Overview
Last week I touched on the benefits of consuming carbohydrates for energy and the role they play in a balanced diet despite the diet claims that they make us "gain weight" (remember anything in excess will cause us to gain weight!)
This week I want to touch on another nutrient that gets a bad rap - FAT!
Before diving into today’s topic, I recommend reading last week’s blog post: The SKINNY on Carbohydrates. I will be referencing a few key points from that post throughout this blog.
Ok, let's get to it!
Fats are one of the three primary macronutrients in your diet, including carbohydrates and protein. They are called macronutrients because they are needed in large quantities. Unlike protein and carbohydrates, fat is hydrophobic and is not soluble in water. Therefore fat soluble vitamins A, D, E, and K can't be absorbed unless dietary fat moves them from your intestine, into your blood stream, and then to your liver, where they're stored until your body needs them. Since they are stored, fat-soluble vitamins can also become toxic if consumed in excess.
Fat is dense in calories and contains 9 kilocalories/gram, as opposed to protein and carbohydrates which contain only 4 kilocalories/gram. For this reason, fats provide you with more energy stores than carbohydrates and protein. When glucose stores are depleted (refer to last week’s topic to read about glucose for energy), your body dips into its adipose tissue (fat cells) and breaks it down into fatty acids for fuel. If you had to, you could live off fat reserves for a very long time: A pound of stored fat equals approximately 3500 kilocalories of energy! WOW!
The calorie density of fat is also the reason it has become one of the targeted nutrients for weight loss and reducing cardiovascular disease. While overconsumption of this high-energy density nutrient can lead to weight problems and other poor health outcomes such as cardiovascular disease, consuming the recommended amount of dietary fat, as well as eating heart-healthy fats and oils, is important for improving overall health and well-being.
Dietary fats are essential to give your body energy and to support cell growth. They also protect your organs, keep your body warm, and help your body absorb vital nutrients.
Unlike the debate about carbohydrates being “essential", there is no debate that dietary fats are essential to life.
Types of Fats and Recommendations
There are four major dietary fats in the foods we eat:
1. Saturated fats
2. Transfats
3. Monounsaturated fats
4. Polyunsaturated fats
The four types of fats have different chemical structures and physical properties. All fats are either saturated or unsaturated fatty acids.
The word “saturated” refers to the number of hydrogen atoms surrounding each carbon atom. The chain of carbon atoms holds as many hydrogen atoms as possible-it’s saturated with hydrogens. Saturated fats are known as the "bad" and "unhealthy" fats and they are solid at room temperature (i.e. bacon grease cooled).
Monounsaturated (MUFAs) and polyunsaturated fats (PUFAs) are considered the "good" and "healthy" fats. They differ from saturated fats by having fewer hydrogen atoms bonded to their carbon chains. Healthy fats are liquid at room temperature, not solid.
The American Heart Association (AHA) and the Dietary Guidelines for Americans 2020-2025 recommends 20-35% of our calories come from dietary fat and less than 10% of our total fat intake should come from saturated fats. Trans fat should be avoided when possible and limited to less than 2% per day.
Saturated Fats
The BAD fat.
Saturated fats are consumed in abundance in the American diet. Common sources of saturated fat include butter, cheese, whole milk, ice cream, cream, fatty meats, and many prepared baked goods and other overly processed foods.
A diet rich in saturated fats can increase total cholesterol, tipping the balance towards the more harmful LDL cholesterol, which causes blockages to form in your heart's arteries and elsewhere in the body. Diets high in saturated fat are also linked to obesity and type 2 diabetes. For this reason, American Heart Association recommends limiting saturated fat to less than 10% of your dietary calories.
Leading nutrition scientists, government policymakers, and agencies suggest replacing saturated fat with better fat such as polyunsaturated or monounsaturated fat to help reduce the risk of heart disease and other health related problems.
Trans Fats
Another BAD fat.
Actually, correction- the WORST type of fat!
Trans fat is a byproduct of a process called hydrogenation that is used to turn healthy oils into solids and to prevent them from becoming rancid. Trans fats have NO known health benefits and there is no safe level of consumption.
Early in the 20th century, trans fats were found mainly in solid margarines and vegetable shortenings. Then as food makers learned new ways to partially hydrogenate vegetable oils, they began appearing in everything from cookies and pastries, to fast-food french fries.
In 2015, The Food and Drug Administration (FDA) officially banned trans fats in the United States and gave food makers three years to eliminate them from the food supply with a deadline of June 18, 2018. Now World Health Organization (WHO) is working to eliminate trans fats from the global food supply by 2023.
It's important to mention, if a food has less than 0.5 grams of trans fat in a serving, the food label can read "0 grams." Thus, traces of these harmful fats can accumulate quickly, It's best to scan a food label's ingredients and look for "partially hydrogenated...." which means the product contains trans fat.
Eating foods rich in trans fats increases the amount of harmful LDL cholesterol in the bloodstream and reduces the amount of beneficial HDL cholesterol. Trans fats create inflammation, which is linked to heart disease, stroke, diabetes, and other chronic health conditions. Trans fats contribute to insulin resistance, which increases the risk of developing type 2 diabetes.
Every 2% of calories consumed from trans fat daily, has been shown to increase the risk of heart disease rise by 23%.
Even small amounts of trans fats can harm your health!
Monounsaturated and Polyunsaturated Fats
The GOOD fats. Finally, we get into the good stuff!
Good fats come mainly from vegetables, nuts, seeds, and fatty fish.
Monounsaturated Fats (MUFAs)
The discovery of this “good fat” was first recognized in the 1950's by Scientist Ancel Keys, when he revealed that people in Greece and other parts of the Mediterranean region had a lower rate of heart disease despite their “high fat diet.” Discovering their main dietary fat was from olive oil, not saturated fat was groundbreaking and produced the surge of interest in olive oil and gave birth to the “Mediterranean diet,” style of eating.
Good sources of MUFAs are plant-based oils such as olive, peanut, canola, sesame, and safflower oils. Other good sources include avocado, peanut butter, and most nuts and seeds.
Evidence shows that MUFAs have a number of health benefits such as aiding in weight loss, reducing cholesterol, blood pressure, the risk of heart disease, and decreasing inflammation.
Polyunsaturated Fat (PUFAs)
If you pour liquid oil in your pan for cooking, there’s a good chance you’re using a PUFA. Corn, sunflower, peanut, soybean, and safflower oils are some of the better choices when using PUFA oils, since they contain less saturated fat than others (i.e. coconut oil).
There is much debate over which PUFAs are best for cooking (or if they should be used at all) and it is difficult to sift through what is evidence-based or biased-based.
The primary problem with PUFAs is that they’re highly unstable. All fats oxidize at a specific temperature (i.e. become unstable, go rancid, become toxic). PUFAs temperature is very low (MUFAs are more resistant to heating). Unstable fats are prone to oxidation which can lead to free radicals and cellular damage in your body.
I don’t want to take you too far down this rabbit hole, but I would say know the smoke points of the oils you cook with and use them in moderation. There are plenty of other ways to consume your PUFAs outside of heating them.
I digress-back on track!
Polyunsaturated fats are essential fats. This means they’re required for normal bodily functions, but your body CAN’T make them and you must get them from food. Polyunsaturated fats are essential for blood clotting, brain health, muscle movement, and nerve function.
There are two types of PUFAs: omega-3 fatty acids and omega-6 fatty acids. The number refers to the distance between the beginning of the carbon chain and the first double bond.
Both types of PUFAs offer health benefits and have been shown to prevent (and even treat) heart disease and stroke. PUFAs have also been shown to lower blood pressure, triglycerides and blood sugar, raise HDL (good cholesterol), and prevent heart arrhythmias. There is growing evidence that suggests PUFAs may also reduce the need for corticosteroid medicines in people with rheumatoid arthritis (an autoimmune disease which the immune system attacks healthy cells causing inflammation and joint pain in the affected parts of the body.)
Good sources of omega-3s include fatty fish and shellfish such as salmon, sardines, lake trout, canned light tuna, pollock, shrimp, and catfish. Other good sources include chia seeds, flaxseeds, and walnuts.
A caveat: When choosing fatty fish, avoid the ones that are known to have high levels of mercury. The FDA recommends avoiding shark, swordfish, king Mackerel, and tilefish due to their high mercury levels.
Good sources of omega-6s include flaxseed oil and seeds, hemp, sesame, and sunflower seeds, acai berries, and nuts including pecans and walnuts.
Omega-6 fatty acids have many health benefits, however there is conflicting information out there and not all experts agree, so it can be confusing.
The issue is that most Americans consume omega-6s in the form of processed foods such as chips, crackers and pastries. Some experts hypothesize that omega-6s are pro-inflammatory and omega-3s are anti-inflammatory, therefore optimizing this ratio may be best by eating less omega-6s. While other experts believe the answer is not eating less omega-6s, but eating a higher quality of omega-6s and eating more omega-3s. Again, mixed information on omega-6s, but the latest nutrition guidelines recommends replacing saturated fat with omega-6's and AHA, along with the Institution of Medicine, recommends omega-6 fats be 5-10% of your daily calories.
I think the quality of omega-6s is an important factor when choosing to eat them or not.
Dietary Fat Take Home
Dietary fats are essential for survival and play key roles in your health and the way your body functions. As with many nutrients, quality is key, so it's important to choose your fats wisely.
Try to keep your total daily fat intake to 20-35% of your calories and make most of them in the form of MUFAs and PUFAs instead of saturated and trans fats. If you’re cooking with oil, then know your smoke points and make sure the oils you choose are low in saturated fat.
Of your total dietary fat, have less than 10% of your intake be from saturated fat. Look at your labels to identify trans fats and keep in mind a trace amount is allowed to be in your food (and this can accumulate.) Keep trans fat to less than 2% per day-there are no benefits to consuming this kind of fat.
A simple strategy to "take home" is to add a little healthy fat to every meal!