This week, we will explore the topic of fat.  This group of nutrients has gotten a bad reputation in the name of unwanted weight gain and heart disease.  While certain types of fat are associated with poor health outcomes, others are necessary for life.  By the end of this article, my hope is that you will have a better understanding of and relationship to fat. 

Fat in the Human Body: 

Before we begin looking at the fat we eat, let’s get a better understanding of the role of fat in our bodies. 

First, where do we find fat?

When you think of fat in your body, you probably think of the fat stored under your skin.  This is the fat that we see move when we dance and that gives us our exterior shape.  This fat is called subcutaneous adipose tissue -- quite literally the fat below our skin.  Like other fat storage sites, this fat is like a savings account of energy that we can tap into when we use energy faster than we can replace it.  

If we look deeper, we find fat in many other places too. 

Our livers store fat and actually create our cholesterol from the fat we eat and the fat we make.  Yes, we make fat!  Fat is a very efficient way to store extra energy for later, and with the exception of two essential fatty acids, we can make every different kind of fat we need, and there are many!  Sometimes the liver can make and store too much fat, a condition known as fatty liver disease.  This can happen when the liver is damaged from alcohol consumption, chronic choline deficiency, high fructose corn syrup overconsumption, and a few other medical situations.  

Our muscles store fat for energy production during exercise - this is why we see fat marbling in meat cuts.  We also find fat deposits as shock absorbing padding around our organs and in the pads of our hands and feet.  Fat surrounds our nerve fibers to speed the conduction of our electrical system enabling us to wiggle our big toes the moment we think about it.  In the form of phospholipids, fat creates the membrane of each and every cell in our body.  Additionally, fat is made into hormones and other chemicals in our body.  This is a very incomplete list, but you get the picture; fat is everywhere!

Fat is not our enemy, it is vital!  Sometimes we have an excess of fat and this can create issues, just like everything else -- too much of a good thing isn’t so good.  Where that excess fat is found will determine what effects those are, and where we tend to store that fat is determined by a combination of our genetics and our lifestyles. 

Digestion of Fat: 

The breakdown of fat occurs mostly in the small intestine.  Digestive chemicals from the pancreas and liver meet there to break fat molecules down into an absorbable form.  The fat we eat is mostly in a form known as a triglyceride.  This is a glycerol backbone with three fatty acids attached (tri).  Triglyceride levels in our blood are commonly measured to check on our health.  We need to be fasting when these levels are measured so we can determine how many triglycerides our body is actively making in response to a short period with no energy consumption. 

Back to digestion.  In our small intestine, fatty acids are broken off the glycerol backbone and then absorbed into our intestine cells where they are put together into packages called chylomicrons and sent through the bloodstream to all the hungry cells of our body.  What isn’t broken down into energy or turned into other useful chemicals is stored for later use. 

Things can get complicated here in the digestive tract when we eat more fat than our body can handle.  If we are having problems with our liver or pancreas, we may not be able to make enough digestive chemicals to handle all the fat in our small intestine resulting in abdominal pain and loose stools that may float or even leave a greasy layer in our toilet water.  If we are eating substances that irritate our digestive tract, food may move along faster as the body attempts to get rid of those irritating substances also resulting in loose fat filled stools.  Another problem can result from having your gallbladder removed.  

Our gallbladders and livers work together as a team.  The liver makes bile and the gallbladder stores it until fat enters the small intestine and needs to be broken down.  When the gallbladder is removed, bile cannot be stored and used in larger amounts when needed.  This results in a lower tolerance to fatty foods.  If you do not have a gallbladder, low fat meals are helpful for this problem. 

Turning Fat into Energy: 

Our bodies burn fat, carbohydrates, alcohol, and proteins to produce energy.  Just like oil, these energy rich chemicals are long strands of carbon with oxygen and hydrogen atoms attached - hydrocarbons.

Through a process using the oxygen we breathe and enzymes the body makes, the mitochondria in our cells break these large molecules down into smaller and smaller substances until they finally harvest the now electrically charged hydrogen atoms.  Through a beautiful and complex dance across the inner membrane of the mitochondria, those hydrogen ions are used to create the energy molecule known as ATP.  Once fat is broken down and ATP is produced carbon dioxide and water are all that is left of the original molecule.  

When we need energy faster than we can provide oxygen, fat can be broken down in a less efficient process known as anaerobic respiration (without oxygen).  This process produces a substance called lactic acid and is one of the culprits behind sore muscles after an intense workout. 

Lastly, we can break fat down into energy in one other way.  This method is reserved for periods of starvation or long-term carbohydrate restriction.  This emergency pathway exists to keep our brains fed as they cannot use fat or proteins for energy through the above two pathways.  This pathway is called ketosis.  Our brains are hungry, hungry organs that rely on carbohydrates and their ability to be very quickly turned into energy, but in a pinch, they can survive on ketones. 

Ketogenic diets are all the rage these days and are promoted as a way to force your body to burn its fat for energy.  Over the short-term, this works and a great way to create this is by fasting for 12 hours every day - stop eating after dinner and eat breakfast 12 hours later.  For me, this means finishing eating by 7pm each night and eating breakfast at 7am - easy peasy!  Your window may look different.

Over the long run, a ketogenic diet that is high in fat and low in carbohydrates deprives the body of needed nutrients, puts a LOT of stress on your metabolism, creates acidic compounds that can damage your tissues, and results in the breakdown of muscle and bone tissue to make up for what you aren’t eating.  It also greatly increases cholesterol levels creating a higher risk for cardiovascular disease.  As cardiovascular disease is the number one killer in the United States, this is not good news for public health!

That being said, for some with a genetic predisposition for obesity, a high carbohydrate diet translates to a metabolism that slows the use of fat for energy.  Those with high insulin levels due to insulin resistance also have a hard time using fat for energy.  This is because the presence of insulin stops the release of a chemical we need to free up stored fat for energy production.  A balanced diet that incorporates all needed nutrients and accounts for a person’s genetics and lifestyle is the answer here -- not a fad diet!  

A note: ketosis in a person with diabetes is an emergency scenario that requires immediate hospital level blood sugar intervention to prevent them from falling into a coma.  However, a medically monitored ketogenic diet can be beneficial for children suffering from epilepsy - this down-regulates brain activity helping to prevent the damage of repeated and long-lasting seizures.  

Types of Fat and Where They are Found: 

Now that we have a better idea of how our bodies use fat, let’s look at the fat we put into them.

When considering fats, there are a few different categories to consider: saturated fats, monounsaturated fats, polyunsaturated fats (PUFA), and trans fats.  Let’s take a look at each category and where we can find them in our diets. 

Saturated Fat: 

Saturated fat tends to be solid at room temperature.  When we look at the structure of saturated fat, this long molecule made up entirely of carbon, oxygen, and hydrogen atoms lacks any double bonds, this means it has as many hydrogen atoms as possible or is saturated with hydrogen - hence the name.  Because this structure is mostly straight without any big bends, the molecules can pack really tightly together, this is why it is solid at room temperature - think lard and coconut oil. 

Animals like us, can make all the saturated fat we need from any excess calories.  This makes it a nonessential nutrient for us - we don’t need to eat it except as an energy source.  

Mostly, we find saturated fats in animal products like eggs, milk, butter, cheese, and meat.  Some saturated fat is found in plant foods like coconut oil and cocoa butter; however, outside of concentrated sources like these, saturated fat is much less abundant in plant foods. 

Monounsaturated Fat:

Monounsaturated fats, unlike saturated fats, tend to be liquid at room temperature, we consider these oils.  A monounsaturated fat contains one double bond in its chemical structure.  This means a monounsaturated fat has two fewer hydrogen atoms than a saturated fat and a bend in its shape.  The single double bond gives this form of fat its name - one double bond = mono. 

We find monounsaturated fats abundantly in animal products, nuts and seeds, avocados, and canola and olive oil. (2)

Just as with saturated fats, we animals can make all the monounsaturated fats we need for functioning.  This makes monounsaturated fats another nonessential nutrient. 

Polyunsaturated Fat: 

Here is where things begin to get interesting.  Polyunsaturated fats (PUFAs), like monounsaturated fats, are liquid oils at room temperature.  Some can stay liquid at even colder temperatures due to their multiple double bonds and multiple bends making it harder for these molecules to pack tightly together.  You can probably guess that the presence of multiple double bonds yields the name polyunsaturated.

PUFAs are found in small amounts in land animals, more in plants such as flaxseeds, walnuts, chia seeds, and sunflower seeds, and in significant amounts in cold water fish such as cod, tuna, and salmon. (1)  

Of the PUFAs, one Omega-6 fat and one Omega-3 fat play important roles in our bodies but we cannot make them ourselves.  Since we need them and we cannot make them, we must eat them; this makes them essential nutrients.  They are: linoleic acid and alpha-linolenic acid.

Linoleic acid: 

Linoleic acid is an omega-6 fatty acid.  It is the precursor to arachidonic acid (AA), a very important building block of our cells that also acts in many of our body’s biochemical pathways.  Without enough linoleic acid in our diet, growth slows and a scaly rash will develop. (2) 

We can find linoleic acid abundantly in safflower oil, sunflower seeds/oil, pine nuts, soybean oil, corn oil, pecans, brazil nuts, and sesame seeds/oil. (1) 

Alpha-Linolenic acid:

Alpha-linolenic acid is an omega-3 fatty acid.  It is the precursor to both EPA and DHA which are commonly seen in omega-3 supplements.  Without enough alpha-linolenic acid in the diet, growth will slow and neurological symptoms such as changes in eyesight will appear. (2)  

We can find alpha-linolenic acid abundantly in flax seeds/oil, walnuts, chia seeds, canola oil, soybean oil, and tofu. (1)

Trans Fats: 

Like saturated fats, trans fats appear solid at room temperature.  These fats contain a double bond in them, however the way their hydrogens are arranged around those double bonds takes away the bend that we see in monounsaturated and polyunsaturated fats.  This change in shape allows trans fats to fit more closely together and remain solid at room temperature.  (2) 

Trans fats occur in small amounts naturally in meat, eggs, and dairy products and are also manufactured by humans in the form of margarine, vegetable shortening, and other hydrogenated oils. 

Trans fats have no beneficial effect in the human body and humans cannot make them.  They are not only nonessential, they are connected to an increased risk of several diseases, and they should be avoided as much as possible. 

Recommendations for Consumption: 

Total Fat: 

According to the Institute for Medicine, a good range for total fat intake falls between 20-35% of the daily calories for healthy adults.  Increasing or decreasing the percentage of fat in the diet outside of this range isn’t associated with any improvements in health over the long run.  (2)

Saturated Fat: 

As saturated fat is a nonessential nutrient, there is no minimum recommendation for its consumption.  However, as we saw above, fat in our diet is packaged as triglycerides (a glycerol backbone with three fatty acids) and they come in combinations of saturated and unsaturated fats making it impossible to avoid all saturated fat.  Any attempt to do so would result in a deficiency of fat soluble vitamins (A, D, E, K) and other needed nutrients. 

That being said, a high intake of saturated fats in addition to overconsumption of calories is associated with an increased risk of cardiovascular disease, diabetes, obesity, and overall death. (2)

We can minimize our intake of saturated fat by reducing the amount of animal products we eat, cutting down on coconut and palm oils, and eating proportionally more whole plant foods.  The USDA’s 2020-2025 dietary guidelines for Americans recommends no more than 10% of our calories come in the form of saturated fat. (3)

Monounsaturated Fat: 

Again, there are no minimum recommendations for monounsaturated fats.  We do not see the same health risks associated with saturated fat, so no maximum recommendation has been set at this time either. 

Polyunsaturated Fat: 

Here is where we get more specific with fat recommendations.  Remember our two essential fatty acids?  Let’s revisit them, shall we?

Linoleic acid: 

This omega-6 fatty acid is a necessary part of our daily diet and luckily it is found in many different food sources.  

Masculine adults ages 19-50 should aim for around 17 grams daily.  After age 51, that recommendation decreases to 14 grams daily, but if you are a highly active 51 year old, go ahead and stick with that higher recommendation.  

For female presenting bodies, the recommendation is 12 grams from ages 19 to 51 and 11 grams thereafter, but, if you remain highly active, stick to 12 grams.  No recommendations have been set for individuals who do not identify as male or female; consider your personal balance of testosterone and estrogen and choose the intake that best suits your biological needs. 

Alpha Linolenic acid: 

For our omega-3 fatty acid friend, we are looking at smaller numbers.  Male presenting individuals can aim for 1.6 grams throughout adulthood, and feminine adults can shoot for 1.1 grams unless they are pregnant when it’s healthier to reach for 1.4 grams. (1)  Again, if you don’t fit within the binary offered above look to support your biological needs to the best of your ability or aim for the middle of the range based on your size and activity level. 

EPA/DHA

The omega-3 fatty acids do bring up a bit of controversy which you will see in the supplement industry.  Conversion of alpha linolenic acid to EPA and DHA decreases with age and is much more robust in those with more estrogen.  For this reason, the American Heart Association and the Linus Pauling Institute recommend the consumption of fish twice weekly for adequate EPA and DHA intake.  For those who already have heart disease, doctor supervised use of a supplement containing EPA and DHA with Vitamin E is recommended.  (1)

What about vegans?  Lucky for us, there are DHA supplements made from algae and fungi that we can take.  The body readily converts DHA to EPA, so this is a realistic strategy for those actively avoiding fish. (1)

With supplements care must be taken.  Fish oil contains triglycerides, so you are getting more fat than just your EPA and DHA; be sure to account for this when considering your needs and intake.  Additionally, all polyunsaturated fats are quite unstable outside of a body; Vitamin E can help prevent damage.  Then we look at cod liver oil which can carry high amounts of Vitamin A in the retinol form which is toxic to the liver in high amounts.  Finally, as with all supplements, there are the perpetual issues of safety, contamination, and fraud.  Be a careful and informed consumer and be sure to verify your supplements before you invest your money, time, and tissues!

After we consider the source itself, we also need to be aware that the act of taking extra omega-3 supplements carries risks in and of itself.  Increased omega-3 levels have been associated with increased risk of bleeding, including hemorrhagic stroke, depression of certain immune functions, and oxidative damage to red blood cells, liver cells, kidney cells, and DNA damage in the bone marrow.  This is why a doctor’s supervision is recommended!  We don’t know how big the risk is, but it isn’t zero, and until we know how a supplement is working in your body, it’s a good idea to have a second set of trained eyes on things. (2)

Trans Fat: 

Simply put, avoid them.  The days of margarine and vegetable shortening are over.  Avoid any foods containing hydrogenated oils - read those labels! (2)

Applications: 

If you wish to dive down the biochemistry rabbit hole, I highly recommend the second resource listed in the references, you can download the pdf version of the book and geek out to your heart’s content!  As this is an article for the general public, I went light on the details here.  We didn’t even go down the eicosanoid pathways that explain how specific fatty acids are more or less inflammatory; the summary is omega-3 fatty acids are less inflammatory. 

For general recommendations, aim to consume a diverse source of dietary fat.  If you eat animal products, great, but be sure to mind that saturated fat and incorporate nuts and seeds too!  I recommend you keep track of your food intake for a week or so to see how your fat stacks up.  

Aim for 20-35% of your calories from fat, no more than 10% from saturated fat.  Eat fish twice weekly even if it’s tuna fish.  Eat nuts and seeds, and remember, flax seeds are a great source of alpha-linolenic acid and fiber!

If you are vegan and worried about your EPA and DHA levels, consider a DHA supplement made from algae or fungi -- especially if you have low levels of estrogen circulating. 

Next Week: 

Next week we will shift our focus a bit.  I will be attending the NUNM Food as Medicine Symposium and plan on sharing some of the more interesting information I pick up.  How often do you get to have a two day professional conference picked over and summed up for you?  

I hope you picked up some new information, have a few new questions, and have developed a new appreciation for fat. 

To our health!

References

1. Higdon, J, “Essential Fatty Acids”, Linus Pauling Institute, Oregon State University, 2003, Reviewed and Updated 2019, https://lpi.oregonstate.edu/mic/other-nutrients/essential-fatty-acids, Accessed 2/15/2021

2. Institute of Medicine 2005. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: The National Academies Press. https://doi.org/10.17226/10490.

3. USDA, “Dietary Guidelines for Americans 2020-2025: Make Every Bite Count With the Dietary Guidelines - Ninth Edition”, www.dietaryguidelines.gov, Accessed 2/15/2021