The human body needs both saturated fats and unsaturated fats to remain healthy. Most dietary recommendations suggest that, of the daily intake of fat, a higher proportion should be from unsaturated fats, as they are thought to promote good cholesterol and help prevent cardiovascular disease, whereas an overabundance of saturated fats is thought to promote bad cholesterol. However, a few studies have found that little evidence for a strong link between the consumption of saturated fat and cardiovascular disease.
Note: It is technically more accurate to call saturated and unsaturated fats types of fatty acids, as it is specifically the fatty acid found in a fat that is either saturated or unsaturated. However, referring to fatty acids as fats is common.
|Saturated Fats||Unsaturated Fats|
|Type of bonds||Consist of SINGLE bond||Consist of at least 1 DOUBLE bond|
|Recommended consumption||Not more than 10% of total calories per day||Not more than 30% of total calories per day|
|Health Effects||Excessive consumption is not good because of their association with atherosclerosis and heart diseases.||Unsaturated fats are considered good to eat if you are watching your cholesterol. Also high in antioxidants.|
|Cholesterol||Saturated fats increase Low Density Lipoproteins (LDL or bad cholesterol) & Very Low Density Lipoproteins (VLDL's).Sources of bad cholesterol are foods rich in trans fatty acids, refined carbohydrates, such as white sugar, and flour.||Unsaturated fats increase High-Density Lipoprotein (HDL or good cholesterol) and decrease Low Density Lipoproteins (LDL or bad cholesterol). Sources of HDL include onions and Omega-3 fatty acids like flax oil, fish, foods rich in fiber like grains.|
|Commonly found in||Butter, coconut oil, whole milk, meat, peanut, butter, margarine, cheese, vegetable oil, fried foods, & frozen dinners||Avocado, soybean oil, canola oil and olive oil, sunflower oil, fish oils walnuts, flax, & red meats|
|Shelf Life||These are long lasting and do not spoil quickly||These spoil quickly|
|Physical state at room temperature||Solid (Trans Fats & Saturated Fats)||Liquid (Monounsaturated & Polyunsaturated Fats- Omega 3's & 9's)|
|Examples||Hydrogenated Oils, Butter, Processed Meats||Olive Oil, linoleic acid, alpha-linolenic acid|
Types of Saturated and Unsaturated Fats
While it is well known that there are saturated and unsaturated fats, fewer people are aware that unsaturated fats are further classified into two other groups: monounsaturated fats (sometimes seen as an acronym — MUFA) and polyunsaturated fats (PUFA). Polyunsaturated fats are where omega fatty acids, such as omega-3s and omega-6s, are found.
There are many different kinds of saturated and unsaturated fatty acids, and science is still trying to understand how they all function in the body. For a list of saturated fatty acids, see here. For unsaturated fatty acids, see this list.
There is a third type of fat known as a trans fat. Trans fats are actually a kind of unsaturated fat, but they stand out from other types of fat because they very rarely occur in foods naturally.
A trans fat is created when an otherwise naturally unsaturated fat — often vegetable oil — is hydrogenated (i.e., hydrogen atoms are added to the food). Hydrogenation extends the shelf-life of foods, but it also solidifies fats that would otherwise be liquids. Manufacturers created this process partly because saturated fats, which had been used previously, had grown very unpopular; however, there was still a need to create foods that would last. Unfortunately, these solid trans fats have the same effects that saturated fats have: they clog the arteries. Numerous studies found trans fats were even worse for heart health than saturated fats.
Food industries around the world have been phasing out trans fats since the mid-2000s, often due to public demand or government regulation, but even food products that claim to have "0g of trans fat" may usually contain up to 0.5g legally. In late 2013, the FDA stated that trans fats are not generally considered safe. Many see this as the start of an eventual all-out ban of trans fats from foods. They are being replaced with interesterified saturated fats and sometimes with traditional saturated fats, such as lard or palm oil.
See also Cis Fat vs Trans Fat.
Health Effects of Saturated and Unsaturated Fats
Fat cannot and should not be removed from a diet. Healthy diets include saturated and unsaturated fats. Even so, these fats are processed differently in the body.
Saturated fats are more solid and have a chemical structure that is more tightly packed. Too many saturated fats, too often, may increase bad cholesterol (LDL), clog arteries, and increase the risk of cardiovascular disease and events, such as heart attacks and strokes.
In general, monounsaturated and polyunsaturated fats are believed to promote good cholesterol (HDL) by helping move bad cholesterol to the liver, where it can be metabolized. (This is why news media and some doctors talk about fats as being either "good" or healthy fats or "bad" or unhealthy fats.) People are often encouraged to eat polyunsaturated fats, in particular, as some studies have found omega-3s and omega-6s to be beneficial.
Relationship Between Saturated Fats, Diseases, and Cancers
Understanding how carbohydrates, saturated fats, and unsaturated fats operate in the body is a topic of ongoing scientific research. While numerous studies since the 1960s have found links between saturated fats, diseases, and cancers, several other large studies in recent years have found no significant correlation. It is possible that saturated and unsaturated fatty acids are much more complex and nuanced than previously thought.
Currently, most all health associations (e.g., American Dietetic Association and American Heart Association), governmental institutions (e.g., British National Health Service), and the World Health Organization (WHO) recommend limiting the consumption of saturated fats to help maintain cardiovascular health.
In a widely-reported 2014 meta-analysis of 72 studies, researchers said there was little evidence to support the idea that saturated fats can be clearly linked to cardiovascular problems or that polyunsaturated fats are as beneficial as typically claimed. Walter Willett, the current chair of the Department of Nutrition in the Harvard School of Public Health, has been critical of this meta-analysis, saying it "contains multiple errors and omissions" and is "seriously misleading."
While most studies have focused on the alleged connection between saturated fats and cardiovascular disease, others have looked at possible links between these fats and cancer. Various studies have found links between saturated fatty acids and breast cancer, colorectal cancer, ovarian cancer, pancreatic cancer, and prostate cancer; and at least one study found saturated fats contributed to the failure of prostate cancer treatments. Other studies have found no or little association. Further research is required to know if there is an actual link between saturated fat and these illnesses.
Sources of Saturated and Unsaturated Fats
Most saturated fats come from animal-based products, like milk, butter, and ice cream; red meat and poultry; and a few oils derived from plants (e.g., coconut oil and palm oil). Unsaturated fats are primarily found in vegetable oils (e.g., olive oil), nuts and nut butters, avocados, and fish.
It is important to know, though, that many foods have a combination of saturated and unsaturated fats. For example, a pasta dish might use olive oil — mostly monounsaturated fat — and feta — mostly saturated fat. The pasta itself contains a tiny amount of both saturated and unsaturated fat, too.
Recommended Daily Intake
Doctors and dietitians usually follow what is presently mainstream science by telling their patients to limit the amount of saturated fats they eat in a day. Most experts recommend that no more than 25-35% of one's daily calories come from any fat, and that only 7-10% specifically come from saturated fats. This roughly equals 60 to 65 grams of fat (and specifically 16 to 20 grams of saturated fat) in a daily diet of 2,000 calories.
Because many studies have found low-carb, low-saturated fat diets to be beneficial, some experts now recommend vegetarianism or at least less meat consumption. Others are highly critical of some popular diets, such as the paleo diet, that may increase one's daily consumption of saturated fat.
Fats — or triglycerides — are made up of glycerol (an alcohol) and fatty acids, which are long carbon-hydrogen chains that end in a carboxyl group. Triglycerides are either saturated (with hydrogen) or unsaturated. Saturated fatty acids contain carbon atoms that connect with each other in a chain of single bonds. So each carbon atom can bond with two hydrogen atoms, and is said to be "saturated" with hydrogen. Unsaturated fatty acids contain some carbon atoms that bond with each other using double bonds. So these carbon atoms can only bond with one hydrogen atom instead of two, and are said to be "unsaturated".A fatty acid with a single double bond is a monounsaturated fatty acid, while a fatty acid with two or more double bonds is known as a polyunsaturated fat.
These different chemical structures result in different physical properties for saturated and unsaturated triglycerides. Saturated fats, like butter or bacon grease, solidify at room temperature, while unsaturated fatty acids, like olive oil, tend to be liquid at room temperature. Unsaturated fatty acid molecules are not tightly packed, which makes it easier for them to pass more fluidly through the body.
There are a few oils that are saturated fats which are double-bonded, but they are still tightly packed with hydrogen; these oils often solidify at room temperature (e.g., coconut oil).
While scientific research and debate is ongoing, the general consensus is as follows:
- Watch your calorific intake to make sure you do not consume too many calories, especially if you have a sedentary lifestyle.
- Eat fewer carbs. Carbs convert to sugar, and too many carbs increase the risk of diabetes and cardiovascular diseases.
- Less than 10% of your total recommended calorific intake should be sourced from saturated fats. However, if in the pursuit of this goal, you replace saturated fat with carbs or partially hydrogenated oils, the effect on your health may be just as bad, if not worse.
- Avoid trans fats.
- Dietary fat and heart disease study is seriously misleading - Harvard School of Public Health
- Dietary Fat Information - CDC.gov
- Fatty Acids - Stanford University
- The Questionable Link Between Saturated Fat and Heart Disease - WSJ
- Wikipedia: Saturated fat and cardiovascular disease controversy
- Wikipedia: Saturated fat
- Wikipedia: Unsaturated fat