Published: Oct 23, 2013
By Todd Neale
Full Story: http://www.medpagetoday.com/Cardiology/Prevention/42448
In a commentary in BMJ, Aseem Malhotra, MBChB, an interventional specialist registrar from Croydon University Hospital in London, argues that a focus on saturated fat as a major player in heart disease has been misguided and potentially harmful.
“Scientists universally accept that trans fats — found in many fast foods, bakery products, and margarines — increase the risk of cardiovascular disease through inflammatory processes,” he wrote. “But ‘saturated fat’ is another story.”
In a commentary in BMJ, Aseem Malhotra, MBChB, an interventional specialist registrar from Croydon University Hospital in London, argues that a focus on saturated fat as a major player in heart disease has been misguided and potentially harmful.
“Scientists universally accept that trans fats — found in many fast foods, bakery products, and margarines — increase the risk of cardiovascular disease through inflammatory processes,” he wrote. “But ‘saturated fat’ is another story.”
A major problem, Malhotra said, is that after studies suggested that high levels of cholesterol and saturated fat were associated with increased cardiovascular risk the food industry started replacing saturated fat with sugar (to compensate for loss of taste).
“The scientific evidence is mounting that sugar is a possible independent risk factor for themetabolic syndrome …,” he wrote.
“It is time to bust the myth of the role of saturated fat in heart disease and wind back the harms of dietary advice that has contributed to obesity,” he concluded.
Here’s a sampling of the reactions from leaders in nutrition and prevention who were contacted by MedPage Today (edited for length and clarity).
Walter Willett, MD, DrPH, Chair of the Department of Nutrition at the Harvard School of Public Health
For many years, saturated fat was deemed by many to be the major cause of cardiovascular disease (CVD). What we have learned is that it is part of the picture, although far from the whole picture. If compared with the typical carbohydrate in the U.S. diet, saturated fat has almost no effect on the LDL/HDL ratio or risk of heart disease. However, if compared with polyunsaturated fat, and probably monounsaturated fat in vegetable oils, it has an adverse effect. Thus, the advice in the late 1960s and 1970s to replace saturated fat with vegetable oils was almost certainly beneficial and contributed much to the large reduction in cardiovascular mortality. Unfortunately, with almost no evidence, in the 1980s the advice shifted to replacing saturated fat and total fat with carbohydrates, which was not helpful and probably harmful to many. We have started to recover from this, but it is taking a long time.
Malhotra is correct that a Mediterranean-type diet focused on the type of fat and that includes many fruits and vegetables, whole grains, nuts, legumes, and low amounts of red meat will be better (and it will be low in saturated fat, but not because that is the focus). Where the commentary goes too far is that red meat or dairy are not a problem; in an optimal diet they will be low because they will be mainly replaced by nuts, legumes, fish, and some poultry.
Scott Grundy, MD, PhD, Director of the Center for Human Nutrition at UT Southwestern Medical Center
The best evidence that saturated fats do raise cholesterol levels and contribute to coronary heart disease comes from Finland. Thirty years ago, Finnish people consumed diets very high in saturated fats. They also had very high cholesterol levels and high rates of heart disease. Through public health measures, intakes of saturated fats declined and so did coronary heart disease. Many other metabolic studies show that saturated fats raise cholesterol levels, and many epidemiological studies show that for every 1% rise in cholesterol there is a corresponding 1% to 2% rise in heart risk. Since saturated fats definitely raise cholesterol levels, it can be deduced that there is a corresponding increase in risk. Finally, a few smaller scale clinical trials show that people given high saturated fats have higher heart attack rates than those getting unsaturated fats.
David Katz, MD, MPH, Director of the Yale University Prevention Research Center
My opinion in general is that the current effort to exonerate saturated fat is guilty of all the same over-generalizations and misinterpretations as the effort to vilify saturated fat. Consider that a diet high in saturated fat was, of necessity, always proportionately lower in “other things” — such as unsaturated fat, vegetables, fruits, etc. People who eat a lot of meat eat fewer beans and lentils. The active ingredient in a “bad diet” that happened to be high in saturated fat may always have been the “bad diet,” with high saturated fat just one of its many liabilities. See, for instance, this quote below lifted directly from the commentary:
“In the past 30 years in the U.S. the proportion of energy from consumed fat has fallen from 40% to 30% (although absolute fat consumption has remained the same), yet obesity has rocketed.”
The author uses this to support his argument that saturated fat is not harmful: we’ve cut fat and still gotten fatter. But he seems to ignore the far more important implication of his own statement: if fat intake has fallen as a percentage of calories, but absolute fat intake has remained constant, it means, ipso facto, that calorie intake has gone up! And yet, the author argues against the importance of calories to weight. This is, in fact, the very problem: we didnot cut our fat intake. We just increased our calorie intake, adding lots of sugar and starches. The message to reduce saturated fat intake was, I believe, a message intended to mean: eat less cream, eat more spinach. It was perverted into: eat Snackwell cookies. We have modern epidemiology to show for it.
C. Noel Bairey Merz, MD, Director of the Preventive and Rehabilitative Cardiac Center at Cedars-Sinai Medical Center
Food is complex but it is clear that a Western diet that is high in animal protein, saturated fat, dietary cholesterol, oxidative stress (chips, fries) and low in polyunsaturated fatty acids (nuts, legumes, fish), fiber, and B vitamins (fruits and vegetables) is linked with higher rates of cardiovascular disease. Ancel Keys demonstrated long ago that saturated fat and dietary cholesterol raise serum cholesterol levels, but it is more complex than just saturated fat. Saturated fat and cholesterol were what could be identified at the time. We have moved on, but the U.K. has not.
Contemporary U.S. guidelines moved away from saturated fat and dietary cholesterol 10 years ago and now recommend a Mediterranean pattern of diet. History shows this is also what Ancel Keys proposed. In addition to U.S. studies, this is also supported by the most recent Spanish PriMed study that the author cites but he conveniently skipped over the part about shifting from animal (meat) to vegetable (legumes) protein and monounsaturated fat (olive oil) rather than butter and lard (saturated fat and dietary cholesterol).
The dietary change embraced by the U.S. in the 1960s (reducing butter and lard, whole milk, bacon, eggs, red meat) resulted in a population fall in total cholesterol in NHANES from approximately 220 to 210 mg/dL, which was accompanied by Ancel Keys’ predicted percent reduction in CVD, falling right on the line. Rates have now fallen even further with the widespread use of statins lowering of serum cholesterol. Small changes in large populations make a difference for society that is not always measurable at the individual level. So it had an impact. The reverse is playing out in developing countries: China has dramatically increased their animal consumption as they have become prosperous and CVD rates are concurrently dramatically rising.
Michael Blaha, MD, MPH, Director of Clinical Research at the Johns Hopkins Ciccarone Center for the Prevention of Heart Disease
Saturated fat, as a whole, probably plays a modest role in determining cardiovascular risk. However, it is probably inappropriate to lump all saturated fats together. Some saturated fats (like coconut oil and palm oil), may be, in fact, healthy. Indeed, it is pretty clear that dairy products consumed in moderation are probably healthy. Other sources of saturated fat, like those in red meat, may be modestly atherogenic. But this is hard to disentangle from other unhealthy aspects of processed red meat, including preservatives and the nitrate byproducts of high-temperature cooking.
I think it is pretty clear that the emphasis on reducing fat intake has led to increased intake of carbohydrates. Unfortunately, for the most part, this has been in the form of highly processed simple carbohydrates that drive the blood sugar up and tend to induce insulin resistance. There is little doubt that diet shifts in the last 20 to 30 years have directly contributed to the current epidemic of obesity, metabolic syndrome, and diabetes.
The message about what to eat needs to be more nuanced. It is probably inappropriate to single out a single macronutrient as harmful. The message should be to eat more fresh foods and less pre-packaged and pre-prepared foods.
I disagree with the statement in the article that the “government’s obsession” with total cholesterol has led to overmedication of millions of people with statins. Statins have many beneficial effects independent of blood cholesterol levels, and current guidelines appropriately stress giving these medications to people at high cardiovascular risk, not exclusively on the basis of cholesterol levels.
Carl Lavie, MD, Medical Director of Cardiac Rehabilitation and Prevention at the John Ochsner Heart and Vascular Institute
It is true that replacing saturated fats with omega-6 fatty acids and carbohydrates is associated with potential problems, as there are concerns about linoleic acid, the main fatty acid in polyunsaturated fatty acids, which were raised by Scott Grundy almost 30 years ago. Also, in a society where energy expenditure — including household management and occupational physical activity — has markedly fallen during the past 5 decades, coupled with failure to make up for this with increased leisure-time physical activity, high-carbohydrate diets may be increasing insulin resistance and many of its consequences (whereas with high physical activity, eating sugars and complex carbohydrates would not be so detrimental). Ideally, without very high levels of physical activity, many would be better off with lower carbohydrate intakes, and higher fat intake — probably of omega-3 fatty acids (fish oils) and omega-9 fatty acids (monounsaturated fats such as oleic acid or olive oil) — would be ideal. But even so, saturated fats may be better than super high levels of carbohydrates. Saturated fats and cholesterol are safer than the trans fats.
Nevertheless, Malhotra says several things in his editorial that would be hard to defend. Statins have not been demonstrated to reduce short-term mortality in the primary prevention trials, where mortality is low in the control groups. Demonstrating mortality reductions would require studying higher-risk populations or following a low-risk population for much longer periods of time. Several of the primary prevention studies were stopped early (e.g., the ASCOT-LIPID trial in mild hypertensives), whereas projecting the mortality lines out a few more years likely would show a mortality benefit, and the CARDS trial (primary prevention in diabetes) almost had statistically significant mortality benefits in fewer than 3,000 patients followed for less than 4 years. Patients in both trials received only the very low dose of atorvastatin, 10 mg.
Finally, I favor a Mediterranean diet, but his statement that this has more benefits than statins is unfounded. The recent high-profile NEJM paper’s results were all based on a relatively few number of strokes reduced with this diet, with no trends even for reducing coronary heart disease or total mortality. On the other hand, the statin trials in secondary prevention have reduced stroke, coronary heart disease, and total mortality, and the primary prevention statin trials have reduced coronary heart disease and stroke and were not powered for mortality.