Fats Aren’t the Enemy

For decades fats have been targeted as a major obstacle to fitness. The health and fitness industry often ties fats to high cholesterol, heart disease, and obesity. Specifically this negative stigma revolves around saturated and trans fats. Saturated fats are linked to high cholesterol making them widely perceived as unhealthy. Examples of foods that contain saturated fats include meats, cheese, and butter. Meanwhile, trans fats are mainly artificially formed through a process called hydrogenation. They are also linked to heart disease, specifically strokes. Because of the various side effects, trans fats were deemed unsafe and banned from the US in 2018 by the US Food and Drug Administration (FDA). But, what exactly are these fats? Are they really unsafe and should we avoid them? 

Fats fall under a class of macromolecules called lipids. Lipids are a diverse group that fall under three categories: storage, structural, and others. Fats can be an example of a storage lipid like triglycerides or structural lipids like phospholipids. The difference between saturated, unsaturated, and trans fats as well as the importance of fats lies in the fatty acid chain. The fatty acid chain is a chain of carbons coming off of the head group. This makes fats more efficient for fuel storage because each carbon is more reduced compared to those carbons of a carbohydrate. More reduced means there are more hydrogens attached to each carbon atom allowing them to be used for long term energy needs and slow delivery. Fatty acids are the building blocks of fats and they bundle or pack together distinctly due to one difference: double bonds. Saturated fatty acids have no double bonds, while unsaturated either have one (monounsaturated) or multiple (polyunsaturated) cis double bonds in their alkyl chain. Saturated fats pack in an orderly way due to there being no bends and kinks in their chains making them solid at room temperature. Butter, cheese, and whole milk are just a few examples of foods with saturated fats. Unsaturated on the other hand are much less orderly when they pack making them liquid at room temperature like olive oil. Trans fats, on the other hand, resemble unsaturated fats but their double bonds are in trans formation instead of cis. This structural difference influences the physical state as well as how fats interact with the body. 

Cholesterol modulates the fluidity and permeability of the membranes in eukaryotic cells. Mammals obtain cholesterol through food or synthesis in the liver and high cholesterol is usually linked to high fat diets. Cholesterol is transported to tissues via blood vessels. When they reach cell membranes they insert themselves between phospholipid tails and keep membranes at the optimal fluidity. At high temperatures membranes become too fluid and cholesterol stabilizes this. And at low temperatures membranes become too rigid and cholesterol keeps them flexible. In addition, unsaturated and saturated fats both interact with cholesterol. Unsaturated fats pack loosely so cholesterol can stabilize this. Saturated fats pack tightly so cholesterol will disrupt the tight packing. Clearly fats and cholesterol are necessary for a high functioning group of cells. So, where does the problem with fats really lie and why are they viewed so negatively?

Many fats are seen as bad for two reasons: how they are stored and how they affect blood lipids. All excess fats are stored in adipose tissue as triglycerides whether they be saturated, unsaturated or trans fats. The real issue is in how they affect metabolism and inflammation. Saturated fats increase risk of fat around organs as well as promote inflammation. Unsaturated fats, particularly omega-3s, can assist in building brain cells and improve insulin sensitivity. Fats also play a role with our blood lipids which can be associated with cardiac diseases. In our blood vessels low density lipids (LDLs) and high density lipids (HDLs) carry cholesterol from the liver to cells or vice versa. LDLs deliver cholesterol to tissues while HDLs act as a clean up crew and remove cholesterol from the bloodstream. Too much LDLs lead to plaque buildup and narrows arteries. This can result in strokes and heart attacks. HDLs will assist and lower this risk. Saturated and trans fats increase the levels of LDL in the bloodstream while unsaturated raise our HDL levels. 

Saturated fats are not inherently bad. Processed foods and an excessive amount of saturated fats will no doubt harm one’s body, but saturated fats are still necessary. They are important for membrane structure, hormone production, and supporting vitamins such as vitamins A, D, E, and K. Whole food sources such as eggs and even dark chocolate can be great sources of saturated fats. Most health organizations suggest that 10% of your daily calories should come from saturated fats. On that other side, trans fats should be considered harmful and avoided. To improve shelf life of processed foods liquid oils are turned to semi solid fats through hydrogenation. Trans fats can be linked to increased heart disease, lowering HDL cholesterol, increasing insulin resistance, and other chronic diseases. Although banned in the USA foods can contain <0.5 g of trans fat and say 0 g on their label. This is why many snacks and baked goods can contain small traces. Instead of fearing fats all together we should be weary on source and amount. The goal isn't to eliminate fat, but to understand how to utilize it in a healthy way. 

References

1. PMF IAS. Fats: Saturated, Unsaturated & Trans Fat – Comparison Chart. https://www.pmfias.com/fats-saturated-unsaturated-trans-fat/

2. U.S. Food & Drug Administration (FDA). Trans Fat. https://www.fda.gov/food/food-additives-petitions/trans-fat

3. Harvard T.H. Chan School of Public Health. The Truth About Fats: The Good, the Bad, and the In-Between. https://www.health.harvard.edu/staying-healthy/the-truth-about-fats-bad-and-good