the outset, given the design, and the quality of the proposed data to be collected, what could this have added to our knowledge of nutrition? The trial states that its goal was to conduct a randomized trial to compare low-carb versus low-fat diets on body weight and CVD risk factors in a diverse population without comorbidities. Beyond the overly reductionist paradigm of low-carb/fat, the study design is questionable in that “neither diet included a specific calorie or energy goal.” Ultimately, the trial tested whether a macronutrient goal, coupled with education and a meal replacement bar would spontaneously lead individuals to lose weight, in a diverse population without comorbid conditions. Not surprisingly, after being sent into an environment with highly palatable, minimally nutritious high carbohydrate/ high calorie foods, the low-carbohydrate group fared better. Is this substantially improving our understanding of nutrition and energy balance? If there’s any theme that holds true with weight loss and disease risk reduction, it’s that choosing a well-planned, reduced energy diet which an individual can adhere to is most important (4,5,6,7). Given the failure to reach recommended fiber intakes and minimal weight loss seen in this trial, nothing about the previous statement appears to change.
Even worse than the limited information to be gained from this kind of trial is the media reporting and subsequent public response to this research. The public’s perception of nutrition recommendations isn’t that great, as acknowledged in what I would argue is the most pertinent point of the Nutrition Research Priorities report:
“Perhaps the greatest barrier to advancing the connections between food and health is the variability in individual responses to diet; it is also the origin of public skepticism to acceptance of dietary advice….”
If individual variability spurs public skepticism, we should seek to explain that variability. One only needs to look to the original 1980’s Dietary Guidelines for Americans (4) to see that we’ve known that there is individual variation in weight gain/loss and in biomarker response to diets high/low in fat. Yet here we are, 3 decades later, and we’re conducting trials that do nothing to further isolate and understand the factors that contribute to this variation. However, what we are doing is deepening this public skepticism, as history shows us the controversial topic of low-carb vs. low-fat undoubtedly garners a lot of press.
Don’t get me wrong, research that attempts to understand individual variation in response to food and nutrients is being done, but, despite being identified as a major priority, it does not appear to be so. It’s truly a shame to be in this field and see examples of researchers employing the most cutting edge techniques to answer pressing questions, only to be overshadowed by overly simplistic paradigms that incite more sentiment than they do advance science. It is essential that scientists, and more importantly funding agencies, are aware of the field’s established research priorities, so that we can stop asking the uninformative questions that tantalize a public controversy and start generating truly substantial evidence, which fosters public trust in recommendations. These established Nutrition Research Priorities can be found in full here.
References:
1. https://www.ncbi.nlm.nih.gov/pubmed/24529976
2. https://www.ncbi.nlm.nih.gov/pubmed/23784071
3. https://annals.org/article.aspx?articleid=1900694
4. https://www.health.gov/dietaryguidelines/1980thin.pdf
5. https://www.nejm.org/doi/full/10.1056/NEJMoa022207
6. https://www.nejm.org/doi/full/10.1056/NEJMoa0804748
7. https://jama.jamanetwork.com/article.aspx?articleid=200094
8. https://www.health.gov/dietaryguidelines/1980thin.pdf
