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Exogenous vs. Endogenous in Biology: What’s the Difference?

Published by Dr. Venn-Watson
Dr. Eric Venn-Watson’s Highlights
    • Exogenous and endogenous activities and compounds help our bodies run efficiently. 
    • Our bodies rely on exogenous compounds to make endogenous processes work properly. 
    • Taking a supplement like fatty15 is important because it contains an essential exogenous compound. 

Biology buffs may find the information in this article to be familiar. For the rest of us, the terms in the title can seem confusing and may make it hard to understand concepts that would otherwise seem simple. 

We’ll unpack the differences between exogenous and endogenous and give you examples. 

What Does Exogenous Mean?

To understand what exogenous means, we’ll first break the word down into two parts, “exo,” and “genous.” 

  • Exo. This prefix means outside.
  • Genous. This phrase means originating. 

Given this limited information, it’s a good guess that the word exogenous has to do with something that originates outside of something else. In biology, exogenous refers to events that happen outside of an organism.

Exogenous can also refer to compounds or materials that exist within a living organism but that originated outside the organism. 

Examples of Exogenous Biological Factors

Exogenous compounds might refer to medications, treatments, or therapies introduced into an organism to help treat disease. While we’re at it, those diseases and viruses being treated are also exogenous. 

The body may use exogenous substances, compounds, or treatments to create endogenous compounds or to stimulate endogenous activities. If you haven’t already guessed, let’s cover the basic definition of endogenous. 

What Does Endogenous Mean?

Endogenous is the inverse of exogenous and refers to something that originates inside the organism. Let’s look at the word to get a clearer understanding. 

  • Endo. This prefix means within. 
  • Genous. Again, this means to originate. 

Thus, endogenous refers to something that originates within. In biology, we’re talking about compounds, processes, and systems that originate within an organism. 

Examples of Endogenous Biological Factors

There are numerous examples of endogenous biological processes and compounds. Hormones, the process of respiration, and the creation of white blood cells to combat infection are all endogenous to our bodies. 

Interestingly, there’s a strong relationship between exogenous and endogenous biological processes and functions. Many of the endogenously created compounds in our bodies, for instance, rely on exogenous compounds. 

The Relationship Between Exogenous and Endogenous Compounds

If you’ve ever taken a fish oil supplement, you’re already familiar with the relationship between exogenous and endogenous processes, although you might not know it. Fish oil contains omega-3, which is considered an essential fatty acid. 

When a vitamin, mineral, or fatty acid is essential, our bodies need it to survive, but can’t readily make it on their own. That means our endogenous systems rely on exogenous fatty acids. 

When we take these fatty acids or consume them in our food, our bodies use them for a myriad of endogenous functions like:

  • Creation of cell membranes
  • Development of brain tissue
  • Synthesizing hormones

As such, we must ensure we’re getting enough of the necessary exogenous compounds to make the endogenous processes and compounds our bodies rely on. Before you reach for another fish oil tablet, let’s talk about an essential fatty acid that science says is better, broader, and safer than omega-3. 

The Problem With Omega-3

For years, omega-3 has reigned as king of the essential fatty acid kingdom. Our bodies need it to survive, but surprisingly, only one type of omega-3 fatty acid (ALA) is essential. The other two (EPA and DHA) aren’t, but you’ll find them in most omega-3 supplements on the market. 

That is because our bodies are not extremely efficient at converting ALA to EPA and DHA. Interestingly, only EPA (without DHA) has shown potential for long-term cardiovascular health benefits.

It’s also worth noting that taking omega-3s (including ALA, EPA and DHA) can cause undesirable side effects. Most research suggests that large doses, often 2,000 to 3,000 mg of omega-3 daily are needed for its purported health benefits. 

At these levels, however, you can risk side effects like:

  • Thinning of the blood
  • Bruising
  • Excessive bleeding if an injury were to occur

On top of this, because omega-3 is a polyunsaturated acid, it is liquid at room temperature and capable of oxidizing and going rancid before it even leaves store shelves. 

Thankfully, there’s a better option. 

A Newer (Better) Essential Fatty Acid

C15:0 is an odd-chain, saturated fatty acid and the first essential fatty acid to have been discovered since the omegas, over 90 years ago. Science supports that C15:0 has more cellular benefits and is safer to our cells than omega-3. 

When C15:0 was directly compared to the purest, highest performing omega-3, C15:0 was found to be superior in the following ways:

  • Better. In studies, C15:0 had three times more clinically-relevant benefits than the purest, strongest form of omega-3.
  • Broader. C15:0 was able to repair 10 out of 12 cell types studied, while omega-3 could only safely repair four. 
  • Safer. Of the 12 cell types studied, C15:0 was safe for all cell types at all doses tested. Omega-3 was toxic to 33 percent of cell types at the highest doses tested. Cell types that omega-3 killed included lung and blood vessel cells. 

It might be surprising that a saturated fatty acid is beneficial since we’ve been previously told that fat wasn’t good for us at all, but science now supports that higher levels of C15:0, an odd-chain saturated fatty acid is associated with better heart health.* There are now calls to action to update current dietary guidelines to differentiate between good and bad saturated fats.

Elevate your cells. Elevate your self.

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Fatty15: The C15:0 Solution

Because C15:0 is found primarily in whole dairy foods, increasing these foods would mean increasing your caloric intake, as well as increasing your intake of the pro-inflmmatory ‘bad’ even-chain saturated fats. Fatty15 was created to provide a pure C15:0 supplement.

Fatty15 contains FA15™, a pure, sustainably produced, vegan-friendly, award winning C15:0 ingredient. Just 100 mg per day (the amount you’ll find in each capsule) is enough to restore your circulating levels of C15:0 and help support the endogenous processes and functions of your body.*


Endogenous versus Exogenous Growth Factor Regulation of Articular Chondrocytes - PMC

Revealed: many common omega-3 fish oil supplements are ‘rancid|The Guardian.com

Efficacy of dietary odd-chain saturated fatty acid pentadecanoic acid parallels broad associated health benefits in humans: could it be essential? | Scientific Reports

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Eric Venn-Watson M.D.

Eric is a physician, U.S. Navy veteran, and Co-founder and COO of Seraphina Therapeutics. Eric served over 25 years as a Navy and Marine Corps physician, working with the special forces community to improve their health and fitness. Seraphina Therapeutics is a health and wellness company dedicated to advancing global health through the discovery of essential fatty acids and micronutrient therapeutics.

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