A short history of saturated fat: the making and unmaking of a scientific consensus.

PURPOSE OF REVIEW: This article recounts the history of the diet-heart hypothesis from the late 1950s up to the current day, with revelations that have never before been published in the scientific literature. Insights include the role of authorities in launching the diet-hypothesis, including a potential conflict of interest for the American Heart Association; a number of crucial details regarding studies considered influential to the hypothesis; irregularities in the scientific reviews on saturated fats, for both the 2015 and 2020 Dietary Guidelines for Americans; and possible conflicts of interest on the relevant subcommittee reviewing saturated fats for the 2020 Dietary Guidelines Advisory Committee. Information obtained via the Freedom of Information Act (FOIA) on emails from the 2015 process is published here for the first time. These findings are highly relevant to the 2025-2030 Dietary Guidelines process, now underway, which has plans for a new review on saturated fats. RECENT FINDINGS: Recent findings include shortcomings in the scientific review processes on saturated fats, for both the current 2020-2025 Dietary Guidelines for Americans and the previous edition (2015-2020). Revelations include the fact the 2015 Advisory Committee acknowledged, in an e-mail, the lack of scientific justification for any specific numeric cap on these fats. Other, previously unpublished findings include significant potential financial conflicts on the relevant 2020 guidelines subcommittee, including the participation of plant-based advocates, an expert who promotes a plant-based diet for religious reasons, experts who had received extensive funding from industries, such as tree nuts and soy, whose products benefit from continued policy recommendations favoring polyunsaturated fats, and one expert who had spent more than 50 years of her career dedicated to 'proving' the diet-heart hypothesis. SUMMARY: The idea that saturated fats cause heart disease, called the diet-heart hypothesis, was introduced in the 1950s, based on weak, associational evidence. Subsequent clinical trials attempting to substantiate this hypothesis could never establish a causal link. However, these clinical-trial data were largely ignored for decades, until journalists brought them to light about a decade ago. Subsequent reexaminations of this evidence by nutrition experts have now been published in >20 review papers, which have largely concluded that saturated fats have no effect on cardiovascular disease, cardiovascular mortality or total mortality. The current challenge is for this new consensus on saturated fats to be recognized by policy makers, who, in the United States, have shown marked resistance to the introduction of the new evidence. In the case of the 2020 Dietary Guidelines, experts have been found even to deny their own evidence. The global re-evaluation of saturated fats that has occurred over the past decade implies that caps on these fats are not warranted and should no longer be part of national dietary guidelines. Conflicts of interest and longstanding biases stand in the way of updating dietary policy to reflect the current evidence.

Conflicts of interest for members of the U.S. 2020 Dietary Guidelines Advisory Committee.

OBJECTIVES: To measure incidence of conflicts of interest (COI) with food and pharmaceutical industry actors on the advisory committee for the 2020- 2025 U.S. Dietary Guidelines for Americans (DGA) and assess the adequacy of current mechanisms to disclose and manage COI among the committee's members. DESIGN: We compiled longitudinal data from archival sources on connections between members of the DGA's advisory committee and actors. We hypothesed that these committee members, who oversee the science for the most influential dietary policy in the U.S, might have significant COI that would be relevant to their decision making. Disclosure of COI on this committee was recommended in 2017 by the National Academies of Sciences in order to increase transparency and manage bias, but public disclosure of the committee's COI does not appear to have taken place. SETTING: the committee was comprised of 20 experts. PARTICIPANTS: None. RESULTS: Our analysis found that 95% of the committee members had COI with the food, and/or pharmaceutical industries and that particular actors, including Kellogg, Abbott, Kraft, Mead Johnson, General Mills, Dannon, and the International Life Sciences had connections with multiple members. Research funding and membership of an advisory/executive board jointly accounted for more than 60% of the total number of COI documented. CONCLUSIONS: Trustworthy dietary guidelines result from a transparent, objective, and science-based, process. Our analysis has shown that the significant and widespread COI on the committee prevent the DGA from achieving the recommended standard for transparency without mechanisms in place to make this information publicly available.

An analysis of the recent US dietary guidelines process in light of its federal mandate and a National Academies report.

The US Dietary Guidelines for Americans is an enormously influential policy that has guided US nutrition programs since 1980. During these last 40 years, some researchers have expressed concern that the guidelines are based on an insufficiently rigorous assessment of the scientific evidence, a view that was largely substantiated by a Congressionally mandated 2017 report by the National Academies of Sciences, Engineering, and Medicine, which identified a need for enhanced transparency, greater scientific rigor, and updates to the scientific methodology for the DGA process. This paper traces the history of these ideas and contextualizes the DGA within the law and regulations that govern its process. The paper also discusses how recent iterations of the Dietary Guidelines have not fully adhered to these guiding documents, which has resulted in diminished independence of the expert committee in charge of evaluating the science for the DGA and a continued lack of a fully rigorous scientific process for producing consistent and trustworthy guidelines for the public.

Alternative Dietary Patterns for Americans: Low-Carbohydrate Diets.

The decades-long dietary experiment embodied in the Dietary Guidelines for Americans (DGA) focused on limiting fat, especially saturated fat, and higher carbohydrate intake has coincided with rapidly escalating epidemics of obesity and type 2 diabetes (T2D) that are contributing to the progression of cardiovascular disease (CVD) and other diet-related chronic diseases. Moreover, the lack of flexibility in the DGA as it pertains to low carbohydrate approaches does not align with the contemporary trend toward precision nutrition. We argue that personalizing the level of dietary carbohydrate should be a high priority based on evidence that Americans have a wide spectrum of metabolic variability in their tolerance to high carbohydrate loads. Obesity, metabolic syndrome, and T2D are conditions strongly associated with insulin resistance, a condition exacerbated by increased dietary carbohydrate and improved by restricting carbohydrate. Low-carbohydrate diets are grounded across the time-span of human evolution, have well-established biochemical principles, and are now supported by multiple clinical trials in humans that demonstrate consistent improvements in multiple established risk factors associated with insulin resistance and cardiovascular disease. The American Diabetes Association (ADA) recently recognized a low carbohydrate eating pattern as an effective approach for patients with diabetes. Despite this evidence base, low-carbohydrate diets are not reflected in the DGA. As the DGA Dietary Patterns have not been demonstrated to be universally effective in addressing the needs of many Americans and recognizing the lack of widely available treatments for obesity, metabolic syndrome, and T2D that are safe, effective, and sustainable, the argument for an alternative, low-carbohydrate Dietary Pattern is all the more compelling.

Dietary Saturated Fats and Health: Are the U.S. Guidelines Evidence-Based?

The last decade has seen nearly 20 papers reviewing the totality of the data on saturated fats and cardiovascular outcomes, which, altogether, have demonstrated a lack of rigorous evidence to support continued recommendations either to limit the consumption of saturated fatty acids or to replace them with polyunsaturated fatty acids. These papers were unfortunately not considered by the process leading to the most recent U.S. Dietary Guidelines for Americans, the country's national nutrition policy, which recently reconfirmed its recommendation to limit saturated fats to 10% or less of total energy intake, based on insufficient and inconsistent evidence. Continuation of a cap on saturated fat intake also fails to consider the important effects of the food matrix and the overall dietary pattern in which saturated fatty acids are consumed.