A user guide to saturated fat

For decades, consuming saturated fat has been considered an unhealthy practice that can lead to heart disease. This is based mostly on observational studies showing saturated fat can increase LDL cholesterol, and replacing it with PUFAs may decrease LDL cholesterol.1

But is this harmful reputation warranted? The data is not-so clear.

In a recent analysis, 19 leading researchers concluded that evidence does not support the general advice to reduce saturated fat intake, and that the topic is far more nuanced than commonly reported.2

Another recent analysis published in BMJ Evidence-Based Medicine concluded that: “The preponderance of evidence indicates that low-fat diets that reduce serum cholesterol do not reduce cardiovascular events or mortality. Specifically, diets that replace saturated fat with polyunsaturated fat do not convincingly reduce cardiovascular events or mortality. These conclusions stand in contrast to current opinion.”3

How do we make sense of the controversy? This guide explains what is known about saturated fat, discusses the scientific evidence about its role in health, and explores whether we should be concerned about how much of it we eat.

Disclaimer: The effects of saturated fats on human health is controversial, with inconclusive evidence for long-term health effects. While many guidelines recommend lowering intake of saturated fats, this is based mostly on lower quality epidemiology studies. Adequately controlled studies and randomized studies do not show any clear long-term health benefits of doing so.4
This guide is our attempt at summarizing what is known. It is written for adults who are concerned about saturated fat intake and health. Discuss any lifestyle changes with your doctor. Full disclaimer

For even more details and relevant research on connected topics, see our guides to healthy fats, vegetable oils and cholesterol. Also see our list of core scientific studies related to heart disease, cholesterol and saturated fats.


First, what is saturated fat?

A fat (or fatty acid) is classified as saturated or unsaturated based on its molecular structure. Every fatty acid contains a chain of carbon and hydrogen atoms.

fat

Saturated fats don’t have any double bonds between their chain of carbons, allowing more hydrogen atoms to be attached to the carbon atoms. This means they are “saturated” with hydrogens. This structure makes them solid at room temperature.

By contrast, an unsaturated fat contains at least one double bond between its carbon atoms — notice in the illustration fewer hydrogen atoms attached to the carbons with the double bond. This chain is now “unsaturated” with hydrogen atoms and remains liquid or semi-liquid at room temperature.

Learn more about different types of fats:


Which foods contain saturated fat?

Saturated fats are found in both plant and animal products. Many foods we eat contain a combination of saturated and unsaturated fats. For instance, although olive oil, nuts, and avocados are typically considered unsaturated fat sources, these foods provide some saturated fat as well.

Here are the amounts of saturated fat in some popular low-carb foods:

  • 1 tablespoon (14 grams) coconut oil: 13 grams
  • 3.5 ounces (100 grams) pork belly: 10-12 grams
  • 3.5 ounces (100 grams) ribeye steak: 8-12 grams
  • 1 ounce (30 grams) dark chocolate (70-85% cacao): 7-9 grams
  • 1 tablespoon (14 grams) butter: 7 grams
  • 1 ounce (30 grams) cheese: 5-7 grams
  • 1 tablespoon (14 grams) tallow: 6 grams
  • 1 tablespoon (14 grams) lard: 5 grams
  • 1 ounce (30 grams) macadamia nuts: 4 grams
  • 3.5 ounces (100 grams) chicken drumstick: 4 grams
  • 1 medium avocado: 4 grams
  • 1 tablespoon (14 grams) heavy cream: 4 grams
  • 1 tablespoon (14 grams) olive oil: 2 grams

Keep in mind that many other keto-friendly foods contain at least a small amount of saturated fat.


What do foods’ saturated fat levels mean for the typical low-carber?

It means that you might consume 30 or more grams of saturated fat most days, which is significantly above the levels currently advised by the US Dietary Guidelines for Americans (DGA, about 22 grams a day) and American Heart Association, (AHA, 13 grams).

Is that a problem? Probably not. Available evidence shows that consuming that amount of saturated fat is unlikely to be a concern for most people. Although much of the science for and against saturated fat consumption is weak overall, natural saturated fats seem to be neutral from a health perspective.

Read on to learn more about the 50-year history of recommendations against consuming saturated fat and the inconclusive evidence behind them. Note that the small grey note symbols can be clicked for links to the studies discussed.5

Videos about saturated fat

Why do health authorities advise us to restrict our saturated fat intake?

The belief that saturated fat is unhealthy has been widely held since the 1960s. For decades, we’ve repeatedly heard terms like “artery-clogging saturated fat” and, as of 2018, the message hasn’t really changed among mainstream health authorities.

When discussing new recommendations to restrict saturated fat to less than 10% of daily calories in early 2018, Director of the WHO’s Department of Nutrition and Health Development Francesco Branco stated:

 

“Dietary saturated fatty acids and trans-fatty acids are of particular concern because high levels of intake are correlated with increased risk of cardiovascular diseases.”

 

Recently, a Harvard professor characterized coconut oil as “pure poison” due to its high saturated fat content.

The fear of saturated fat can be traced back to the diet-heart hypothesis first proposed in the 1950s by American scientist Ancel Keys. He promoted the theory that dietary fat raises cholesterol levels, thereby increasing the risk of heart disease.


The weak evidence behind the diet-heart hypothesis

After traveling to Europe and conducting informal surveys in different populations there between 1951 and 1952, Keys published a paper suggesting that as a country’s intake of fat increased, its rates of coronary heart disease (CHD) and related deaths likewise increased.6

Importantly, this was based entirely on observational data, which is considered weak evidence unless correlations are strong and have been repeatedly duplicated in other studies. Even then, this type of research can only show that a behavior and an outcome are associated but not that the behavior causes the outcome.

That wasn’t the only problem with Keys’ research.

In a 1953 paper, he included a graph showing a strong association between fat intake and CHD mortality in middle-aged male residents of six countries.7However, in 1957, researchers Yerushalamy and Hilleboe published this same data, but included all 22 countries for which information was available, greatly reducing the apparent association between the amount of fat these populations consumed and their rates of CHD mortality.8

In the late 1980s, Keys and his research team published the results of their “Seven Countries Study,” which tracked diet, health and death data in a selection of male residents of the US, Japan, and Europe over 25 years. In this paper, Keys stated that although total fat and cholesterol intake weren’t associated with death from CHD, saturated fat intake was. He concluded that populations that ate little saturated fat had low rates of CHD mortality, whereas those with higher saturated fat intake (like the US) were at increased risk for CHD and CHD-related death.9 But these findings were limited in significant ways: they only applied to men, they didn’t adequately control for other health habits, and data from countries where people consumed high amounts of saturated fat but had low rates of CHD mortality — such as France and Switzerland — weren’t part of the Seven Countries Study.

Yet these results would end up influencing nutrition policy for decades to come.

In 1961, based on Keys’ ongoing research and other papers favorable to the diet-heart hypothesis, the American Heart Association endorsed low-fat diets for the prevention of heart disease for men with a strong family history of heart disease or who had already had one or more heart attacks or strokes. 10

About two decades later, both US and UK dietary guidelines recommended that everyone should reduce total and saturated fat intake, despite the absence of strong evidence that this would be beneficial. 11


Other problems with saturated fat research

Although Keys acknowledged that his findings were based on observational evidence, he strongly believed that they proved the diet-heart hypothesis to be true. However, a controlled clinical trial is the only way a cause-and-effect relationship can be shown. But when the National Institute of Health began conducting clinical trials on saturated fat, there were other issues — some of which weren’t revealed until several years later.

Controlled trials that failed to find any relationship between saturated fat and risk of heart-related or all-cause mortality often weren’t published within a reasonable time frame. In the Minnesota Coronary Experiment, conducted from 1968 to 1973, more than 9,500 people participated in a randomized study that looked at the effect of replacing saturated fat with linoleic acid (an omega-6 polyunsaturated fat found in vegetable and seed oils). This study has been described as the largest, most rigorous controlled study of its kind to date.12

No benefit was found in the linoleic acid group; however, these results weren’t published until 1989.13 In 2016, an analysis of additional, previously unpublished data from the Minnesota Coronary Experiment confirmed the lack of association between saturated fat and CHD, heart attacks, and risk of death. Moreover, although the linoleic acid group experienced a decrease in LDL cholesterol levels, these participants actually had a slightly higher risk of CHD mortality. The 2016 researchers hypothesized this was likely due to adverse metabolic changes resulting from intake of linoleic acid, which may be inflammatory when consumed in high amounts.14

Similarly, a 2013 analysis of data recovered from the Sydney Diet Heart Study, which was conducted between 1966 and 1973, found that replacing saturated fat with linoleic acid slightly increased the risk of death from CHD and other causes.15

Fact or Fake concept, Hand flip wood cube change the word, April fools day


Saturated fat and health risks: the evidence to date

A few years ago, we shared some interesting WHO statistics that revealed that people living in European countries with the highest consumption of saturated fat have the lowest risk of dying from heart disease. Of course, these are just observational associations, but they contradict the associations that Keys found.

What do systematic reviews of observational studies and controlled studies tell us about saturated fat intake and the risk of CHD, other diseases, and death from any cause?

  • A 2009 meta-analysis of 28 cohort studies and 16 randomized controlled trials (RCTs) concluded “The available evidence from cohort and randomised controlled trials is unsatisfactory and unreliable to make judgement about and substantiate the effects of dietary fat on risk of CHD.” 16
  • A 2010 meta-analysis of 21 cohort studies found no association between saturated fat intake on CHD outcomes.17
  • A 2014 systematic review and meta-analysis of observational studies and randomized, controlled trials found that the evidence does not clearly support dietary guidelines that limit intake of saturated fats and replace them with polyunsaturated fats.18
  • A 2015 meta-analysis of 17 observational studies found that saturated fats had no association with heart disease, all-cause mortality, or any other disease.19
  • A 2017 meta-analysis of 7 cohort studies found no significant association between saturated fat intake and CHD death.20

One systematic review of clinical trials — considered the strongest, most reliable evidence — found that replacing saturated fats with unsaturated fats may slightly reduce the risk of heart attack and other cardiovascular events. Another systematic review of clinical trials also found a small reduction of risk of cardiovascular events when polyunsaturated fat replaced saturated fat in the diet. This effect only applied to men, however, and had no impact on total mortality or death from heart disease. Other extensive and similarly high-quality reviews have failed to establish any benefit.21

It appears that high saturated fat intake may increase LDL cholesterol concentrations in some people, either modestly or significantly. Additionally, researchers report that myristic acid (a saturated fat found in many foods like coconut oil, palm kernel oil, butter, cream, cheese and meat) has a greater effect on both LDL and HDL cholesterol levels than most other saturated fats.22

However, intervention studies that have used low-carb, high fat diets (including saturated fat) have shown on average no significant change in LDL cholesterol. Instead, they have shown an overall reduction in heart disease risk.23

Recently, Mente and colleagues published a large observational study that examined dietary patterns and lipid data from over 100,000 people in 18 countries around the world. Called the PURE study, its data analysis found that higher saturated fat intake was associated with beneficial effects on a number of cardiovascular risk factors, including higher HDL levels, lower triglyceride levels, and – what seemed to be the strongest predictor of CHD risk — a decreased ratio of ApoB (found in LDL particles) to Apo A (found in HDL particles).24

What’s more, although eating a lot of saturated fat was linked to higher LDL cholesterol levels in this study, these elevated values didn’t reliably predict future heart attack events or deaths. Although, like all observational studies, this one cannot show cause-effect relationships, it does indicate that eating less saturated fat (and consequently having lower LDL cholesterol) was not linked to a decrease in the risk of cardiovascular events. Additional follow up seven years later in the PURE study revealed no association between saturated fat intake and heart disease but did show saturated fat was linked to decreased risk for all-cause mortality and stroke.25


Should saturated fat ever be restricted?

Despite evidence that saturated fat itself is not harmful for most people, in some instances limiting it might be beneficial. For instance, results from a recent study suggest that in patients with cardiovascular disease, eating a lot of saturated fat might lead to higher concentrations of small and medium LDL particles — changes that could promote disease progression.26 This study was only three weeks long, so it’s unknown if this potentially detrimental pattern persisted over time.

An earlier study found a beneficial increase in LDL particle size and other improvements in patients with cardiovascular disease who followed a high-saturated-fat, starch-free diet.27 In addition, low-carb diets that were naturally higher in saturated fats showed overall improvement in lipid parameters compared to low fat diets.28

Importantly, some experts in the field of lipidology and cardiology disagree about whether elevated LDL cholesterol and particle concentrations increase the risk of CHD when other biomarkers related to heart health, such as inflammation and metabolic health, are within normal limits. This comes, in part from studies showing LDL has less prediction for CAD with normal HDL and TG:HDL ratios.29 Although this is not well accepted as medical consensus, it is an emerging area of interest that will hopefully have stronger data one way or the other soon.


Should you be worried about saturated fat?

As discussed above, there is little high-quality evidence to indicate saturated fats are a concern for most people, especially those following a low-carb diet. Overall the evidence both for and against saturated fats is weak and inconsistent, and individual responses vary greatly.

What’s more, saturated fat research has typically been conducted in people following all types of diets, mostly high in carbohydrates. There is emerging evidence that consuming a lot of fat on a carbohydrate-restricted diet may be even less of a concern and could lead to overall reductions in cardiovascular risk.30

Many low-carb whole foods that provide valuable nutrients and satiety — such as meat and full-fat dairy products — are also rich in saturated fat. For people with metabolic conditions that can be improved with a low-carb diet, the benefits of these foods may be more important than a risk that may or may not exist.

On the other hand, the relationship between saturated fat intake and elevated LDL cholesterol and particle levels seems to vary from person to person, especially for those on a low-carb diet. If your own LDL values increase significantly after adopting a keto or low-carb diet, you may be able to help lower them by cutting back a bit on saturated fat and eating more nuts, olive oil, avocados and fatty fish31.

Importantly, saturated fat is part of our evolutionary history. Foods that contain saturated fat are central to the traditional cuisines of many cultures. Foods that are manufactured to replace naturally occurring saturated fats with vegetable oils, sugars, and artificial flavors and fillers aren’t necessarily a healthier choice.

Aiming for a saturated intake below 10% of calories, as most health authorities recommend, can be a difficult task that may require detailed tracking of macronutrients, doesn’t necessarily encourage eating naturally, and can diminish pleasure at mealtimes. Limiting fat may also decrease meal satiety and increase hunger and cravings between meals.

Additionally, coconut oil, butter, lard and other saturated fat sources are more stable for cooking at high temperatures than unsaturated fats like vegetable oils.32

Conclusion

An across-the-board recommendation to limit your consumption of saturated fat to a small percentage of daily calories isn’t based on sound scientific evidence. In general, saturated fats appear neutral from a health perspective.

/ Franziska Spritzler, RD


  1. World Health Organization 2016: Effects of saturated fatty acids on serum lipids and lipoproteins:a systematic review and regression analysis [overview article; ungraded]

  2. British Medical Journal 2019: WHO draft guidelines on dietary saturated and trans fatty acids: time for a new approach? [overview article; ungraded evidence]

  3. BMJ Evidence-Based Medicine 2019: Fat or fiction: the diet-heart hypothesis [overview article; ungraded]

  4. Nutrition Journal 2016: The effect of replacing saturated fat with mostly n-6 polyunsaturated fat on coronary heart disease: a meta-analysis of randomised controlled trials [strong evidence]

    BMJ Evidence-Based Medicine 2019: Fat or fiction: the diet-heart hypothesis [overview article; ungraded evidence]

    British Medical Journal 2019: WHO draft guidelines on dietary saturated and trans fatty acids: time for a new approach? [overview article; ungraded evidence]

  5. This is an example note symbol.

  6. American Journal of Public Health and the Nation’s Health 1953: Prediction and possible prevention of coronary disease [observational research; very weak evidence]

  7. Journal of the Mount Sinai Hospital, New York 1953: Atherosclerosis: a problem in newer public health [observational research; very weak evidence]

  8. New York State Journal of Medicine 1957: Fat in the diet and mortality from heart disease: a methodological note [observational research; very weak evidence]

  9. The American Journal of Clinical Nutrition 1989: Food consumption patterns in the 1960s in seven countries [observational research; very weak evidence]

  10. Journal of the American Medical Association 1961: Dietary Fat and Its Relation to Heart Attacks and Strokes [consensus report article; ungraded]

  11. Open Heart 2015: Evidence from randomised controlled trials did not support the introduction of dietary fat guidelines in 1977 and 1983: a systematic review and meta-analysis [strong evidence]

  12. British Medical Journal 2016: Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment (1968-73) [systematic review of randomized trials; strong evidence]

  13. Arteriosclerosis: an official journal of the American Heart Association, Inc. 1989: Test of effect of lipid lowering by diet on cardiovascular risk [randomized controlled trial; moderate evidence]

  14. British Medical Journal 2016: Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment (1968-73) [systematic review of randomized trials; strong evidence]

  15. British Medical Journal 2013: Use of dietary linoleic acid for secondary prevention of coronary heart disease and death: evaluation of recovered data from the Sydney Diet Heart Study and updated meta-analysis [strong evidence]

  16. Annals Nutrition & Metabolism 2009: Dietary fat and coronary heart disease: Summary of evidence from prospective cohort and randomised controlled trials [moderate evidence]

  17. The American Journal of Clinical Nutrition 2010: Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease [observational studies; weak evidence]

  18. Annals of Internal Medicine 2014: Association of dietary, circulating, and supplement fatty acids with coronary risk: a systematic review and meta-analysis[weak evidence]

  19. British Medical Journal 2015: Intake of saturated and trans unsaturated fatty acids and risk of all cause mortality, cardiovascular disease, and type 2 diabetes: systematic review and meta-analysis of observational studies [observational studies; weak evidence]

  20. British journal of sports medicine 2017: Evidence from prospective cohort studies does not support current dietary fat guidelines: a systematic review and meta-analysis [observational studies; weak evidence]

  21. These two studies showed a slight benefit to replacing saturated fatty acids with PUFAs
    Public Library of Science medicine 2010: Effects on coronary heart disease of increasing polyunsaturated fat in place of saturated fat: A systematic review and meta-analysis of randomized controlled trials [strong evidence]

    The Cochrane database of systematic reviews 2012: Reduced or modified dietary fat for preventing cardiovascular disease [systematic review of randomized trials; strong evidence]

    However, the following studies found no such benefit.

    British Medical Journal 2013: Dietary fatty acids in the secondary prevention of coronary heart disease: a systematic review, meta-analysis and meta-regression[strong evidence]

    British Medical Journal 2016: Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment (1968-73) [systematic review of randomized trials; strong evidence]

    Nutrition Journal 2017: The effect of replacing saturated fat with mostly n-6 polyunsaturated fat on coronary heart disease: a meta-analysis of randomised controlled trials[strong evidence]

  22. The American Journal of Clinical Nutrition 1997: Individual fatty acid effects on plasma lipids and lipoproteins: human studies [overview article; ungraded]

    Journal of Lipid Research 1997: Effects of medium chain fatty acids (MCFA), myristic acid, and oleic acid on serum lipoproteins in healthy subjects [non-randomized trial; weak evidence]

  23. Nutritional Reviews 2019: Effects of carbohydrate-restricted diets on low-density lipoprotein cholesterol levels in overweight and obese adults: a systematic review and meta-analysis. [systematic review of randomized trials; strong evidence]

    Cardiovascular Diabetology 2018: Cardiovascular disease risk factor responses to a type 2 diabetes care model including nutritional ketosis induced by sustained carbohydrate restriction at 1 year: an open label, non-randomized, controlled study [non-controlled study; weak evidence]

  24. The Lancet Diabetes and Endocrinology 2017: Association of dietary nutrients with blood lipids and blood pressure in 18 countries: a cross-sectional analysis from the PURE study [observational study; very weak evidence]

  25. The Lancet 2017: Associations of fats and carbohydrate intake with cardiovascular disease and mortality in 18 countries from five continents (PURE): a prospective cohort study [observational study; very weak evidence]

  26. Of note, these subjects were eating a baseline diet comprised of 55% carbohydrates, and then were changed to a diet of 39% carbohydrates for 3 weeks.
    Public Library of Science one 2017: Effects of a very high saturated fat diet on LDL particles in adults with atherogenic dyslipidemia: A randomized controlled trial [moderate evidence]

  27. Mayo Clinic Proceedings 2003: Effect of a high saturated fat and no-starch diet on serum lipid subfractions in patients with documented atherosclerotic cardiovascular disease [non-randomized trial; weak evidence]

  28. American Journal of Epidemiology 2012: Effects of Low-Carbohydrate Diets Versus Low-Fat Diets on Metabolic Risk Factors: A Meta-Analysis of Randomized Controlled Clinical Trials [systematic review of randomized trials; strong evidence]
    Lipids 2009: Carbohydrate Restriction has a More Favorable Impact on the Metabolic Syndrome than a Low Fat Diet[randomized trial; moderate evidence]

  29. Canadian Journal of cardiology 1998: Cholesterol and lipids in the risk of coronary artery disease–the Framingham Heart Study. [observational study; weak evidence]

    Atherosclerosis Thrombosis and Vascular Biology 1997: Relation of high TG-low HDL cholesterol and LDL cholesterol to the incidence of ischemic heart disease. An 8-year follow-up in the Copenhagen Male Study. [non-controlled study; weak evidence]

  30. Lipids 2010: Limited effect of dietary saturated fat on plasma saturated fat in the context of a low carbohydrate diet [randomized trial; moderate evidence]

    Public Library of Science One 2014: Effects of step-wise increases in dietary carbohydrate on circulating saturated fatty acids and palmitoleic acid in adults with metabolic syndrome [non-randomized trial; weak evidence]

  31. This is based on consistent clinical experience of low-carb practitioners. [weak evidence]

  32. Acta Scientific Nutritional Health 2018: Evaluation of chemical and physical changes in different commercial oils during heating [overview article]

    Journal of Foodservice 2006: Health effects of oxidized heated oils [overview article]

    Journal of the American Oil Chemists’ Society 2002: Formation of 4-hydroxynonenal, a toxic aldehyde, in soybean oil at frying temperature [mechanism study.]