Let’s Talk About Dietary Fats

Types of Dietary Fats

Fats are a necessary part of an individual’s diet. Some benefits include organ protection, nutrient absorption, and energy metabolism. There are three main types of dietary fats: unsaturated, saturated, and trans-fat. Saturated fats are solid at room temperature, and are known to increase one’s cholesterol levels, specifically the ‘bad’ cholesterol, LDLs. The most common American foods with a  high saturated fat content include:

• Pizza and cheese

  

• Whole and reduced fat milk
• Meat products (beef, sausage, etc.)
• Grain-based desserts (cookies, brownies, etc.)
• Variety of fast food

Saturated fat is found mainly in foods from animals, but may also be found in plants such as coconut and palm oil (coconut oil may not be as great as you think)! On the      other hand, we have unsaturated fats. These are liquid at room temperature and are considered to be the ‘good’ fats through improving blood cholesterol levels (lowering LDLs and raising HDLs), easing inflammation, and stabilizing the heart. There are two types of unsaturated fats: monounsaturated and polyunsaturated.

1. Monounsaturated fats:
   1. Oils (peanut, canola, olive)
   2. Avocado
   3. Nuts (almonds, pecans, peanuts)
   4. Seeds (pumpkin, sesame, etc.)
2. Polyunsaturated fats:
   1. Oils (sunflower, corn, soybean, flaxseed)
   2. Walnuts
   3. Flaxseeds
   4. Seafood

Within polyunsaturated fats, there are fatty acids known as omega-3. The body is unable to produce omega-3 fats on its known, so it is important to obtain these from one’s diet. These are mainly found in seafood (fish) and walnuts or flaxseeds. Lastly, trans-fats is a fat produced through the process of hydrogenation to elongate shelf-life. This fat is considered to be the most detrimental to one’s health through increased inflammation, insulin resistance, and raise bad LDLs while lowering good HDLs. These are often known as partially hydrogenated oils (PHOs), and are banned in many countries.

Saturated Fatty Acids (SFAs) in the Brain

It has been shown that specific fatty acids, specifically saturated fatty acids (SFAs), are linked to hypothalamic inflammation, disrupt insulin and leptin signaling, as well as trigger inflammatory signaling cascades. The induction of SFAs are able to trigger Toll-like receptor (TLR2/4) signaling. TLR4 activates the response gene, MyD88, activates the kinase complex, IKK. Under conditions of high-fat diets (HFDs), IKK phosphorylates IĸBα, an inhibitor of the pro-inflammatory cytokine producer, NF-ĸB. This allows NF-ĸB to translocate to the nucleus of the cell and transcribe pro-inflammatory cytokines such as TNF-α and IL-1ß, as well as SOCS3. This signaling cascade increases neuronal inflammation in brain tissue as SFAs are able to cross the blood-brain-barrier (BBB) (Jais and Brüning, 2017). SFAs also disrupt insulin signaling through the increased production of ceramides within the brain. Ceramides activate protein kinase C (PKC), which is a primary inhibitor of PI3K. PI3K plays a major role in the insulin signaling pathway, and its inhibition will cause nuclear exclusion of FOXO1 and contribute to insulin resistance (Jais and Brüning, 2017).

How Much Fat Should I Eat?

The dietary intake reference for total fat should be around 20-35% of total calories per day (44-77 grams depending on caloric intake). This intake should primarily consist of mono and polyunsaturated fat, with little saturated fat, and no trans-fat. In a low-fat diet, fat intake should be about 30% of total calories. In high-fat diets, such as Keto, total caloric intake will consist of around 75% of fats due to lack of carbohydrates. The Mediterranean diet, considered to be an ideal diet for humans, provides about 35-40% of calories from fats, focusing on unsaturated fat intake. According to the Dietary Guidelines for Americans 2020-2025, saturated fat intake should be limited to less than 10% of one’s calories per day. In order to do this, saturated fats should be replaced

with unsaturated fats, primarily polyunsaturated. Also, around 5% of saturated fats in one’s diet are inherent in common foods such as lean meat, eggs, nuts and seeds, and grains. Due to this, there is very little room left for additional saturated fats found in foods with added butter or sugar.

Reference

Jais, A., & Brüning, J. C. (2017). Hypothalamic inflammation in obesity and metabolic disease. Journal of Clinical Investigation, 127(1), 24–32. https://doi.org/10.1172/jci88878