Let’s start off with an overview of saturated fatty acids, and how they differ from poly or monounsaturated fatty acids.
Saturated fatty acids (SFA’s) have the following characteristics distinguishing them from other fatty acids (trans, monounsaturated & polyunsaturated):
- solid at room temperature
- referred to as ‘saturated’ due to their having no double bonds along the carbon chains that comprise these saturated fatty acids
Unsaturated oils, on the other hand, are liquid at room temperature, primarily found in higher concentrations in plant sources (with the exception of fatty fish) and have one (mono) or multiple (poly) double bonds along the carbon chain.
Contrary to popular belief, foods do not consist of one type of fatty acid. Rather, foods are composed of varying percentages of unsaturated and saturated fatty acids.
For example, SFA’s comprise roughly 13% of the fatty acids in olive oil, and 65% of the SFA’s in butter.
SFA’s are found in higher amounts in dairy products (ex: cream, butter, milk, cheese) as well as in meats (bacon, sausage, chicken fat, mutton), ghee, suet and lard.
Palm oil, palm kernal, coconut and cottonseed oils contain a larger percentage of SFA’s (relative to the other plant based fats), though they lack the cholesterol contained in animal sources.
Examples of SFA’s include:
- lauric (palm kernal oil, coconut oil, vegetable shortening and is also used in )
- palmitic (palm oil, tallow, processed foods to enhance texture)
- myristic (palm kernal oil, coconut oil, butter)
- stearic acids (cheese, sausage, bacon, ribs, beef/ground beef, candy, cocoa butter)
These fatty acids are also commonly used in conjunction with sodium hydroxide, creating a product commonly found in soaps, shampoos and cosmetics (ex: sodium laurate and sodium palmitate).
For several decades, foods high in SFA’s were demonized by public health and nutrition experts, citing numerous studies suggesting that SFA’s were disease promoting.
Saturated fats were linked to increased LDL (‘bad’ cholesterol), a primary risk factor for heart disease.
Current American Heart Association guidelines suggest limiting calories from saturated fat to less than 7% per day (or roughly less than 16g or 140 calories).
SFA’s were somewhat vindicated when evidence emerged several years ago suggesting that trans fatty acids (partially hydrogenated oil) were more offensive, as they not only raise LDL, but decrease HDL (or ‘good’ cholesterol).
Recently, however, results of a meta-analysis of 72 studies (including both observational studies and randomized controlled trials) on saturated fat intake and heart disease published in the Annals of Internal Medicine found no association with SFA intake and risk of heart disease – basically stating saturated fats were found to have no influence, positively or negatively, on heart disease.
The results were highly publicized, and largely misconstrued by media.
Results of the published study actually read as follows:
“Current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fats.”
Critics of the study, including nutrition experts from the Harvard School of Public Health (one of whom actually authored the study) called for a retraction or revision of the paper.
Critics have pointed to the limitations of meta-analyses as one potential problem, as numerous studies are combined and summarized, despite vast differences in methodologies (particularly across nutrition literature).
They also cite conflicting findings from numerous large scale population studies that link plant based/vegetarian diets (and lower intake of animal products) with health and longevity (Framingham, Adventist Health Study, China Study).
Another author (there were fourteen) has stood by the study’s findings, but insists that the conclusion of the meta analysis only suggested that we need further research to better understand the relationship between SFA’s and heart disease.
She has also supported continued adherence to American Heart Association’s parameters for SFA intake, stating that relaxing the guidelines would be premature at this point.
There are a number of studies in progress looking at the influence of particular saturated fatty acids on health outcomes, inspired by recent findings that suggest that all fatty acids are created equally.
The results of Annals of Internal Medicine study are intriguing indeed, and warrant further attention.
But until we have more evidence, the large majority of experts recommend continuing to keep SFA intake to a minimum and acquiring dietary fat from plant based sources (examples include olive oil, avocado, nuts and seeds). We must also consider the steep environmental cost of meat consumption (10-15 pounds of grain is required to produce 1 pound of meat).
Bottom line: It’s a bit too soon to begin piling sausage and cheese on your plate, but the results do suggest that more work needs to be done before we fully understand the relationship between SFA’s and heart disease.
And please be cautious when relying on media to interpret results of complex studies.
What can we conclude from the referenced study and other similar studies on SFA’s and health?
- It seems that not all SFA’s are ‘equal’, and the way that they influence disease risk is not well understood and deserves further attention, so avoid dogmatic teachings around good food/bad food.
- While we seek to better understand the SFA/health relationship and await further study results, please still proceed with caution when adding SFA’s to your intake.
- Foods that are high in SFA’s (meats, dairy) are also often high in preservatives (and other artificial fillers) and sodium. Quality of meat/dairy DOES have a meaningful effect on the nutrient density, so going organic/grass fed IS worthwhile if you’re able.
- Good nutrition is a complex picture with many shifting parts, and research is moving away from studying the influence of single nutrients on health outcomes, so be wary of these kinds of studies.
- Lean on a plant based diet for necessary fats and proteins such as beans, lentils, nuts, seeds and whole grains (budget friendly AND protective), and supplementing with high quality (organic/grass fed) meat and dairy products when you do want to include animal fats.
Questions, thoughts and reflections? Please post them below. I look forward to continuing this important discussion with you.
In good health –
Rajiv Chowdhury, Samantha Warnakula, Setor Kunutsor, Francesca Crowe, Heather A. Ward, Laura Johnson, Oscar H. Franco, Adam S. Butterworth, Nita G. Forouhi, Simon G. Thompson, Kay-Tee Khaw, Dariush Mozaffarian, John Danesh, Emanuele Di Angelantonio; Association of Dietary, Circulating, and Supplement Fatty Acids With Coronary Risk: A Systematic Review and Meta-analysis. Annals of Internal Medicine. 2014 Mar; 160(6):398-406.
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