Everything you need to know about dietary fats.
Hello friends! Today I’m going to be adding to my “macronutrient” category of info, by telling you what you need to know about dietary fats and nutrition. Dietary fat is one of the three essential macronutrients, along with protein (which I wrote all about here), and carbohydrates. There is constant confusion about what’s good and bad in terms of fat, so I thought I’d break down the current state of science for all my lovely readers.
Side note: welcome to my new site! I will slowly be updating all of the previous posts to look more polished with printable recipe cards, and will be working on a more user-friendly recipe tab page, and pumping out a lot more nutrition and environmental health science-based content! Whoo! I appreciate your patience as I get the page to exactly where I want it aesthetic/interface-wise, as I’m a one-woman show without the budget for a web-designer over here :-).
What even is “Fat?”
Now back to dietary fats! As I mentioned above, fats are one of three macronutrients (along with protein and carbohydrate). Macronutrients are what make up the human diet and give the body energy, meaning they have calories. This is how they differ from micronutrients (like vitamins and minerals), which are also essential, but do not contain energy (calories).
As I mention in this article, fats contain 9 calories per gram. This makes them the most calorically dense macronutrient, as both protein and carbohydrates contain 4 calories per gram.
Fats, also known as “lipids” in much of the science world, are comprised of carbon, hydrogen, and oxygen atoms, with both hydrophilic (water-loving) and a hydrophobic (water adverse) ends.
Lipids are important structural molecules in the body, and serve a variety of functions, including making up the phospholipid bilayer that surrounds every cell. Lipids are also important for making hormones and steroids, which serve important cell-to-cell communication functions. They also serve a role in the growth and development of tissues.
How Much Fat Should I Eat?
Dietary fats were once demonized as “low fat” diets took over in the 80s and 90s. It seems these days, fats are making a comeback. Some people even take it to the extreme with the “keto” trend (which I will devote an entire separate post to talking about), and consume lots of fat and protein and minimal carbohydrates.
Yet, fat is still often feared by many dieters hoping to loose weight, and many products still market their “low fat” content as an asset. So it is often, understandably confusing, for most people to know much fat they should eat.
According to the Institute of Medicine, fat should make up 20-35% of total caloric intake for healthy adults, meaning roughly 1/5-1/3 of the calories you take in should come from fat.
Obviously, different individuals in different stages of life with varying medical conditions may have slightly different needs. But for most, 20-35% of dietary intake from fat is considered optimal.
So What Fats Are Not Good For Human Health?
I don’t often make statements about thing being “bad” for you (as I believe deeming foods ‘good’ and ‘bad’ oversimplifies things much of the time), but I can tell you this: there is substantial evidence that trans fatty acids (aka ‘trans fat’) raises LDL cholesterol and is detrimental to heart health, and considered a risk factor for cardiovascular diseases and stroke.
There is also speculation that trans fat impacts the metabolic system and may be linked to insulin resistance and type II diabetes. The lack of certainty due to these later two points may be due to differences in study designs and the inherent difficulty of studying and measuring the human diet.
But one thing seems quite certain: trans fats are linked to coronary heart disease. And they should be avoided, whenever possible.
Trans fatty acids were once widely found in processed foods in the United States; however, artificially produced were banned from packaged food products by the FDA. The FDA gave companies several years to rework their products with a final deadline to remove it from consumer products completely by 2018. This is why some foods (like packaged cookies and cakes) may have changed slightly over the past few years. It’s for your own good, I promise :-).
Trans fatty acids may still be found in restaurant food, primarily fast food. Local government authorities within the United States (including New York City) have placed bans on trans fats in restaurants.
This means if you eat at McDonalds in NYC, you enjoy a trans fat-free meal. But if you eat the same meal in another city, it may contain trans fats. Some restaurants have pushed back against the ban, citing that consumers will ‘taste a difference’ and it will negatively impact sales. However, I’ve yet to meet someone who eats McDonalds in NYC (or Europe, for that matter) and goes “Wow, this tastes like it’s missing something…something bad for my heart.”
Trans fatty acids are also found naturally in small amounts animal products, including some red meats like beef and lamb, as well as in dairy and egg products. Some believe these naturally occurring trans fats are less detrimental to health than artificially-produced trans fats. At present, I personally think there have not been enough rigorous scientific studies to make a firm judgement call either way.
Other Fats Many Avoid:
Besides trans fats, saturated fats are often targeted as a type of fat that you should limit in consumption Presently, the USDA recommends adults consume no more than 10% of their total calories from saturated fats, citing concerns that saturated fatty acids have been linked to chronic diseases such as diabetes, hypertension, and heart disease.
The American Heart Association has an even more stringent recommendation, suggesting people limit 5-6% of their total calories to come from saturated fatty acids.
Saturated fats are often solid at room temperature, and are found in whole-fat dairy products, meat, coconut oil*, cheese, and many commercially prepared baked goods as well as packaged snack foods.
Most scientists agree saturated fats are associated with adverse cardiovascular outcomes. Some believe the concern isn’t as large was once thought.
Either way, substantial evidence suggests replacing saturated fats with healthful fats (mono and polyunsaturated fats, see below) is best for health.
And What Fats Are Best For Human Health?
Unsaturated fatty acids are considered the most healthful fats to consume. These fats differ from unsaturated fatty acids in structure (with fewer Hydrogen atoms bonded to their carbon chains) and are typically liquid at room temperature.
There are two major types of unsaturated fatty acids: monounsaturated and polyunsaturated.
Monounsaturated fats are found in foods like olive oil, peanuts, avocados, and most nuts.
Polyunsaturated fatty acids (PUFAs) are found in foods like walnuts, canola oil, salmon, sunflower seeds, and corn oil. PUFA include omega-3 fatty acids (found in fatty fish, flax seeds, among other foods) and omega-6 fatty acids (found in safflower oil, sunflower oil, walnuts, and wheat germ). These are considered essential fats, meaning your body can’t make them and you need to obtain them from your diet. Omega-3s and Omega-6s are important for brain health, among other things.
Of all the fats, PUFAs considered best for heart health when you replace other fats, or in some studies, high levels of carbohydrates, with them.
It’s important to note that most foods contain not just one type of fat, but rather, a combination of a couple types of fat (ie, olive oil contains mostly monounsaturated fatty acids, but also has some PUFA content).
The Bottom Line?
Fat is nothing to be afraid of. It is an essential source of energy, and required for proper cell function, cell communication, as well as brain function.
Strive to eat fats from plant-based sources, such as plant oils, nuts, and other foods like avocados. Avoid trans fatty acids whenever possible. Consuming polyunsaturated fatty acids (found in sunflower seeds, canola oil, flax, etc) over other fats is associated with the best heart-health outcomes.
That’s all for now folks, I hope you enjoyed this post of “what you need to know about dietary fats.” I certainly had fun writing it! Genuinely! I am a nutrition science nerd. I welcome questions and post requests, as always!
*Side note: I know there’s lots of confusion on coconut oil; would a post on that be of interest? Let me know!