Documents released recently revealed that in the 1960s, the sugar industry paid Harvard researchers to downplay sugar’s role in obesity and focus on saturated fat instead. One of the scientists in question went on to become head of nutrition at the US Department of Agriculture and helped draft the forerunner of the federal dietary guidelines. Research norms and nutritional recommendations have of course changed since the 1960s. To what extent is industry involved in nutrition research today? How was the research that informed the current federal dietary guidelines vetted? To answer those questions, we speak with nutritional epidemiologist Barbara Millen, who chaired the scientific advisory committee for today’s US dietary guidelines.
ResearchGate: Last week’s revelations about the sugar industry’s influence involves research conducted fifty years ago. How do you see industry influence over nutrition research today?
Barbara Millen: There’s no doubt that investigators get different sources of funding for their research. Typically, peer-reviewed journals require that sources of funding for the research be disclosed. So, if industry funding is used, it’s specified in the articles that are published. I’ve been an editor or on the editorial board of a number of journals. We consider that very carefully when we’re reviewing papers, and it’s really important to do. The reality is that researchers are often reliant on outside funding to support their work, because research is a very costly endeavor. That includes industry funding, but there’s an effort with the peer-review system to be certain that results are as objective and unbiased as possible. That may not always happen, but it’s certainly something an effective peer-review process tries to maintain.
RG: What steps did the scientific advisory committee you chaired take to evaluate the integrity of the research behind the current federal dietary guidelines?
Millen: Our assessment of the literature—both original papers and review papers with meta-analysis—involved several different levels of quality review. We had assistance on this from the US Department of Agriculture’s Nutrition Evidence Library. We also did reviews as investigators. We first set the scope of our research questions and then identified some criteria that we wanted to use to assess the quality of the literature. We also imposed an external set of criteria that are used both domestically and internationally as a level of quality rating. We looked at things like the conclusion rates for randomized clinical trials, setting certain criteria for acceptable levels of drop-out. Depending on the research question, we also wanted to have studies of a particular size. If a study failed to meet these and other criteria, we excluded it. Then, as we began to summarize the data across the different studies, we also did an overall quality rating of the literature. So we not only rated individual papers and excluded those that we felt didn’t meet sufficient quality standards, we also graded the quality and consistency of the research in each area as a whole.
RG: What do the current dietary guidelines have to say about sugar consumption?
Millen: We made some strong statements in our report about the link between added sugar intake and the risk of various disease end points, recommending limits on added sugar intake in a healthy dietary pattern. That particular set of recommendations was carried forward in the dietary guidelines themselves. Current guidelines recommend a healthy dietary pattern that limits added sugars to less than ten percent of calories. So recommending that people limit added sugar intake, limit saturated fat intake, and limit sodium intake is now part of our national nutrition and health policy. Because of their importance, we took on those three topics separately, really looking at the strength of the research in terms of health-related outcomes. And we felt that the overall literature on added sugar was sufficiently strong to recommend a cap.
RG: And what about fat? Are the guidelines still influenced by the events from 50 years ago?
Millen: The guidelines on total fat intake have evolved since the initial dietary goals recommendations in the late 1970s. Earlier guidelines recommended total fat intake at 30 percent of calories or less. Recent changes reflect evolving high-quality research that demonstrates the importance of the type of fat on risk factors for disease, including plasma lipids. The current guidelines recommend that a healthy dietary pattern limit trans-fat intake; they also recommend limiting saturated fats to less than 10 percent of total calories per day by replacing them it with unsaturated fats, keeping total fat intake within the age-appropriate acceptable macronutrient distribution range.
RG: Are there other dietary recommendations you think could be prone to influence by the food industry?
Millen: I don’t think that our dietary recommendations were influenced by industry at all. Our recommendations involved an open, transparent process that included a lot of public commentary: input from clinicians, the public at large, and also from industry. We were obligated to review those data, and consider them if we felt they were sufficiently strong after review. That process was clear, and it met very high standards in terms of quality review and objectivity.
RG: Were you approached by any industry representatives outside of that official process?
Millen: No, our process was really carefully scrutinized and there was not an opportunity for anybody to try to sway it one way or another. Industry representatives were given time to make comments at the public hearings, and did so. I think it’s important to understand how serious the review and the oversight is on the federal dietary guidelines. Whenever two or more members of the advisory committee conversed about a topic, we were required under federal law to have a federal representatives present. That ensures a high level of quality and transparency, which are incredibly important. I really stand by the committee’s process, the quality and objectivity of the recommendations, and the standards that were maintained.
RG: In your own work as a researcher and reviewer, what do you look for in research to determine its integrity?
Millen: As a reviewer and someone who’s asked to review papers and proposals from different research groups all the time, I certainly do look at the quality of the fundamental research design, and also the techniques the investigators use to design and implement their research. I consider whether or not they have maintained quality throughout the course of an investigation: the maintenance of protocols, the compliance of subjects, drop-out, and so forth. I look at the characteristics of study participants. I look at the size of the study overall. Do they have just a handful of research subjects? Are there a sufficient number of subjects to assess the statistical power of the research? Another thing to consider is whether or not there seems to be consistency between how I as a researcher interpret the findings as presented, and how the authors are presenting their data. I’m looking for an objective presentation, an objective summary, and recommendations and conclusions that don’t overstate what’s found in the research or go beyond the purpose of the study design. So there are many different dimensions that can be indicators for the quality of a study, or indicate if it’s objectivity might be compromised. When you review, you really do need to consider them all.
RG: Does the source of funding change the way that you read a paper?
Millen: I would typically be mindful of the funding source and be certain that there appears to be complete and objective interpretation of results and an unbiased presentation of conclusions and recommendations. There cannot be an over-statement of conclusions, nor promotion or endorsement of any commercial products.
Image credit: Mandy Jansen
This article was originally written for and published by ResearchGate.