Estimated reading time: 7 minutes
We’re all aware of the aggressive campaign driven by public health authorities and medical professionals to decrease blood cholesterol.
It all started more than fifty years ago when the Framingham Heart Study reported that high blood cholesterol was a major risk factor for coronary heart disease (1).
Central to the dogma was the belief that lowering blood cholesterol would lower the risk of heart disease.
So, it was a foregone conclusion that dietary saturated fats and dietary cholesterol would cause heart disease because they supposedly raised blood cholesterol.
However, recently evidence questioning a lack of a causal relationship between the intake of saturated fats and heart disease has accumulated (3). Even so, restriction of dietary saturated fats is still included in most current dietary guidelines and recommendations on cardiovascular prevention (4,5).
Although some recent studies have suggested that replacing saturated fatty acids with monounsaturated or polyunsaturated fatty acids may be beneficial, replacing saturated fats with carbohydrates may increase risk (6).
Before I go further, keep in mind that the lack of evidence for a causal relationship between the intake of saturated fats and heart disease doesn’t necessarily defy or contradict the lipid hypothesis.
Although high intake of saturated fats may raise total cholesterol and LDL cholesterol, it also tends to elevate HDL cholesterol (the “good” cholesterol).
In addition, high intake of saturated fats is associated with a higher concentration of large cholesterol-enriched LDL particles and lower concentration of small, dense LDL particles (7). The presence of small, dense LDL particles is associated with an increased risk of subsequently developing heart disease (8), and appears a strong predictor of blockage in the coronary arteries (9).
So, a lack of relationship between high intake of saturated fats and the occurrence of heart disease may indeed fit quite well with the lipid hypothesis. However, it suggests that the simplified version of this hypothesis, the one that only targets LDL cholesterol may be misleading (10).
What About Saturated Fats if You Already Have Heart Disease?
The public recommendation to restrict the intake of saturated fats has been primarily targeted at healthy people in order to reduce the risk of heart disease. However, the same advice has been given extensively to patients diagnosed with cardiovascular disease, whether it be coronary heart disease or stroke.
Very few studies have investigated the impact of saturated fat intake in patients already diagnosed with heart disease. For this reason, I became quite interested to find a scientific paper on the issue published very recently in the Journal of Nutrition (11).
The study included 2,412 patients who underwent coronary angiography because of coronary artery disease or aortic valve stenosis between 1994 and 2004 at two university hospitals in Norway (Haukeland University Hospital, Bergen and Stavanger University Hospital, Stavanger).
Information on dietary intake was obtained at baseline by an FFQ (Food Frequency Questionnaire) developed at the Department of Nutrition, University of Oslo.
The patients were divided into quartiles based on the amount of saturated fat consumed (percentage of energy consumed). In group 1, the amount of saturated fat intake was between 3.9-9.8%, in group 2 it was between 9.8-11.5%, in group 3 between 11.5-13.2 and group 4 between 13.2-28.7.
There were some quite interesting findings at baseline. For example, patients with a higher intake of saturated fats were less likely to have a history of heart attack, prior coronary artery bypass surgery or to have triple heart disease (blockages of all three main coronary arteries) at baseline.
Increased intake of saturated fatty acids corresponded to an increased intake of both total energy and total fat. Participants with the highest saturated fatty acid intake also had higher consumption of mono-and polyunsaturated fat and dietary cholesterol.
High intake of saturated fats was associated with lower consumption of total carbohydrates, dietary fibre and alcohol. Patients with higher intake of saturated fats had higher intakes of meat, cheese, butter, milk, eggs, cakes, sugar and sweets.
Interestingly, despite higher calorie consumption among those with the highest saturated fatty acid intake, body mass index (BMI) was similar in all four groups.
Patients with higher intake of saturated fats were less likely to have high blood pressure but more likely to smoke. Their blood levels of total and LDL cholesterol tended to be higher but triglycerides lower compared to those with lower intake of saturated fats. There were no significant differences in the blood levels of HDL cholesterol between the groups.
The prevalence of diabetes was similar in all four groups.
During a median follow-up of 4.8 years, a total of 292 (12%) patients experienced a coronary event (heart attack, unstable angina or coronary death), and 137 patients died from any cause.
During follow-up, most of the patients were on conventional medication such as aspirin (90%), statins (89%) and beta-blockers (78%).
There were no significant associations between the intake of saturated fatty acids and coronary events or death from any cause. In other words, patients with high intake of saturated fats did not do worse than those with lower intake of saturated fatty acids. This was true also after multivariate adjustments for possible confounding factors.
Of course, this study has several strength and limitations. For example, it is important to understand that dietary intake was estimated at baseline only. No such information was collected during follow-up. For this reason, it is not possible to account for changes in dietary habits during the study period.
However, the authors point out that the majority of patients selected for participation in the study had known coronary heart disease at baseline. Thus, it may be assumed that most patients willing to change their dietary habits towards less SFA intake had already done so before inclusion in the study.
The Bottom Line
For decades, cardiologists have advised patients with heart disease to restrict the intake of saturated fats and dietary cholesterol. Many patients still believe this to be the cornerstone of their lifestyle modification.
The main reason for avoiding saturated fats is the assumption that they adversely affect the lipid profile of our patients.
Public authorities and medical societies usually recommend restricting the intake of saturated fats to less than 10 percent of total energy consumption. In the above study, only 27% of the patients met these dietary recommendations.
The American Heart Association goes even further by recommending a dietary pattern that achieves 5% to 6% of calories from saturated fat. That means, for example, if you need about 2,000 calories a day, no more than 120 of them should come from saturated fats. That’s about 13 grams of saturated fats a day (12). That equals two slices of cheddar cheese.
Recent studies suggest that the recommendation to avoid saturated fats may have been premature and not based on solid scientific evidence.
Now, a recently published Norwegian study shows that dietary intake of saturated fatty acids was not associated with risk of future events or death among patients with established coronary artery disease.
It is important to keep in mind that most of the patients were receiving secondary prevention drug therapy including aspirin, beta blockers and statins.
Anyhow, the results of the study certainly suggest that high intake of saturated fats is not a risk factor among patients with coronary heart disease receiving modern-day treatment.
These recent scientific data don’t imply hat we should urge our patients to consume high amounts of saturated fats. They only tell us that there is no association and accordingly, restriction won’t help.
So, it’s certainly a lifeline for those who believe red meat, whole-fat milk, cheese, cream, butter and eggs can be a part of a healthy diet.
On the other hand, we must realise that scientific studies often provide contradictory results. A US study published last year suggested that greater adherence to a low carbohydrate diet high in animal sources of fat and protein was associated with higher all-cause and cardiovascular mortality following acute heart attack (13).
It appears the jury is still out…