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U.S. Dietary Guidelines: An Evidence-Free ZoneU.S. Dietary Guidelines: An Evidence-Free Zone

Steven E. Nissen, MD
[+] Article, Author, and Disclosure Information

This article was published at www.annals.org on 19 January 2016.


From The Cleveland Clinic, Cleveland, Ohio.

Disclosures: The author has disclosed no conflicts of interest. The form can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M16-0035.

Requests for Single Reprints: Steven E. Nissen, MD, Department of Cardiovascular Medicine, The Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195; e-mail, nissens@ccf.org.

Author Contributions: Conception and design: S.E. Nissen.

Drafting of the article: S.E. Nissen.

Critical revision for important intellectual content: S.E. Nissen.

Final approval of the article: S.E. Nissen.


Ann Intern Med. 2016;164(8):558-559. doi:10.7326/M16-0035
© 2016 American College of Physicians
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On 7 January 2016, the U.S. Department of Health and Human Services and Department of Agriculture released the Dietary Guidelines for Americans 2015–2020. This commentary discusses the new guidelines and the strength of the scientific evidence supporting them.

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Comment
Posted on January 22, 2016
Frank B. Hu, MD, PhD, Marian L. Neuhouser, PhD, RD, Rafael Perez-Escamilla, PhD, Miguel A. Martinez-Gonzalez, MD, PhD, MPH, Walter C. Willett, MD, DrPH
Harvard, Yale, Fred Hutchinson Cancer Center,University of Navarra
Conflict of Interest: None Declared
Dr. Nissen’s comments on the dietary guidelines and nutritional sciences (1) in general are highly misleading and in many cases, factually incorrect. He wrongly equates the “Dietary Guidelines Advisory Committee” (DGAC) report (2) with the “Dietary Guidelines for Americans” (DGAs). (3) The DGAC report was developed by 14 experts who reviewed and summarized peer-reviewed evidence on diet and health. This report served as the scientific basis for the federal government to develop DGAs, a policy document subject to strong congressional and industry influences. The DGAs were written by federal staff without involvement of the DGAC committee. Therefore, Nissen’s question “How can the same committee arrive at diametrically opposite conclusions?” should not even be a question. The DGAC report did not carry forward the 300 mg/day upper limit for dietary cholesterol based on the weak relationship between dietary cholesterol and serum cholesterol. (4) The DGAs followed the recommendation of the DGAC and emphasized that a healthy dietary pattern such as a Mediterranean-type diet is typically low in saturated fat and dietary cholesterol.
The PREDIMED Trial was built on prior observational evidence from both ecologic and prospective cohort data (e.g. the Nurses’ Health Study and other large cohorts) that supported benefits of the Mediterranean diet. (5) In the DGAC report, PREDIMED was extensively cited, along with consistent evidence from large cohort studies, to recommend a Mediterranean-style diet as one of several healthy eating patterns.
Nissen’s assertion that limitation of saturated fat is not supported by evidence is unfounded. The DGAC reviewed extensive evidence from seven recent systematic reviews or meta-analyses, including the controversial meta-analysis cited by Nissen. (6) Based on evidence from both RCTs and large cohorts, the committee concluded that replacing saturated fat with polyunsaturated fat significantly reduces LDL cholesterol and CVD risk, but replacing saturated fat with overall carbohydrate has few if any benefits. Thus, the DGAs removed the upper limit on total fat and put greater emphasis on specific types of fat.
We are troubled by Nissen’s accusation of lack of scientific integrity by Dr. Ancel Keys citing a reporter’s controversial popular book. We urge Nissen to offer credible evidence to support his claim. Keys’ seminal Seven Countries’ Study documented for the first time the huge variation in rates of coronary heart disease among countries, spurring further research to identify the modifiable causes. (7)
Although we agree with Nissen’s plea for more NIH support of nutritional research, including RCTs, we believe his commentary reflects misunderstanding of the dietary guidelines process and nutritional science.

Reference
1. Nissen SE. U.S. Dietary Guidelines: An Evidence-Free ZoneU.S. Dietary Guidelines: An Evidence-Free Zone. Annals of Internal Medicine. 2016;N/A(N/A):N/A-N/A.
2. Dietary Guidelines Advisory Committee. Scientific Report of the 2015 Dietary Guidelines Advisory Committee. February 2015. Accessed at http://health.gov/dietaryguidelines/2015-scientific-report/ on January 21, 2016
3. U.S. Department of Health and Human Services, U.S. Department of Agriculture. 2015 – 2020 Dietary Guidelines for Americans. 8th Edition. December 2015. Accessed at http://health.gov/dietaryguidelines/2015/ on January 21, 2016
4. Eckel RH, Jakicic JM, Ard JD, Hubbard VS, de Jesus JM, Lee IM, 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. Circulation. 2013.
5. Martinez-Gonzalez MA, Bes-Rastrollo M. Dietary patterns, Mediterranean diet, and cardiovascular disease. Current opinion in lipidology. 2014;25(1):20-6.
6. Chowdhury R, Warnakula S, Kunutsor S, Crowe F, Ward HA, Johnson L, et al. Association of dietary, circulating, and supplement fatty acids with coronary risk: a systematic review and meta-analysis. Ann Intern Med. 2014;160(6):398-406.
7. Blackburn H. Introduction to Ancel Keys Lecture. Ancel Keys, pioneer. Circulation. 1991;84(3):1402-4.

Frank B. Hu, MD, PhD
Professor Nutrition and Epidemiology
Harvard T. H. Chan School of Public Health
Professor of Medicine
Harvard Medical School
2015 DGAC member

Marian L. Neuhouser, PhD, RD
Cancer Prevention Program
Fred Hutchinson Cancer Research Center
University of Washington, Seattle
2015 DGAC member

Rafael Perez-Escamilla, PhD
Professor of Epidemiology and Public Health
Yale School of Public Health
2015 DGAC member

Miguel A. Martinez-Gonzalez, MD, PhD, MPH
Professor and Chair, Department of Preventive Medicine and Public Health
Medical School at University of Navarra, Spain
Coordinator of the PREDIMED Network

Walter C. Willett, MD, DrPH
Chair, Department of Nutrition
Harvard T.H. Chan School of Public Health
Professor of Medicine
Harvard Medical School
In defense of Ancel Keys
Posted on January 26, 2016
Miguel A. Martinez-Gonzalez, Antonia Trichopoulou
CIBEROBN (Spain), Hellenic Health Foundation
Conflict of Interest: None Declared

Dr. Nissen(1) is inaccurate in atttributing any state of confusion in nutritional knowledge to Ancel Keys. His famous Seven Countries Study, following an ecological design, found a strong correlation (r=0.84) between mean intake of saturated lipids (as percentage of total energy intake) and coronary mortality in 16 regions. These results, with the inherent limitations of an ecological design, are in agreement with subsequent stronger evidence and with the US Dietary Guidelines Advisory Committee in limiting saturated lipids (and its main sources, whole-fat dairy and red/processed meats) but not total lipids.
In Seven Countries, the percentage of energy from total lipids had a negligible association with coronary heart disease(2-3). Keys showed that total cholesterol was raised by saturated fatty acid intake but not by total fat intake: “in almost all natural human diets the effect of fat on the serum cholesterol level seems to be dominated by palmitic acid which makes up the bulk of the saturated fatty acid which affects serum-cholesterol.”(4)
Ancel Keys was positively impressed by the dramatically low rates of heart disease in Crete and other Mediterranean areas despite a high total fat intake (mainly from olive oil in the 1950s). The low content of saturated lipids could explain this low incidence of coronary heart disease. Consequently, Keys was also pioneer in attributing this benefit to a “good Mediterranean diet”, and in stark contrast with the unsubstantiated affirmations by Dr. Nissen(1), he was anticipatory in observing “low all-causes death rates  in populations whose diets were high in total fats with oleic acid dominating the picture.”(3). This perspicaz and insightful view was later confirmed by large prospective cohort studies, with good control of potential confounding, long-term follow-up and appropriate ascertainment of hard clinical events, including large cohorts  conducted in Mediterranean areas where a high total lipid intake is accompanied by olive oil consumed in great amounts. The hypotheses defended by Keys are also in agreement with the subsequent results of the Lyon randomized trial and the PREDIMED  randomized trial(5). Therefore, there is consensus and consistency, not controversy, in guidelines promoting a reduction in the saturated fat intake, but not establishing an upper limit for total lipid intake if it comes from healthy natural vegetable sources, such as olive oil, tree nuts or other vegetal foods. There is also consensus on the Mediterranean diet as an optimal dietary model for a healthy life.
Miguel A. Martinez-Gonzalez
Antonia Trichopoulou

References
1) Nissen SE. U.S. Dietary Guidelines: An Evidence-Free Zone. Ann Intern Med. 2016; Published online 19 January 2016 doi:10.7326/M16-0035.
2) Keys A. Seven countries: a multivariate analysis of death and coronary heart disease. Cambridge (MA): Harvard University Press, 1980.
3) Keys A, Aravanis C, Van Buchem FSP, Blackburn H, Buzina R, Djordjevic BS, et al. The diet and all-causes death rate in the Seven Countries Study. Lancet. 1981;2:58-61.
4) Keys A, Anderson JT, Grande F. Prediction of serum cholesterol responses of man to changes in fats in the diet. Lancet 1957;ii:959-66.
5) Tracy SW. Something new under the sun? The Mediterranean diet and cardiovascular health. N Engl J Med. 2013;368:1274-6.

Author's Response
Posted on March 18, 2016
Steven E. Nissen, MD
Cleveland Clinic
Conflict of Interest: None Declared
The criticism of our commentary by Drs. Hu and Martinez-Gonzalez et al does not stand up well to careful scientific scrutiny. It is simply not credible to suggest that the Dietary Guidelines and the Scientific Report are somehow not linked. The Scientific Report explicitly states that it is designed to “inform the next edition of the Guidelines.” Attempts to de-link these two documents cannot be accepted as reasonable. While it is correct the Dietary Guidelines did not carry forward the previous 300 mg per day limit on cholesterol, at the same time, the report states that “individuals should eat as little dietary cholesterol as possible.” This recommendation directly contradicts the guideline recommendation against numerical caps on cholesterol. The impassioned defense of the Seven Countries Study by both letter writers ignores two fundamental realities: 1) Correlation does not prove causation 2) The country selection for the study was biased. In the initial study of 6 countries, data were available for 21 countries, including some where saturated fat consumption is high, such as France, but these countries were not included. (1) The subsequent Seven Countries Study was similarly flawed. (2) There have now been 4 meta-analyses, 5 systematic reviews, and 3 non-systematic reviews examining clinical trials that found no effect of saturated fats on either heart disease, cardiovascular mortality or total mortality. In some analyses, replacing saturated fats with polyunsaturated vegetable oils reduced some types of cardiovascular events (but not deaths). In one analysis looking only at cardiovascular events (not deaths), a benefit was seen in replacing saturated fats with polyunsaturated vegetable oils. A summary of these studies is available. (3) Many other authors have pointed out that guidelines suggesting limitation of dietary fats including saturated fat were not evidence based. (4) Neither letter attempts to defend the extreme claims about relationships between food consumption and disease based on observations from the Nurses Health Study that we pointed out in the commentary. As a medical profession, we can continue to perpetuate the poor quality science that has dominated nutritional research or transition to a new era where dietary evidence is derived from high quality randomized trials. That was the principal proposition offered by our commentary.

1) Yerushalmy J, Hilleboe HE. Fat in the diet and mortality from heart disease. A methodologic note. NY State J Med 1957;57:2343–54.
2) DiNicolantonio, James J. The cardiometabolic consequences of replacing saturated fats with carbohydrates or Ω-6 polyunsaturated fats: Do the dietary guidelines have it wrong?, Open Heart. doi:10.1136/openhrt-2013-000032
3) http://www.nutrition-coalition.org/saturated-fats-do-they-cause-heart-disease/
4) Harcombe Z, Baker JS, Cooper SM, et al. Evidence from randomised controlled trials did not support the introduction of dietary fat guidelines in 1977 and 1983: a systematic review and meta-analysis Open Heart 2015;2:e000196. doi:10.1136/openhrt-2014-000196
The DASH Diet
Posted on April 22, 2016
George A. Bray, MD, MACP, Ronald M. Krauss, MD
Children’s Hospital of Oakland Research Institute
Conflict of Interest: None Declared
The article by Nissen entitled “U.S. Dietary Guidelines: An Evidence-Free Zone” points out the deficiencies in the process by which the 2015 Dietary Guidelines were drafted (1). In particular, he cites the lack of randomized clinical trials (RCTs) supporting many of the guidelines’ recommendations, including the limitation of saturated fat intake to reduce risk of cardiovascular disease (CVD).
In his discussion, however, Nissen overlooked RCT evidence for the benefits on CVD risk of the DASH (Dietary Approached to Stop Hypertension) diet (2), which is one of the dietary patterns recommended in the current. Dietary Guidelines. This diet, which is high in fruits, vegetables and low fat dairy products, resulted in clinically significant reductions blood pressure compared with either a standard American diet or a diet with increased fruits and vegetables alone (2). A subsequent RCT showed that the DASH diet was effective for lowering blood pressure over a range of sodium intakes varying from 50 to 150 mMol/d (3). Although there have been no RCTs testing the effects of the DASH diet on clinical CVD end points, the well-established benefits of blood pressure reduction for both ischemic heart disease and stroke strongly support the inclusion of this dietary pattern in current dietary recommendations.
An additional potential benefit of the DASH diet on CVD risk was that relative to the control diet, it resulted in lower LDL cholesterol levels (4). While it seemed plausible to attribute this reduction, at least in part, to the lower level of saturated fat in the DASH diet, the design of the RCTs did not permit assessment of the extent to which either the beneficial lipid or blood pressure response was dependent on the inclusion of low-fat vs. higher fat dairy products. We therefore conducted a RCT to test the effects of substituting full-fat for low-fat dairy foods in the DASH diet, with a corresponding increase in total and saturated fat and a reduction of sugar intake (5). Notably, the higher fat DASH diet lowered blood pressure to the same extent as the standard DASH diet, but also reduced plasma triglyceride and very low density lipoprotein concentrations without significantly raising LDL cholesterol. This finding further supports the evidence for the clinical benefit of the DASH dietary pattern, and is consistent with the concerns raised by Nissen as to the experimental evidence underlying current recommendations for limiting saturated fat intake to reduce CVD risk.


References:

1.Nissen SE U.S. Dietary Guidelines: An Evidence-Free Zone Ann Intern Med. 2016;164:558-559.

2.Appel, L.J., T.J. Moore, E. Obarzanek, W.Vollmer, L.P.Svetkey, F.M. Sacks, G.A. Bray, T.M. Vogt, J.A. Cutler, D. Simons-Morton, P0H, Lin, N Karanja, E.R. Miller III and D.W. Harsha. A clinical trail of the effects of dietary patterns on blood pressure. New Engl J Med 1997;338:1117-1124.

3.Sacks, F.M., L.P. Svetkey, W.M. Vollmer, L.J. Appel, G.A. Bray, D.W. Harsha, E. Obarzanek, P.R. Conlin, E.R. Miller, D. Simons-Morton, N Karanja, P-H Lin for the DASH-Sodium collaborative research group. A clinical feeding trial of the effects on blood pressure of reduced dietary sodium and the DASH dietary pattern (The DASH-Sodium Trial). New Engl J Med 2001;344:3-10.

4.Obarzanek E, Sacks FM, Vollmer WM, Bray GA, Miller ER 3rd, Lin PH, Karanja NM, Most-Windhauser MM, Moore TJ, Swain JF, Bales CW, Proschan MA; DASH Research Group. Effects on blood lipids of a blood pressure-lowering diet: the Dietary Approaches to Stop Hypertension (DASH) Trial. Am J Clin Nutr. 2001 Jul;74(1):80-9

5.Chiu S, Bergeron N, Williams PT, Bray GA, Sutherland B, Krauss RM. Comparison of the DASH (Dietary Approaches to Stop Hypertension) diet and a higher-fat DASH diet on blood pressure and lipids and lipoproteins: a randomized controlled trial. Am J Clin Nutr. 2016 Feb;103(2):341-7.



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