For some sixty years, cardiologists have told Americans to limit saturated fat for the sake of their hearts. But in those decades, multiple studies haven’t supported the advice, a team of 12 cardiologists and researchers reports (Astrup et al., 2020).
People don’t need to be told to eat less fat, but rather to eat fewer carbs, they say in a new overview in the Journal of the American College of Cardiology. The advice to avoid saturated fat, they note, can lead consumers to exclude options like “whole-fat dairy, unprocessed meat, eggs and dark chocolate,” all rich in saturated fatty acids (SFAs), yet foods that are not linked to elevated heart disease risk (Astrup et al., 2020).
To be sure, this exoneration of saturated fat is not universal. Send this report to your personal physician and you may hear that the American Heart Association recommends consuming no more than six percent of your calories from saturated fat (heart.org, 2020), and replacing any saturated fat with polyunsaturated vegetable oil to meet that six percent goal (Sacks et al., 2017).
We trust that if you want to enjoy a rich cheese or organic red meat, you’ll respond that the science isn’t so settled. You might even want to direct them to read our explanation below.
What Is Saturated Fat Anyway?
Scientists focus on SFAs, defined as containing only carbon-to-carbon single atomic bonds. Some dairy fats contain a short chain of 4-6 atoms, while other SFAs vary between medium chains (8-12 carbons), long (14-20) and very long (22 or more). The longer the chain, the more heat it takes for the fat to melt. Longer chains are plentiful in red meat and coconut oil as well as butter. That’s why these fats tend to remain solid at room temperature.
Fats also fall into other categories based on whether its molecules have certain kinds of carbon-based branches (beef is an example) and whether they have an odd (often dairy) or even number of atoms. All of these details contribute to the effect of an SFA on your body. In short, saying an unequivocal “no” to SFAs was always too simple, the new team notes (Astrup et al., 2020).
But Where Did That Anti-Saturated Theory Come From?
Decades ago, scientists observed that people near the Mediterranean Sea were less likely to die from heart disease and stroke than were Americans and northern Europeans. The big difference: they ate less red meat and dairy. Finlanders, for example, ate a great deal of butter, a source of mostly long-chain SFAs, compared to Greeks, who use olive oil, which contains more medium-chain SFAs. (The Finns now no longer eat so much butter, though more than old-school U.S. cardiologists recommend.) The case for the “Mediterranean diet” was born.
Our readers know the many proven benefits of eating fish and seafood, the main protein of the Mediterranean diet. But the arguments against butter and red meat haven’t held up.
At first, the studies failed to support the advice that came from wealthier countries. More recently, they’ve come from research among poorer populations. In a study of 135,000 people mostly without cardiovascular disease from 18 countries, most of them low or middle-income, participants who ate about 14 percent of daily calories in saturated fats proved to have a lower risk of stroke (Deghan et al.,2017). In March, researchers reported the results of a 10-year study of nearly 200,000 participants: substituting polyunsaturated for saturated fat was linked with more cardiovascular risk, and there was no link between saturated fat and cardiovascular events (Ho et al., 2020).
LDL Cholesterol May Be Okay Too!
During the anti-saturated fat regime, we heard often about the dangers of cholesterol. Over time, if you read carefully, you learned that there was a “good” cholesterol, known as high-density lipoprotein or HDL, and a “bad” cholesterol, called low-density lipoprotein or LDL. If you eat protein foods rich in SFAs rather than carbohydrates, LDL levels rise. Doctors still monitor the level of LDL cholesterol as a marker of cardiovascular risk.
However, there are problems with this paradigm. To choose one example, post-menopausal estrogen plus progestin therapy and other drugs that substantially lower LDL do not protect the heart (Armitage et al., 2019). Other therapies that increase LDL and lower glucose do cut cardiovascular events (Scheen, 2018).
It became clear that the ratio of total cholesterol to HDL, not LDL alone, is a better marker for cardiovascular risk. But when people eat less SFAs they also cut their HDL cholesterol, so the diet doesn’t change the key ratio.
Indeed, cardiologists may have been relying on the wrong measure for decades. It may be that cardiovascular risk is linked to small, dense LDL particles rather than larger ones, and it turns out that SFAs are more likely to raise the volume of larger ones.
To make things even more complex, it’s true that people with higher-than-normal blood levels of even-chain SFAs have a greater risk of metabolic syndrome, diabetes, heart failure, and death. But those blood levels track carbs rather than SFAs in the diet. You can double or triple your SFAs consumption and lower your carb intake and end up with the same or lower levels of the dangerous blood ratios (Volk et al., 2014).
Eat What Works For You
This brings us to the caveat to any all-purpose advice. Genes matter and we all have different ones. Some people are more sensitive to SFAs. Other people, particularly those with type 2 diabetes or pre-diabetes, may especially need to restrict carbs and get more calories from fat.
Ultimately, it’s important to remember that there is no longer a universal consensus that eating saturated fat raises cardiovascular disease risk, and a growing collection of evidence that a diet rich in SFAs is neutral or even beneficial for many of us.
Armitage J, Holmes MV, Preiss D. Cholesteryl Ester Transfer Protein Inhibition for Preventing Cardiovascular Events. JACC. https://www.onlinejacc.org/content/73/4/477. Published February 5, 2019.
Astrup A, Magkos F, Bier DM, et al. Saturated Fats and Health: A Reassessment and Proposal for Food-based Recommendations: JACC State-of -the-Art Review. JACC. https://www.onlinejacc.org/content/early/2020/06/16/j.jacc.2020.05.077. Published June 17, 2020.
Dehghan M, Mente A, Zhang X, et al. Associations of fats and carbohydrate intake with cardiovascular disease and mortality in 18 countries from five continents (PURE): a prospective cohort study. Lancet (London, England). https://www.ncbi.nlm.nih.gov/pubmed/28864332. Published November 4, 2017.
Ho FK, Gray SR, Welsh P, et al. Associations of fat and carbohydrate intake with cardiovascular disease and mortality: prospective cohort study of UK Biobank participants. The BMJ. https://www.bmj.com/content/368/bmj.m688. Published March 18, 2020.
Sacks FM, Lichtenstein AH, Wu JHY, et al. Dietary Fats and Cardiovascular Disease: A Presidential Advisory From the American Heart Association. Circulation. 2017;136(3):e1-e23. https://www.ahajournals.org/doi/full/10.1161/CIR.0000000000000510?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed Published June 15, 2017
Saturated Fat. www.heart.org. https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/fats/saturated-fats. Accessed July 7, 2020.
Scheen AJ. Cardiovascular Effects of New Oral Glucose-Lowering Agents. Circulation Research. https://www.ahajournals.org/doi/10.1161/CIRCRESAHA.117.311588. Published June 18, 2018.
Volk BM, Kunces LJ, Freidenreich DJ, et al. Effects of Step-Wise Increases in Dietary Carbohydrate on Circulating Saturated Fatty Acids and Palmitoleic Acid in Adults with Metabolic Syndrome. PLOS ONE. https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0113605. Published November 21, 2014.