Saturated Fats and the Heart

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Since the 1960s, official dietary dogma has classified saturated fats (also called saturated fatty acids, or SFA) as being very bad for our health. Current American Heart Association (AHA) guidelines are more restrictive than ever, recommending that SFA comprise “no more than 5 to 6 percent of total calories.” But recently, research has emerged suggesting that SFA may not be bad for us after all - or at least, not nearly as bad as we have been led to believe.

Whether SFA are really harmful to health is an area of intense controversy today, even among leading nutrition scientists, and there is no consensus on the question. In this article I will try to provide an objective look at the current evidence on SFA, and provide a cogent summary of where we stand today regarding SFA and the heart.

The Effect of Saturated Fats on Blood Lipids

Since the early 1960s SFA have been considered “bad” for heart health, simply because they raise the level of LDL cholesterol. But we now know that the relationship between LDL levels and cardiac risk is far more complicated than previously thought.

While SFA increases LDL levels, they do so by increasing the size of LDL particles. Large LDL particles (as opposed to the small, dense LDL particles which are measured by the APO-B test), appear not to increase cardiac risk. So the kind of elevation in LDL cholesterol produced by SFA may not be such a bad thing.

Furthermore, SFA also increase “good” HDL cholesterol levels, and reduce triglyceride levels, which benefits cardiac health. Many experts now view the overall effect of SFA on blood lipids as being, at worst, neutral rather than harmful. In any case, the underlying theory that has driven our dietary recommendations on SFA, from the very beginning, is now known to be seriously flawed.

Clinical Studies With Saturated Fats

Clinical studies have have failed to show a clinical benefit from limiting dietary SFA. Most notable is the Women’s Health Initiative (WHI). In this rigorous study, 20,000 postmenopausal women were randomized to an aggressively controlled diet in which both total fat intake and SFA were strictly limited. This was to be the definitive study that, once and for all, proved the benefits of a low-fat, low-SFA diet. So, many nutrition scientists were stunned when women consuming this “ideal” diet failed to show any reduction in cardiovascular disease.

Similarly, in a recent meta analysis of over 70 clinical studies, investigators found no association between the consumption of dietary SFA and the risk of cardiovascular disease.

Furthermore, another recent meta-analysis showed that, even back when the original government guidelines were published urging everyone to to restrict dietary SFA (1977 in the US, and 1983 in the UK), the clinical evidence available at that time did not support this recommendation.

Therefore, clinical science has not confirmed that low SFA diets are helpful in reducing heart disease.

Not All SFA Are the Same

The SFA are actually a family of compounds, and it is becoming apparent that different SFA have different implications regarding our health.

For instance, in the MESA study, eating the SFA found in dairy foods was associated with an improved cardiovascular risk, and a reduction in the risk of type 2 diabetes. On the other hand, the EPIC study reported that eating the SFA found in processed meats (such as bacon or sausage) can increase cardiac risk. Red meat, however, did not appear to increase risk.

The differences among the various SFA have have not been sufficiently characterized to allow firm recommendations on which SFA we should allow in our diets. As long as official dietary guidelines insist on limiting all SFA (for instance, specifying that we limit our dairy products to the low-fat variety), the research necessary to sort this out may be slow in coming.

What You Eat Instead of SFA Makes A Difference

Experts who support the current dietary guidelines point out, correctly, that it is difficult to evaluate studies on low SFA diets, unless you know exactly what nutrients the study participants ate in substitution for SFA. This kind of information is not available from many of those studies.

For instance, it is now known that if dietary carbohydrates are increased as SFA are reduced, there is no improvement in cardiovascular outcomes. (Experts now regard this fact as a “given,” but just a few years ago these same experts were encouraging high-carb diets, and the AHA was certifying products containing highly-processed carbs as being “Heart Healthy.”)

Also, studies have shown that when polyunsaturated fatty acids (PUFA) are substituted for SFA in the diet, cardiac outcomes are improved. For this reason, current dietary recommendations generally urge high-PUFA-low-SFA diets (instead of the high-carb-low-fat diets they urged a few years ago). Even this high-PUFA recommendation, however, is not without controversy.

The Bottom Line

In my view, based on current evidence a blanket recommendation to strictly limit all dietary SFA is not justifiable. It seems clear that SFA are not the scourge against cardiac health they have been advertised as being for the past 50 years. It also seems clear that more research is required to more accurately tease out which sources of SFA are safe (or perhaps even good for us), and which are not.

On the other hand SFA have not been completely vindicated, as some seem to be saying. They seem to be no worse than carbs, but that might not be saying much.

The nutrition experts at the moment are engaged in a very nasty fight about SFA, and seeing as they haven’t been able to resolve this issue for 50 years, the fight is likely to continue for a while. Since the experts can’t agree, then obviously it is impossible for me to give you definitive advice on SFA.

I can only tell you what I’m doing about SFA, as an older man who would like to continue to avoid cardiovascular disease. In addition to trying to follow a Mediterranean-type diet, I have gone back to using whole milk instead of low-fat milk, cooking with olive oil (at low or moderate temperatures) or butter (if higher temperatures are required), and allowing myself to eat red meat (but not processed meat) a couple of times a week.

If the experts ever really figure out the final word on SFA, I’ll try to let you know. Given recent history, however, I expect to be dead - of old age, if nothing else - well before that ever happens.

Sources:

Howard BV, Van Horn L, Hsia J, et al. Low-fat dietary pattern and risk of cardiovascular disease: the Women’s Health Initiative Randomized Controlled Dietary Modification Trial. JAMA. 2006;295:655–666.

Rohrmann S, Overvad K, Bueno-de-Mesquita HB, et al. Meat consumption and mortality–results from the European Prospective Investigation into Cancer and Nutrition. BMC Med. 2013;11:63.

Chowdhury R, Warnakula S, Kunutsor S, et al. Association of dietary, circulating, and supplement fatty acids with coronary risk: a systematic review and meta-analysis. Ann Intern Med. 2014;160:398–406.

de Oliveira Otto MC, Mozaffarian D, Kromhout D, et al. Dietary intake of saturated fat by food source and incident cardiovascular disease: the Multi-Ethnic Study of Atherosclerosis. Am J Clin Nutr. 2012;96:397–404.

Forouhi NG, Koulman A, Sharp SJ, et al. Differences in the prospective association between individual plasma phospholipid saturated fatty acids and incident type 2 diabetes: the EPIC-InterAct case-cohort study. Lancet Diabetes Endocrinol. 2014;2:810–818.

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