Updated: Aug 25
Stearic acid is known mostly to people as magnesium stearate, an additive used in medication capsules. Dietary stearic acid, a saturated fatty acid, is popping up in nutrition conversations because recent research reveals that it could play a role in reducing visceral fat and improving metabolic markers. Is this a promising development, or simply more diet fluff?
What is Stearic Acid?
Stearic acid is a solid saturated fatty acid obtained from animal or vegetable fats. As a waxy solid, it’s one of the most common fatty acids found in nature. Fats and oils that are rich in stearic acid are more abundant in animal fat than in vegetable fat, with the only exception being cocoa butter, which has a high stearic acid level.
Not the Same as Magnesium Stearate
Magnesium stearate is a magnesium salt, meaning it’s a compound containing two stearic acids and one magnesium. It’s been used, sometimes controversially overused, in dietary supplements and medications as a binder during the manufacturing process. Essentially it enables medicine tablets to be punched without sticking to the machinery. Similarly, with capsules, the magnesium stearate allows them to glide shut easily and eject from the machinery.
New Research with Stearic Acid
For years, stearic acid was recognized mostly for its role in magnesium stearate, and any benefits from it were mostly overlooked or ignored. But recent studies shine a new light on this fatty acid, and with it some intriguing nutritional implications.
In the early 2000s, researchers and food scientists began to look at stearic acid as a substitute for trans fatty acids. Trans fatty acids, such as those found in hydrogenated oils, had recently become the nutrition world’s bad child because of its role in cardiovascular disease, diabetes, and systemic inflammation.
Researchers suggested that stearic acid could be a healthy alternative given studies that revealed a “low impact” on human health. In other words, stearic acid wasn’t necessarily thought of as “healthy”, but rather just a good neutral substitute for the food industry’s needs.
The Mice Study
In 2014, PLoS One published a mice study where results demonstrated promise for stearic acid as a beneficial fatty acid. Researchers used four groups of mice where each group was placed on a different diet: a low fat diet (5% corn oil) , a 20% safflower oil diet, a mixed diet of 17% corn oil/3% safflower oil, and finally another mixed diet of 17% stearic acid/3% safflower oil.
The researchers evaluated the mice at the conclusion of the 18-week study. Despite differences in food intake, there were no significant increases in weight gain across the four groups of mice. The group consuming the stearic acid, however, had a 25% reduction in total body fat. Specifically, abdominal fat was found to have decreased by 67% in the stearic acid group compared to the low fat group.
Abdominal fat is classified as visceral fat, and high levels of visceral fat are associated with inflammation and metabolic dysfunction. The conclusion that a high stearic acid diet could have positive metabolic effects was encouraging, particularly given the recent increases in metabolic diseases such as diabetes and heart disease.
The Banana Milk Shake Study with Humans
In 2018, Nature Communications published another study that revealed how dietary stearic acid was shown to regulate mitochondria in humans. The study sought to demonstrate different biological consequences of fatty acids. Ten healthy volunteers and 11 type-2 diabetic volunteers participated in the study.
In the study scientists first asked subjects to eat a low-fat vegan diet (with no stearic acid) for two days to bring all participants to a low-stearic acid baseline regardless of their usual diet. Then subjects drank a banana milk shake containing 24 grams of stearic acid. Measurements were taken and at a later time the subjects drank a mock banana milk shake without the stearic acid. The scientists took measurements and analyzed the results again. The study was double-blinded, so neither the scientists nor the participants knew when they were drinking each kind of shake.
In both the healthy and diabetic participants, the stearic acid milk shake caused significant mitochondrial fusion (merging) of human neutrophils. Additionally, the researchers determined that the stearic acid-infused milk shakes caused a decrease in acylcarnitine levels, suggesting that stearic acid intake increases fatty-acid beta oxidation. This may sound like a lot of science-speak, but a loose translation is that stearic acid regulates mitochondria in humans, a very positive result.
The results of these two studies identified previously unknown information about stearic acid as a saturated fatty acid. Other saturated fatty acids, such as palmitic and myristic, were previously show to have adverse effects on metabolic measurements. To some extent stearic acid was considered guilty by association because of its saturated status. But stearic acid is a long-chain fatty acid with an 18-carbon backbone, and this is biochemically different than other saturated fatty acids. These studies showed that not all fatty acids have the same negative biological consequences.
Where to Find Stearic Acid
Food sources of stearic acid include meat/poultry/fish, grain products, and milk/milk products, but the largest concentrations are found in the fat of red meat and cocoa butter. Fats that are rich in stearic acid include cocoa butter, mutton tallow, beef tallow, lard, and butter. Cocoa butter contains the highest percentage, at approximately 33% of total fat. Mutton tallow is close behind at nearly 20%. In meat (beef, pork, lamb, veal), stearic acid ranges from approximately 9% to 16% of total fat. Chicken, specifically breast meat, contains considerably less stearic acid at approximately 8%.
Stearic Acid’s Role in Nutrition
This relatively new information on stearic acid adds new strength to arguments that challenge long-held beliefs around red meat consumption. For many years enlightened scientists, doctors, and nutritionists have educated people on studies that conclude not only that red meat is not metabolically harmful but that it can be part of a healthy diet. Other experts continue to disagree based on older studies. The focus of the debates is typically saturated fatty acids, and specifically their role in cholesterol levels and the perceived correlation to cardiovascular disease. Causal relationships between the two, however, have proven to be much more complicated, and there appears to be much more nuance in analyzing common heart-health markers.
Paul Saladino, M.D., the “Carnivore M.D.” and interventional cardiologist Nadir Ali, M.D. recently discussed the topic of cholesterol and its relationship to cardiovascular disease as well as other metabolic diseases on the popular podcast, Fundamental Health. Contrary to mainstream opinion, the doctors agreed that metabolic markers should be analyzed in the context of numerous metabolic variables of a patient. This includes LDL and HDL cholesterol data as well as many other metabolic measurements. Furthermore, both doctors agreed that saturated fats, including animal fats, are not causative for heart disease and are in fact, beneficial to metabolic health. In particular, Dr. Saladino believes stearic acid from animal fats is critical to encouraging adipocytes (fat cells) to burn fat rather than store it.
Nutrition research continues to reveal new information about the role of fatty acids, and it’s certainly not as simple as the nearly century-old hypothesis that all fats cause cardiovascular disease. Modern scientific studies show that there is much more subtlety in fatty acid metabolism across different categories.
Stearic acid is emerging as a promising fatty acid that could be beneficial in reducing visceral fat and improving metabolic markers. More research will hopefully confirm these developments.
Rather than interpret this data as a reason to isolate stearic acid intake in an effort to achieve weight or other metabolic targets, I believe it supports the effort of eating a diet consistent with what our ancestors ate. That is, a diverse diet that includes unprocessed plants and animal meat will provide the many nutrients that our bodies need to thrive.
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