How Nutrition Science Should Mature

how nutrition science should mature

Dennis Bier, MD, was this year’s W.O. Atwater Memorial Award Winner and Lecturer at ASN’s Scientific Sessions and Annual Meeting on Tuesday, sponsored by USDA-ARS and ASN. His talk, titled “Traveling the Road From Precision to Imprecision- Have I Gone in the Wrong Direction?” was a broad critique on the state of nutrition science, contrasting his long research career using isotopics for precise kinetic measurements in humans to some of the more imprecise techniques being used in nutrition. Human nutrition today remains an immature science, says Dr. Bier, because it is so difficult to accurately measure what people eat.

Among his critique along this line, he noted that individual nutrient intake measurement methods are “validated” against other imprecise methods, and even these correlations are generally weak within the 0.2 to 0.5 range. Further, it generally takes between 5-15 24-hour diet recalls, sometimes many more, to achieve an adequate estimation of nutrient intakes in overweight and obese participants, which is never done in practice. Another problem is the seasonal variability of nutrients in foods, using vitamin C as an example, or variation from changes during processing and cooking. If such variation is considered in epidemiological studies associating foods with disease outcomes, it greatly reduces the power to detect a statistically significant result, or can change a result from a positive association to a neutral one.

Should we think about nutrition as a science in the same manner as other disciplines like physics? Bier thinks we should. The differences are obvious now. It is extremely difficult to do long-term experiments in people for many reasons of practicality and cost. But if we concede to this difficulty, our confidence in certain areas of nutrition science will remain stagnant. There are some examples where observational data seems to have led us astray, for example with vitamin E and a follow-up negative trial, and similarly with homocysteine reduction with folic acid and a follow-up negative trial. Dr. Bier noted that more than 15 randomized controlled trials have failed to support nutrient hypotheses generated from observational studies of food intake. There may be many reasons for this: differences in subjects, inclusion criteria, dose or duration, therapeutic window, etc., but we also must consider that the observational data may lead us astray. There are underappreciated interdependencies in observational variables that cannot all be statistically accounted for. Bier’s cautions on such data should be uncontroversial. Associations uncovered in observational studies are hypothesis, they cannot infer causality, and drawing conclusions from them are fine as long as their uncertainty is acknowledged where they are used. In practice, however, these rules are often not followed.

Bier concluded by talking about the many issues that plague science in general that make the literature less reliable. For instance, 95% of the biomedical literature contains a significant result, suggesting a severe publication bias in favor of positive results. Other issues arise with a large researcher degrees of freedom; that is, the number of choices the researcher makes when designing a study or analyzing the results. Asking a lot of questions, changing the primary endpoints, focusing on positive endpoints and discounting negative ones. In reporting of results, implying causality from associations is often done inappropriately, or inflating the effect of the finding by only reporting relative risk instead of absolute risk.

“Transparent science, like transparent government, means releasing your tax returns.” Dr. Bier wants the field to think more about reporting. Among a long list of ways that scientific integrity can be improved: require a priori registration of all studies and a data analysis plan, report all primary endpoints together, require perspective in reporting of the results (e.g. effect sizes, confidence intervals, absolute risks, NNT, etc.), mandatory use of reporting guidelines, report alternative analyses (e.g. alternative models that fit the data with equivalent statistical confidence), making the original data available for scrutiny, and improving the disclosure of conflicts of interest. Everyone has some form of conflicts, for example, money, grants, fame, etc., and Bier thinks that allegiance biases are at least as common as financial ones, so we need to come up with a universal conflict of interest system to make this standardized and fair.

While Dr. Bier’s views may be too idealistic for some, he promotes a necessary conversation about how we improve nutrition science and reduce our uncertainties. To that end, the field should continuously strive to enforce policies and practices that better our measurement techniques and limit bias.


Interview with Juan Rivera Dommarco

March 2017 Member Highlight Interview for ASN Nutrition Notes eNewsletter:

Interview with Juan Rivera Dommarco, Director of the National Institutes of Public Health (INSP) of Mexico, President of the Latin American Nutrition Society (SLAN), and Executive Board Member of the Ibero-American Nutrition Foundation (FINUT)

Dr. Rivera is the newly appointed Director of the National Institutes of Public Health, where he has been since 1993. There he founded the Center for Research in Nutrition and Health in 2001. He is also Professor of Nutrition in the School of Public Health of Mexico and Adjunct Professor at Emory University. Dr. Rivera has published more than 400 scientific articles, book chapters, and books, and made more than 500 presentations and conferences at scientific events. He is past recipient of the Kellogg International Nutrition Research Award from ASN, granted for active engagement in research to benefit populations in nonindustrialized countries, as demonstrated through publications in the scientific literature, and actively engaged in training new scientists for international nutrition research.

1. How did you first get involved in nutrition epidemiology and research? What made you interested in the field of nutrition science?

My original motivation was poverty and inequity. Most Latin American Countries, including Mexico have profound inequities. Since childhood, I felt social inequalities were morally wrong. During high school, I read several books about social injustice, including Josue de Castro’s recounts of inequity, and a direct indicator of inequity was hunger and undernutrition. After high school, I spent some time in an indigenous community in Chiapas, where I witnessed poverty very closely. That is when I decided to devote my life to fight undernutrition, hunger, and their health effects. My undergraduate training was in nutrition and food sciences at the Universidad Iberoamericana, a Jesuit University in Mexico City with a mystic about poverty alleviation. I did my internship training with Dr. Joaquín Cravioto, a prominent Mexican scientist interested in undernutrition and mental development. He inspired me to become a nutrition scientist. I started reading the works of Scrimshaw, Habicht, and Martorell at INCAP in Guatemala and I corresponded with Jean-Pierre Habicht, who invited me to visit the Division of Nutritional Sciences at Cornell. After my visit, I decided to undergo postgraduate training in Nutrition at that University.

2. When and why did you first join ASN? What convinced you to join the organization?

I was first introduced to ASN in 1983, while I was a graduate student at Cornell University, and I officially became a member in 1991. My Committee Chair and mentor, Jean-Pierre Habicht, considered as part of the training of his students to attend the then called FASEB Meetings to present the results of our research. As many other of his students, I joined ASN and attended the meetings.

3. What aspects of ASN membership have you found most useful, professionally? What other aspects of your membership do you find useful as your career has progressed?
I appreciate the opportunity to keep up-to-date about new knowledge in the area of global nutrition, along with the high quality of the research results presented and lively discussions at Experimental Biology. I also advocate for ASN journals, in which I have published repeatedly, and I enjoy the opportunity to meet with colleagues and old friends during ASN meetings, where we often discuss new research and explore collaborations. More recently, ASN meetings have exposed my students to high quality works and allowed them to share the results of their studies with other nutrition scientists.

4. What aspects of your research do you foresee being most important for ASN members?

In Mexico, we face the double burden of undernutrition and obesity; therefore, we are conducting research aimed at solving these two problems, which together are of great interest to the Global Nutrition Council and to much of the ASN membership:
 We have been monitoring the magnitude and trends of the double burden of malnutrition in Mexico during the last 30 years through national nutrition surveys.
 We are conducting birth cohort studies looking at the relationship between maternal feeding and weight status and gain during gestation, as well as infant feeding practices and several outcomes at different points in time during childhood and adolescence, including appetite and satiety, growth, weight gain, cardiometabolic risks, and neurodevelopment.
 We are also generating knowledge for the design of policies for the prevention and control of the double burden of malnutrition, including programs for the prevention for stunting, anemia, and micronutrient deficiencies and policies for the prevention and control of obesity, including fiscal measures and school regulations, among others.
 Finally, we are conducting evaluations of the effects of several programs and policies applied by the Government for the prevention and control of the double burden of malnutrition.

5. Can you tell us more about your current position and the research activities in which you are involved?

On February 16, I was appointed as Director General of the Mexican National Public Health Institute (INSP), the research and training institution that houses the Mexican School of Public Health. We conduct research in several public health topics including: nutrition, obesity and non-communicable chronic diseases, infectious diseases, environmental health, health systems research, reproductive health, health promotion, etc. and we offer twenty-eight Masters and PhD programs. We have around 1,200 employees and close to 500 students in three campuses. I am personally involved in the research activities mentioned above: monitoring the double burden in the population, birth cohort studies to assess the effects of infant feeding practices, generation knowledge for the design of policies for the prevention and control of the double burden, and evaluating the effects of some of those policies applied by the Government.

6. What do you feel are the biggest challenges facing nutrition researchers today? Are there any areas where you would like to see more research?

One of the biggest challenges in Public Health Nutrition is translating research results into clinical and public health large-scale interventions and their rigorous evaluation for further improvement. To do this we need research from subcellular particles (molecular biology) to programs and policy. This includes linking the wealth of information coming from basic research, particularly from molecular biology, to clinical and public health innovative actions. We also need to study the drivers and determinants of the double burden of malnutrition and its health and environmental consequences using a systems approach, since nutrition problems are multifactorial and complex. We need to understand the food system but also the factors influencing behaviors (food and physical activity). We also need to study how to influence sound policy-making, including the roles of direct advising to policy makers and of social mobilization to generate demand for policy. Finally, we need to conduct rigorous evaluations in order to inform policy makers about improvements in current policies.
March 2017 ASN Nutrition Notes Member Highlight
Interview with Dr. Juan Rivera Dommarco – Page 3

7. Is there anything else you’d like to tell ASN members, especially students and postdocs?

To Students and postdocs: The phrase “First do no harm” (Latin Primum non nocere) is believed to have been part of the original Hippocratic oath taken by physicians. We nutritionists do not take a similar oath, but we should. You have the privilege to be a fraction of people in the world who have access to postgraduate training. You chose Nutritional Sciences, a field that can have a profound impact on the health and wellbeing of millions of people. You should be generous, because life has been generous to you. You should pay back to those in poverty, to the neediest persons in the world, for the privilege to have reached postgraduate training, in an activity that can change the lives of many. However, most importantly, do not harm the nutrition and health of people by promoting or endorsing unhealthy food and beverage products. To the general ASN membership, I would like to invite you to attend the SLAN Congress in Mexico in late 2018, showcasing the best nutrition research from Mexico and Latin America.

Dr. Rivera’s research interests include the epidemiology of stunting (under-nutrition and obesity), the short- and long-term effects of under-nutrition during early childhood, the effects of zinc and other micronutrient deficiencies on growth and health, the study of malnutrition in Mexico, and the design and evaluation of policies and programs to improve nutritional status of populations.