– by Dr. Irving Loh, MD
The 2015 edition of Dietary Guidelines for Americans has not yet been finalized, but will likely give providers, patients and the food industry fits and confusion. When the preliminary dietary outline became public and indicated that dietary cholesterol was being de-emphasized, and that eggs were off the no-fly list, a relatively high profile media commentator stated on air that he was going to toss his Lipitor™. NOT THE SAME!
A bit of history. Since 1980, the Dietary Guidelines for Americans has been written by the Dietary Guidelines Advisory Committee, which has been appointed by the U.S. Department of Health and Human Services and the U.S. Department of Agriculture and jointly published every five years. Based on reviews of the literature, best evidence-based science, personal opinions of the appointed experts, and an unknown amount of industry lobbying, these guidelines are tasked to encourage a disparate American population to eat a healthy diet by encouraging the selection of foods and beverages to help us reach and maintain optimal health, weight, and prevent preventable diet impacted diseases.
Data sources include epidemiologic surveys like NHANES (National Health and Nutrition Examination Survey), National Health Interview Survey, CDC, SEARCH for Diabetes in Youth Study and data from the Alzheimer’s Association.
Not surprisingly for those of us watching the eating habits of our patients, the committee found that excess dietary sodium and saturated fat are the greatest dietary risks for all Americans over the age of 50. In contrast, dietary fiber, vitamin D, calcium and potassium were under-consumed by Americans. And, somewhat surprisingly, given the negative inculcation surrounding eggs since Framingham, dietary cholesterol is not considered a nutrient of concern for over-consumption.
The committee also reiterated the prior recommendations of eating more fruits, fresh vegetables, legumes, nuts and whole grains, and restricting fats and sugars. Modest caffeine intake is now acceptable, but only if, I may add, it does not contribute to dysrhythmias or hypertension which I’m sure many of us have observed in our susceptible patients. The panel did go a bit further than prior panels in that they suggested some policy changes to help effect their recommendations. One such suggestion was a tax on sugary foods and beverages. Such a tax was implemented in Berkeley, CA, but was voted down in San Francisco and New York after heavy lobbying by the beverage industry.
More prominent nutrition labeling, perhaps to emphasize added sugar content, was also a possible suggestion. Regardless of what this committee suggests, this Congress will likely limit any recommendations that have adverse economic impact on the food and beverage industry. The lobbyists of the American Beverage Association will see to that.
But let’s go back to the dietary cholesterol issue. Do these proposed guidelines mean that cholesterol as a risk factor for atherothrombotic cardiovascular disease is now not an issue? How many of our patients will now ask you about whether they need to continue their statins and other lipid lowering regimens? Moreover, how many will discontinue their lipid therapy and not tell even tell you?
Clearly, and I mean that, CLEARLY, hyperlipidemia remains an extremely important risk factor for both primary and secondary cardiovascular prevention. The lipids themselves, i.e., the cholesterol in LDL-cholesterol, IDL-cholesterol, VLDL-cholesterol, remnant particle cholesterol, may not be the ultimate culprit, but they are the readily measured surrogates for the protein moieties that may be the atherogenic particles that trigger the immunologic and inflammatory processes that initiate and exacerbate atherothrombosis.
The most critical factor that mitigates one’s lipoprotein values is picking one’s parents carefully. Genetics dominantly control lipoprotein values, especially LDL-C and, perhaps less so, HDL-C. Given that genetic “nature”, dietary “nurture” probably impacts LDL-C levels by no more than 15%. That is not to say that extremely volatile lipid values can be demonstrated when our patients go on extreme diets (however one defines “good or bad” or “extreme”), but the important caveat here is that if the diet is isocaloric, the values may not vary all that much. The greatest variability in lipid values occur if the patient is gaining or losing weight, not if the weight is stable. Once the weight stabilizes, the LDL-C tends to creep back to where the genetic rheostat set it originally, correcting for slight upward creep as one ages. Triglyceride values, and consequently HDL-C to a lesser degree, can be more permanently impacted by weight change.
Remember, all guidelines foisted upon us are really about attempts to modify behavior. People (including we physicians) don’t really follow guidelines unless they correspond to preconceived ideas. I’ve evolved my ideas from the perspective of having been involved with research and clinical management of lipids and cardiovascular disease for over four decades.
So, I’m actually OK with the de-emphasis on dietary cholesterol per se, but as clinicians, we need to maker sure our patient’s weight does not fluctuate, which may be associated with significant perturbations in the lipid profile. But the lipid therapies in at-risk patients need to remain aggressively in place.
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Dr. Irving Kent Loh MD, FACC, FAHA (Epidemiology & Prevention), FCCP, FACP is a board certified internist and sub-specialty board certified cardiac specialist with an emphasis on preventive cardiology. He founded and directs the Ventura Heart Institute, which conducts education, research and preventive cardiovascular programs. Dr. Loh is a former Assistant Professor of Medicine at UCLA School of Medicine. He is Chief Medical Officer and Co-founder of Infermedica, an artificial intelligence company for enhancing clinical decision support for patients and healthcare providers.