- Are there significant flaws in the decision making process behind the dietary guidelines?
- Is there evidence supporting U.S. Dietary Guidelines on saturated and polyunsaturated fat?
- Do the guidelines increase or decrease the risk of cardiovascular disease?
- The decision making process behind the U.S. dietary guidelines is deeply flawed. Dietary guidelines are based on the viewpoints of an insular group. The group uses scientific language but focuses effort on defending a thesis (effort which is suitable for advancement within universities) versus focusing effort on identifying weaknesses in a hypothesis (scientific effort). The group discounts or dismisses conflicting evidence and makes no mention of the risks associated with their recommendations.
- There is no credible evidence supporting the dietary intervention of replacing saturated fat with polyunsaturated fat. There are risks with consumption of some sources of saturated fat but that risk is not reduced when replaced by polyunsaturated fat.
- The guidelines increase the risk of cardiovascular, liver disease and cancer. They increase the risk because polyunsaturated fatty acid deficiencies are extremely rare and polyunsaturated fats are unstable and susceptible to oxidation (which means risk increases as consumption increases).
- The language being used by the American Heart Association (AHA) and the language used by the 2015 Dietary Guidelines Advisory Committee (DGAC) exaggerates both the benefits of dietary guidelines and the strength of the evidence supporting dietary recommendations.
- The recommendations of the AHA and DGAC in a trilogy of documents from 2013, 2015 and 2017 missed the mark because the committees attention and effort were focused on grading food studies to defend a thesis, rather than measuring the risks and benefits of a medical intervention.
- Nutrients are chemicals. Chemicals in the body follow the rules of Goldilocks, not gold. With gold, more gold has more value. With nutrients there are zones of too little, beneficial and too much. With nutrients there is danger in both too little and too much. Every nutrient, even water and oxygen, has a safe upper limit.
- Saturation is a measure of stability. Saturated is fat is stable, polyunsaturated fat is not.
- Polyunsaturated fatty acid deficiencies are extremely rare.
- The damage mechanism of excess polyunsaturated fatty acid (lipid perioxidation) is well understood from a molecular biology point of view.
- The hypothesis of the AHA and 2015 DGAC is based on an assumption that saturated fat increases LDL-C and the increase in LDL-C causes heart disease. During the 2013 AHA Systematic Evidence Review, the 2015 DGAC Evidence Review and an independent 2015 review by the Credit Suisse Research Institute there were zero studies which showed a link between saturated fat and cardiovascular disease.
- Nutrition recommendations are dominated by professors from Harvard and Tufts. The Nutrition Departments of Harvard and Tufts are dominated by Epidemiologists (where epidemiology is the study of the spread of disease)
- The primary tool of Epidemiology is statistical analysis.
The 2015 Dietary Guidelines recommend restricting saturated fat consumption to no more than 10% of calories. The American Heart Association (AHA) is more restrictive, recommending no more than 6% of calories.
To meet these restrictions, the 2015 Dietary Guidelines Advisory Committee (DGAC) and the AHA recommend replacing saturated fat with polyunsaturated fat.
A trilogy of documents captures the thought process of the individuals from the 2015 DGAC and the 2013 and 2017 AHA committees who developed the recommendations.
There are three significant issues with the DGAC and AHA recommendations:
1) The recommendation is a dietary intervention. Every intervention has both benefits and risks.
2013 American Heart Association / American College of Cardiology (AHA / ACC) Report from the Lifestyle Work Group
2015 Report from the Dietary Guidelines Advisory Committee
2017 American Heart Association Advisory Statement
Professor Alice Lichtenstein
New York Times Editorial
The 2013 ACC/AHA Review cited by Professor Lichtenstein did not investigate links between saturated fat and heart disease (cardiovascular disease or CVD)
The Lifestyle Work Group provided recommendations on dietary changes to lower LDL-C (low density lipoprotein – cholesterol).
The 2013 AHA/ACC Review was a systematic review of Nutrition Studies. What the 2013 AHA / ACC Report focused on (a database review of nutrition studies):
What the 2013 AHA / ACC recommended (consume a diet with 6% or less of saturated fat. Replace saturated fat with polyunsaturated fat) and the basis for the recommendations (Evidence Statements (ES) 11, 12 and 13).
The grading criteria for a 1A (highest) recommendation (multiple randomized controlled trials or meta-analysis, diverse population base, benefits >>> (much greater than) risks).
The evidence base used:
ES 11: Three Studies (DASH, DASH-S, DELTA). In two of the studies (DASH and DASH-S) the relationship between saturated fat and LDL-C could not be determined.
ES 12 & 13: Two meta-analysis, conducted 11 years apart by the same authors. The meta-analysis generated a prediction of ‘what would have happened, if…’ dietary changes were made. They were not a measure of actual results.
To summarize the evidence base, 6048 studies were reviewed and for the recommendations on saturated and polyunsaturated fat, 5 studies were chosen.
Three evidence statements were made to justify the recommendations on saturated and polyunsaturated fat. For a 1A rating (the highest rating level) multiple (two or more) studies were required showing the benefits outweighed the risk. For ES 11, three studies were cited but only 1 of the 3 showed a link between saturated fat consumption and LDL-C.