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 the observation in experimental trials that replacing saturated fat with unsaturated fat lowers low-density lipoprotein (LDL) cholesterol, and that LDL cholesterol itself is linked to heart disease.
But is this harmful reputation warranted?
Recently, better quality research has demonstrated that saturated fat’s effect on heart disease is a lot more complicated. Factors that need to be considered include individual responses to saturated fat intake, food sources of saturated fat, and how the rest of the diet changes when a person increases their saturated fat intake.
Highlighting these points, in a recent article, 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.
A similar article was also published in a major mainstream cardiology journal in 2020.
All of this is further confused by the fact that most studies combine all sources of saturated fat together. That means saturated fat from a steak is counted the same as saturated fat in cookies, cake or other baked goods, which have a combination of saturated fats, trans fats and sugars.
How can someone make sense of all this? 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.
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
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.
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 (200 grams): 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.
Saturated fat and health risks: the evidence to date
Guidance to reduce saturated fat is based on studies which show 1) a causal link between saturated fat and LDL cholesterol and 2) a causal link between LDL cholesterol and coronary heart disease.
However, convincing evidence for a direct link between saturated fat and heart disease is lacking
Let’s take a closer look at what systematic reviews of observational studies and controlled studies tell us about saturated fat intake and the risk of coronary heart disease (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.”
- A 2010 meta-analysis of 21 cohort studies found no association between saturated fat intake on CHD outcomes.
- 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.
- 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.
- A 2017 meta-analysis of 7 cohort studies found no significant association between saturated fat intake and CHD death.
Two systematic reviews 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. 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.
A 2020 Cochrane review of RCTs likewise showed a reduction in cardiovascular events for lower saturated fat intake, but this effect was modest. This study also found no difference on cardiovascular death or all-cause death.
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 heart disease 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).
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.
However, this observational study had many limitations.
As we discuss below, the food or nutrient that replaces saturated fat is critical. Observational trials like these make it difficult to account for the nutrient quality of the food eaten and the food replaced. So the conclusions of PURE, like many large-scale observational studies should be taken with a pinch of salt.
In addition, as we noted in the introduction, recent data has shown us that we need to be much more nuanced when considering the effect of saturated fat on heart disease. We’ll run through the most important nuances next.
The food or nutrient which replaces saturated fat determines whether the switch might be beneficial, neutral or even harmful.
If you think about the studies which reduced saturated fat intake – what did they replace it with? Carbohydrates (such as refined grains), unsaturated fats, or protein? This really matters.
It’s now clearer that replacing saturated fat with refined carbohydrates does not improve heart disease risk, whereas replacing saturated fat with polyunsaturated fat might.
This nuance could explain some of the conflicting results from meta-analyses.
Clearly, there’s no point recommending a person reduce their saturated fat intake if they just end up replacing it with sugary cereals and white bread.
Food sources of saturated fat
A variety of foods are rich sources of saturated fat, including red meat, butter, cheese and coconut oil. Most studies combine all sources of saturated fat together. That means saturated fat in cream is counted the same as saturated fat in yogurt or cheese.
Many foods, including meat and dairy, contain other nutrients and non-nutrient components which can influence heart disease risk, such as probiotics, magnesium, potassium and vitamin D. They also contain other types of fats.
For instance, most beef products have nearly equal amounts of saturated and monounsaturated fats. Therefore, even though meat, yogurt and butter are relatively high in saturated fat, their effects on heart disease may be divergent due to these “confounding” factors.
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.
Likewise, there are a number of controlled studies showing that cheese and butter have very different effects on LDL-cholesterol.
And dairy fat including yogurt and cheese has been shown to be protective against heart disease in observational studies.
As leading scientists claimed in their 2020 review paper, we should discuss health implications of specific foods rather than lumping them all together as “saturated fats.”
As described above, the whole diet is important. Most people eating a high-carb diet get their carbs from refined grains and sugars, which themselves may be harmful to health. If a low-carb (but high-saturated fat) diet helps them to omit the harmful types of carbs and consume more non-starchy vegetables, then this could be a net health benefit.
Processed foods that are manufactured to replace naturally occurring saturated fats with refined carbs, sugars, and artificial flavors and fillers are rarely a healthier choice.
Most of the studies on high-saturated fat diets and human health are done against a background of high carb intake. Lipid (fat) metabolism changes a lot when a person cuts carbs, and it is possible that the effect of saturated fat on cholesterol differs in potentially important ways when the background diet is low in carbs.
Dietary recommendations assume that all people respond the same way to nutrients. In the case of saturated fat, there is clear evidence that there are large differences in how people respond to changing the saturated fat content of the diet.
Just as the studies show different responses among individuals, so does real life clinical experience.
What do foods’ saturated fat levels mean for the typical low-carber?
Someone following a typical low-carb or keto diet 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 (about 22 grams a day) and American Heart Association (13 grams).
Is that a problem? We don’t know for sure, but for many people, probably not. In general, the effect of one nutrient on any outcome is very small.
It’s also important to consider all other factors which might influence a person’s risk of heart disease, and how an increase in saturated fat in the context of a low-carb diet might affect them.
For example, if by eating a low-carb diet (which happens to be high in saturated fat) a person is able to lose 10 lbs (4.5 kilos) of weight, improve their blood sugars and lower their blood pressure, a small rise in LDL cholesterol is unlikely to result in a net increase in heart disease risk.
In fact, weight loss 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.
In summary, for many or even most people, increasing saturated fat intake in the context of a healthful low-carbohydrate diet will have a negligible impact on their heart disease risk.
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.
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.
In addition, low-carb diets that were naturally higher in saturated fats showed overall improvement in lipid parameters compared to low-fat diets.
Importantly, some experts in the field of lipidology and cardiology disagree about whether elevated LDL cholesterol and particle concentrations increase the risk of heart disease 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.
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.
Many low-carb whole foods that provide valuable nutrients and help you feel full — 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 fish.
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.
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, focusing on your whole diet diet is a better health strategy than limiting a single nutrient like saturated fat.