Fat is such a complex topic. Especially when it comes to saturated fat. Should I eat it? Should I avoid it? Will it make me fat? Lead to cardiovascular disease? Much like all nutrition related topics, the research is ever-changing and the answers are rarely black and white.
Today, I’m going to break down the different types of fat and try to answer some of your burning questions.
Saturated Fats
Saturated fat simply means the chemical structure of the fat molecule is “saturated” with atoms. Each carbon atom forms a single bond with two hydrogen atoms. The carbon chain is therefore “filled” with hydrogen. Saturated fats tend to be more solid at room temperature. They are straight and can tightly bind together making a nice compact substance. When we think of saturated fat you might think of butter, animal fat, coconut oil, and palm oil.
Unsaturated Fats
Unsaturated fats contain one or more double bonds in their chemical structure. Meaning that not all carbons are “full” of hydrogen. These double bonds form kinks in the chain and are no longer tightly packed like saturated fats, making these fats more liquid at room temperature. Olive oil, peanut oil, avocado, high-oleic safflower and sunflower oils are examples of monounsaturated fats. Then there are polyunsaturated fats, which means it has two or more double bonds in its carbon chain. Two main types of polyunsaturated fats are omega-3 fatty acids and omega-6 fatty acids. Both of these are considered essential fats meaning they are required for normal body function, but your body cannot make them, so they must come from food sources.
Most dietary fat is made up of a combination of saturated, monounsaturated, and polyunsaturated fatty acids. It’s the ratio of the fats that labels the food one or the other. For example, butter contains 66% saturated, 26% monounsaturated and 3% polyunsaturated fatty acids. (2). Where olive oil contains 19% saturated, 68% monounsaturated and 13% polyunsaturated.(2)
Trans Fats
Then there are trans fats. These are the fats you really need to look out for. Trans fats are unsaturated fats that go through a chemical process called hydrogenation. Some trans fats occur naturally in ruminant meats and dairy foods.(3) Most dietary sources of trans fats are from processed foods. These are used in processing because they can extend the shelf life of foods. Trans fats are the worst of the fats. These have been directly linked to an increase in cardiovascular disease, cancers, diabetes, and obesity. (3) In 2015, the FDA found that partially hydrogenated oils (artificial trans fats) in the food supply are no longer “Generally Recognized As Safe”.(4) Even with FDA determining trans fats as unsafe, they continue to circulate though our food system. Vegetable shorting, margarines, some cooking oils and many processed foods and baked goods still contain trans fats that should be avoided as much as possible.(3)
So why is it saturated fats get a bad rep? Saturated fats are common in the American diet. These fats, when consumed in excess, can elevate total cholesterol and shift the balance towards more harmful LDL cholesterol. An increase in LDL cholesterol increases the risk of cardiovascular disease.(1,6) Americans have some of the highest rates of heart disease and obesity when compared to other countries.(5) We also know that the standard American diet is high in meats, dairy, processed foods, and lower in vegetable, whole grains, and healthy fats from nuts, seeds and olives.
Recent studies state that there is not enough evidence to conclude that dietary saturated fats increase the risk of cardiovascular events.(7) These same studies acknowledge that shifting the balance to a more protective monounsaturated and polyunsaturated balance by adding more plant sources and seafood into one’s diet can decrease the risks associated with cardiovascular disease (6,7).
The long and short of it is, as always, balance is key. Limit saturated fats to under 10% of daily calories, include a variety of healthy fats from plant sources and fish, and most importantly avoid those processed trans fats.(8)
Resources:
1. Tvrzicka, Eva et al. “Fatty acids as biocompounds: their role in human metabolism, health and disease–a review. Part 1: classification, dietary sources and biological functions.” Biomedical papers of the Medical Faculty of the University Palacky, Olomouc, Czechoslovakia vol. 155,2 (2011): 117-30.
2. bmjopen-2018-March-8-3—inline-supplementary-material-2.pdf
3. Dhaka, Vandana, Neelam Gulia, Kulveer Singh Ahlawat, and Bhupender Singh Khatkar. 2011. “Trans Fats-Sources, Health Risks and Alternative Approach – A Review.” Journal of Food Science and Technology 48 (5): 534–41.
4. Center for Food Safety, and Applied Nutrition. n.d. “Trans Fat.” Accessed January 13, 2021.
5. Wang, Y. C., McPherson, K., Marsh, T., Gortmaker, S. L., & Brown, M. Health and economic burden of the projected obesity trends in the USA and the UK. Lancet, 378(9793), 815-825 (2011).
6. Wang, Dong D., Yanping Li, Stephanie E. Chiuve, Meir J. Stampfer, Joann E. Manson, Eric B. Rimm, Walter C. Willett, and Frank B. Hu. 2016. “Association of Specific Dietary Fats With Total and Cause-Specific Mortality.” JAMA Internal Medicine 176 (8): 1134–45.
7. Siri-Tarino, Patty W et al. “Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease.” The American journal of clinical nutrition vol. 91,3 (2010): 535-46.
8. Liu, Ann G., Nikki A. Ford, Frank B. Hu, Kathleen M. Zelman, Dariush Mozaffarian, and Penny M. Kris-Etherton. 2017. “A Healthy Approach to Dietary Fats: Understanding the Science and Taking Action to Reduce Consumer Confusion.” Nutrition Journal 16 (1): 53.