Feature Nutrition

The scientific report guiding the US dietary guidelines: is it scientific?

BMJ 2015; 351 doi: https://doi.org/10.1136/bmj.h4962 (Published 23 September 2015) Cite this as: BMJ 2015;351:h4962

Re: The scientific report guiding the US dietary guidelines: is it scientific?

Thank you to all those who have commented on my article. I will attempt to respond to all points raised, but will particularly respond here to Barbara Millen, chair, 2015 Dietary Guidelines Advisory Committee (DGAC), and Bonnie Liebman, nutrition director of the Center for Science in the Public Interest.

Firstly, Barbara Millen for the DGAC suggests that I was wrong to claim that the committee failed to use a systematic methodology for searching and selecting evidence. However, my article documents a lack of systematic methodology in several places in their report. For example, two statements in the report’s methodology section (Part C Methodology, page 11-12) indicate an approach that is not reproducible. To quote from the report:

When Committee members were aware of high-quality existing reports that addressed their question(s), they decided a priori to use existing report(s), rather than to conduct a de novo NEL SR. A literature search was then conducted to identify other existing reports to augment the existing report(s) identified by the Committee. The literature was searched by a NEL librarian to identify relevant studies."

I contend that committee members being “aware of high quality evidence” does not reach the standards of transparency and reproducibility. For example, the systematic approach the committee claims to have taken missed more than 70 trials from a review of low-carbohydrate diets, published during the period the report covered.(Table C in original article)

Again to quote from the report:

if two or more SRs/MAs appropriately answered a question and there was substantial reference overlap, the Committee chose to only use one of the SRs/MA to answer the question."

I contend that allowing the committee to “choose” a systematic review/meta-analysis reflects a subjective approach that is neither transparent nor replicable. This methodology was problematic, for example, in the case of saturated fats and heart disease, where the committee included reviews that tended to support its conclusion while omitting a number that were contradictory. (1,2,3, 4, 5) Many of these papers covered the same original data, and the committee did not state its rationale for either the inclusion or exclusion of specific reviews on this topic.

In response to my statement that the committee relied on systematic reviews by “external professional associations, almost exclusively the AHA and ACC,” Dr Millen says, “The vast majority of these reports came from the NIH and other federal agencies as well as the IOM, and not as suggested by Ms. Teicholz, from other sources such as professional organizations.”

I accept that the committee relied on reports by IOM and NIH, but in reviews of key issues, it relied upon AHA/ACC reports. These issues include: Dietary Patterns and obesity, Dietary Patterns and heart disease, the DGAC post 2009 review of the evidence on saturated fats and heart disease, and at least one review on sodium.

Dr Millen writes, “In some cases, the federal reports that were utilized were subsequently endorsed and/or published by professional organizations.”

The two reports I cite in my analyses on key topics were all published virtually simultaneously by the AHA/ACC and NIH. The AHA/ACC versions make clear, in their titles, that these reports come from their own task forces. There is no suggestion that the AHA/ACC did not play a full role in the writing and development of these reports. (6)

I did not claim, as Dr Millen for the DGAC suggests, that the committee omitted the Women’s Health Initiative (WHI) in its review of post-2009 literature on saturated fat. WHI results were published in 2006 and therefore rightfully belonged in the 2010 NEL review on the subject, which covered the preceding five years. It is this 2010 review that omitted WHI. I apologize if this reference was not clear in my piece.

Dr Millen states that "Although many RCTs have examined the efficacy of low-carb diets vs. other diet interventions on weight loss, very limited data exist on the long-term health effects of low-carb diets." In fact, by the time the committee began its work, there had been three sizeable randomized controlled clinical trials on low-carb diets of two-years duration, which is generally considered to be long enough to see any adverse health effects. (7)
Dr Millen for the DGAC says my report is “highly misleading” because it states that the 2015 DGAC “continues to recommend low-fat high carb eating patterns." However, my article does not state this. What it says is that the “foundation” of DGA advice for the past 35 years has been to eat “less fat and fewer animal products and eat more plant foods for good health.”

Dr Millen also says I was mistaken to suggest that an “outside” food policy analyst oversaw their work related to food insecurity and sustainability. However, my statement that “the USDA hired a food policy analyst focused on environmental issues to oversee the guideline committee’s work," referred to Angie Tagtow, who was hired to be Executive Director, Center for Nutrition Policy and Promotion, USDA. This is the position that oversees “developing and promoting dietary guidance,” including the DGA guidelines

In her response, the Center for Science in the Public Interest’s Nutrition Director Bonnie Liebman points out that, contrary to my statement that recent meta-analyses “failed to confirm an association between saturated fats and heart disease,” one of these reviews, by Hooper et al, 2012, concluded that “reducing saturated fat by reducing and/or modifying dietary fat reduced the risk of cardiovascular events by 14%. That figure was increased to 17% in a 2015 update.”

Liebman was correct to point this out. The full sentence in my article was: "When the committee started its work in 2012, there had been several prominent papers, including a meta-analysis (8) and two major reviews (one systematic) (9) (10) that failed to confirm an association between saturated fats and heart disease." This statement did not aptly reflect the findings of the more authoritative of these reviews, by Hooper et al, which did find an effect of saturated fats on cardiovascular events but failed to confirm an effect between saturated fats on cardiovascular mortality." A correction to this statement will be posted.

Bonnie Liebman for the CSPI points out that the Women’s Health Initiative was never designed to lower cardiovascular disease. It is true that WHI looked primarily at cancer outcomes, but other outcomes were also measured, including weight and cardiovascular markers. The inclusion of secondary outcomes in trials is standard practice in systematic reviews which attempt to combine studies when each individual study may be underpowered to draw conclusions. In fact, the NEL itself cites WHI for its secondary outcomes, in reviews on the Dietary patterns, one on obesity and the other on cardiovascular disease.
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Reijo P. Laatikainen correctly comments that, in describing the body of literature that had been overlooked by the DGAs, I omitted a 2014 review paper by Fardet and Boirie, a review of pooled, meta-analyses and systematic reviews on food and health. This review found that plant food groups are associated less with diet-related chronic disease than are animal food groups. Among animal food groups, dairy/milk products, were found to have no association with the risk of diet-related chronic disease, while red/processed meats were associated with higher risk. (11)

However, I did not review any observational findings in my article, because I prioritized the more conclusive clinical trial data, as the DGAC itself did in its reviews.

Dr Millen for the DGAC says that I am on a “quest’ to promote my book. I do indeed have a book available. However, so too do four members of the DGAC, as authors mostly of popular diet books. (12) Because there is no public disclosure of conflicts of interest for DGAC members, this is not generally known.

Dr Millen complains that the process of peer review for my article was not adequately described. However, my article carries the same provenance statement as other features in The BMJ; “Commissioned; externally peer reviewed.”

The article was peer reviewed by several external experts and subject to fact checking and in-house editing in line with The BMJ's standard procedures.

1) Mente, Andrew, Lawrence de Koning, Harry S. Shannon, Sonia S. Anand, “A Systematic Review of the Evidence Supporting a Causal Link Between Dietary Factors and Coronary Heart Disease,” JAMA Internal Medicine, April 13, 2009, Vol 169, No. 7, 659-669

2) Siri-Tarino PW, Sun Q, Hu FB, Krauss RM, “Saturated fat, carbohydrate, and cardiovascular disease,” Am J Clin Nutr. 2010 Mar;91(3):502-9

3) Lawrence, G. D., “Dietary Fats and Health: Dietary Recommendations in the Context of Scientific Evidence,” Adv Nutr May 2013 vol. 4: 294-302

4) U. Ravnskov, “Is saturated fat bad? Modern dietary fat intakes in disease promotion.” Nutr Health (Pt 2) (2010), pp. 109–119

5) Ravnskov, Uffe, James J. DiNicolantonio, Zoë Harcombe, Fred A. Kummerow, Harumi Okuyama, Nicolai Worm, “The Questionable Benefits of Exchanging Saturated Fat With Polyunsaturated Fat” Mayo Clin Proc. April 2014;89(4):451-453.

(6)
Two simultaneously published reports on cardiovascular risk:
National Heart Lung and Blood Institute. Lifestyle Interventions to Reduce Cardiovascular Risk: Systematic Evidence Review from the Lifestyle Work Group. Bethesda, MD: U.S. Department of Health and Human Services, National Institutes of Health; 2013;
Eckel RH, Jakicic JM, Ard JD, de Jesus JM, Houston Miller N, Hubbard VS, et al. 2013 AHA/ACC guideline on lifestyle management to reduce cardiovascular risk: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol. 2014;63(25 Pt B):2960-84.
Two simultaneously published reports on obesity:
National Heart Lung and Blood Institute. Managing overweight and obesity in adults: Systematic evidence review from the Obesity Expert Panel, 2013. Bethesda, MD: U.S. Department of Health and Human Services, National Institutes of Health; 2013;
Jensen MD, Ryan DH, Apovian CM, Ard JD, Comuzzie AG, Donato KA, et al. 2013 AHA/ACC/TOS guideline for the management of overweight and obesity in adults: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and The Obesity Society. J Am Coll Cardiol. 2014;63(25 Pt B):2985- 3023.

(7) Sacks, Frank M., George A. Bray, Vincent J. Carey, et al. “Comparison of Weight-Loss Diets with Different Compositions of Fat, Protein, and Carbohydrates.” New England Journal of Medicine 360, no. 9 (February 26, 2009): 859–873; Foster, Gary D., Holly R. Wyatt, James O. Hill, et al. “Weight and Metabolic Outcomes After 2 Years on a Low-Carbohydrate Versus Low-Fat Diet: A Randomized Trial.” Annals of Internal Medicine 153, no. 3 (August 3, 2010): 147–157; Shai, Iris, Dan Schwarzfuchs, Yaakov Henkin, et al. “Weight Loss with a Low-Carbohydrate, Mediterranean, or Low-Fat Diet.” New England Journal of Medicine 359, no. 3 (July 17, 2008): 229–241.

(8) Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. Am J Clin Nutr 2010;91:535-46.

(9) Hooper L, Summerbell CD, Thompson R, et al. Reduced or modified dietary fat for preventing cardiovascular disease. Cochrane Database Syst Rev2012;5:CD002137

(10) Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Saturated fat, carbohydrate, and cardiovascular disease. Am J Clin Nutr 2010;91:502-509.

(11) Fardet A, Boirie Y. Associations between food and beverage groups and major diet-related chronic diseases: an exhaustive review of pooled/meta-analyses and systematic reviews. Nutr Rev. 2014 Dec;72(12):741-62.

(12) Escamilla, Rafael, At Risk Latino Children's Health, Houston, TX: Arte Público Press, 2011; Hyman, Jane and Barbra Millen Posner. The Fitness Book, New York: Julian Messner, 1984; Nelson, Miriam and Alice Lichtenstein, Strong Women, Strong Hearts, New York: G. P. Putnam’s Sons, 2005; Nelson, Miriam, and Jennifer Ackerman, The Social Network Diet: Change Yourself, Change the World, New York: FastPencil Premiere, 2011; Nelson, Miriam and Jennifer Ackerman, The Strong Women’s Guide to Total Health, New York: Rodale Books, 2010; Nelson, Miriam and Judy Knipe, Strong Women Eat Well, New York: G.P. Putnam’s Sons, 2001; Nelson, Miriam and Kristin Baker, Strong Women and Men Beat Arthritis, New York: G.P. Putnam’s Sons, 2002; Nelson, Miriam and Lawrence Lindner, Strong Women, Strong Backs: Everything You Need To Know to Prevent, Treat, and Beat Back Pain, New York: G.P. Putnam’s Sons, 2006; Nelson, Miriam and Lawrence Lindner, The Strong Women’s Journal, New York: The Berkley Publishing Group, 2003; Nelson, Miriam and Sarah Wernick, Strong Women Stay Slim, New York: Bantam Books, 1998; Nelson, Miriam and Sarah Wernick, Strong Women Stay Young, New York: Bantam Books, 1997; Nelson, Miriam and Sarah Wernick, Strong Women, Strong Bones, New York: G.P. Putnam’s Sons, 2000.

Competing interests: Stated in original article, The scientific report guiding US dietary guidelines: is it scientific? BMJ 2015;351:h4962
22 October 2015
Nina Teicholz
Journalist
New York, NY​

Competing interests: No competing interests

22 October 2015
Nina E. Teicholz
Journalist
New York, NY
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