Saturated Fat Does Not Cause Heart Disease?!

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The late Dr. Robert Atkins claimed a high saturated fat diet does not adversely impact blood lipids and promote heart disease. Now according to a recent study hyped in the media Dr. Atkins was right after all. For example, the Washington Post published an article by Jennifer LaRue Hugert on March 4, 2010 with the headline “Atkins diet’s return reflects idea that saturated fat shouldn’t be demonized."

The late Dr. Robert Atkins claimed a high saturated fat diet does not adversely impact blood lipids and promote heart disease. Now according to a recent study hyped in the media Dr. Atkins was right after all. For example, the Washington Post published an article by Jennifer LaRue Hugert on March 4, 2010 with the headline “Atkins diet’s return reflects idea that saturated fat shouldn’t be demonized." To bolster this questionable claim, Ms. Huget refers repeatedly to a study published in the March issue of the American Journal of Clinical Nutrition (AJCN).1 This new study simply re-analyzed several earlier epidemiological studies (lasting from 5 to 23 years) which found no significant correlation between reported dietary saturated fat intake and the subsequent risk of developing cardiovascular disease. In addition, this same issue of AJCN ran an opinion article by the same authors suggesting refined carbohydrates and obesity rather than saturated fat are the real culprits promoting heart disease. [AJCN pp 502-9]. This AJCN article was perfectly timed to promote the release of "The New Atkins for a New You" book authored by long-time Atkins proponent Eric Westman, MD at Duke University. Does this new research really prove that Atkins was right after all? Not even close. Why? The ability to find a positive correlation between saturated fat (or salt or cholesterol for that matter) and heart disease in most epidemiological studies has always been very difficult especially within a fairly homogeneous population where day-to-day intra-individual variation in saturated fat intake is often greater than the average inter-individual variation between individual subjects. As a result of this statistical "noise" the real association between higher saturated fat intake and higher LDL cholesterol and ultimately more coronary heart disease is obscured. The data collected to measure saturated fat intake were very imprecise in all the studies used in this new meta-analysis. These epidemiological studies relied on dietary recall data from a food frequency questionnaire or from 24 hour dietary recalls even though both measures are notoriously inaccurate. In numerous investigations on the efficacy of 24- hour dietary records, researchers have found that the majority of people grossly over or under estimate their actual food intake either because they forget some of what they had eaten or because their estimates of the amount they ate were way off. Even when 24-hour food recalls give an accurate assessment of a particular day's diet it may still provide very inaccurate estimates of the subject's overall food intake over the long term because people often eat very different amounts of saturated fat, salt, etc. from day to day. Moreover, people, especially in industrialized countries like the U.S., sometimes change their diets over time further complicating the issue. Hence, what their daily diet was at the beginning of a study period may change significantly over several years making it far more difficult to show a correlation between saturated fat intake and CVD events over many years. When the measurement of dietary variables is unreliable the odds of finding a significant correlation between what people ate and disease development years later becomes difficult or impossible. However, unreliable data cannot mean saturated fat doesn't cause heart disease, especially if far more reliable data indicate it does.

Saturated Fat Raises "Bad" LDL Cholesterol

In all short-term clinical trials where saturated fat intake was carefully controlled, the data consistently show that replacing saturated fat with unsaturated fat, carbohydrate, and/or protein consistently lowers LDL-cholesterol levels. Add to that data from several large studies proving that people with higher LDL-cholesterol levels are at far greater risk of developing coronary heart disease over time than those with much lower LDL-cholesterol levels.2 Now putting these two proven facts together the inescapable conclusion must be that diets higher in saturated fat raise LDL cholesterol levels in the short term and promote atherosclerosis and coronary heart disease in the long term. That being the case, any epidemiological study that fails to find a correlation between saturated fat intake and heart disease as seen in this recent AJCN meta-analysis simply demonstrate that the data used in those studies was seriously flawed.

Bottom Line:

Clinical trials have proven that increased saturated fat intake raises LDL-cholesterol levels. Other research has proven that higher LDL cholesterol levels promote more atherosclerosis and cardiovascular disease in the long term. So the only thing this recent AJCN study actually showed was the methods used to assess dietary intake in epidemiological studies are far too inaccurate to find an already well-established scientific relationship.

By Dr. James J. Kenney, PHD, RD, FACN

References:

1. Am J Clin Nutr 2010;91:535-46

2. Am J Clin Nutr 2010;91:497-99

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