Told you so.
Two of the recommendations in the new DGAC report represent a major
change from earlier versions of the Dietary Guidelines. (2) First, dietary cholesterol is no longer listed as a "nutrient of concern." This change is based on recent studies indicating there is no significant association between dietary cholesterol intake and serum cholesterol or risk of cardiovascular disease. Second, In contrast to previous versions of the Dietary Guidelines, which recommended limiting fat intake to 20% to 35% of total calories, people will no longer be advised to restrict their fat Intake. Instead, the new recommendation is to emphasize the use of healthful fats (such as olive oil and nuts), while avoiding harmful fats (such as trans fatty acids).
For half a century we were told to avoid cholesterol and fat (mainly saturated fat), because they will give us heart disease. These recommendations spawned foods such as egg substitutes which, despite being low In cholesterol, destroyed the health of experimental animals and led to their early death. (3) Fat-phobia helped create a huge market for fat-free and low-fat yogurt, which Is typically loaded with added sugar and frequently contains no probiotic organisms. People were all too willing to believe that these sweet-tasting, addictive quasi milkshakes were good for them because they were low In fat. And over the years, many other foods of questionable nutritional value pervaded the marketplace, as consumers happily ignored the fact that low-fat junk food Is still junk food.
It is encouraging that the new Dietary Guidelines will promote healthful foods such as nuts and fish (despite their relatively high fat content), as well as fruits, vegetables, and legumes, while recommending lower Intake of sugars and refined grains. However, the satisfaction of knowing that these sensible recommendations are about to become official Is tempered by the awareness that it took the "experts" so long to accept what some scientists and nutritionists have been saying for decades. As early as the 1960s, John Yudkin presented both epidemiological and biochemical data to support the concept that sucrose, not fat, Is the key dietary contributor to cardiovascular disease. (4-6) In his 1970 book, Nutrition Against Disease, biochemist Roger Williams cited evidence that trans fatty acids and fats heated to high temperatures are harmful, whereas there is little evidence that dietary fat per se is dangerous. Others, Including this author on multiple occasions, have emphasized the dangers of refined carbohydrates while arguing that dietary cholesterol and saturated fat are less of a problem than Is commonly believed. Yet, the "experts" generally Ignored the dissenters and the research they cited. (7) Instead, they clung to the "lipid hypothesis," even, Ironically, while acknowledging that their dogma was Indeed merely a hypothesis.
And when they did come around to the dissenters' point of view, they did so in such a way as to protect their position of authority. For example, an editorial In the New England Journal of Medicine In 2014 about trans fatty acids stated, "In the early 1990s, studies began [Italics mine] revealing negative health effects of trans fats, and by the mid-20005, It was clear beyond doubt that trans fats Increase the risk of coronary heart disease...." (8) That statement is not accurate. A more accurate statement would have been something like, "Research as early as the 1950s Indicated that consumption of trans fatty acids can exacerbate a deficiency of cardioprotective essential fatty acids, and a 1975 study demonstrated that trans fatty acids are atherogenic in swine. Although this research was preliminary, it should have alerted us to the possibility that recommending trans fatty acids as a heart-healthy alternative to other types of fat is unwise." (9,10)
I present this historical perspective hopefully not as an ego-driven "I told you so," but to point out that people who are recognized by the mainstream as authorities do not necessarily have the knowledge, big-picture viewpoint, or wisdom to get things right. This point is important, because it reminds us that we should not automatically accept everything that the "experts" tell us. For example, while historical fears regarding dietary cholesterol were probably overblown, so likely is the new official position that dietary cholesterol is of no concern at all. Cholesterol is an unstable molecule, readily oxidized in the presence of air to form highly atherogenic cholesterol oxides. These toxic molecules are less likely to be produced when an egg is boiled inside its shell than when it is scrambled, when meat is cooked at low rather than high temperatures, and when butter is kept covered in the refrigerator rather than left uncovered on the table. The simplistic evolution of cholesterol from a nutrient of concern to one of no concern ignores these nuances. Similarly, the many "experts" who claim that micronutrient supplementation of nondeficient persons is not beneficial seem unable or unwilling to evaluate the scientific literature in its entirety and in an unbiased way. As always, we should evaluate scientific claims not by the status of the person making the claims, but by the strength of their arguments.
Alan R. Gaby, MD
(1.) 2015 Dietary Guidelines [Web page], http://www.health.gov/dietaryguidelines/2015.asp. Accessed August 7, 2015.
(2.) Mozaffarian D, Ludwig DS. The 2015 US Dietary Guidelines: lifting the ban on total dietary fat. IAMA. 2015;313:2421-2422.
(3.) Navidi MK, Kummerow FA. Nutritional value of Egg Beaters" compared with "farm fresh eggs." Pediatrics. 1974;53:565-566.
(4.) Yudkin J. Nutrition and payability with special reference to obesity, myocardial infarction, and other diseases of civilisation. Lancet. 1963;1:1335-1338.
(5.) Yudkin J. Evolutionary and historical changes in dietary carbohydrates. Am J Clin Nutr. 1967;20:108-115.
(6.) Yudkin J et al. Sugar intake, serum insulin and platelet adhesiveness in men with and without peripheral vascular disease. Postgrad Med). 1969;45:608-611.
(7.) Siri-Tarino PW et al. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. Am J Clin Nutr. 2010;91:535-546.
(8.) Brownell KD, Pomeranz JL. The trans-fat ban--food regulation and long-term health. N Engl J Med. 2014;370:1773-1775.
(9.) Holman RT, Aaes-Jorgensen E. Effects of trans fatty acid isomers upon essential fatty acid deficiency in rats. Proc Soc Exp Biol Med. 1956;93:175-1 79.
(10.) Kummerow FA, et al. Swine as an animal model in studies on atherosclerosis. Fed Proc. 1975;33:235.
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|Title Annotation:||nutritional guidelines by promoting healthy food habits|
|Author:||Gaby, Alan R.|
|Date:||Nov 1, 2015|
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