By Dr. Atli Arnarson
The health effects of saturated fats are a controversial topic. In the past, saturated fat was widely believed to be a major cause of heart disease. Today, scientists are not so sure.
However, one thing is clear: saturated fat is not a single nutrient. It is a group of different fatty acids with varying effects on health and metabolism.
This article takes a detailed look at the most common saturated fatty acids, their health effects and dietary sources.
What Is Saturated Fat?
Saturated fat is one of the two main classes of fat, the other being unsaturated fat.
These groups differ slightly in their chemical structure and properties. For instance, saturated fat is generally solid at room temperature, while unsaturated fat is liquid.
The main dietary sources of saturated fat are fatty meat, lard, tallow, cheese, butter, cream, coconut oil, palm oil and cocoa butter.
All fats are composed of molecules called fatty acids, which are chains of carbon atoms. The different types of saturated fatty acids can be distinguished by the length of their carbon chains.
Here are the most common saturated fatty acids in the human diet:
- Stearic acid: 18 carbon atoms long
- Palmitic acid: 16 carbon atoms long
- Myristic acid: 14 carbon atoms long
- Lauric acid: 12 carbon atoms long
- Capric acid: 10 carbon atoms long
- Caprylic acid: 8 carbon atoms long
- Caproic acid: 6 carbon atoms long
It's rare to find saturated fatty acids other than these in the diet.
Saturated fatty acids that are less than six carbon atoms long are collectively known as short-chain fatty acids.
These are produced when gut bacteria ferment fiber. They are created in your gut from the fiber you eat and can also be found in trace amounts in some fermented food products.
Bottom Line: Saturated fatty acids are one of the two major categories of fat. Common dietary saturated fatty acids include stearic acid, palmitic acid, myristic acid and lauric acid.
How Does Saturated Fat Affect Health?
Most scientists now accept that saturated fats are not as unhealthy as previously assumed.
This doesn't necessarily mean that saturated fats are unhealthy. It simply suggests that certain unsaturated fats are protective, while saturated fats are neutral.
In comparison, replacing saturated fat with carbs doesn't provide any health benefits and even impairs the blood lipid profile. This is a measurement of the levels of lipids in your blood, such as cholesterol and triglycerides (5).
Although it is clear that some saturated fats may raise the "bad" low-density lipoprotein (LDL) cholesterol, the association between cholesterol levels and heart disease is a bit more complex than that.
For more information on the issue, read this article.
Bottom Line: Saturated fats are not as harmful as previously believed. Growing evidence suggests there are no strong links between saturated fat and heart disease.
1. Stearic Acid
Stearic acid, which consists of 18 carbon atoms, is the second most common saturated fat in the American diet (8).
Compared with carbs or other saturated fats, stearic acid lowers the "bad" LDL cholesterol slightly or has neutral effects. This suggests it may be healthier than many other saturated fats (9, 10, 11).
Research shows that stearic acid is partly converted to oleic acid, a healthy unsaturated fat, within the body. However, according to some estimates, the conversion rate is only 14 percent and may not have much relevance to health (12, 13).
The main dietary source of stearic acid is animal fat. The levels of stearic acid are usually low in plant fat, with the exception of coconut oil, cocoa butter and palm kernel oil.
Stearic acid is considered a healthy saturated fat.
It does not appear to raise the risk of heart disease. This seemed to be true even in a study of people whose stearic acid intake constituted up to 11 percent of their total calorie intake for 40 days (9).
Bottom Line: Stearic acid is the second most common saturated fat in the American diet. It appears to have neutral effects on the blood lipid profile.
2. Palmitic Acid
Palmitic acid is the most common saturated fat in plants and animals. It is 16 carbon atoms long.
In 1999, palmitic acid made up an estimated 56.3 percent of the total saturated fat intake in the U.S. (8).
The richest dietary source is palm oil, but palmitic acid also makes up approximately a quarter of the fat in red meat and dairy, as shown in the chart below.
Compared to carbs and unsaturated fats, palmitic acid raises the levels of total cholesterol and LDL cholesterol without affecting the levels of "good" high-density lipoprotein (HDL) cholesterol (9, 11, 14).
High levels of LDL cholesterol are a well-known risk marker of heart disease.
Although palmitic acid raises the levels of total LDL cholesterol, this is mainly due to an increase in large LDL particles. Many researchers consider high levels of large LDL particles to be less of a concern, but some people disagree (6, 16, 18).
Additionally, when other fatty acids, such as linoleic acid, are eaten at the same time, they can offset some of palmitic acid's effects on cholesterol (19).
These aspects of palmitic acid need to be studied further before clear conclusions can be reached.
Bottom Line: Palmitic acid is the most common saturated fatty acid, making up over half of all the saturated fat eaten in the US. It raises LDL cholesterol levels without changing HDL cholesterol.
3. Myristic Acid
Myristic acid consists of 14 carbon atoms.
Consuming myristic acid causes a significant increase in total cholesterol and LDL cholesterol compared to consuming palmitic acid or carbs. However, it doesn't appear to affect levels of HDL cholesterol (11, 25).
These effects are much stronger than those of palmitic acid. Yet similar to palmitic acid, myristic acid appears to increase the levels of large LDL particles, which many scientists consider to be less of a concern (6).
Myristic acid is a relatively rare fatty acid, not found in high amounts in most foods. Yet certain oils and fats do contain decent amounts, as shown in the chart below.
Although coconut oil and palm kernel oil do contain relatively high amounts of myristic acid, they also contain other types of fats, which may offset the effects of myristic acid on the blood lipid profile (26).
Bottom Line: Myristic acid is a long-chain, saturated fatty acid. It raises LDL cholesterol more than other fatty acids.
4. Lauric Acid
Lauric acid is 12 carbon atoms long, making it the longest of the medium-chain fatty acids.
It raises the levels of total cholesterol more than most other fatty acids. However, this increase is largely due to an increase in the "good" HDL cholesterol.
In other words, lauric acid reduces the amounts of total cholesterol relative to HDL cholesterol. These changes are associated with a reduced risk of heart disease (27).
In fact, lauric acid appears to have more beneficial effects on HDL cholesterol levels than any other saturated fatty acid (11).
Lauric acid makes up approximately 47 percent of palm kernel oil and 42 percent of coconut oil. In comparison, other commonly eaten oils or fats contain only trace amounts of it.
Bottom Line: Lauric acid is the longest medium-chain fatty acid. Although it raises total cholesterol significantly, this is largely due to an increase in HDL cholesterol, which is beneficial for health.
5–7. Caproic, Caprylic and Capric Acid
Caproic, caprylic and capric acid are medium-chain fatty acids (MCFAs). They range from 6–10 carbon atoms in length.
Their names are derived from the Latin "capra," which means "female goat." They are sometimes referred to as capra fatty acids, due to their abundance in goat's milk.
MCFAs are metabolized differently than long-chain fatty acids. They are more easily absorbed and transported straight to the liver where they are rapidly metabolized.
Evidence suggests that MCFAs may have the following benefits:
- Weight loss: Several studies indicate that they may slightly increase the number of calories burned and promote weight loss, especially when compared with long-chain fatty acids (28, 29, 30, 31, 32).
- Increased insulin sensitivity: There is also some evidence that MCFAs increase insulin sensitivity, compared to long-chain fatty acids (33).
- Anti-seizure effects: MCFAs, especially capric acid, may have anti-seizure effects, especially when combined with a ketogenic diet (34, 35, 36).
Because of their potential health benefits, MCFAs are sold as supplements, known as MCT oils. These oils usually consist primarily of capric acid and caprylic acid.
Capric acid is the most common of these. It constitutes around 5 percent of palm kernel oil and 4 percent of coconut oil. Smaller amounts are found in animal fat. Otherwise, it is rare in foods.
Bottom Line: Capric, caprylic and caproic acid are medium-chain fatty acids with unique properties. They may promote weight loss, increase insulin sensitivity and reduce the risk of seizures in certain epileptic patients.
8–10. Short-Chain Fatty Acids
Saturated fatty acids that contain fewer than six carbon atoms in their chains are known as short-chain fatty acids (SCFAs).
The most important SCFAs are:
- Butyric acid: 4 carbon atoms long
- Propionic acid: 3 carbon atoms long
- Acetic acid: 2 carbon atoms long
SCFAs are formed when beneficial gut bacteria ferment fiber in the colon.
Their dietary intake is minimal compared to the amounts of SCFAs produced in the colon. They are uncommon in food and only found in small amounts in dairy fat and certain fermented food products.
SCFAs are responsible for many of the health benefits associated with fiber intake. For instance, butyric acid is an important source of nutrition for the cells lining the colon (37).
For more information on the potential health benefits of SCFAs, read this article.
Bottom Line: The smallest saturated fatty acids are known as short-chain fatty acids (SCFAs), which are formed when friendly bacteria ferment fiber in the colon. They have many potential health benefits.
Take Home Message
Not all saturated fat is the same. Its health effects vary depending on the type.
Although certain types of long-chain saturated fat may raise your levels of "bad" LDL cholesterol, no strong evidence proves any of them cause heart disease.
Reposted with permission from our media associate Authority Nutrition.
EcoWatch Daily Newsletter
Independence Day weekend is a busy time for coastal communities as people flock to the beaches to soak up the sun during the summer holiday. This year is different. Some of the country's most popular beach destinations in Florida and California have decided to close their beaches to stop the surge in coronavirus cases.
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For some combat veterans, the Fourth of July is not a time to celebrate the independence of the country they love. Instead, the holiday is a terrifying ordeal. That's because the noise of fireworks – loud, sudden, and reminiscent of war – rocks their nervous system. Daily fireworks in many U.S. cities in recent weeks have no doubt been interfering with the sleep and peace of mind of thousands of veterans.
What Is PTSD?<p><a href="https://theconversation.com/veterans-refugees-and-victims-of-war-crimes-are-all-vulnerable-to-ptsd-130144" target="_blank">PTSD</a> can occur when someone is exposed to extreme exposure traumatic experience. Typically, the trauma involves a threat of death, serious injury, or sexual violence. Along with war veterans, it happens to refugees; to victims of gun violence, rape and other physical assaults; and to survivors of car accidents and natural disasters like earthquakes or tornadoes.</p><p>PTSD can also happen by witnessing trauma or its aftermath, often the case with <a href="https://www.psychiatry.org/patients-families/ptsd/what-is-ptsd" target="_blank">first responders</a> and <a href="https://www.psychologytoday.com/us/blog/the-many-faces-anxiety-and-trauma/202006/invisible-wounds-the-frontline-heroes" target="_blank">front-line workers</a>.</p><p>All this adds up to tens of millions of Americans. Up to 30% of combat veterans and first responders, and 8% of civilians, <a href="https://www.ptsd.va.gov/professional/treat/essentials/epidemiology.asp" target="_blank">fulfill the diagnostic criteria for PTSD</a>. And that criteria is not easily met: symptoms of PTSD include nightmares, flashbacks, intrusive trauma memories, difficulty sleeping, avoidance of reminders of trauma, negative emotions, and what we call "hyperarousal symptoms."</p>
Fireworks Can Trigger Flashbacks<p>Hyperarousal, a core component of PTSD, occurs when a person is hyper-alert to any sign of threat – constantly on edge, easily startled and continuously screening the environment.</p><p>Imagine, for instance, stepping down the stairs in the dark after hearing a noise; you're worried an intruder might be downstairs. Then a totally unpredictable loud sound explodes right outside your window.</p><p>For people with PTSD, that sound – reminiscent of gunfire, a thunderstorm or a car crash – <a href="https://theconversation.com/veterans-refugees-and-victims-of-war-crimes-are-all-vulnerable-to-ptsd-130144" target="_blank">can cause</a> a panic attack or trigger flashbacks, a sensory experience that makes it seem as if the old trauma is happening here and now. Flashbacks can be so severe that combat veterans may suddenly drop to the ground, the same way they would when an explosion took place in combat. Later, the experience can trigger nightmares, insomnia or worsening of other PTSD symptoms.</p><p>Those of us who set off fireworks need to ask ourselves: Are those few minutes of fun worth the hours, days, or weeks of torment that will begin for some of our friends and neighbors – including many who put their lives on the line to protect us?</p>
Who Else Is Affected?<p>Millions of others, though not diagnosed with PTSD, may similarly be affected by fireworks. <a href="https://adaa.org/about-adaa/press-room/facts-statistics" target="_blank">One in five Americans</a> have an anxiety disorder, many with symptoms of hyperarousal. Also impacted are those with autism or developmental disabilities; they find it difficult to cope with the noise, or just the drastic change from life routines. Then there are people who have to work, holiday or not: nurses, physicians and first responders, who have to be up at 4 a.m. for a 30-hour shift.</p><h3>How to Reduce the Negative Impact</h3><p>There are ways to reduce how fireworks affect others:</p><ul><li>For those with PTSD, the unexpected nature of fireworks is probably the worst part. So at least make it as predictable as possible. Do it in designated areas during designated times. Don't explode one, for instance, two hours after the designated time window. And avoid setting them off <a href="https://www.theguardian.com/society/2018/jul/04/fireworks-ptsd-fourth-of-july-veterans-shooting-survivors" target="_blank">on the 3rd</a>. People are less prepared then.</li><li>If you're aware that a veteran or trauma survivor lives in the neighborhood, move the noise as far as possible from their home and give them prior warning. Consider putting a sign in your front yard noting the time you'll set the fireworks.</li><li>Remember, it doesn't have to be super loud to make it fun. Consider using <a href="https://thehill.com/opinion/energy-environment/504964-its-time-for-silent-fireworks" target="_blank">silent fireworks</a>. And you don't have to be the one who lights the fireworks. Simply enjoy watching while your city or township does it safely.</li></ul>
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By Jeff Berardelli
For the past year, some of the most up-to-date computer models from the world's top climate modeling groups have been "running hot" – projecting that global warming may be even more extreme than earlier thought. Data from some of the model runs has been confounding scientists because it challenges decades of consistent projections.
International Effort to Evaluate Climate Models<p>For the past 25 years the international community has been evaluating and comparing the world's most sophisticated climate models produced by various teams at universities, research centers, and government agencies. The effort is organized by the World Climate Research Programme under the United Nations World Meteorological Organization.</p><p>Climate models are complicated computer programs composed of millions of lines of code that calculate the physical properties and interactions between the main climate forces like the atmosphere, oceans, and solar input. But models also go a lot further, incorporating other systems like ice sheets, forests, and the biosphere, to name a few. The models are then used to simulate the real-world climate system and project how certain changes, like added pollution or land-use changes, will alter the climate.</p><p>Every few years there is a new comprehensive international evaluation called the Coupled Model Intercomparison Project (CMIP). In the sixth such effort, known as CMIP6 and now under way, experts are reviewing about 100 models.</p><p>Information gleaned from this effort will act as a scientific foundation for the U.N.'s Intergovernmental Panel on Climate Change (IPCC) next major assessment report, scheduled for release in 2021. The goal of the report – the sixth in 30 years – is to inform the international community about how much the climate has changed, and, importantly, how much change can be expected in coming decades.</p>
A Conundrum Emerges<p>Over the past year, the CMIP6 collection of models being reviewed threw researchers an unexpected curveball: a significant number of the climate model runs showed substantially more global warming than previous model versions had projected. If accurate, the international climate goals would be nearly impossible to achieve, and there would be significantly more extreme impacts worldwide.</p><p>A foundational experiment in every report addresses "sensitivity": If you double levels of carbon dioxide (CO2) that were in the air before the Industrial Revolution, how much warming do the models show? This doubling is not expected for a few more decades, but it is a quick way to communicate the critical role of greenhouse gases in changing the climate.</p><p>The amount of CO2 in the atmosphere has increased by 35% since the 1800s because of the burning of fossil fuels. As a result, global temperatures have already increased by more than 2 degrees Fahrenheit.</p><p>In the first IPCC assessment report, published in 1990, the answer to that question about the impact of doubling carbon dioxide gave a fairly wide range of results – between 2.7-8 degrees F of global warming. Since then, four more assessments issued six to seven years apart reached nearly the exact same conclusion on sensitivity.</p><p>But that sensitivity may, for the first time, change significantly in next year's assessment. Why? Because starting last year, numerous models in the CMIP6 collection displayed even bigger spikes in temperature upon doubling of CO2 concentrations. We're in serious trouble if the climate sensitivity falls in the mid or upper range of the previous assessments. But if the new, higher estimates are correct, the impacts on civilization would be catastrophic.</p>
In the above CarbonBrief interactive visualization, the bars offer a comparison in the range of sensitivity in the CMIP5 models (gray) and CMIP6 models (blue).
New and Encouraging Evidence Is Emerging<p>At first, scientists were uncertain whether the new model runs were on to something, so the international modeling community dug in to produce multiple studies. The results are not yet conclusive, but a gradual collective sigh of relief seems to be materializing.</p><p>"Evidence is emerging from multiple directions that the models which show the greatest warming in the CMIP6 ensemble are likely too warm," explains Dr. Gavin Schmidt, director of NASA's Goddard Institute for Space Studies.</p><p>For example, <a href="https://www.earth-syst-dynam-discuss.net/esd-2020-23/" target="_blank">a study</a> released April 28 evaluated the past performance of the models making up the CMIP6 ensemble. The team assigned weights to each model based upon historical performance of their warming projections, weighing the poorer performing models less. By doing so, both the mean warming and the range of warming scenarios in the CMIP6 ensemble decreased, meaning the warmest models were the ones with weaker historical performance. This result supports a finding that a subset of the models are too warm.</p><p>That conclusion is supported by another new study evaluating one particular model – the Community Earth System Model (CESM2) – that showed greater warming. Using that model, the researchers simulated the climate in the early Eocene era, about 50 million years ago, when rainforests thrived in the Arctic and Antarctic. The CESM2 simulated a historical climate that seems way too warm compared with what is known about that era from geological data, indicating that the model is likely also too warm in its future projections.</p><p>Two other recent studies of the CMIP6 models being evaluated use clever analysis methods to <a href="https://www.google.com/url?q=https://www.earth-syst-dynam-discuss.net/esd-2019-86/&sa=D&ust=1589209938203000&usg=AFQjCNHYwFB-1KqndGfJ4sXdrrm9DpbLaQ" target="_blank">narrow the range</a> of future warming projections and also <a href="https://www.google.com/url?q=https://advances.sciencemag.org/content/6/12/eaaz9549&sa=D&ust=1589209938203000&usg=AFQjCNEhKY1YZ19qgjSZ_hJM14JmzqXOXw" target="_blank">reduce the projected warming</a> of the CMIP6 models by 10 to 15%.</p><p>Through the intensive research spurred by the CMIP6 climate-sensitivity curveball, scientists have been able to turn a confounding challenge into a confidence builder, providing even greater certainty than they had before in both the abilities of the climate science community and in the computer models used. Moreover, the experience has helped unearth uncertainties remaining in the modeling process.</p><p>Experts conclude much of this uncertainty probably lies in the complexity of clouds. "We have been looking as a community at why the models with greater warming are doing what they are doing – and it's tied to cloud feedbacks in the southern mid-latitudes mostly," explains Schmidt.</p><p>In fact, <a href="https://advances.sciencemag.org/content/6/26/eaba1981" target="_blank">a new study</a> addressing the increased sensitivity was published in Science Advances stating, "Cloud feedbacks and cloud-aerosol interactions are the most likely contributors to the high values and increased range of ECS [sensitivity] in CMIP6."</p>
Understanding the Complexity of Clouds<p>It's long been known in climate modeling circles that cloud processes and interactions are a potential weak link for climate modeling. That reality has been brought front and center by the urgent challenges posed during this CMIP6 evaluation period, but the current evaluation of models also provides an opportunity for discovery and improvement.</p><p>Cloud complexity comes from the reality that clouds have a multitude of sizes, altitudes, and textures. Some clouds cool Earth by providing shade, reflecting sunlight back into space. Others act like a blanket, trapping heat and warming the world.</p><p>Given that about <a href="https://www.nasa.gov/vision/earth/lookingatearth/icesat_light.html" target="_blank">70% of the globe</a> is covered by clouds at any given time, it's no surprise that they play an integral role in regulating the climate. The challenge is to figure out which types of clouds will increase, which will decrease, and what the net effect will be on cooling or warming as the climate changes.</p><p><a href="https://www.nature.com/articles/s41561-019-0310-1" target="_blank">One study</a> last year reached an alarming conclusion: Left unchecked, the release of CO2 into the atmosphere may lead to a tipping point where shallow low clouds disappear – leading to runaway, catastrophic warming of nearly 15 degrees F. While scientists see that outcome as only a remote possibility, it drives home the urgent need to better understand clouds.</p><p>"We have a saying at NOAA: It isn't rocket science – it's much, much harder than that," quips Dr. Chris Fairall, ATOMIC's lead investigator. "One of the major problems for modeling is there is not clean separation of scales." The photo below is one that Fairall took from the NOAA P-3 aircraft.</p>
Investigating the Secrets of Clouds<p>To address the urgent question about the dynamics and role of clouds in a warming world, NOAA and European partners launched their ongoing research effort unprecedented in scale. The U.S. contribution, ATOMIC – short for Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign – is an international science mission that was featured recently on "<a href="https://www.cbsnews.com/video/study-aims-to-examine-links-between-climate-change-and-clouds/" target="_blank">CBS This Morning: Saturday</a>."</p>
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