The scoop on dietary fats

Created date

February 14th, 2018
Variety of nuts

Variety of nuts.

Years of medical research have shown us that certain types of fats are not good for our health, and other types are. While it is true that the good or bad effects of any fats are largely dependent upon your genetics, overall health, the types of foods you cook them with, and the method of cooking, saturated and trans fats in particular cause harmful changes to blood vessels throughout your body. 

The bad guys

“Saturated fats and trans fats cause the lining of blood vessels to inflame or swell,” says Lauri Wright, Ph.D., R.D.N., L.D., assistant professor in the clinical nutrition program at University of North Florida in Jacksonville, and spokesperson for the Academy of Nutrition and Dietetics. “This inflammation is like a jagged area that collects cholesterol circulating in the blood, causing a buildup, or plaque. The larger the plaque grows, the less blood flows through, and eventually the vessel can be entirely blocked.” 

Saturated fats also raise your blood levels of harmful cholesterol (low-density lipoprotein, or LDL) and lower the beneficial type of cholesterol (high-density lipoprotein, or HDL). LDL is harmful because it tends to stick to blood vessel walls. HDL is beneficial because it has been shown to drag LDL away from blood vessel walls.

Saturated fats are primarily found in animal-based foods, such as high-fat dairy products, meat, and meat products. They are solid at room temperature. Some plant-based fats, such as coconut oil and palm oil, are also saturated. These oils are different in composition than meat-based saturated fat. Plant-based fats typically contain other compounds (like antioxidants) that some research shows may counteract bad effects. Nevertheless, Wright recommends that people minimize their intake of saturated fat, no matter where it comes from. 

Trans fats can occur naturally in beef, lamb, and butterfat, but more often they are vegetable oils that have been commercially manufactured in order to solidify them. Eating foods with trans fats also raises LDL and lowers HDL. They are also associated with a higher risk of type 2 diabetes.

Despite the health implications, trans fats are used because they are inexpensive, do not spoil quickly, and (unfortunately) can make food taste good. Increasingly, however, state and local governments are restricting (or outright banning) restaurants from using trans fats. Many food manufacturers have also reduced or eliminated them from products.

Sufficient scientific research has not been conducted to determine whether the type of trans fat found in beef, lamb, and butterfat is detrimental to health.

The good guys

Although high in calories, fat is a necessary part of many bodily functions. Thus, cutting down too drastically can lead to a lack of energy and an inability to absorb crucial nutrients—especially vitamins. So the fat you consume should be the beneficial variety, according to the American Heart Association. 

Enter monounsaturated fats (MUFAs) and polyunsaturated fats (PUFAs). According to the American Heart Association, these fats lower LDL and raise HDL and are thus very good for cardiovascular (and overall) health. PUFAs also play a key role in keeping your body’s cells healthy and are a good source of vitamin E. 

MUFAs and PUFAs are liquids at room temperature, but can begin to solidify when cooled. Good food sources of MUFAs and PUFAs include nuts and nut butters, avocados, sesame seeds, tofu, and avocados. One type of PUFA, omega-3 fatty acids, can be found in salmon, tuna, trout, herring, mackerel, and sardines. Oils high in MUFAs and PUFAs include olive, soybean, corn, peanut, canola, sunflower, and safflower oil. 

Depending on the brand, you may find different amounts of MUFAs and PUFAs on the label. In addition, foods may contain differing ratios of MUFAs and PUFAs (see chart). “There are no definitive guidelines about whether you should try to consume more of one kind or the other,” Wright says. “People should just focus on replacing saturated and trans fats with unsaturated types.”