What Types and How Much Fat Should You Eat?

After a quick lesson on the types of fatty acids; though we did not cover Omega-3 and Omega-6 fatty acids, we can dive into which of these fats should make up our diet. 

What has been clearly illustrated in the nutrition literature is avoiding manmade trans fats (partially hydrogenated vegetable oils) and not the naturally occurring ones created by bacteria in the rumen of cows and/or sheep. Consuming partially hydrogenated vegetable oils increases your risk of many diseases (e.g. CVD, cancer and diabetes), which is why in 2015 the FDA determined these oils were no longer GRAS (Generally Recognized as Safe) and would be phasing them out of our food system.

Where there is more confusion is around saturated fats. I am sure you have been told, at one time or another, to limit your intake of SFA or increase your risk for cancer, heart disease, and diabetes. Then, when you look at which foods are high in saturated fat you realize they are primarily found in animal products, foods like meat, dairy, and eggs.

So, should you avoid them? Because the topic of saturated fat is one that is confusing and controversial, and I do not intend to take a deep dive in this article; instead, I will touch on those topics as time goes on and break them down into easier to digest pieces. 

I want to provide some context into why nutrition and medical professionals are concerned with saturated fat. This has to do with how SFAs can affect our blood lipid markers, such as LDL, HDL, total cholesterol, and triglycerides, to name a few. By the way, cholesterol is another topic much controversy exists, so it will be covered similarly as Saturated Fat.

Typically, we want to see low-density lipoproteins (LDL) below a certain level, high-density lipoproteins (HDL) between a certain range, and total cholesterol and triglycerides below a certain level. What has been shown in some nutrition research is high intakes of SFAs result in undesirable changes to blood lipids. 

Does this mean to avoid this food completely? No. 

What is important to realize is that foods that contain SFAs also contain other fatty acids. For example, the fat in beef is ~46% MUFA, ~5% PUFA, ~46% SFA, and ~3% Trans fat (CLA). So when someone tells you red meat is bad because it is “high” in saturated fat; remember is contains other fats as well, not just saturated fats. If you are eating a diet that consists of whole, minimally-processed foods, that include red meat, and your blood lipid markers are within a healthy range, should you worry and completely cut it out? I don’t believe so. 

What about foods like dairy: cheese, eggs, and milk? Interestingly, when you look at interventional studies with cheese, some experience improvements in blood lipid markers and a meta-analyses by Tong et al. found the consumption of cheese “is not significantly associated with risk of all-cause mortality”. As for eggs, people are often worried about cholesterol, however, in the most recent Dietary Guidelines for Americans, the USDA stated that cholesterol was no longer a nutrient of concern due to a lack of evidence. It may come as a surprise, but our body makes roughly 80% of the cholesterol it needs and the other 20% comes from our diet, so the dietary cholesterol we eat has a small effect on our cholesterol levels. As far as milk goes, a 2017 meta-analysis of prospective cohort studies looking at milk and dairy consumption found a neutral association of total, high, and low-fat dairy, milk, and yogurt with the risk of all-cause mortality. More recently, a 2019 meta-analysis found that a greater intake of total dairy has a beneficial association with mortality; however, there was an association with milk intake and higher CHD mortality.

Okay. Hopefully, you’re still with me! 

We will finish up with monounsaturated fats and polyunsaturated fats. 

The nutrition literature often associates health benefits with consuming foods high in MUFAs and PUFAs. They are associated with decreasing your risk for cardiovascular disease, Alzheimer’s and dementia while improving blood pressure, lowering fasting triglycerides, increasing HDL, and all-cause mortality.

One of the unfortunate outcomes of demonizing saturated fats was the substitution and increased consumption of oils high in polyunsaturated fatty acids. Oils such as corn, vegetable, soybean, peanut, grapeseed, sunflower, and safflower are all higher in PUFAs. Polyunsaturated fatty acids are not bad in and of themselves; however, if you can recall, these fats are highly susceptible to oxidation. An oxidized oil is a rancid oil, so if it exposed to high heat and/or air (oxygen) it goes through this process. (Gropper & Smith, 2013, pg. 138-139) This is why they created the process of partial hydrogenation, to protect these oils from going bad, but remember what that resulted in. 

The oils like olive oil and avocado oil are better choices because they are higher in monounsaturated fats and have lesser amounts of polyunsaturated fatty acids; reducing the likelihood of them being oxidized. Additionally, the polyphenols that olive oil contains further protects the fatty acids from becoming oxidized. 

I will list food sources of all the fatty acids you can include in your diet at the end.